Pipes and tanks

Rørledninger og tanker bilde

Frost protection of pipes and tanks
Frozen water pipes and -tanks may crack and cause very extensive and costly damage. Remember that a water pipe with ambient temperature below 0°C sooner or later will freeze, no matter how well it is insulated. Drainage pipes can also freeze, with the inconveniences this may cause.

The only way to prevent water from freezing is to add energy in the form of heat. Heating cables installed outside of, or inside, pipes and tanks is a very inexpensive and safe way of doing this. In drainpipes which carry clean water / water from melted ice or snow only, a heating cable can be installed both inside of and on the outside of the pipe. On sewer pipes, the heating cable shall be installed on the outside of the pipe only.

Selection of cable type
For frost protection applications, usually the most affordable solution is to use single conductor cable (also called drum cable). Alternatively, both heating cable elements and self-limiting heating cable can be used. When using single conductor heating cable or heating cable elements, the pipe temperature must not exceed 50°C.

Thermostat control
Regardless of choice of cable type, the use of a thermal management system is recommended. Choose a thermostat with external sensor, which will ensure low power consumption and even temperature. In addition, and as an extra precaution, it is often advisable to install a sensor in direct contact with the heating cable, so as to prevent overheating. This requires that the thermal management system has a temperature limiting function.

Calculation of the required power
Calculation of power requirements for pipe heating system is complicated and should be performed by qualified personnel, such as electricians, whether the pipe is above or in the ground, insulated or un-insulated.

In order to calculate the required power and to find the correct heating cable for pipes and tanks, the following data are needed:
•  Pipe dimensions, alternatively the tank surface area
•  Insulation thickness
•  Ambient temperature (buried or in air)
•  Desired temperature of the pipe or tank

Uncontrollable or unforeseen conditions suggest that the calculated values should be rounded up to provide a safety margin. A safety factor of 1.2 is not uncommon.

Generally, a pipe installed in air must be insulated. This is also beneficial (if possible) for pipes in the ground. Without insulation, the heat loss in air is very high even for small pipe sizes. For example, an uninsulated 1"pipe will have a power requirement of approximately 45W/m at -30°C.