Часто задаваемые вопросы

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What does thermal equilibrium mean?

  • This is a common term as it relates to thermodynamics and heat transfer calculations. It is a state of thermal dynamics where the stabilized temperature is a result of the heat input equal to the heat loss.

Can a pipe or vessel be heated up in a short period of time?

  • Typically not. Heat tracing is primarily used for temperature maintenance. Heat-ups in short periods of time (minutes to a few hours) will most likely require more heat than that needed to maintain the temperature at the desired temperature above ambient.

My application involves nonmetallic pipes and vessels. Do I treat nonmetallic (plastic) pipe or vessel application the same as those for metallic pipes and vessels?

  • There are important considerations when designing heat tracing for non-metallic pipes and vessels. It is very important to consider the maximum temperature rating of the pipe or vessel material. The heater cable operating temperature (sheath temperature) must not exceed the maximum temperature rating of the pipe or vessel. In most cases, the maximum operating temperature is calculated during runaway conditions. Runaway conditions are typically calculated at the highest possible ambient and temperature controller failed with contacts closed resulting in a continuously energized heater. Lower power cables will have lower operating temperatures and are therefore the best chose for non-metallic heating applications.Designs must also take into consideration that heat from the tracer does not transfer as easily into a non-metallic material. Constant watt heaters will operate at higher temperatures on non-metallic surfaces. Self-regulating (SR) cables will also operate at higher temperatures resulting in a reduction in power output. Heat transfer aids can help reduce these effects. For example, a good design practice is to cover the cable with a parallel pass of 2″ wide aluminum tape. This will help reduce sheath temperatures on constant watt cables and increase power output on SR cables.

Do pipe supports and valves need any additional heat?

  • Yes. Pipe support (uninsulated) and valves represent a region of much higher heat loss. This local higher heat loss must be made up with additional heating cable.

A heat loss is based on a 25 mph wind. The specification is for a 50 mph wind. Is there a major increase in heat loss?

  • Typically not, because most of the reduction in heat loss is through the thermal insulation. The increase for this change in wind speed may be only 2-5%.

Do all thermal insulation have basically the same products?

  • While thermal insulations have thermal conductivities, or k-factors, that reduce the flow of heat, the k-factors vary depending on the specific thermal insulation type. They also have different maximum temperature ratings. These factors must be addressed in a heat tracing design.

For heat tracing systems, is thermal insulation really necessary?

  • Yes. The heat losses without thermal insulation are excessive and not practical to compensate for with heat tracing.

Can a cable be installed on a pipe that runs through or to/from a heated building to outside? 

  • Yes. However, the method of temperature control must address the fact that the heat loss will be different for the two ambient conditions. For line-sensing control the sensor should be located on the outside portion of the pipe. With ambient sensing the sensor will be outside as well. In both cases, temperatures of the inside/indoors pipe section should be determined to make sure that product, pipe, or cable maximum temperature ratings are not exceeded.

What is a «run-a-way» temperature?

  • When the controller fails and the heating cable remains energized the pipe will increase in temperature to an equilibrium temperature. This is called «run-a-away» temperature. For stabilized designs in hazardous areas, the condition is used to determine the maximum heating cable sheath temperature.

Can you splice two different watt cables together (i.e., 3 watt to a 6 watt)?

  • Two different parallel watt density cables may be spliced together. Being parallel, the power out put in the two spliced sections will be different as rated. Care must be taken to not exceed the maximum circuit length and circuit breaker rating. The simple solution in this case is to use the maximum circuit length of the higher wattage cable.

Can you install the cable on top of the pipe?

  • Installing the cable on top or directly at the bottom of a pipe is not recommended in order to avoid mechanical damage to the cable. On top of the pipe the cable is susceptible to personnel walking on cable. When installed on the bottom of the pipe, damage may be caused by placing the pipe with the cable in a pipe rack. The ideal location is at 5 or 7 o’clock. Locating the cable at 2 or 10 o’clock is acceptable. Installation ease should dictate the selection of these positions (excluding top or bottom).

If it is Self-Regulating Cable, do you need to have a controller?

  • This depends on the temperature control requirements of the application. If tight, temperature control is required within a few degrees, a line sensing device is recommended. For freeze protection applications , ambient sensing is commonly used with self-regulating heating cables. The self-regulating effect reduces the resulting equilibrium pipe temperature during operation. Where the ambient change during the year is small, it may be possible to do a design using a self-regulating heating cable without any controller.

What is the difference between Power-Limiting and Self-Regulating?

  • Both self-regulation and power-limiting cables exhibit a PTC (positive temperature coefficient) resistance characteristic and subsequently power output decreases with increasing temperature. As self-regulating heating cables increase in temperature they eventually reach a «shut-off» temperature. Power-limiting cables provide higher power output at higher temperatures; however, as temperature increases power-limiting cables do reach a «shut-off» temperature.

Explain the term watts per foot, or watts per meter.

  • For pipe heat tracing it is convenient to think of the heat loss and respective heat required in Watts per unit length. Most pipe heat loss calculations are done with a per foot or per meter basis. Then it is only a matter of selecting a heating cable with this watt per unit output or higher.

What are Series Resistance Cables?

  • Series resistance cables are single or multiple metal alloy conductors with a voltage applied at the ends. The power output is a function of the voltage applied and the overall resistance based on type of metal alloy and circuit length. If the length changes the power output of the cable changes, so these heating cables are not considered «cut-to-length».

What are Power Limiting Heating Cables?

  • Parallel resistance heating cables that will reduce their power output as temperatures rise but do not have the high in-rush currents associated with self-regulating heating cables. These cables are capable of delivering high watt per foot heat outputs.

What are Self-Regulating Heating Cables?

  • Any heating cable providing a watt output which increases as temperatures fall and decreases as temperatures rise. Self-regulating heating cables use a carbon matrix-heating element with variable resistance.
  • Self-regulating cables have a conductive polymer-heating element where the resistance exhibits a PTC characteristic, the resistance of the element increases with temperature. Conversely, the cable’s power output decreases with increasing temperature. As the temperature increases the cable power output approaches zero. At this temperature the cable effectively «shuts off». A hazardous area T-rating can be assigned to self-regulating cables regardless of installation conditions.
  • Being a parallel construction, the self-regulating heating cable can adjust its power output for local condition along its length.

What are Parallel Resistance Heating Cable?

  • A heating cable that includes a continuous series of short, independent heating circuits. Повреждение какого-либо участка приводит лишь к частичной потере теплотворной способности. Watt-per-unit length output is relatively unchanged by variations in circuit length up to several hundred feet. Known as «cut-to-length», parallel cables are easy to size because circuit lengths (within limits) do not have to be considered.

Describe heat loss.

  • Heat loss is the rate at which process equipment heat flows to a cooler ambient, stated in either watts or BTU/hour. The purpose of heat tracing is to replace that heat lost through the thermal insulation in order to maintain a desired temperature difference (ΔT or Delta T). Поэтому первым шагом при проектировании системы обогрева является вычисление тепловых потерь. Вычисление уровня тепловых потерь всегда включает три фактора:
    • (ΔT or Delta T) or (Tp –Ta)
    • Nominal Pipe Size or Vessel Dimensions
    • Types and Thickness of Thermal Insulation

What is freeze protection?

  • Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F — 50°F). Проектирование защиты от замерзания заключается в обычном выборе нагревателя с учетом теплопотерь и термоизоляции. Системы защиты от замерзания характеризуются относительно низкой теплоотдачей и сезонностью применения — к ним прибегают обычно только в холодное время года. Термин «защита от замерзания» также иногда применяется для описания систем поддержания средних температур (Tp = 90 °F или ниже).

What is Delta T (ΔT)? steam blow-down at 750°F and 1100°F? process pipes? On a steam -jacketed system? Tansfer compound?

  • Temperature difference, usually used to describe the difference between the required pipe/vessel temperature (Tp) and the anticipated low ambient temperature (Ta). Therefore, δT will usually equal (Tp – Ta).

What do absolute pressure and gauge pressure mean?

  • If a gauge measure pressure above atmospheric, then the atmospheric pressure of 1,013 bar (metric) or 14,7 (Inch-Pound) must be added to the gauge reading to determine absolute pressure.

How is specific heat used in heat calculations?

  • When the temperature of a substance changes, the heat gained or lost is found by multiplying the mass, or weight of the substance by the change in temperature (ΔT) and by the specific heat (sp ht).

What is specific heat?

  • Metric system: The specific heat of a substance is the number of kilojoules (kJ) necessary to raise 1 kilogram (kg) of the substance 1°C compared with the number of kJ required to raise 1 kg of water 1°C. Note: 1 kJ is almost the same as 1 Btu (1,055 kJ = 1 Btu).
  • Inch-Pound system: The specific heat of a substance is the number of Btu’s necessary to raise 1 lb of a substance 1˚ F compared with the number of Btu’s required to raise 1 lb of water 1˚ F.

What is temperature?

  • In measuring heat, there are two properties to be considered: the «intensity» of the heat and the «quantity» of heat. The intensity of heat is denoted by the term «Temperature» and is known as sensible heat because the heat can be sensed by the thermometer or by the sense of human touch.
  • The quantity of heat in a substance is measured in Kilojoules in the Metric system and BTU’s in the Inch-Pound system.

How does heat flow?

  • Heat flows between two objects because of a difference in temperature between them. When two objects are brought together, the molecules of the warm object imparts motion to the molecules of the cooler object.

What is heat?

  • The heat energy detectable in matter is due to the motion of molecules. The molecules move rapidly in an object that is warm. When the object cools down, the molecules slow down. This is known as the Kinetic Theory of Heat.

What is the definition of a pipeline?

  • In a process plant, a pipeline is a length of pipe having valves, pumps or other line equipment attached to transport and control the flow of process, service or utilities materials.
    • Typically, process piping transports fluids from process feed tanks to the plant’s process units then carries the processed material to storage tanks.
    • Service piping transports water, brine, steam, air or other substances to process piping or equipment to bring about the successful completion of the plant’s processes.
    • Utilities piping transports any fluids that are not directly associated with the plant’s primary processes but are necessary for the functioning of the plant; such as fuel gases, fuel oil, water, air, steam, etc.

