Can a weld neck flange be bolted to

[Hully]

Can a weld neck flange be bolted to a slip-on flange and if so, which torque load would be applied from the torque tables. RFWN or RFSO?

 

[LittleInch]

As long as the flanges are the same type and class rating, I can't see any reason why not.

Why do you think there is a difference in torque between SO and WN flanges? I can't see how the flange face is bothered what type of connection it has to the rest of the pipe, but please enlighten me if you can show two different torques for the same flange.

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[Hully]

Thank you for your prompt reply.
I have a set of torque tables that show RFWN and RFSO torque values for their respective flanges. Although most torque values are the same, on occasions there are some diffences, usually with the higher flange sizes. For example: a 14" 300# Weld neck has a torque setting of 512 lbs.ft, whereas a 14" 300# Slip-on is shown as 415 lbs.ft. In cases such as this, which torque setting would be used?

 

[LittleInch]

Can you post some examples and include all the assumptions listed?

I can't see why there should be a difference so it's difficult to say. B16.5 doesn't say anything about different types of flanges needing different mating forces.

Different torque tables exist and different figures exist varying by bolt strength, degree of lubrication, use of washers etc.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Hully]

I am currently doing a bit more research on this matter with the engineers in my company. The torque booklets we currently use show different values for the larger flange sizes however I've been informed that new tables are going to be issued soon with values all the same irrespective of flange size. Watch this space!

 

[racookpe1978]

FIRST! Verify that the two flanges are being compared against the exact same make, thickness, and style number (part number) of gaskets. Bolt flange torques are NOT based on flange type nor for flange manufacturer, but are based on the gasket type BETWEEN the two flanges: a flexitallic gasket, a rubber gasket, and a spiral wound flex gasket from a different maker are going to vary slightly. But,even that small difference is minor compared to the need for correctly making up the two gasket fit, gap, alignment, initial torque, midpoint torques and torque sequence pattern, and then the final torque.

a bad-fitting flange over-tightened by a air hammer one bolt after another will leak faster than an under-torqued pair of aligned flanges properly sequenced in a star-pattern but 85 ft-lbs too little.

 

[bimr]

Yes. The purpose of flange torque is to compress your gasket within the limits of the bolts and flange. The last time I needed torque requirements, I contacted the gasket mfg.

http://vsptechnologies.com/wp-conte...tation_pvp-2008_fastener-preload-guidance.pdf

 

[Hully]

Thank you for your replies, most helpful

 

[ricklts]

No good reason for differences, but conventional practice has been to use somewhat reduced bolt preloads for SO Flanges due to the fact that without the reinforcement of the flange BackFace, these tend to rotatate/deform at lower loads.