Pipe Flange Fabrication Standards 1

[tothepoint]

Does anyone know of ASME/ANSI or any pipe flange fabrication standards that specify the gap necessary between pipe flanges for different styles of gaskets (i.e compressed sheet, SW, etc.)? Being in the gasket business, I know from experience what gap should be allowed during fabrication, however I have clients who are looking for national standards that spell this out. Anyone?

 

[bvi]

I am not aware of any ASME/ANSI standard that provides gasket specific raised face dimensions. I suggest you simply follow the ASME B16.5 raised face dimensions for guidance. These raised faces are considered suitable for any ring type gasket.

 

[LSThill]

tothepoint (Mechanical)

I agree wirth cb4 and look at the new ASME B16.5-2003.

Leonard@thill.biz

http://www.thill.biz

 

[MJCronin]

tothepoint,

It is my understanding that the people who design gaskets for piping systems do no design to a certain "compression gap" ( ie Garlock & Flexitallic etc)

The gasket design people design these products based on a certain amount of bolt compression, not flange gap. They also publish tables of recommended bolt torque necessary to produce a good flanged joint.

I do not believe that you will find what you want.....

See:

http://www.sealsolutions.com/techinfo/boltvalu.htm

for example

My opinion only......

MJC

 

[corrosionman]

Tothepoint
It all depends on the gasket material. If you use
"old fashioned rubber" or if your pipe is rubber lined with the lining being continued as the flange face the allow the joint to compress 30% of the thickness of the rubber by tightening the bolts. but then you must specify the bolt torque. Generally speaking pipe systems are flexible enough to allow small movements between flange faces.If you use the more "modern" gasket material get the gasket supplier to comit in writing their recommendations and torques. We recently experience a problem when the
correct tightening sequence was not followed with rf flanges
and all the gaskets were crush damaged causing high cost.
Its a very long story call me if I can help further. DW

 

[tothepoint]

I know the requirements for gasket material compression, and I know from experience the flange fabrication gap that should be used. I'm asking if there are published pipe or fabrication standards that I can refer to for confirmation. Anyone?
DW- I would love to hear about your experience with gasket crushing. This is a common problem with non-asbestos gasketing, and a common "dodge" by the manufacturers. Please write back.

 

[corrosionman]

Tothepoint
Gasket crushing. Briefly the project had many dozens of rubber line pipes at 2" and 3" size, and even more flanged joints.
It is customary in the rubber lining industry that flanged joints should be flat faced with rubber continuing to the outer diam of flange. Somehow all the flanges were
raised face and the rubber simply lined to the r f outer dia. Usually the rubber is allowed to act as the gasket but someone also specified a thick teflon type gasket what really made things worse was that the inner dia of these gaskets was somewhat larger that the inner dia of the rubber lined pipe. The bolts should have been tightened up a little bit at a time, and in rotation till correct torque is reached. What actually happened was that the first bolt was torqued to full amount, lots of squeeze on the rubber and the gasket, then when the opposite bolt was pulled tight it created a lever arm effect and massively overloaded the area already fully tightened. The rubber underneath the gasket was so overloaded must have gone solid but the rubber near the inner dia was nowhere near as heavily crushed. The teflon gasket "flows" sideways if overloaded and it pushed inwards to the pipe inside and in so doing it created a "failure ring" round the rubber lined face - - Rubber cut through to the steel. All the pipes had to be renewed. Huge cost and delayed project. Cheers DW

 

[allcerts]

The ASME does show the facing dimension for RTJ (Ringed Type Joint Flanges, however for for Flat Faced and Raised Faced Flanges the only dimensions they refer to (That I could Find)do not include this spacing dimension you ask for. With years of experience in refineries, fabrication, pipe fitting and welding I would feel safe to inform your customers that this question correctly answered is determined by the coefficient of expansion of the pipe material used and the length and temperature that the fabrication is installed. The gap between flanges on runs of pipe will change as the temperature rises and falls. Our rule of thumb is to leave just enough spacing to freely install the gasket.

 

[GenB]

Gasket material, fabrication and use for ASME vessels is addressed in sec VIII-1 of the PV Code. The same is used in B31.1
I have not seen anything in the flange ANSI B16.5,
I will look into it some mor and advise.
ER