What is the function of thermal insulation for heat traced pipes?

  • Provides personnel protection (not hot surfaces)
  • Minimizes heat loss and allows the pipe temperature to increase above ambient temperature based on the amount of heat added by the heat tracer
  • Conserves Energy

What does thermal equilibrium mean?

  • This is a common term as it relates to thermodynamics and heat transfer calculations. It is a state of thermal dynamics where the stabilized temperature is a result of the heat input equal to the heat loss.

Can a pipe or vessel be heated up in a short period of time?

  • Typically not. Heat tracing is primarily used for temperature maintenance. Heat-ups in short periods of time (minutes to a few hours) will most likely require more heat than that needed to maintain the temperature at the desired temperature above ambient.

My application involves nonmetallic pipes and vessels. Do I treat nonmetallic (plastic) pipe or vessel application the same as those for metallic pipes and vessels?

  • There are important considerations when designing heat tracing for non-metallic pipes and vessels. It is very important to consider the maximum temperature rating of the pipe or vessel material. The heater cable operating temperature (sheath temperature) must not exceed the maximum temperature rating of the pipe or vessel. In most cases, the maximum operating temperature is calculated during runaway conditions. Runaway conditions are typically calculated at the highest possible ambient and temperature controller failed with contacts closed resulting in a continuously energized heater. Lower power cables will have lower operating temperatures and are therefore the best chose for non-metallic heating applications.Designs must also take into consideration that heat from the tracer does not transfer as easily into a non-metallic material. Constant watt heaters will operate at higher temperatures on non-metallic surfaces. Self-regulating (SR) cables will also operate at higher temperatures resulting in a reduction in power output. Heat transfer aids can help reduce these effects. For example, a good design practice is to cover the cable with a parallel pass of 2″ wide aluminum tape. This will help reduce sheath temperatures on constant watt cables and increase power output on SR cables.

Do pipe supports and valves need any additional heat?

  • Yes. Pipe support (uninsulated) and valves represent a region of much higher heat loss. This local higher heat loss must be made up with additional heating cable.

A heat loss is based on a 25 mph wind. The specification is for a 50 mph wind. Is there a major increase in heat loss?

  • Typically not, because most of the reduction in heat loss is through the thermal insulation. The increase for this change in wind speed may be only 2-5%.

Do all thermal insulation have basically the same products?

  • While thermal insulations have thermal conductivities, or k-factors, that reduce the flow of heat, the k-factors vary depending on the specific thermal insulation type. They also have different maximum temperature ratings. These factors must be addressed in a heat tracing design.

For heat tracing systems, is thermal insulation really necessary?

  • Yes. The heat losses without thermal insulation are excessive and not practical to compensate for with heat tracing.

Can a cable be installed on a pipe that runs through or to/from a heated building to outside? 

  • Yes. However, the method of temperature control must address the fact that the heat loss will be different for the two ambient conditions. For line-sensing control the sensor should be located on the outside portion of the pipe. With ambient sensing the sensor will be outside as well. In both cases, temperatures of the inside/indoors pipe section should be determined to make sure that product, pipe, or cable maximum temperature ratings are not exceeded.

Can you splice two different watt cables together (i.e., 3 watt to a 6 watt)?

  • Two different parallel watt density cables may be spliced together. Being parallel, the power out put in the two spliced sections will be different as rated. Care must be taken to not exceed the maximum circuit length and circuit breaker rating. The simple solution in this case is to use the maximum circuit length of the higher wattage cable.

Can you install the cable on top of the pipe?

  • Installing the cable on top or directly at the bottom of a pipe is not recommended in order to avoid mechanical damage to the cable. On top of the pipe the cable is susceptible to personnel walking on cable. When installed on the bottom of the pipe, damage may be caused by placing the pipe with the cable in a pipe rack. The ideal location is at 5 or 7 o’clock. Locating the cable at 2 or 10 o’clock is acceptable. Installation ease should dictate the selection of these positions (excluding top or bottom).

If it is Self-Regulating Cable, do you need to have a controller?

  • This depends on the temperature control requirements of the application. If tight, temperature control is required within a few degrees, a line sensing device is recommended. For freeze protection applications , ambient sensing is commonly used with self-regulating heating cables. The self-regulating effect reduces the resulting equilibrium pipe temperature during operation. Where the ambient change during the year is small, it may be possible to do a design using a self-regulating heating cable without any controller.

What is the difference between Power-Limiting and Self-Regulating?

  • Both self-regulation and power-limiting cables exhibit a PTC (positive temperature coefficient) resistance characteristic and subsequently power output decreases with increasing temperature. As self-regulating heating cables increase in temperature they eventually reach a «shut-off» temperature. Power-limiting cables provide higher power output at higher temperatures; however, as temperature increases power-limiting cables do reach a «shut-off» temperature.

Explain the term watts per foot, or watts per meter.

  • For pipe heat tracing it is convenient to think of the heat loss and respective heat required in Watts per unit length. Most pipe heat loss calculations are done with a per foot or per meter basis. Then it is only a matter of selecting a heating cable with this watt per unit output or higher.

What are Series Resistance Cables?

  • Series resistance cables are single or multiple metal alloy conductors with a voltage applied at the ends. The power output is a function of the voltage applied and the overall resistance based on type of metal alloy and circuit length. If the length changes the power output of the cable changes, so these heating cables are not considered «cut-to-length».

What are Power Limiting Heating Cables?

  • Parallel resistance heating cables that will reduce their power output as temperatures rise but do not have the high in-rush currents associated with self-regulating heating cables. These cables are capable of delivering high watt per foot heat outputs.

What are Self-Regulating Heating Cables?

  • Any heating cable providing a watt output which increases as temperatures fall and decreases as temperatures rise. Self-regulating heating cables use a carbon matrix-heating element with variable resistance.
  • Self-regulating cables have a conductive polymer-heating element where the resistance exhibits a PTC characteristic, the resistance of the element increases with temperature. Conversely, the cable’s power output decreases with increasing temperature. As the temperature increases the cable power output approaches zero. At this temperature the cable effectively «shuts off». A hazardous area T-rating can be assigned to self-regulating cables regardless of installation conditions.
  • Being a parallel construction, the self-regulating heating cable can adjust its power output for local condition along its length.

What are Parallel Resistance Heating Cable?

  • A heating cable that includes a continuous series of short, independent heating circuits. Повреждение какого-либо участка приводит лишь к частичной потере теплотворной способности. Watt-per-unit length output is relatively unchanged by variations in circuit length up to several hundred feet. Known as «cut-to-length», parallel cables are easy to size because circuit lengths (within limits) do not have to be considered.

Describe heat loss.

  • Heat loss is the rate at which process equipment heat flows to a cooler ambient, stated in either watts or BTU/hour. The purpose of heat tracing is to replace that heat lost through the thermal insulation in order to maintain a desired temperature difference (ΔT or Delta T). Поэтому первым шагом при проектировании системы обогрева является вычисление тепловых потерь. Вычисление уровня тепловых потерь всегда включает три фактора:
    • (ΔT or Delta T) or (Tp –Ta)
    • Nominal Pipe Size or Vessel Dimensions
    • Types and Thickness of Thermal Insulation

What is freeze protection?

  • Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F — 50°F). Проектирование защиты от замерзания заключается в обычном выборе нагревателя с учетом теплопотерь и термоизоляции. Системы защиты от замерзания характеризуются относительно низкой теплоотдачей и сезонностью применения — к ним прибегают обычно только в холодное время года. Термин «защита от замерзания» также иногда применяется для описания систем поддержания средних температур (Tp = 90 °F или ниже).

What is Delta T (ΔT)? steam blow-down at 750°F and 1100°F? process pipes? On a steam -jacketed system? Tansfer compound?

  • Temperature difference, usually used to describe the difference between the required pipe/vessel temperature (Tp) and the anticipated low ambient temperature (Ta). Therefore, δT will usually equal (Tp – Ta).

What do absolute pressure and gauge pressure mean?

  • If a gauge measure pressure above atmospheric, then the atmospheric pressure of 1,013 bar (metric) or 14,7 (Inch-Pound) must be added to the gauge reading to determine absolute pressure.

How is specific heat used in heat calculations?

  • When the temperature of a substance changes, the heat gained or lost is found by multiplying the mass, or weight of the substance by the change in temperature (ΔT) and by the specific heat (sp ht).

What is specific heat?

  • Metric system: The specific heat of a substance is the number of kilojoules (kJ) necessary to raise 1 kilogram (kg) of the substance 1°C compared with the number of kJ required to raise 1 kg of water 1°C. Note: 1 kJ is almost the same as 1 Btu (1,055 kJ = 1 Btu).
  • Inch-Pound system: The specific heat of a substance is the number of Btu’s necessary to raise 1 lb of a substance 1˚ F compared with the number of Btu’s required to raise 1 lb of water 1˚ F.

What is temperature?

  • In measuring heat, there are two properties to be considered: the «intensity» of the heat and the «quantity» of heat. The intensity of heat is denoted by the term «Temperature» and is known as sensible heat because the heat can be sensed by the thermometer or by the sense of human touch.
  • The quantity of heat in a substance is measured in Kilojoules in the Metric system and BTU’s in the Inch-Pound system.

How does heat flow?

  • Heat flows between two objects because of a difference in temperature between them. When two objects are brought together, the molecules of the warm object imparts motion to the molecules of the cooler object.

What is the function of thermal insulation for heat traced pipes?

  • Provides personnel protection (not hot surfaces)
  • Minimizes heat loss and allows the pipe temperature to increase above ambient temperature based on the amount of heat added by the heat tracer
  • Conserves Energy

What is the maximum recommended enclosure maintain temperature possible when using an ESE enclosure heater? 

  • The maximum recommended enclosure maintain temperature is 150°F (66°C). The temperature limitation is governed by an internal thermal cut-out fuse. The cut-out fuse prevents heater over-temperature during runaway conditions. This is a requirement for hazardous location approvals.

