5.2.1.2 Connections

Gas pipework connections shall be metallic and shall be of the threaded, compression, flanged, or welded types. Threaded connections shall be used only for the following pressure/diameter combinations:

• pressures up to 100 mbar, and diameters up to DN 80;
• pressures up to 2 bar, and diameters up to DN 50;
• pressures up to 5 bar, and diameters up to DN 25;
• pressures up to 10 bar, and diameters up to DN 15

For other combinations of pressures and diameters connections shall be by means of welded flanges or welded joints. The number of connections shall be kept to a minimum.

Where the equipment has a threaded connection, this thread shall comply with ISO 228-1 or ISO 7-1 as appropriate. In the case of threads according to ISO 228-1 the tightness shall be ensured by a ring gasket. Sealants for threads according to ISO 7-1 shall comply with EN 751, Part 1 or Part 2 as appropriate. Hemp shall not be used in threaded connections unless re-inforced with a suitable sealant.

Other threaded connections shall only be used providing they ensure tight connections and are suitably identified.

The design of pipework shall be such as to avoid tensile loading of the joints.

Compression fittings shall comply with EN ISO 8434-1 or EN ISO 19879. They shall only be used for pressures up to 5 bar and diameters up to 42 mm.

Any pipe passing through an unventilated space shall not have a connection except welded joints.

Flanges shall comply with ISO 7005, Parts 1 and 2 as appropriate.

Arc welding shall comply with EN ISO 5817, quality Level C.