How do customers specify the jointing method and fittings to be compatible with the pipeline design?
Electrofusion fittings are specified by their pressure rating, such that they are at least rated the same as the pipe pressure rating. It is however usual that the electrofusion fittings are designed and manufactured for the maximum pipe pressure rating of PE pipe, e.g. SDR11 16 bar for water application. These fittings are then also suitable for pipe of lower pressure rating e.g. SDR17 10 bar water pipe.
Fittings are normally designed on a pressure rating basis. It is accepted industry practice to use electrofusion fittings manufactured from a different grade of PE from that of the pipe, e.g. PE80 fittings may be used with PE100 pipe. In such circumstances it is considered essential that the pressure rating of the fittings is at least equivalent to that of the pipe. For example PE80 12 bar rated electrofusion fittings could be used with PE100 SDR17 pipe (10 bar rated) but not with PE100 SDR11 pipe (16 bar rated).
If in doubt advice should be sought from the fittings manufacturer as to their suitability for the particular application.
Butt Fusion fittings:
Butt fusion fittings PE pipes can be joined by butt fusion thus avoiding the need for a fitting. Some spigot end fittings are produced specifically for butt fusion to pipe. These must be specified to match both the pressure rating and the SDR of the pipe. It is normally not acceptable to use a butt fusion fitting of a different SDR rating to that of the pipe even if the pressure rating of the fitting is equivalent or higher than that of the pipe.
Mechanical fittings are usually designed to at least meet the MOP rating of the range of PE100 pipes, i.e. SDR11 pipe 16 bar. However although the bodies of these fittings are compatible across the range of pipe SDR's, the inserts or pipe stiffeners should normally be specified for the particular pipe SDR being used. Advice should be sought from the fittings manufacturer as to their suitability for the particular application.