Can an uncontrolled PSE-75 self-regulating instrument heater overheat a differential pressure transmitter? 

  • Tests show that an uncontrolled PSE-75 self-regulating heater installed in an insulated ThermoCase catalog number ICF-1D-PUF will heat the instrument to 148°F (65°C) when the ambient is 104°F (40°C), 0 wind.

Can TubeTrace be manufactured with different colored outer jackets? 

  • Yes, most any color is possible. Additional manufacturing set-up costs may apply.

Is TubeTrace approved for use in electrically hazardous locations? 

  • The heater cable within TubeTrace, the heater cable design and end terminations are approved as a system for use in electrically hazardous locations. It is important to construct a complete system by only using heater cable end terminations and accessories designed and approved for use with the specific cable. From a hazardous location approvals standpoint, tubing bundles are treated the same as insulated pipe. The approval lies with the heater cable.

What does thermal equilibrium mean? 

  • This is a common term as it relates to thermodynamics and heat transfer calculations. It is a state of thermal dynamics where the stabilized temperature is a result of the heat input equal to the heat loss.

What does “non-hygroscopic” mean? 

  • This is a term that tubing bundle manufacturers use to describe an important feature of fiberglass insulation. It means that the insulation will not wick or «sponge» moisture up into the bundle. This is accomplished by treating the fiberglass insulation with moisture inhibitors like silicone compounds.

What is “high alloy” tubing? 

  • These are high nickel alloy tubes with little or no iron content. They offer better corrosion resistance than stainless steel to most chemicals. They also have superior resistance to chloride ion stress corrosion cracking. The trade-off for these enhanced properties is that they are more expensive.

Can stainless steel tubing be excessively work hardened due to cabling or twisting during the manufacture of tubing bundles? 

  • Any cold working of stainless steel tubing will increase hardness. Coil stainless steel tubing used in tubing bundles is ordered from the tube mills not to exceed a hardness of Rockwell B90. The majority will be below Rockwell B80. Recent studies have shown that cabling of tubing in tube bundles only increases hardness by 1,5 to 3. For example, tubing that was B75 before being manufactured into bundles would typically be no more than B78 after completion. Cabling tubing during manufacture into tubing bundles does not excessively work harden stainless steel tubing.

Why do manufacturers of tubing bundles twist the tubes? 

  • There are several benefits to cabling tubes in bundles. Cabling or twisting helps manage differences in expansion and contraction between individual tubes and the heater cable. This is especially important if the tubes are made of different metals or one tube may be exposed to higher temperatures such as steam out or steam blowdown. Also, tubing bundles with cabled tubes can be bent in any plane during installation. Heat transfer between tubes and heat tracer is even throughout the length of bundle. Finally, in electric traced bundles, there is no possibility that the heater cable can migrate between the tubes and suffer mechanical damage due to stresses incurred during installation.

Can a pipe or vessel be heated up in a short period of time? 

  • Typically not. Heat tracing is primarily used for temperature maintenance. Heat-ups in short periods of time (minutes to a few hours) will most likely require more heat than that needed to maintain the temperature at the desired temperature above ambient.

Do pipe supports and valves need any additional heat? 

  • Yes. Pipe support (uninsulated) and valves represent a region of much higher heat loss. This local higher heat loss must be made up with additional heating cable.

A heat loss is based on a 25 mph wind. The specification is for a 50 mph wind. Is there a major increase in heat loss?

  • Typically not, because most of the reduction in heat loss is through the thermal insulation. The increase for this change in wind speed may be only 2-5%.

Do all thermal insulation have basically the same products? 

  • While thermal insulations have thermal conductivities, or k-factors, that reduce the flow of heat, the k-factors vary depending on the specific thermal insulation type. They also have different maximum temperature ratings. These factors must be addressed in a heat tracing design.

For heat tracing systems, is thermal insulation really necessary? 

  • Yes. The heat losses without thermal insulation are excessive and not practical to compensate for with heat tracing.

If it is Self-Regulating Cable, do you need to have a controller? 

  • This depends on the temperature control requirements of the application. If tight, temperature control is required within a few degrees, a line sensing device is recommended. For freeze protection applications , ambient sensing is commonly used with self-regulating heating cables. The self-regulating effect reduces the resulting equilibrium pipe temperature during operation. Where the ambient change during the year is small, it may be possible to do a design using a self-regulating heating cable without any controller.

What is the difference between Power-Limiting and Self-Regulating? 

  • Both self-regulation and power-limiting cables exhibit a PTC (positive temperature coefficient) resistance characteristic and subsequently power output decreases with increasing temperature. As self-regulating heating cables increase in temperature they eventually reach a «shut-off» temperature. Power-limiting cables provide higher power output at higher temperatures; however, as temperature increases power-limiting cables do reach a «shut-off» temperature.

Explain the term watts per foot, or watts per meter. 

  • For pipe heat tracing it is convenient to think of the heat loss and respective heat required in Watts per unit length. Most pipe heat loss calculations are done with a per foot or per meter basis. Then it is only a matter of selecting a heating cable with this watt per unit output or higher.

What are Series Resistance Cables? 

  • Series resistance cables are single or multiple metal alloy conductors with a voltage applied at the ends. The power output is a function of the voltage applied and the overall resistance based on type of metal alloy and circuit length. If the length changes the power output of the cable changes, so these heating cables are not considered «cut-to-length».

What are Power Limiting Heating Cables? 

  • Parallel resistance heating cables that will reduce their power output as temperatures rise but do not have the high in-rush currents associated with self-regulating heating cables. These cables are capable of delivering high watt per foot heat outputs.

What are Self-Regulating Heating Cables? 

  • Any heating cable providing a watt output which increases as temperatures fall and decreases as temperatures rise. Self-regulating heating cables use a carbon matrix-heating element with variable resistance.
  • Self-regulating cables have a conductive polymer-heating element where the resistance exhibits a PTC characteristic, the resistance of the element increases with temperature. Conversely, the cable’s power output decreases with increasing temperature. As the temperature increases the cable power output approaches zero. At this temperature the cable effectively «shuts off». A hazardous area T-rating can be assigned to self-regulating cables regardless of installation conditions.
  • Being a parallel construction, the self-regulating heating cable can adjust its power output for local condition along its length.

What are Parallel Resistance Heating Cable? 

  • A heating cable that includes a continuous series of short, independent heating circuits. Повреждение какого-либо участка приводит лишь к частичной потере теплотворной способности. Watt-per-unit length output is relatively unchanged by variations in circuit length up to several hundred feet. Known as «cut-to-length», parallel cables are easy to size because circuit lengths (within limits) do not have to be considered.

Describe heat loss. 

  • Heat loss is the rate at which process equipment heat flows to a cooler ambient, stated in either watts or BTU/hour. The purpose of heat tracing is to replace that heat lost through the thermal insulation in order to maintain a desired temperature difference (ΔT or Delta T). Поэтому первым шагом при проектировании системы обогрева является вычисление тепловых потерь. Вычисление уровня тепловых потерь всегда включает три фактора:
    • (ΔT or Delta T) or (Tp –Ta)
    • Nominal Pipe Size or Vessel Dimensions
    • Types and Thickness of Thermal Insulation

What is freeze protection? 

  • Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F — 50°F). Проектирование защиты от замерзания заключается в обычном выборе нагревателя с учетом теплопотерь и термоизоляции. Системы защиты от замерзания характеризуются относительно низкой теплоотдачей и сезонностью применения — к ним прибегают обычно только в холодное время года. Термин «защита от замерзания» также иногда применяется для описания систем поддержания средних температур (Tp = 90 °F или ниже).

What is Delta T (ΔT)? steam blow-down at 750°F and 1100°F? process pipes? On a steam -jacketed system? Tansfer compound?

  • Temperature difference, usually used to describe the difference between the required pipe/vessel temperature (Tp) and the anticipated low ambient temperature (Ta). Therefore, δT will usually equal (Tp – Ta).

What do I specify for steam blow-down at 750°F and 1100°F? 

  • Specify TubeTrace type HT for continuous exposure temperatures to 750ºF
    — Bundle diameter = 3″
  • Specify TubeTrace type HTX for continuous exposure temperatures to 1100ºF
    — Bundle diameter = 3 ½ «

What do I specify for exposure over 400°F? 

  • The outer jacket will be less than 140°F when the process tube is 400°F on a standard bundle
  • Specify extra insulation for exposure temperatures between 400°F and 500°F

How many tubes can you put in a bundle? 

  • You have to decide what is practical. Consider the difficulty of installation. Here are some recommendations:
    • No more than three ½» stainless steel tubes
    • Up to twenty ¼» copper or plastic tubes
    • One tube and a heat tracer for sizes ¾» or larger.

How large can the tubes be? 

  • It is practical to manufacture TubeTrace with 1 ½» diameter tubes
  • Tubing is generally available in long length coils in sizes up to ¾» diameter
  • Tube sizes greater than ¾» diameter are manufactured form 20 straight lengths

How small can the tubes be? 

  • It is practical to manufacture TubeTrace with 1/8 ” diameter tubes
  • For tube smaller than 1/8 ”, consider pulling them into a larger diameter tube

What do absolute pressure and gauge pressure mean? 

  • If a gauge measure pressure above atmospheric, then the atmospheric pressure of 1,013 bar (metric) or 14,7 (Inch-Pound) must be added to the gauge reading to determine absolute pressure.

How is specific heat used in heat calculations? 

  • When the temperature of a substance changes, the heat gained or lost is found by multiplying the mass, or weight of the substance by the change in temperature (ΔT) and by the specific heat (sp ht).

What is specific heat? 

  • Metric system: The specific heat of a substance is the number of kilojoules (kJ) necessary to raise 1 kilogram (kg) of the substance 1°C compared with the number of kJ required to raise 1 kg of water 1°C. Note: 1 kJ is almost the same as 1 Btu (1,055 kJ = 1 Btu).
  • Inch-Pound system: The specific heat of a substance is the number of Btu’s necessary to raise 1 lb of a substance 1˚ F compared with the number of Btu’s required to raise 1 lb of water 1˚ F.

