I can change a welding neck flange by a slip on flange
I can change a welding neck flange by a slip on flange
(OP)
Hello
I am not sure if i can change a welding neck flange by a slip on flange
Thank you for your help
JATE
I am not sure if i can change a welding neck flange by a slip on flange
Thank you for your help
JATE





RE: I can change a welding neck flange by a slip on flange
RE: I can change a welding neck flange by a slip on flange
RE: I can change a welding neck flange by a slip on flange
1. Weldnecks are required for severe cyclic conditions (ref B31.3 sect 308)
2. Slip-ons have a larger ID gasket contact area and may not work with certain size/pressure class spiral wound gaskets.
3. Slip-ons present a larger ID "crevice".
4. Methods of examination (NDT) are limited with slip-ons.
Regards,
donf
RE: I can change a welding neck flange by a slip on flange
RE: I can change a welding neck flange by a slip on flange
It would be wise to question why the weld-neck was required at that location in the first place.
Many piping specifications I have dealt with require a (less expensive) slip-on flange as the first choice and a (more expensive) weld-neck as an acceptable substitution.
As "donf" pointed out, there are legitimate design and code reasons for going with weld-necks.
I would add to "donf's" list that slip-ons are preferred by the erectors because of ease of fit up (flnges can be rotated into position, then bolted up)
Please tell us more....
MJCronin
Sr. Process Engineer
RE: I can change a welding neck flange by a slip on flange
RE: I can change a welding neck flange by a slip on flange
@donf: you point out that weldnecks are required for severe cyclic service.
I once heard (or read) an engineer saying lap joint flanged joints are 'good' in thermal cycling conditions. Regardless of code requirements, which are of course a minimum, can you comment on that?
RE: I can change a welding neck flange by a slip on flange
What is the reason to change from weld neck to slip-on?
Curtis
RE: I can change a welding neck flange by a slip on flange
RE: I can change a welding neck flange by a slip on flange
Because LJ flange hubs are not welded to the pipe, they cannot provide gasket compression loads as high as slip-ons or weldnecks. LJ flanges will start to rotate at lower bolting loads. Note the term "flange rotation" is confusing. It doesn't refer to axial rotation of the LJ flange around the stub end - it is used to describe the distortion or bending of the flanges as the fasteners are being tightened, which can affect the abililty to provide the desired seal.
Remember that flange type is only one of the elements involved. Look also at gasket, fasteners and assembly procedure.
donf