Maintaining the required temperature for a process fluid, i.e., keeping the pipes flowing during freezing weather, is critical to many industries, most notably the petroleum and chemical industries. An electrical heat trace is the most common freeze protection for piping, valves, and instruments along a pipeline.
To design an effective heat trace system, you’ll need to gather information about the pipes, tanks, and other areas to heat. A heat trace diagram is essential for visualizing the system’s layout and the components required.
This article will explain industrial heat tracing and heat tracing diagrams. You’ll find practical examples of typical heat tracing diagrams and general information.
The Purpose of a Heat Trace System
A heat trace system uses heat to increase or maintain a piping system’s process temperature and fluid viscosity.
There are two categories of heat tracing, fluid or steam and electrical. Steam tracing circulates steam or other heated fluid through a series of tubing along the pipeline. It’s cost-effective if there is already steam available within the process. For most applications, an electrical trace is the best and most cost-effective way to heat piping. It uses electrical heating wiring to conduct heat into the process fluid by physically contacting the pipe and valves.
There are three types of heating cables depending on the length and temperature required:
- Self-regulating polymer jacketed cables provide temperatures up to 200°C (329°F) and circuit lengths up to 750 feet.
- Mineral insulated heat trace cables generate temperatures up to 650°C (1,202°F) and circuit lengths up to 3,300 feet.
- Skin effect heating system cables provide moderate heat for much longer heating circuits. They can run up to 82,000 feet (25 km) while heating up to 250°C (482°F).
Electric heat tracing can work on metal and non-metal pipes. For further details, check out How to install heat trace.
A heat tracing diagram is the first step in planning the heat tracing layout for different pipes or equipment.
What is a Heat Tracing Diagram?
A heat tracing diagram is a visual representation of the heat tracing layout for specific pieces of industrial equipment. It maps the path that heat tracing takes through the industrial process.
A carefully designed system will include the following heat trace system components:
Heat Trace Cable – A self-regulating heating cable attaches to the pipes and valves using high-temperature heat trace tape.
Power Connection Boxes – The cable connects to the power source using a power connection box. Adding a heat trace digital thermostat makes monitoring the system easier and provides greater accuracy and temperature control.
Junction Boxes – Where there is a Tee or other junction, a junction box provides the connection for each branch of the heating cable.
End Seals – Wherever there is a termination in the run, an above insulation end seal safely seals the end of the cable. They typically have a signal light so technicians can tell at a glance if the system is working.
Insulation – Insulation is critical for protecting the system from heat loss due to freezing ambient temperature. It may be included as part of the heat trace diagram or require a separate blueprint.
Wherever insulation covers heat trace cables, a caution label should be attached every ten feet to warn of the electrical and heat hazard underneath.
Why Use Heat Tracing Diagrams?
Engineers use heat tracing diagrams to plan the layout of heat tracing systems for proper design, installation, and maintenance.
Heat trace wiring diagrams illustrate the system design for new operators who need to learn the layout. They are essential for designers and engineers to modify or upgrade existing systems.
A heat tracing diagram shows how the equipment, pipes, valves, and fittings are connected and the optimal location for heating cables throughout the facility.
How to Create an Industrial Heat Tracing Diagram
A first look at a heat tracing diagram could be confusing, but it serves the same purpose as a subway map, to get from point A to point B. In this case, the schematic shows the path of the electricity.
To create a heat tracing diagram, engineers need to understand the layout of the industrial process.
- Start by reviewing the process flow diagram to understand the parts of the process requiring heat tracing.
- Next, create a sketch or map of the industrial process. Be sure to include all equipment that has thermostats or thermocouples installed.
- Include the path that the heat tracing takes through the process.
- Document the type and location of the equipment and the type of thermostats installed.
Designing a heat trace system requires a large amount of data, including calculations of pipe lengths, tank surface areas, and the heat loss from each pipe or tank to be traced. You can find apps that simplify the process, such as Thermon’s Computrace®.
Other considerations include the type of heating cable and the thermal output required for the process and environment.