What is temperature? 

  • In measuring heat, there are two properties to be considered: the «intensity» of the heat and the «quantity» of heat. The intensity of heat is denoted by the term «Temperature» and is known as sensible heat because the heat can be sensed by the thermometer or by the sense of human touch.
  • The quantity of heat in a substance is measured in Kilojoules in the Metric system and BTU’s in the Inch-Pound system.

How does heat flow? 

  • Heat flows between two objects because of a difference in temperature between them. When two objects are brought together, the molecules of the warm object imparts motion to the molecules of the cooler object.

What does thermal equilibrium mean?

  • This is a common term as it relates to thermodynamics and heat transfer calculations. It is a state of thermal dynamics where the stabilized temperature is a result of the heat input equal to the heat loss.

Can a pipe or vessel be heated up in a short period of time?

  • Typically not. Heat tracing is primarily used for temperature maintenance. Heat-ups in short periods of time (minutes to a few hours) will most likely require more heat than that needed to maintain the temperature at the desired temperature above ambient.

Do pipe supports and valves need any additional heat?

  • Yes. Pipe support (uninsulated) and valves represent a region of much higher heat loss. This local higher heat loss must be made up with additional heating cable.

A heat loss is based on a 25 mph wind. The specification is for a 50 mph wind. Is there a major increase in heat loss?

  • Typically not, because most of the reduction in heat loss is through the thermal insulation. The increase for this change in wind speed may be only 2-5%.

Do all thermal insulation have basically the same products?

  • While thermal insulations have thermal conductivities, or k-factors, that reduce the flow of heat, the k-factors vary depending on the specific thermal insulation type. They also have different maximum temperature ratings. These factors must be addressed in a heat tracing design.

Describe heat loss.

  • Heat loss is the rate at which process equipment heat flows to a cooler ambient, stated in either watts or BTU/hour. The purpose of heat tracing is to replace that heat lost through the thermal insulation in order to maintain a desired temperature difference (ΔT or Delta T). Поэтому первым шагом при проектировании системы обогрева является вычисление тепловых потерь. Вычисление уровня тепловых потерь всегда включает три фактора:
    • (ΔT or Delta T) or (Tp –Ta)
    • Nominal Pipe Size or Vessel Dimensions
    • Types and Thickness of Thermal Insulation

What is freeze protection?

  • Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F — 50°F). Проектирование защиты от замерзания заключается в обычном выборе нагревателя с учетом теплопотерь и термоизоляции. Системы защиты от замерзания характеризуются относительно низкой теплоотдачей и сезонностью применения — к ним прибегают обычно только в холодное время года. Термин «защита от замерзания» также иногда применяется для описания систем поддержания средних температур (Tp = 90 °F или ниже).

What is Delta T (ΔT)? steam blow-down at 750°F and 1100°F? process pipes? On a steam -jacketed system? Tansfer compound?

  • Temperature difference, usually used to describe the difference between the required pipe/vessel temperature (Tp) and the anticipated low ambient temperature (Ta). Therefore, δT will usually equal (Tp – Ta).

What happens if steam tracing supplies too much heat to the process pipes?

  • Energy is wasted
  • More fuel is burned at the boiler to produce the wasted steam, thus increasing boiler emissions.
  • The process fluid may be damaged
  • Excessive stress in the pipe works may create problems
  • The condensate return system may be overloaded

How is latent heat of condensation controlled in a steam tracer?

  • The heat transfer coefficient or conductance rate of the steam tracer to the pipeline determines the amount of steam that will be condensed.
    • If  a high heat transfer rate is required for the pipe, use tracing with heat  transfer compounds (Conduction Tracing).
    • If  a medium heat transfer rate is required, use BTS (Bare Tracer with Safety  jacket).
    • If a medium-low to low heat transfer rate is required, use Factory insulated and jacketed Isolated Tracers.

Do we use steam just because it is hot?

  • No, we have to heat water to make steam. If the boiling or «change of state» were not desirable we would start with another liquid that would not boil at high temperatures.
  • We use steam for tracing to take advantage of the massive amount of latent heat that accompanies condensation.

Describe the latent heat of vaporization and the latent heat of condensation.

  • For any given substance the latent heat of vaporization and the latent heat of condensation are equal. That is, the exact amount of heat required to vaporize the substance is liberated when the vapor condenses.
  • For example: the amount of heat absorbed when 1 kg of water vaporizes at atmospheric pressure and 100°C is 2257 kJ/kg. Then, 2257 kj’s are liberated when the 1 kg of vapor (steam) is condensed at atmospheric pressure and 100°C. Remember, the heat in the liquid is only 419 kJ/kg.
  • For example: the amount of heat absorbed when 1 lb of water vaporizes at atmospheric pressure and 212˚F is 970 btu/lb. Then, the 970 btu’s are liberated when the 1 lb of vapor (steam) is condensed at atmospheric pressure and 212°F. Remember, the heat in the liquid is only 180 btu/lb.

What is meant by the properties of steam?

  • The properties of steam are given in various steam tables and the information includes the following:
  • The Heat of the Liquid: The heat required to raise the temperature of the water from 0°C (32˚F) to the temperature of the boiling point.
  • The latent Heat of Vaporization: The amount of heat required to change 1 kg (1 lb) of water at the temperature of the boiling point to dry saturated steam at the same temperature.
  • Superheat: The heat added to raise the steam from the boiling temperature to the final superheated temperature.

Where is superheated steam used?

  • Superheated steam is used in steam turbines because high friction losses and erosion of the turbine blades can occur if moisture (condensate) is present in steam.
  • Superheated steam is often transported in steam mains so that it will arrive at its destination as dry saturated steam. In transport, the superheat in the steam will decline due to heat loss through the insulation covering the steam main.

Should steam for tracing purposes be saturated, wet, dry, or superheated dry?

  • Dry saturated steam is needed for an efficient steam tracing system since heating applications require condensation of steam to liberate the large quantity of latent heat contained in it. Although superheated steam is sometimes used, it is not generally recommended for heating applications unless a means of de-superheating is available.

Is saturated steam wet or dry?

  • Saturated steam may be completely free from unvaporized water particles, or it may carry water globules in suspension. Therefore, saturated steam may be either wet or dry.
  • If heat is added to dry saturated steam when there is no moisture present, it will become superheated. If heat is taken away from dry saturated steam it will become wet steam the moment it starts losing heat.

What is superheated steam?

  • Steam having a temperature higher than that corresponding to its pressure is called superheated stream.

What is wet steam?

  • Wet steam is steam-containing moisture.

How is steam classified?

  • Steam is generally classified as saturated, dry, or superheated.

What is meant by «saturated steam»?

  • Steam that exists at the temperature that corresponds to its absolute pressure is defined as “saturated” steam, in other words, for any given pressure there is a known and repeatable corresponding steam temperature.

How is steam formed?

  • Water is fed to a boiler at a temperature determined by local requirements, but obviously it cannot be less than 0°C (32˚F) at which water solidifies. Therefore, by general consent, all heat contained in steam is based on water from 0°C (32˚F).
  • In other words, the heat content of water at 0°C (32˚F) is arbitrarily regarded as zero.

What if the pressure is higher or lower than atmospheric?

  • If the pressure is above normal atmospheric, the boiling temperature of water will be above 100°C (212° F).
  • If the pressure is lower than normal atmospheric, such as at high altitudes, or under vacuum, water will boil at temperatures below 100°C (212° F).
  • For example: at 0,5 bar pressure, water will boil at 82,33°C.
  • For example: at 15” of Hg vacuum, water will boil at 179° F.

At what temperature does boiling take place?

  • The temperature at which boiling takes place depends upon the pressure under which the steam is made. If the pressure is normal atmospheric of 1,013 bar (14,7 psi), water will boil at 100°C (212˚F).

What is steam?

  • Steam is a hot invisible gas or vapor given off by water at its boiling point.

What do absolute pressure and gauge pressure mean?

  • If a gauge measure pressure above atmospheric, then the atmospheric pressure of 1,013 bar (metric) or 14,7 (Inch-Pound) must be added to the gauge reading to determine absolute pressure.

How is specific heat used in heat calculations?

  • When the temperature of a substance changes, the heat gained or lost is found by multiplying the mass, or weight of the substance by the change in temperature (ΔT) and by the specific heat (sp ht).

What is specific heat?

  • Metric system: The specific heat of a substance is the number of kilojoules (kJ) necessary to raise 1 kilogram (kg) of the substance 1°C compared with the number of kJ required to raise 1 kg of water 1°C. Note: 1 kJ is almost the same as 1 Btu (1,055 kJ = 1 Btu).
  • Inch-Pound system: The specific heat of a substance is the number of Btu’s necessary to raise 1 lb of a substance 1˚ F compared with the number of Btu’s required to raise 1 lb of water 1˚ F.

What is temperature?

  • In measuring heat, there are two properties to be considered: the «intensity» of the heat and the «quantity» of heat. The intensity of heat is denoted by the term «Temperature» and is known as sensible heat because the heat can be sensed by the thermometer or by the sense of human touch.
  • The quantity of heat in a substance is measured in Kilojoules in the Metric system and BTU’s in the Inch-Pound system.

How does heat flow?

  • Heat flows between two objects because of a difference in temperature between them. When two objects are brought together, the molecules of the warm object imparts motion to the molecules of the cooler object.

What is spiraled tracing and how well does it work?

  • Spiraled tracing is where the steam tracer is spiraled around the pipe, generally thought to provide more heat and eliminate multiple tracers. However, this method of tracing is very inefficient and is not recommended except for tracing very short runs of horizontal pipe 50mm (2-inch NPS) and smaller lengths of pipe less than 6 meters (20 feet); or to trace vertical pipes. Bare spiraled tracers expand circumferentially causing the tracer to grow away from the pipeline like a coiled spring, thus decreasing the heat transfer rate because of the increased air space between the tracer and the pipeline. On horizontal piping runs, pockets at the bottom of the tracer collect condensate and cause for more frequent trapping.

