Industrial heating 32
VärmeKabelTeknik
Chapter 8
Installation and Thermal insulation
Thermal insulation and installation
To obtain a well functioning application, a good insulation is required. As already been mentioned, we compensate the heat loss through the insulation by supplying heat. A poor insulation gives an application with defective function and a bad operating economy. Here are some tips that can improve the insulation: * The controller of the vents shall be supplied with plastic insulation against openings in the insulation sheath, downward openings in shall be sealed with sealing compound. * Most of the insulation material is hygroscopic. Insulation material with closed cell structure (foam) is not hygroscopic, but have in general a lower operating temperature, max. +100°C.Therefore choose insulation with closed cell structure if the temperature admits it.
Passage for leading‐in of connection cables to heating cables and transmitters, are best done from the underside of the pipe when risk of moisture penetrating is nearly non‐existent.
* Conduit entries through the insulation are carried out on the underside of the pie, if possible, so they are protected against moisture. * Vents and flanges etc, has a larger diameter than the pipe. Of this reason shall the heating cable be installed with an extra coiling at those and to be extra careful so that the insulation not get thin to give a straight and facilitated outer sheath. Another advantage with extra cables at vents is when these have to be dismounted at leakage and a extended cable must be cut. If cable of self‐limiting type is used the emitted output is reduced if the cable don’t have or have poor contact with the object which are to be heated. Heating cables shall always be covered with aluminium tape or aluminium foil before insulation. This in order to secure the fit‐up of the heating cable against the object and to avoid that the heating cable (due to movements in the application and heating cable), is covered with insulation with cable rupture or poor heat transfer as a result. At applications with self‐limiting heating cable the output curves presented for the heating cable presumes that installation is done with aluminium tape or foil. The insulation around pumps and small vessels must be fixed so that it does not came loose (insulation support is welded on the outside of the tank wall).
Important general instructions These instructions must be followed at installations of VärmeKabelTeknik’s industrial cables on pipes. VärmeKabelTeknik’s heating cables are available in three basic types: Self‐limiting, parallel resistive and series resistive. Below you will find a table, which shows some of the characteristics which separate the cable from VärmeKabelTeknik from each other. Self‐limiting Applicable in Ex‐zone Applicable on plastic pipes Can be cut in lengths on site Protects against overheating Can be installed in long lengths Max. temperature °C
Parallel resistive Yes yes Yes Yes No 5 200
Series resistive No1 Yes2 Yes No Yes 2005
1 Exemption can be applied for specific applications 2 With outputs up to 12W/m 3 Emitted output is reduced with rising temperature 4 Can be dimensioned with low outputs/running meter 5 With the supply voltage switched off
No1 Yes4 No No Yes 600