Inner and Outer Threads on Pipes and Pipe Accessories
Today, threaded steel pipes in accordance with EN 10255 (German predecessor standard: DIN 2440/2441) are still commonly used in small-diameter lines for drinking water, fire extinguishing water, heating fluids, coolants and gases. These seamless (S) or welded (W) steel pipes are available with factory-threaded connections or smooth ends for users' threading. The standard outer diameters specified in EN 10255 are the same as those of DIN EN 10220 in piping, hollow steel-pipe profiles and gas and water lines; however their wall thickness classifications differ from those of DIN EN 10220.
When threaded pipes are ordered, specification of the desired end versions is required, i.e. with (w/) or without (w/o) an externally threaded pipe end and with (w/) or without (w/o) an internally threaded steel socket. Typically threaded pipes are ordered in the (w/o + w/o) version or the (w/ + w/) version. In this regard it should be noted that a threaded connection which is nominally self-sealing always uses a tapered thread mated with a cylindrical thread. Our series H and M threaded pipes are supplied, unless ordered otherwise, with external Whitworth threading (tapered). : Our internally threaded steel and mallable-iron fittings are supplied, unless ordered otherwise, with cylindrical threading.