How does a conduction tracing system or a clamp-on heater system compare with a steam -jacketed system?

  • The construction cost of a jacketed system is high in both materials and labor. The system is very expensive to maintain and leakage or failure of the system is difficult to locate. A Conduction Tracing System or a Clamp-On Heater System can generally supply sufficiently high heat transfer rates to provide melt-out or heat up capability for most process materials at a lower cost than a fully jacketed system.

What is steam jacketing?

  • A steam-jacketed pipe is a method whereby a larger pipe, called the jacket, surrounds the core or process pipe transporting the process fluid. Steam is carried in the annular region between the two pipes. This system provides a high heat transfer rate. A jacketed system will maintain the process fluid at or near the steam temperature when covered with thermal insulation and there is no flow in the pipeline.

What is the difference in performance between conduction steam tracers and clamp-on heaters with heat transfer compound?

  • The heat transfer rates for Clamp-On heaters and Conduction Tracing are substantially the same when larger tracer sizes are employed for the tracing system. Recent tests conducted on multiple pipeline sizes using steam as the heating media show that the two systems have the same heat transfer rates when 3/4-inch tubing tracers with heat transfer compound and Strap-On jackets were compared with Clamp-On heaters with heat transfer compound. This is true primarily because both systems have the same contact area (m2 or ft2) at the surface of the pipeline upon which they are attached and both have a steel structure whereby strapping material can provide a tight connection between the tracer/heater and the pipeline.

What are clamp-on pipeline heaters?

  • Clamp-On heaters are rectangular steel tubes approximately 2-inches wide and 1-inch high. The side of the heater in contact with the pipeline is formed to the radius of the pipeline to provide a close fit to the pipe surface. Ends of the specially formed tubing are capped, and couplings are installed at each end for inlet and outlet of heating media. These heaters have a maximum length of 6m (20 feet) and jumpers are used to connect a series of the heaters along the pipeline. Manufacturers recommend the use of heat transfer compound on the curved surface of these heaters to improve the thermal connection to the pipe surface. Generally, these heaters are anchored to the pipeline by the use of steel or stainless steel strapping material.

How do conduction tracers compare with bare tracers?

  • Conduction Tracers can generally replace from 3 to 6 Bare Tracers where multiple Bare Tracers are used to hold pipeline temperatures.

Do heat transfer compounds break and lose contact with the pipeline over time?

  • It should be understood that not all heat transfer compounds are the same just as all paints and primers are not the same. Field experience and tests carried out over the years indicate that widely varying properties exists between heat transfer compounds produced by various manufacturers. High quality heat transfer compounds will not degrade when installed and used in accordance with defined procedures and temperature limitations. The method of installation described in the previous question/answer virtually eliminates any separation at the interface between the heat transfer compound and the pipeline.
  • No third party technical standards on characteristics and performance of materials exists for heat transfer compounds and many small «garage shop» manufacturers produce inferior products. Therefore, the selection of heat transfer materials from an ISO 9000 registered manufacturer having qualified technical back up and testing capability is the best means of assuring a successful and durable system.

How are modern conduction tracers installed on pipelines?

  • In a modern conduction tracing system, the tracer and heat transfer compound are completely covered and held in place by «Strap-On» galvanized steel or stainless steel jackets (sometimes referred to as channels). The steam tracers are held firm and always in contact with the pipeline due to the restraining action of the heat transfer compound surrounding the tube and the Strap-On metal jackets that are held in place by stainless steel straps tightened with a force of up to 4 448 N (1000 lbs). The tightly attached Strap-On jackets assure that the steam tracers and heat transfer compound are permanently fixed to the surface of the pipeline. Short sections of the jacket may be miter cut and placed over the tracer and heat transfer compound at elbows and bends to permanently hold the tracer against the pipe at these locations or, «flexible» stainless steel jackets are available for any irregular shapes such as elbows, valves, pumps or other equipment.

How does heat transfer compound work?

  • Conductive heat transfer compounds create and uninterrupted thermal connection between the steam tracer and the wall of the pipeline by filling the normal air voids between them. Heat transfer is primarily by conduction directly into the wall of the traced pipeline or equipment providing very high heat transfer coefficients.

What is heat transfer compound?

  • Heat transfer compounds are highly conductive material used to enhance the heat transfer rate of steam (fluid) tracers that are attached to pipelines, valves, pumps or other equipment. These materials come in several different forms and consistencies. Some of the compounds are extruded rubbery-like materials that soften and adhere to the substrate upon which they are applied when heated above 95°C (200°F). Some are mastic materials that never harden but provide a tacky adhesive thermal connection to the heated surface, while other types adhere to the tracer and pipeline with a rock-like hardness when cured.

What is conduction tracing?

  • The term «Conduction Tracing» refers to steam tracing systems utilizing a heat transfer compound to thermally bond the steam tracer to a pipeline to provide an increased heat transfer rate. The tracer is simply a semi-rigid tube, flexible tube, or rigid small bore pipe that has been attached to a pipeline and covered with heat transfer compound. The primary heat transfer means is by conduction directly into the metal wall of the pipeline.

What methods are used to isolate steam tracers?

  • There are primarily two methods of isolated tracing. The first one is a factory-insulated tracer designed to deliver moderate to low heat transfer rates for heating pipelines and equipment. Modern factory fabricated isolated tracers are available for touch safety, energy conservation, and sensitive lines handling caustics, acids, amines and other such materials. In this system, the tracer tube is separated from the process pipe or equipment by a low conductive (heat retarding) material. Heat transfer is primarily by air convection movement of heat in the annular space between the oversized thermal insulation and the process pipe. Steam energy savings in the 20% to 50% range can be realized over conventional Bare Tracing. Reduced steam consumption results in lower hydrocarbon emissions.
  • The second method of isolated tracing is an older method that requires the placement of «spacer blocks» under the tracer at certain intervals as it is being secured to the pipeline. The spacer blocks are generally made of wood or a rigid type of thermal insulation. Under «Tips» in this website, look for the title: SafeTrace® Isolated Tracers Versus Tracers On «Spacer Blocks.»

What is isolated steam tracing?

  • Steam tracers that are separated or kept from direct contact with the pipeline they are meant to heat are called «Isolated Tracers.» These tracers are often used to provide «soft heat» for sensitive materials. A hot tracer at or near steam temperature in contact with a pipeline handling fluids such as caustics or acids can cause corrosion of the pipeline and traced equipment.

What is meant by «bare tracer with a safety jacket?»

  • A steam tracer having a yellow silicone rubber outer jacket for safety identification and personnel protection among other features is called a BTS tracer for Bare Tracer with Ssafety-Jacket. It is a patented steam tracer and provides the same heat transfer rate as a conventional Bare Tracer of the same size when the tracers are mounted on a pipeline in the same manner and covered with thermal insulation.

How does natural convection heat the process pipe in a bare tracing system?

  • When Bare Tracers are installed on a pipeline and the traced line is covered with thermal insulation, heat circulates by natural convection from the steam tracer to the annular space between the oversized insulation and the traced pipe and from the annular space to the pipe. Some of the heat in the annular space will also pass through the insulation material to the ambient air. It must be remembered that a certain amount of heat will be transferred to the process pipe by radiation. Some heat will also be transferred by conduction at the contact points between the tracer and the pipe.

How does bare tracing work?

  • Tracers that are attached but not thermally bonded to a pipeline or equipment are frequently called «Air Convection» tracers. This term is used because the primary method of heat transfer from the steam tracer to the pipeline is by the movement of air in the annular space between the oversized insulation and the traced pipeline due to natural convection resulting from a difference in temperature between the steam tracer and the pipeline.

What is bare steam tracing?

  • Bare Tracing, sometimes called «Air Convection» tracing, is where semi-rigid tubing, flexible tubing, or rigid small bore pipes for carrying steam are placed directly on, and attached parallel to a process, service or utility pipeline or equipment with high temperature tape, metallic banding material, or tie-wire. The pipeline and tracer should be covered with thermal insulation to lower heat losses to the ambient air in order to reduce energy consumption and hydrocarbon pollution. Generally, the insulation is sized to fit the next larger pipe size to allow space for the steam tracer(s)).

What are the various methods of steam tracing?

  • There are several tracing methods for heating a pipeline, tank, or other equipment using steam as the heating media. These methods include: 1) Bare Tracing; 2) Bare Tracing with a «Safety Jacket;» 3) Isolated Tracing; 4) Conduction Tracing; 5) Clamp-On or Bolt-On Heaters; 6) Steam Jacketing; and, 7) Spiraled Tracing.

Where and why is steam tracing used?

  • Steam tracing is used in refineries, chemical plants, pulp and paper plants, and other industries.
  • Steam tracing is used to prevent fluids from freezing, condensing, crystallizing or becoming too viscous to pump.
  • Steam tracers covered with heat transfer compound are sometimes called “Conduction Tracers” (see below) and are often used to heat-up process materials; sometimes this entails melting a material that has solidified in a pipeline.

How does steam work inside a steam tracer?

  • When steam is inside the tracer, the original heat in the steam basically splits into two parts:
    • The large amount of latent heat which is transferred to the process pipeline when the steam condenses and,
    • The sensible heat that is retained in the condensate and removed from the tracer by a steam trap located at the end of the steam tracing circuit.

What is steam tracing?

  • Steam tracing is a method of heating a pipeline whereby a semi-rigid tube, flexible tube, or rigid small bore pipe carrying steam is placed parallel and attached to the surface of the pipeline.
  • Since the steam carrying tube or small bore pipe follows or traces the pipeline, it is called “steam tracing”.

What is the definition of a pipeline?

  • In a process plant, a pipeline is a length of pipe having valves, pumps or other line equipment attached to transport and control the flow of process, service or utilities materials.
    • Typically, process piping transports fluids from process feed tanks to the plant’s process units then carries the processed material to storage tanks.
    • Service piping transports water, brine, steam, air or other substances to process piping or equipment to bring about the successful completion of the plant’s processes.
    • Utilities piping transports any fluids that are not directly associated with the plant’s primary processes but are necessary for the functioning of the plant; such as fuel gases, fuel oil, water, air, steam, etc.

