Below we will display the detailed procedure of Using Slip-on Flanges.

#1 Slip the flange over the end of the pipe base.

#2 Thread the flange pins to tighten the flange’s grasp on the pipe. The pins will keep the pipe securely in place inside the flange. There are usually six to eight pins in place. Use a screwdriver to tighten the pins all the way.

#3 Try to pull the pipe out of the flange to make sure that the pins are efficiently tightened. If they aren’t, re-tighten them with the screwdriver. Inspect the pins to make sure they are down all the way and that the pipe cannot move inside the flange.

#4 Use a hammer to slightly tap the flange in place. The flange face should be flush with the end of the steel pipe.

#5 Use a 12-inch wrench with 85 pounds force to tighten the pins. Apply 80 to 85 foot-per-pounds torque on the pins, or until the pin heads break off.

#6 Lubricate the gasket of the pipe and stretch it over the pipe end, with the beveled edge positioned in the field flange.

#7 Two fillets ARE easier and quicker to do than one butt weld completed 100% from the outside and which must pass RT. Both welds are available for inspection visually and by MP/LP etc. when the piping is disassembled- just not RT. And contrary to another poster’s assertion, you have 1/2 the risk of a single weld leading to failure since you have two welds EACH of which should be strong enough for the job.

#8 Some folks drill a small hole through the flange to vent the cavity between the two welds:  it helps vent trapped air during the completion of the 2nd weld and helps detect cracks in the face weld earlier.

#9 At 2″and smaller we use socket weld flanges:  one fillet weld is quicker to do than two.

#10 There’s a lot less material in a Slip-On Flanges than in a Weld Neck Flange a benefit if you’re using something other than carbon steel and Lap Joint Flanges are off the table.

#11 All of that said, I just plain STOP using either Socket Weld Flange or Slip-On Flange beyond 600# class on piping. As body flanges on small vessels made of piping, where the flange never sees moments or forces other than hydrostatic and bolt loading, I’ll permit their use beyond 600 class.

#12 In piping, the stress concentrations on the fillet welds and the thermal stress/cycling fatigue risk, and the residual stress on these welds due to the heat input during completion of the 2nd weld and subsequent shrinkage make a SO flange riskier than a single butt welded WN, and make a SW flange very risky. Hence the reduced fatigue life stated previously.

#13 Don’t forget that they also need gaskets with a bore equal to the OD of the pipe, NOT its ID.  Use the wrong spiral-wound gasket and you could have the gasket unraveling inside the piping.