If the line is insulated, we have to insulate the flange? I remember my supervisor told me when I was starting the that we don't insulate flanges. However, I read somewhere that there are times that we insulate flanges, so it got me confused. When are we supposed to insulate flanges?
Insulating flanges depends on a number of issues! My time in Alaska ALL flanges are insulated, but now in the high desert of California I see a number of lines where none of the flanges on insulated lines are insulated. The piping/insulation spec that's been assign to the piping you're design dictates exactly what it is, how it's applied, & where ...the only time I can think of where it might be an issue for you is if that line where run in a pipe rack with other piping and you were calculating the pipe spacing! AND if that were the case I'd asked either your supervisor or the project engineer ...part of their job to know, or find out for you.
This product is used break the flow of stray current in a line that runs underground and then rises above ground. This stray current causes corrosion that eats the pipe on cooling Water Lines or any other product.
2.) Hot Insulation for Steam or other high temperature applications it is the normal practice to Not insulate the Flanges or Valve Bodies.
3.) Cold Insulation for cryogenic services it is the normal practice to insulate EVERYTHING even a horizontal Dummy Leg (Trunnion) support in the pipe rack. The length of the Insulation on such a support would be Minimum 4 times the thickness of the support on the pipe (if the Cold Insulation is 100mm thick then the trunnion would be insulated for a minimum distance of 400mm)
Jop... 2.) Hot Insulation for Steam or other high temperature applications it is the normal practice to Not insulate the Flanges or Valve Bodies.
JOP ...I have to disagree with you on this one, I see personal protect insulation used on every aspect of a heated line that can come into contact with operating personnel. In cold climates I've seen steams line totally jacketed in insulation to conserve every degree of heat, And here locally (more arid high desert) when we use heat conserving insulation I "semi" routinely see laced on insulating blankets used on valving.
In my opinion the criteria for insulating and or not insulating the flange joint depends on factors like
1 . Location of the plant.
2 . If the line is Hot insulated, flange joint kan be kept un-insulated.
3 . If line is carrying cryogenic fluids, then everything including pipe, valves, fittings, flange joints and piping supports(Dummy, Shoe) needs insulation to avoid ice formation.