What is the function of thermal insulation for heat traced pipes?

  • Provides personnel protection (not hot surfaces)
  • Minimizes heat loss and allows the pipe temperature to increase above ambient temperature based on the amount of heat added by the heat tracer
  • Conserves Energy

What is the maximum recommended enclosure maintain temperature possible when using an ESE enclosure heater? 

  • The maximum recommended enclosure maintain temperature is 150°F (66°C). The temperature limitation is governed by an internal thermal cut-out fuse. The cut-out fuse prevents heater over-temperature during runaway conditions. This is a requirement for hazardous location approvals.

Can an uncontrolled PSE-75 self-regulating instrument heater overheat a differential pressure transmitter? 

  • Tests show that an uncontrolled PSE-75 self-regulating heater installed in an insulated ThermoCase catalog number ICF-1D-PUF will heat the instrument to 148°F (65°C) when the ambient is 104°F (40°C), 0 wind.

Can TubeTrace be manufactured with different colored outer jackets? 

  • Yes, most any color is possible. Additional manufacturing set-up costs may apply.

Is TubeTrace approved for use in electrically hazardous locations? 

  • The heater cable within TubeTrace, the heater cable design and end terminations are approved as a system for use in electrically hazardous locations. It is important to construct a complete system by only using heater cable end terminations and accessories designed and approved for use with the specific cable. From a hazardous location approvals standpoint, tubing bundles are treated the same as insulated pipe. The approval lies with the heater cable.

What does thermal equilibrium mean? 

  • This is a common term as it relates to thermodynamics and heat transfer calculations. It is a state of thermal dynamics where the stabilized temperature is a result of the heat input equal to the heat loss.

What does “non-hygroscopic” mean? 

  • This is a term that tubing bundle manufacturers use to describe an important feature of fiberglass insulation. It means that the insulation will not wick or «sponge» moisture up into the bundle. This is accomplished by treating the fiberglass insulation with moisture inhibitors like silicone compounds.

What is “high alloy” tubing? 

  • These are high nickel alloy tubes with little or no iron content. They offer better corrosion resistance than stainless steel to most chemicals. They also have superior resistance to chloride ion stress corrosion cracking. The trade-off for these enhanced properties is that they are more expensive.

Can stainless steel tubing be excessively work hardened due to cabling or twisting during the manufacture of tubing bundles? 

  • Any cold working of stainless steel tubing will increase hardness. Coil stainless steel tubing used in tubing bundles is ordered from the tube mills not to exceed a hardness of Rockwell B90. The majority will be below Rockwell B80. Recent studies have shown that cabling of tubing in tube bundles only increases hardness by 1,5 to 3. For example, tubing that was B75 before being manufactured into bundles would typically be no more than B78 after completion. Cabling tubing during manufacture into tubing bundles does not excessively work harden stainless steel tubing.

Why do manufacturers of tubing bundles twist the tubes? 

  • There are several benefits to cabling tubes in bundles. Cabling or twisting helps manage differences in expansion and contraction between individual tubes and the heater cable. This is especially important if the tubes are made of different metals or one tube may be exposed to higher temperatures such as steam out or steam blowdown. Also, tubing bundles with cabled tubes can be bent in any plane during installation. Heat transfer between tubes and heat tracer is even throughout the length of bundle. Finally, in electric traced bundles, there is no possibility that the heater cable can migrate between the tubes and suffer mechanical damage due to stresses incurred during installation.

Can a pipe or vessel be heated up in a short period of time? 

  • Typically not. Heat tracing is primarily used for temperature maintenance. Heat-ups in short periods of time (minutes to a few hours) will most likely require more heat than that needed to maintain the temperature at the desired temperature above ambient.

My application involves nonmetallic pipes and vessels. Do I treat nonmetallic (plastic) pipe or vessel application the same as those for metallic pipes and vessels?

  • There are important considerations when designing heat tracing for non-metallic pipes and vessels. It is very important to consider the maximum temperature rating of the pipe or vessel material. The heater cable operating temperature (sheath temperature) must not exceed the maximum temperature rating of the pipe or vessel. In most cases, the maximum operating temperature is calculated during runaway conditions. Runaway conditions are typically calculated at the highest possible ambient and temperature controller failed with contacts closed resulting in a continuously energized heater. Lower power cables will have lower operating temperatures and are therefore the best chose for non-metallic heating applications.Designs must also take into consideration that heat from the tracer does not transfer as easily into a non-metallic material. Constant watt heaters will operate at higher temperatures on non-metallic surfaces. Self-regulating (SR) cables will also operate at higher temperatures resulting in a reduction in power output. Heat transfer aids can help reduce these effects. For example, a good design practice is to cover the cable with a parallel pass of 2″ wide aluminum tape. This will help reduce sheath temperatures on constant watt cables and increase power output on SR cables.

Do pipe supports and valves need any additional heat? 

  • Yes. Pipe support (uninsulated) and valves represent a region of much higher heat loss. This local higher heat loss must be made up with additional heating cable.

A heat loss is based on a 25 mph wind. The specification is for a 50 mph wind. Is there a major increase in heat loss?

  • Typically not, because most of the reduction in heat loss is through the thermal insulation. The increase for this change in wind speed may be only 2-5%.

Do all thermal insulation have basically the same products? 

  • While thermal insulations have thermal conductivities, or k-factors, that reduce the flow of heat, the k-factors vary depending on the specific thermal insulation type. They also have different maximum temperature ratings. These factors must be addressed in a heat tracing design.

For heat tracing systems, is thermal insulation really necessary? 

  • Yes. The heat losses without thermal insulation are excessive and not practical to compensate for with heat tracing.

Can a cable be installed on a pipe that runs through or to/from a heated building to outside? 

  • Yes. However, the method of temperature control must address the fact that the heat loss will be different for the two ambient conditions. For line-sensing control the sensor should be located on the outside portion of the pipe. With ambient sensing the sensor will be outside as well. In both cases, temperatures of the inside/indoors pipe section should be determined to make sure that product, pipe, or cable maximum temperature ratings are not exceeded.

What is a «run-a-way» temperature? 

  • When the controller fails and the heating cable remains energized the pipe will increase in temperature to an equilibrium temperature. This is called «run-a-away» temperature. For stabilized designs in hazardous areas, the condition is used to determine the maximum heating cable sheath temperature.

Can you splice two different watt cables together (i.e., 3 watt to a 6 watt)? 

  • Two different parallel watt density cables may be spliced together. Being parallel, the power out put in the two spliced sections will be different as rated. Care must be taken to not exceed the maximum circuit length and circuit breaker rating. The simple solution in this case is to use the maximum circuit length of the higher wattage cable.

Can you install the cable on top of the pipe? 

  • Installing the cable on top or directly at the bottom of a pipe is not recommended in order to avoid mechanical damage to the cable. On top of the pipe the cable is susceptible to personnel walking on cable. When installed on the bottom of the pipe, damage may be caused by placing the pipe with the cable in a pipe rack. The ideal location is at 5 or 7 o’clock. Locating the cable at 2 or 10 o’clock is acceptable. Installation ease should dictate the selection of these positions (excluding top or bottom).

If it is Self-Regulating Cable, do you need to have a controller? 

  • This depends on the temperature control requirements of the application. If tight, temperature control is required within a few degrees, a line sensing device is recommended. For freeze protection applications , ambient sensing is commonly used with self-regulating heating cables. The self-regulating effect reduces the resulting equilibrium pipe temperature during operation. Where the ambient change during the year is small, it may be possible to do a design using a self-regulating heating cable without any controller.

What is the difference between Power-Limiting and Self-Regulating? 

  • Both self-regulation and power-limiting cables exhibit a PTC (positive temperature coefficient) resistance characteristic and subsequently power output decreases with increasing temperature. As self-regulating heating cables increase in temperature they eventually reach a «shut-off» temperature. Power-limiting cables provide higher power output at higher temperatures; however, as temperature increases power-limiting cables do reach a «shut-off» temperature.

Explain the term watts per foot, or watts per meter. 

  • For pipe heat tracing it is convenient to think of the heat loss and respective heat required in Watts per unit length. Most pipe heat loss calculations are done with a per foot or per meter basis. Then it is only a matter of selecting a heating cable with this watt per unit output or higher.

What are Series Resistance Cables? 

  • Series resistance cables are single or multiple metal alloy conductors with a voltage applied at the ends. The power output is a function of the voltage applied and the overall resistance based on type of metal alloy and circuit length. If the length changes the power output of the cable changes, so these heating cables are not considered «cut-to-length».

What are Power Limiting Heating Cables? 

  • Parallel resistance heating cables that will reduce their power output as temperatures rise but do not have the high in-rush currents associated with self-regulating heating cables. These cables are capable of delivering high watt per foot heat outputs.

What are Self-Regulating Heating Cables? 

  • Any heating cable providing a watt output which increases as temperatures fall and decreases as temperatures rise. Self-regulating heating cables use a carbon matrix-heating element with variable resistance.
  • Self-regulating cables have a conductive polymer-heating element where the resistance exhibits a PTC characteristic, the resistance of the element increases with temperature. Conversely, the cable’s power output decreases with increasing temperature. As the temperature increases the cable power output approaches zero. At this temperature the cable effectively «shuts off». A hazardous area T-rating can be assigned to self-regulating cables regardless of installation conditions.
  • Being a parallel construction, the self-regulating heating cable can adjust its power output for local condition along its length.

What are Parallel Resistance Heating Cable? 

  • A heating cable that includes a continuous series of short, independent heating circuits. Повреждение какого-либо участка приводит лишь к частичной потере теплотворной способности. Watt-per-unit length output is relatively unchanged by variations in circuit length up to several hundred feet. Known as «cut-to-length», parallel cables are easy to size because circuit lengths (within limits) do not have to be considered.

Describe heat loss. 

