Unitemp Blog

19.03.2015

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...

19.03.2015

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...

19.03.2015

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.

19.03.2015

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.

19.03.2015

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.

19.03.2015

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).

19.03.2015

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).

19.03.2015

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.

19.03.2015

Freeze protection is a heat tracing application. Usually refers to maintaining water line temperatures at slightly above freezing (Tp = 40°F - 50°F).

Freeze protection design is simply a matter of selecting a heater to offset the heat loss through the thermal insulation. Freeze protection systems are characterized by relatively low heat delivery and by the fact that their use is generally seasonal during cold weather months.

“Freeze protection” is sometimes used to describe...

19.03.2015

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). Therefore, the first step in heat tracing system design is to calculate the heat loss.

Heat loss calculations always involve three factors: (ΔT or Delta T) or (Tp –Ta) Nominal Pipe Size or Vessel Dimensions...