0191 5166636 enquiries@ht-uk.com


What is Heat Tracing?

  • Heat Tracing (or Trace Heating, or Surface Heating) is the method of applying heat to a body, or to a product (liquid, powder, or gas) contained within a system (pipework, vessel or equipment) for storage or transportation, in order to avoid processing problems or difficulties.

Heat may be applied to:-

  • Liquids
    • to prevent freezing
    • to enable pumping by reducing the viscosity of the liquid
  • Powders
    • to eliminate condensation from the walls of equipment  that could result in ‘clogging’of the product
  • Gases
    • to prevent hydration due to a drop in gas pressure across pipework fittings such as valves


  • The two main types of heat tracing employed in industry today


  • Electric Surface Heating
    • Heaters that use electrical power, either single or three phase
  • Steam Surface Heating
    • Heating that utilises steam from the plant either as a by-product or is created solely for the purpose of heating


  • Electric heat tracing is governed by a number of International and National Standards covering Industrial (Safe) and Industrial (Hazardous) locations


Steam Trace Heating

  • A typical steam heating system utilises, as the name suggest, steam that is either created for the purpose of heating, or steam that is a by-product of the process used on the plant.
  • Advantages of Steam
  • Steam does not produce electrical arcs and therefore is a useful option in explosive areas to prevent gases and dusts in the atmosphere igniting
  • Steam is considered ‘free’energy, although maintenance reduces the advantage of steam somewhat


  • Disadvantages of Steam
  • Steam is high temperature and;
  • It is very difficult to control without expensive valve arrangements.
  • Labour intensive to install to equipment.
  • Expensive to produce, use and maintain.
  • The system is prone to leaks, especially on high pressure steam systems.
  • Is very dangerous to personnel
  • Is very inefficient mainly due to the lack of control


Electric Trace Heating


  • Parallel Heating Cables
  • Self-Regulating Cables
  • Zoned Power-Limiting Cables
  • Zoned Constant Wattage Heating Cables


  • Series Heating Cables
  • Single Phase Series Cables
  • Three Phase Series Cables
  • Mineral Insulated


Self-Regulating Cables

  • These are one of the most common types of heating cables available on the market today.
  • The general construction is that there are two bus-wires (Live and Neutral) carrying the supply voltage.
  • A conductive matrix is extruded over the bus-wires. This is actually the heating element and not an insulating layer.
  • To provide electrical insulation, a layer of thermoplastic is then extruded over the matrix and conductors.
  • As an option, a further layer of metallic braiding is normally applied to the cable. This layer provides both mechanical protection and also an earth path for earth leakage detection.
  • As a final option, a layer of thermoplastic or fluoropolymer is extruded over the final cable. This final layer provides UV and further mechanical protection.


Zoned power limiting cables

  • These types of cables differ in the construction to self-regulating cables. In this construction the two bus-wires are extruded with an insulating layer over each conductor.
  • At pre-determined distances, the insulation is removed from alternate conductors, exposing the base conductor. A heating wire (or element) is wrapped around the two conductors, and where the wire meets these two areas, a heating ‘zone’ is created.
  • Sometimes the heating element is strengthened with fiberglass thread to absorb the high stresses created (especially at higher voltages) in the relatively thin heating wire.
  • A layer of insulation is then extruded over the cable. Similar to the self-regulating cable, a further optional layer of metallic braid and a final thermoplastic or fluoropolymer insulation can be extruded over the cable to provide a finished product.


Series Constant Wattage Cables

  • These cables are either provided as a flexible, cut-to-length version, or as a mineral insulated type cable.
  • The design of the cable relies on insulated conductors which are wired in series (for single phase supplies) or connected in a star connection at the remote end (for three phase supplies).


Principles of Heat Loss

  • All pipes/equipment that are above the ambient temperature will experience heat loss.
  • Heat loss is the loss of heat to the environment.
  • If no heating is applied to the pipe/equipment it will eventually equal the ambient temperature, at which point the heat loss will be zero.
  • The heat loss can be delayed by the application of thermal insulation. However, over a period of time, without heating the equipment will eventually match that of the ambient.
  • To keep equipment above the ambient, it is essential to add heatingand insulationto offset the heat loss.



Heat Loss from a Pipe

Q =              2π x K x (Tp-Ta)+ sf


       Q            Heat Loss (Watts/m)
       K            ‘k’-factor for the insulation at Mean Temperature Tm (W/m°K)
      Tp           Process Temperature (°C)

                Ta           Ambient Temperature (°C)
                d2           Outer diameter of insulation
                d1           Inner diameter of insulation
                sf            Safety Factor (typically an extra 10%)


Selecting a Cable

  • Heating cables come in a variety of ranges and outputs.
  • Check the Pipe Maximum Temperature
  • Check the Hazardous Area T-Rating
  • Adjust for the Voltage
  • Match the Heat Loss


The Design Checklist

  • Is this Maintain or Raise and Maintain?
  • What are the material(s) to be heated
  • Hazardous Location information.
  • Pipe/tank/vessel dimensions
  • Temperature to be held
  • Insulation type and thickness
  • Voltage available
  • Minimum Ambient temperature
  • Maximum permissible pipe temperature



























Leadership is founded in talented employees effectively applying sound business management. We add more value at lower cost with faster response. We each lead through our competence, creativity and teamwork.


Leadership is founded in talented employees effectively applying sound business management. We add more value at lower cost with faster response. We each lead through our competence, creativity and teamwork.