  • Heat loss is the rate at which process equipment heat flows to a cooler ambient, stated in either watts or BTU/hour. The purpose of heat tracing is to replace that heat lost through the thermal insulation in order to maintain a desired temperature difference (ΔT or Delta T). Поэтому первым шагом при проектировании системы обогрева является вычисление тепловых потерь. Вычисление уровня тепловых потерь всегда включает три фактора:
    • (ΔT or Delta T) or (Tp –Ta)
    • Nominal Pipe Size or Vessel Dimensions
    • Types and Thickness of Thermal Insulation

What is freeze protection? 

  • Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F — 50°F). Проектирование защиты от замерзания заключается в обычном выборе нагревателя с учетом теплопотерь и термоизоляции. Системы защиты от замерзания характеризуются относительно низкой теплоотдачей и сезонностью применения — к ним прибегают обычно только в холодное время года. Термин «защита от замерзания» также иногда применяется для описания систем поддержания средних температур (Tp = 90 °F или ниже).

What is Delta T (ΔT)? steam blow-down at 750°F and 1100°F? process pipes? On a steam -jacketed system? Tansfer compound?

  • Temperature difference, usually used to describe the difference between the required pipe/vessel temperature (Tp) and the anticipated low ambient temperature (Ta). Therefore, δT will usually equal (Tp – Ta).

What do I specify for steam blow-down at 750°F and 1100°F? 

  • Specify TubeTrace type HT for continuous exposure temperatures to 750ºF
    — Bundle diameter = 3″
  • Specify TubeTrace type HTX for continuous exposure temperatures to 1100ºF
    — Bundle diameter = 3 ½ «

What do I specify for exposure over 400°F? 

  • The outer jacket will be less than 140°F when the process tube is 400°F on a standard bundle
  • Specify extra insulation for exposure temperatures between 400°F and 500°F

How many tubes can you put in a bundle? 

  • You have to decide what is practical. Consider the difficulty of installation. Here are some recommendations:
    • No more than three ½» stainless steel tubes
    • Up to twenty ¼» copper or plastic tubes
    • One tube and a heat tracer for sizes ¾» or larger.

How large can the tubes be? 

  • It is practical to manufacture TubeTrace with 1 ½» diameter tubes
  • Tubing is generally available in long length coils in sizes up to ¾» diameter
  • Tube sizes greater than ¾» diameter are manufactured form 20 straight lengths

How small can the tubes be? 

  • It is practical to manufacture TubeTrace with 1/8 ” diameter tubes
  • For tube smaller than 1/8 ”, consider pulling them into a larger diameter tube

What happens if steam tracing supplies too much heat to the process pipes? 

  • Energy is wasted
  • More fuel is burned at the boiler to produce the wasted steam, thus increasing boiler emissions.
  • The process fluid may be damaged
  • Excessive stress in the pipe works may create problems
  • The condensate return system may be overloaded

How is latent heat of condensation controlled in a steam tracer? 

  • The heat transfer coefficient or conductance rate of the steam tracer to the pipeline determines the amount of steam that will be condensed.
    • If  a high heat transfer rate is required for the pipe, use tracing with heat  transfer compounds (Conduction Tracing).
    • If  a medium heat transfer rate is required, use BTS (Bare Tracer with Safety  jacket).
    • If a medium-low to low heat transfer rate is required, use Factory insulated and jacketed Isolated Tracers.

Do we use steam just because it is hot? 

  • No, we have to heat water to make steam. If the boiling or «change of state» were not desirable we would start with another liquid that would not boil at high temperatures.
  • We use steam for tracing to take advantage of the massive amount of latent heat that accompanies condensation.

Describe the latent heat of vaporization and the latent heat of condensation. 

  • For any given substance the latent heat of vaporization and the latent heat of condensation are equal. That is, the exact amount of heat required to vaporize the substance is liberated when the vapor condenses.
  • For example: the amount of heat absorbed when 1 kg of water vaporizes at atmospheric pressure and 100°C is 2257 kJ/kg. Then, 2257 kj’s are liberated when the 1 kg of vapor (steam) is condensed at atmospheric pressure and 100°C. Remember, the heat in the liquid is only 419 kJ/kg.
  • For example: the amount of heat absorbed when 1 lb of water vaporizes at atmospheric pressure and 212˚F is 970 btu/lb. Then, the 970 btu’s are liberated when the 1 lb of vapor (steam) is condensed at atmospheric pressure and 212°F. Remember, the heat in the liquid is only 180 btu/lb.

What is meant by the properties of steam? 

  • The properties of steam are given in various steam tables and the information includes the following:
  • The Heat of the Liquid: The heat required to raise the temperature of the water from 0°C (32˚F) to the temperature of the boiling point.
  • The latent Heat of Vaporization: The amount of heat required to change 1 kg (1 lb) of water at the temperature of the boiling point to dry saturated steam at the same temperature.
  • Superheat: The heat added to raise the steam from the boiling temperature to the final superheated temperature.

Where is superheated steam used? 

  • Superheated steam is used in steam turbines because high friction losses and erosion of the turbine blades can occur if moisture (condensate) is present in steam.
  • Superheated steam is often transported in steam mains so that it will arrive at its destination as dry saturated steam. In transport, the superheat in the steam will decline due to heat loss through the insulation covering the steam main.

Should steam for tracing purposes be saturated, wet, dry, or superheated dry? 

  • Dry saturated steam is needed for an efficient steam tracing system since heating applications require condensation of steam to liberate the large quantity of latent heat contained in it. Although superheated steam is sometimes used, it is not generally recommended for heating applications unless a means of de-superheating is available.

Is saturated steam wet or dry? 

  • Saturated steam may be completely free from unvaporized water particles, or it may carry water globules in suspension. Therefore, saturated steam may be either wet or dry.
  • If heat is added to dry saturated steam when there is no moisture present, it will become superheated. If heat is taken away from dry saturated steam it will become wet steam the moment it starts losing heat.

What is superheated steam? 

  • Steam having a temperature higher than that corresponding to its pressure is called superheated stream.

What is wet steam? 

  • Wet steam is steam-containing moisture.

How is steam classified? 

  • Steam is generally classified as saturated, dry, or superheated.

What is meant by «saturated steam»? 

  • Steam that exists at the temperature that corresponds to its absolute pressure is defined as “saturated” steam, in other words, for any given pressure there is a known and repeatable corresponding steam temperature.

How is steam formed? 

  • Water is fed to a boiler at a temperature determined by local requirements, but obviously it cannot be less than 0°C (32˚F) at which water solidifies. Therefore, by general consent, all heat contained in steam is based on water from 0°C (32˚F).
  • In other words, the heat content of water at 0°C (32˚F) is arbitrarily regarded as zero.

What if the pressure is higher or lower than atmospheric? 

  • If the pressure is above normal atmospheric, the boiling temperature of water will be above 100°C (212° F).
  • If the pressure is lower than normal atmospheric, such as at high altitudes, or under vacuum, water will boil at temperatures below 100°C (212° F).
  • For example: at 0,5 bar pressure, water will boil at 82,33°C.
  • For example: at 15” of Hg vacuum, water will boil at 179° F.

At what temperature does boiling take place? 

  • The temperature at which boiling takes place depends upon the pressure under which the steam is made. If the pressure is normal atmospheric of 1,013 bar (14,7 psi), water will boil at 100°C (212˚F).

What is steam? 

  • Steam is a hot invisible gas or vapor given off by water at its boiling point.

What do absolute pressure and gauge pressure mean? 

  • If a gauge measure pressure above atmospheric, then the atmospheric pressure of 1,013 bar (metric) or 14,7 (Inch-Pound) must be added to the gauge reading to determine absolute pressure.

How is specific heat used in heat calculations? 

  • When the temperature of a substance changes, the heat gained or lost is found by multiplying the mass, or weight of the substance by the change in temperature (ΔT) and by the specific heat (sp ht).

What is specific heat? 

  • Metric system: The specific heat of a substance is the number of kilojoules (kJ) necessary to raise 1 kilogram (kg) of the substance 1°C compared with the number of kJ required to raise 1 kg of water 1°C. Note: 1 kJ is almost the same as 1 Btu (1,055 kJ = 1 Btu).
  • Inch-Pound system: The specific heat of a substance is the number of Btu’s necessary to raise 1 lb of a substance 1˚ F compared with the number of Btu’s required to raise 1 lb of water 1˚ F.

What is temperature? 

  • In measuring heat, there are two properties to be considered: the «intensity» of the heat and the «quantity» of heat. The intensity of heat is denoted by the term «Temperature» and is known as sensible heat because the heat can be sensed by the thermometer or by the sense of human touch.
  • The quantity of heat in a substance is measured in Kilojoules in the Metric system and BTU’s in the Inch-Pound system.

How does heat flow? 

  • Heat flows between two objects because of a difference in temperature between them. When two objects are brought together, the molecules of the warm object imparts motion to the molecules of the cooler object.

What is heat? 

  • The heat energy detectable in matter is due to the motion of molecules. The molecules move rapidly in an object that is warm. When the object cools down, the molecules slow down. This is known as the Kinetic Theory of Heat.

What is spiraled tracing and how well does it work? 

  • Spiraled tracing is where the steam tracer is spiraled around the pipe, generally thought to provide more heat and eliminate multiple tracers. However, this method of tracing is very inefficient and is not recommended except for tracing very short runs of horizontal pipe 50mm (2-inch NPS) and smaller lengths of pipe less than 6 meters (20 feet); or to trace vertical pipes. Bare spiraled tracers expand circumferentially causing the tracer to grow away from the pipeline like a coiled spring, thus decreasing the heat transfer rate because of the increased air space between the tracer and the pipeline. On horizontal piping runs, pockets at the bottom of the tracer collect condensate and cause for more frequent trapping.

How does a conduction tracing system or a clamp-on heater system compare with a steam -jacketed system? 

  • The construction cost of a jacketed system is high in both materials and labor. The system is very expensive to maintain and leakage or failure of the system is difficult to locate. A Conduction Tracing System or a Clamp-On Heater System can generally supply sufficiently high heat transfer rates to provide melt-out or heat up capability for most process materials at a lower cost than a fully jacketed system.

