Introduction to Double Flanged Pipes and Flanged Fittings

In some project practice such as water supply, sewage treatment and irrigation pipeline, pre-langed pipes and fittings are widely utilized during the construction. "Flanged" or "Pre-Flanged" denotes that mating flanges are already assembled/fitted to each end of pipes and fittings by manufacturer. When it arrives at site, it can be assembled to the pipeline conveniently. It saves a lot of cost from on-site welding and RT inspection of welding because this job was done by professional manufacturer in their workshop. 

Usually flanged pipes(also called double flanged pipe) or flanged fittings can be divided into two categories:

1) Integral Cast Iron / Ductile Iron Flanged Pipe & Fitttings. It's easy to develop a mold to cast pipes or fittings with mating flanges integrally. The length of pipe depends on centrifugal cast technique and usually it is not very long(less than 3 meters). The cast products are usually bitumen painted.

Cast Iron Double Flanged Pipe & Fittings

2) Carbon Steel / Stainless Steel Double Flanged Pipes and All Flanged Fittings. A double flanged pipe is made of a welded/seamless steel pipe with mating flanges welded to each end. The mating flanges can be either slip on/plate(two welding seams) or weld neck(one welding seam) type. In prefabricated pipe conduit system, precise axial alignment of bolt holes between two end flanges is very important. For all flanged fittings such as double flanged elbow, all flanged tee and double flanged reducer, plenty space for bolting must be considered in design step. Sometimes butt weld pipe fittings in conformance to ASME/ANSI B16.9 or EN10253 may not meet this requirement especially for sizes smaller than 4". Extension of radius of elbow or length of tee outlet is necessary.

CS/SS Double Flanged Pipes and All Flanged Fittings