Hadi Engineers

Sihor, Bhavnagar, Gujarat

The Lap joint flanges are used with stub ends when piping is of a costly material. For example, in a stainless steel pipe system, a carbon steel flange can be applied, because flange will not come in contact with the product in the pipe. The stub ends will be butt-welded to the piping and the flanges are kept loose over the same. The inside radius of these flanges is chamfered to clear the stub end radius.These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End. Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of Weld Neck flanges. Thus this flange connections are applied in low-pressure and non critical applications.

The Slip On type flanges are attached by two fillet welds, inside as well as outside the flange. The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of Welding Neck flanges, and their life under fatigue is about one-third that of the latter. Normally, these flanges are of forged construction and are provided with hub. Sometimes, these flanges are fabricated from plates and are not provided with the hub.The disadvantage of the flange is that a combination of flange and elbow or flange and tee is not possible because named fittings have not a straight end that complete slid in the Slip On flange.