ANSI Torque Specifications for 300 lb raised face flanges

[mieklewis]

Curious what is ANSI Torque Specifications for 300 lb raised face flanges. I am currently following the torque specifications for the gasket but I am cracking cast iron raised face flanges on control valves.

 

[TBP]

I've never actually heard of anybody who could (using appropriately sized wrenches) torque Class 300/250 flange bolts to the point where they cracked the CI flange. There are several possiblities - these are nasty counterfeit valves, they're using "cheaters" on the wrenches (for reasons that baffle me), or you've got a bunch of fitters that should be going to the Olympics as weightlifters.

What's the service? It can't be that severe - the CI valve bodies will only have a 250 saturated steam rating. Are the flanges cracking while the bolts are being tightened, or after the system has been in service for a while?

 

[mieklewis]

They are using only a torque wrench and per the gasket supplier they are trying to torque these valve flanges to 200 ft-lbs. They are cast iron raised face flanges that utilize 3/4" bolts. Biggest guy goes about 150lbs, but he loks a little like the Governor of California.

 

[unclesyd]

What is the flange size?
What type gasket are you try to use on The CI flanges that requires a 50,000 # bolt stress?
Who called out raised face on CI valves.?

 

[mieklewis]

Flange size - 4"
Gasket - Garlock compressed sheet
Customer provided the raise faced flanged CI valves, we are trying to mount them

 

[unclesyd]

You are going to have to do flange/gasket calculation using the data from Garlock for this particular gasket material. The maximum bolt stress ever used on a CI full face flange should be neighborhood of 30,000 # max. The norm was 20,000 # bolt stress for nearly all gasket materials used for CI valves.
You might go back to the gasket supplier and tell him that the raised face flange is made from CI not alloy steel I’m pretty sure he will come off the 200 ft. lb. torque figure in a big rush. If says that this fiqure is required change gasket material or vendor.
Even if you did get some flanges to makeup any load imposed by the piping would probably break the flange. Even making up the flange using a 3 step tightening process would be tricky with the best of pipe fitters.

What is the process fluids and conditions?

 

[mieklewis]

Thanks for the help, the gasket manufacture has relaxed the requirement, but I find it difficult to understand why the valve vendor does not have a torque specification.

 

[unclesyd]

You have to consider every bolted flange connection as a separate entity in respect to the gasket material, type flange, fasteners, and several others.

A valve manufacturer can not know under what his conditions that his valve will be used so he cannot recommend a standard torque. The only thing in situation such as yours he could publish the maximum load his valve flange can sustain safely.

In your case the gasket is requiring a clamping load in excess of what the CI flange can sustain. All different gaskets have to seated, compressed, to function. To seat a particular gasket you have to have the physical components that will allow you to do this without undue forces on the other components, flanges and fasteners.

Don't get discouraged as bolted connections with gaskets are very complex subject of which many books and standards have been written.

 

[StressGuy]

You know, I can't say I've ever heard of raised face CI flanges. It seems every specification I've ever seen with CI flanges has been for flat flace because the bending that the bolts put into the flange due to the raised face often leads to cracking.

Any possiblity of getting the raised faces machined off or getting flat face flanges provided?

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[DSB123]

StressGuy,
Agree with you entirely. Cast iron flanges should not be Raised Face and should always be procured flat face as it's too easy to crack cast iron flanges (RF) with bolt loads.

mieklewis,
Suggest you tell the Customer he has got his specification for the valves wrong and they should have been FF.

 

[TBP]

ASME B31.1 permits the use of raised face Class 250 flanges, and these are very common with control valves used in general industrial applications. I've never seen torque specs supplied with valves like this.

3/4" studs or bolts will require 1-1/4" wrenches if 2H nuts are being used. (15/16" wrenches if SAE fasteners are being used - which shouldn't be the case, but often is.) This will typically be a 1/2" drive ratchet with an 1-1/4" socket, and an 1-1/4" combination wrench, for 2H nuts. As long as the nuts are tightened evenly, in a crossing pattern, I can't imagine anyone (including me - and I go over 250 lbs) being able to - or NEEDING to - pull hard enough on these wrenches to crack the CI flanges. The torque wrench must have a very long handle indeed.

And we STILL don't know what the service conditions are. I've seen lots of 250 CI valves, strainers, etc get spec'd and installed on steam systems that OPERATE at 250 PSIG, but the safety valves are set for 300. "Oh, it's always been like that." That seems to make it OK, somehow...