Insulating Bolted Connections
Insulating Bolted Connections
(OP)
Can anyone point me in the right direction to obtain technical information to show why one should NOT insulate over flanges, especially those in hot service?
Our Energy Team wants to insulate to reduce heat loss; others want to leave them exposed since potential bolt relaxation will cause leaks, and as such, will create HSE incidents, and add cost for removal and replacement of the insulation every time there's a leak.
Thanks for your help.
Our Energy Team wants to insulate to reduce heat loss; others want to leave them exposed since potential bolt relaxation will cause leaks, and as such, will create HSE incidents, and add cost for removal and replacement of the insulation every time there's a leak.
Thanks for your help.





RE: Insulating Bolted Connections
Mroz
RE: Insulating Bolted Connections
Of course you could always ask the pipefitters, the old guys might not always have the Education but they've got a ton of experience and "Horse Sense"
RE: Insulating Bolted Connections
The use of spring washers (i.e. Belleville washers) can sometimes eliminate the leak potential by maintaining a minimum bolt load above the critical load required for a seal. Spring washers are available for pipe flanges from both Key Bellevilles and Solon. Other spring washer manufacturers may have them also.
The correct size and number of washers have to be determined by differential thermal expansion calculations of the flanged joint, including the gasket, and the bolts. Watch out that the bolt load needed to seal the flange with spring washers may exceed the strength of the flange at the new higher temperature and cause rotation (i.e. cupping) of the ring of the flange, especially in the lower pressure classes. This will almost guarantee leakage, even with the washers installed.
As I said earlier, if the joint is designed in the beginning to be insulated it is possible to have leak free joints. Retrofits are more difficult.
RE: Insulating Bolted Connections