Insulating Flange Gaskets Assembly

[1969grad]

We have just purchased insulating type flange gaskets and are concerned with over tightening the bolts. On a past project with this same client two sets of gaskets were damaged using the bolt torques listed in the client's specifications for the applicable lubricant which we do not want to happen again. Unfortunately, I do not know how much the field backed off from the client's values.

The gaskets are neoprene faced phenolic for 16" Class 600 flanges.

Does anyone have any guidelines for the min seating stress and max face stress that this type of gasket can stand?

I called the gasket manufacturer and got one of those "that information is not published and we do not have any information" responses. Does not seem plausible to me that the gasket manufacturer does not know but that is the case. Must be a liability thing.

FYI, the client's specifications call for tensioning for 20" and larger flanges and torqueing for smaller flanges.

Thank you in advance.

 

[KernOily]

Did you try posting your question over in the Piping and Fluid Mechanics forum? There are some pipe stress guys over there. I need to go look this up first. Pete

Thanks!
Pete

 

[corrosionman]

1969GRAD Two thoughts on your query
1) Minimum seating stress for gasket. Its a while since I did flange gasket theory but if Class 600 means 600 psi then any gasket that is less than 600 psi is certain to leak Hence minimum seat stress is 600 psi.
2) maximum stress for phenolicmaterial. If the gasket supplier does not know or tell you, get a new supplier who will. This material is well documented, I will check it out tomorrow

Watch out to progressively tighten the bolts in correct sequence. Met a job recently when they applied 100% of theoretical torque to first bolt, then to the diametrally opposite one thus creating a lever on the gasket near first bolt. This crushed the rubber lined flange face. Many dozens of pipes had to be taken down and relined.

I,ll get phenolic data tomoorrow. DW

 

[1969grad]

Design pressure for Class 600 CS flanges is 1480 psig at 100 F.

For a typical spiral wound gasket the minimum seating stress is 10,000 psi and the max is 25,000 psi.

What I am trying to determine is the above for a neoprene faced phenolic gasket.

 

[Screwman]

The response from the gasket guys is pretty much what I have always recieved from gasket mfg. Even when I have gotten gasket factors from them, more often than not they have proven to be grossly in error.
I don't have any information on the type of gasket that you are using.
One thing to make sure of is to tighten the bolts using a criss cross pattern and bring them up to full torque in two or three passes to reduce the effects of cross talk on the joint.

dick

 

[dugal]

I have been involved for many years doing up small insulated flanges on large generators. Nothing in the size range you are talking about. A lot of large buried natural gas lines have insulating flanges just before the pipes go underground. They maybe a good source for your info.
In insulated flanges you also have small phenolic washers under each bolt head and those are always what break first when over tightening ocurrs. I have never seen us crack the phenolic full face sheet before breaking the small ones under the bolt heads.

 

[donf]

I have no personal experience with this particular manufacturer, but have you checked with Pikotek?

http://www.pikotek.com

Donf