What is steam jacketing? 

  • A steam-jacketed pipe is a method whereby a larger pipe, called the jacket, surrounds the core or process pipe transporting the process fluid. Steam is carried in the annular region between the two pipes. This system provides a high heat transfer rate. A jacketed system will maintain the process fluid at or near the steam temperature when covered with thermal insulation and there is no flow in the pipeline.

What is the difference in performance between conduction steam tracers and clamp-on heaters with heat transfer compound? 

  • The heat transfer rates for Clamp-On heaters and Conduction Tracing are substantially the same when larger tracer sizes are employed for the tracing system. Recent tests conducted on multiple pipeline sizes using steam as the heating media show that the two systems have the same heat transfer rates when 3/4-inch tubing tracers with heat transfer compound and Strap-On jackets were compared with Clamp-On heaters with heat transfer compound. This is true primarily because both systems have the same contact area (m2 or ft2) at the surface of the pipeline upon which they are attached and both have a steel structure whereby strapping material can provide a tight connection between the tracer/heater and the pipeline.

What are clamp-on pipeline heaters? 

  • Clamp-On heaters are rectangular steel tubes approximately 2-inches wide and 1-inch high. The side of the heater in contact with the pipeline is formed to the radius of the pipeline to provide a close fit to the pipe surface. Ends of the specially formed tubing are capped, and couplings are installed at each end for inlet and outlet of heating media. These heaters have a maximum length of 6m (20 feet) and jumpers are used to connect a series of the heaters along the pipeline. Manufacturers recommend the use of heat transfer compound on the curved surface of these heaters to improve the thermal connection to the pipe surface. Generally, these heaters are anchored to the pipeline by the use of steel or stainless steel strapping material.

How do conduction tracers compare with bare tracers? 

  • Conduction Tracers can generally replace from 3 to 6 Bare Tracers where multiple Bare Tracers are used to hold pipeline temperatures.

Do heat transfer compounds break and lose contact with the pipeline over time? 

  • It should be understood that not all heat transfer compounds are the same just as all paints and primers are not the same. Field experience and tests carried out over the years indicate that widely varying properties exists between heat transfer compounds produced by various manufacturers. High quality heat transfer compounds will not degrade when installed and used in accordance with defined procedures and temperature limitations. The method of installation described in the previous question/answer virtually eliminates any separation at the interface between the heat transfer compound and the pipeline.
  • No third party technical standards on characteristics and performance of materials exists for heat transfer compounds and many small «garage shop» manufacturers produce inferior products. Therefore, the selection of heat transfer materials from an ISO 9000 registered manufacturer having qualified technical back up and testing capability is the best means of assuring a successful and durable system.

How are modern conduction tracers installed on pipelines? 

  • In a modern conduction tracing system, the tracer and heat transfer compound are completely covered and held in place by «Strap-On» galvanized steel or stainless steel jackets (sometimes referred to as channels). The steam tracers are held firm and always in contact with the pipeline due to the restraining action of the heat transfer compound surrounding the tube and the Strap-On metal jackets that are held in place by stainless steel straps tightened with a force of up to 4 448 N (1000 lbs). The tightly attached Strap-On jackets assure that the steam tracers and heat transfer compound are permanently fixed to the surface of the pipeline. Short sections of the jacket may be miter cut and placed over the tracer and heat transfer compound at elbows and bends to permanently hold the tracer against the pipe at these locations or, «flexible» stainless steel jackets are available for any irregular shapes such as elbows, valves, pumps or other equipment.

How does heat transfer compound work? 

  • Conductive heat transfer compounds create and uninterrupted thermal connection between the steam tracer and the wall of the pipeline by filling the normal air voids between them. Heat transfer is primarily by conduction directly into the wall of the traced pipeline or equipment providing very high heat transfer coefficients.

What is heat transfer compound? 

  • Heat transfer compounds are highly conductive material used to enhance the heat transfer rate of steam (fluid) tracers that are attached to pipelines, valves, pumps or other equipment. These materials come in several different forms and consistencies. Some of the compounds are extruded rubbery-like materials that soften and adhere to the substrate upon which they are applied when heated above 95°C (200°F). Some are mastic materials that never harden but provide a tacky adhesive thermal connection to the heated surface, while other types adhere to the tracer and pipeline with a rock-like hardness when cured.

What is conduction tracing? 

  • The term «Conduction Tracing» refers to steam tracing systems utilizing a heat transfer compound to thermally bond the steam tracer to a pipeline to provide an increased heat transfer rate. The tracer is simply a semi-rigid tube, flexible tube, or rigid small bore pipe that has been attached to a pipeline and covered with heat transfer compound. The primary heat transfer means is by conduction directly into the metal wall of the pipeline.

What methods are used to isolate steam tracers? 

  • There are primarily two methods of isolated tracing. The first one is a factory-insulated tracer designed to deliver moderate to low heat transfer rates for heating pipelines and equipment. Modern factory fabricated isolated tracers are available for touch safety, energy conservation, and sensitive lines handling caustics, acids, amines and other such materials. In this system, the tracer tube is separated from the process pipe or equipment by a low conductive (heat retarding) material. Heat transfer is primarily by air convection movement of heat in the annular space between the oversized thermal insulation and the process pipe. Steam energy savings in the 20% to 50% range can be realized over conventional Bare Tracing. Reduced steam consumption results in lower hydrocarbon emissions.
  • The second method of isolated tracing is an older method that requires the placement of «spacer blocks» under the tracer at certain intervals as it is being secured to the pipeline. The spacer blocks are generally made of wood or a rigid type of thermal insulation. Under «Tips» in this website, look for the title: SafeTrace® Isolated Tracers Versus Tracers On «Spacer Blocks.»

What is isolated steam tracing? 

  • Steam tracers that are separated or kept from direct contact with the pipeline they are meant to heat are called «Isolated Tracers.» These tracers are often used to provide «soft heat» for sensitive materials. A hot tracer at or near steam temperature in contact with a pipeline handling fluids such as caustics or acids can cause corrosion of the pipeline and traced equipment.

What is meant by «bare tracer with a safety jacket?» 

  • A steam tracer having a yellow silicone rubber outer jacket for safety identification and personnel protection among other features is called a BTS tracer for Bare Tracer with Ssafety-Jacket. It is a patented steam tracer and provides the same heat transfer rate as a conventional Bare Tracer of the same size when the tracers are mounted on a pipeline in the same manner and covered with thermal insulation.

How does natural convection heat the process pipe in a bare tracing system? 

  • When Bare Tracers are installed on a pipeline and the traced line is covered with thermal insulation, heat circulates by natural convection from the steam tracer to the annular space between the oversized insulation and the traced pipe and from the annular space to the pipe. Some of the heat in the annular space will also pass through the insulation material to the ambient air. It must be remembered that a certain amount of heat will be transferred to the process pipe by radiation. Some heat will also be transferred by conduction at the contact points between the tracer and the pipe.

How does bare tracing work? 

  • Tracers that are attached but not thermally bonded to a pipeline or equipment are frequently called «Air Convection» tracers. This term is used because the primary method of heat transfer from the steam tracer to the pipeline is by the movement of air in the annular space between the oversized insulation and the traced pipeline due to natural convection resulting from a difference in temperature between the steam tracer and the pipeline.

What is bare steam tracing? 

  • Bare Tracing, sometimes called «Air Convection» tracing, is where semi-rigid tubing, flexible tubing, or rigid small bore pipes for carrying steam are placed directly on, and attached parallel to a process, service or utility pipeline or equipment with high temperature tape, metallic banding material, or tie-wire. The pipeline and tracer should be covered with thermal insulation to lower heat losses to the ambient air in order to reduce energy consumption and hydrocarbon pollution. Generally, the insulation is sized to fit the next larger pipe size to allow space for the steam tracer(s)).

What are the various methods of steam tracing? 

  • There are several tracing methods for heating a pipeline, tank, or other equipment using steam as the heating media. These methods include: 1) Bare Tracing; 2) Bare Tracing with a «Safety Jacket;» 3) Isolated Tracing; 4) Conduction Tracing; 5) Clamp-On or Bolt-On Heaters; 6) Steam Jacketing; and, 7) Spiraled Tracing.

Where and why is steam tracing used? 

  • Steam tracing is used in refineries, chemical plants, pulp and paper plants, and other industries.
  • Steam tracing is used to prevent fluids from freezing, condensing, crystallizing or becoming too viscous to pump.
  • Steam tracers covered with heat transfer compound are sometimes called “Conduction Tracers” (see below) and are often used to heat-up process materials; sometimes this entails melting a material that has solidified in a pipeline.

How does steam work inside a steam tracer? 

  • When steam is inside the tracer, the original heat in the steam basically splits into two parts:
    • The large amount of latent heat which is transferred to the process pipeline when the steam condenses and,
    • The sensible heat that is retained in the condensate and removed from the tracer by a steam trap located at the end of the steam tracing circuit.

What is steam tracing? 

  • Steam tracing is a method of heating a pipeline whereby a semi-rigid tube, flexible tube, or rigid small bore pipe carrying steam is placed parallel and attached to the surface of the pipeline.
  • Since the steam carrying tube or small bore pipe follows or traces the pipeline, it is called “steam tracing”.

What is the definition of a pipeline? 

  • In a process plant, a pipeline is a length of pipe having valves, pumps or other line equipment attached to transport and control the flow of process, service or utilities materials.
    • Typically, process piping transports fluids from process feed tanks to the plant’s process units then carries the processed material to storage tanks.
    • Service piping transports water, brine, steam, air or other substances to process piping or equipment to bring about the successful completion of the plant’s processes.
    • Utilities piping transports any fluids that are not directly associated with the plant’s primary processes but are necessary for the functioning of the plant; such as fuel gases, fuel oil, water, air, steam, etc.

What is the function of thermal insulation for heat traced pipes? 

  • Provides personnel protection (not hot surfaces)
  • Minimizes heat loss and allows the pipe temperature to increase above ambient temperature based on the amount of heat added by the heat tracer
  • Conserves Energy

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