Pipe protection and special applications

The anti-freeze protection of pipes
Sometimes situations arise in which water distribution pipes freeze up even though they are equipped with thermal insulation. Not only pipes which lead through outdoor environments are affected but also distribution networks which lead through non-heated areas – cellars or basements, agricultural buildings etc. This problem can be solved with the help of heating cables. It is necessary to point out that when a heating cable is used, the pipes always need to be fitted with thermal insulation (over the heating cables). The cable isn’t meant as a substitute for thermal insulation - it only compensates for the heat losses which cannot be prevented completely by any insulation. Cables can be used not only for the protection of pipes against freezing but also for preventing other transported liquids from dropping under a certain temperature – known as the technical heating of pipes. However, in these cases we recommend consultation regarding the solution with a specialized company so that heating cables used have not only sufficient output but also suitable thermal endurance.

Installation principles
Both plastic and metal pipes can be protected against icing. The cable is attached to metal pipes directly, while plastic pipes need to be covered by a metal, ideally self-adhesive aluminium tape or foil. After installation, the heating cable is attached with self-adhesive aluminium tape along its whole length concurrently. Self-adhesive aluminium foil helps to transfer the heat from the jacket of the cable to the protected pipes. With the exception of self-regulating cables, the heating cables must not touch or cross one another. Finally, the pipes are fitted with suitable thermal insulation. Heating cables can be wound around the pipes or they can run concurrently. As with the winding it is difficult to estimate the degree of twist needed, we recommend that the heating cable is divided into even sections – attach the beginning and the end of the cable, and again, attach the middle of the created sag to the pipe. By continuing with this procedure several even sags are created which are then wound around the pipe in opposing directions.

Cover the plastic pipe with aluminium foil along its whole length	Create even sags
Wind the sags in opposite directions to each other	Attach the cable to the pipe along its whole length with aluminium tape and furnish the pipe with thermal insulation.

Where the heating cable follows the length of the pipe, we recommend that the cable is placed onto the bottom part of the pipe so that the heat warms the jacket better due to the natural conduction of heat in the upward direction. Place the device for reading the temperature of the pipe’s surface in such a way that it isn’t affected by the heating cable. If the heating cable is attached along the length of the pipe in more loops, it is advantageous to place them so that they best cover the cross-section of the pipe – see the picture.

Selecting the cable wattage
The wattage of the cable is dependent on the ambient temperature, the thickness and type of thermal insulation and on the required temperature of the transported medium. For pipe protection, cables with a wattage of 10-15 W/m are usually used. The required wattage of the cable per 1m of length can be roughly estimated from the following table; the stated values are valid for the maintenance of the temperature of the transported medium at 5 °C.

Example:
Pipe diameter G 1" (DN 25), length of pipe 48 m, ambient temperature -25 °C, pipe insulation 20 mm thick. The temperature of the transported medium mustn’t drop below 5 °C (non-freeze temperature). Result from the table: You’ll find the required wattage per 1m = 10 W in the table. The needed total output will thus be approx. 480 W (48 m x 10 W/m). Therefore, use a heating cable with a total output of at least 480W. The cable has to be installed in such a way that it will evenly cover the whole length of the pipe. ATTENTION – the length of the cable shouldn’t be shorter than the pipe – this situation may occur if a cable is chosen with a higher specific wattage per 1 m.

Cables with an integrated thermostat

Cables with an integrated thermostat and plug are specially produced for the protection of pipes. The contact thermostat switches on the heating cable automatically when the temperature of the pipe drops below 3°C. The cable is produced in lengths of up to 50 m. Thanks to the plug and the integrated thermostat, installation is very simple and doesn’t require any specialized connection to the electrical system. Because of this the cable is suitable particularly for do-it-yourself installations in non-commercial or residential buildings. 

Heating circuits
Heating circuits made from resistance heating cables are produced in lengths of up to 200 m. As the thermostat isn’t part of the circuit for these cables, suitable regulation is necessary, for example an industrial thermostat with a separate sensor. Due to the greater lengths involved, the necessity of combination with an external thermostat and connection to a wiring box, such cables are more suitable for industrial applications which are installed by a specialized firm.

Self-regulating cables
As with outdoor surfaces, self-regulating cables can also be used for the heating of pipes. The disadvantage in the form of a higher price is compensated for by the option of shortening the cable to any length. The self-regulation of the cable is also advantageous in situations when the pipes pass through environments with different temperatures. However, even self-regulating cables require the installation of suitable regulation – see Regulation of ECOFLOOR heating systems. More detailed information about self-regulating cables can be found here…

PDS1P heating cables
PDS1P heating cables are products for special applications – in this specific case, these are cables for short-term, single-use in the winter period to accelerate the curing and hardening of concrete. The installation and use of heating cables is possible up to a temperature of -10°C. After the completion of the curing process, the cables are disconnected (severed) and remain “lost” in the concrete slab. These cables are intended exclusively for industrial use and are produced in compliance with IEC 1423-1 and IEC 1423-2. The heating circuit ends with a 3m long H07RN-F supply lead with a pressed-in Schuko plug. A table of recommended spacings and wattages can be found below.

D-MAT heating sheets
D-MAT heating sheets are intended for outdoor use as anti-freeze protection in industrial applications and in the building industry – for example, for the warming of the ground in earthworks or the storage of friable materials, the heating of cables on reels, the warming of parts of machines or tools etc. These sheets are also suitable for use in extreme winter conditions.