How to Choose a Flange

16 bar (233psi +/-) @ 190c (374 F+/-)

My vote would be the Weld Neck flange.

1. The Weld Neck flange is slightly higher in cost than the Slip On flange but the cost of welding one butt weld vs. two fillet welds is less. Also the Butt weld is stronger then the fillet weld.

2. With the Butt weld you can do a single pass Radiographic Examination (RT) as part of the Non-Destructive Examination (NDE). With the Slip On flange you would have to do both the inside fillet and the outside fillet (more cost) with not the same quality.

3. Depending on the skill, training and experience of your welderd there is a higher possibility of damage to the Gasket face during the welding of the inside fillet on the Slip-On flange.

Does the gasket exist when inside fillet weld is done? Probably you are saying that weld protrusions will damage the gasket when inserted.

He meant the flange face where the gasket seats.

I have seen this problem when unqualified/careless welders are at work. Just a slight movement and you have the face damaged. And then there are spatters too to take care of.

And as to RF vs RTJ ?

RE- face

It is TOTALLY dependent on the connecting flange.

If the connecting flange is steel, then the raised face is better- higher overall clamping force on small face, giving a tight bond to the gasket for minimal risk of leakage. Loose fit bolts on one side will align the ring gasket at assembly. Just be sure to install ALL bolts before beginning tightening sequence.

If the connecting flange is iron, malleable or cast, then the mating flange MUST be flat face- to avoid any bending strain on the receiving flange which could fracture and destroy any seal, plus be a real bear to repair. This can happen even if all bolts are carefully torqued because any secondary force (bending, twist, etc.) on the pipe can cause fracture of the receiving flange. Proper tightening torque will still assure a tight seal. Full face also requires full face gasket.

There has been some very clear guidance so far.

My 2p would be to say that I would be surprised if you went for an RTJ at these conditions. My experience is to use RTJ at 900# and higher and even then some services use RF flanges.

Simonsd

If you speak:

>>>My experience is to use RTJ at 900# and higher and even then some services use RF flanges

Wherefore then exist RING GASKET R-76, at which pressure class-150 #. (according to ASME B16.20, table 4)?

Thanks for excellent answers!

And where behind which basil the situation is considered those limits critical when RF it is not so expedient to use and it is necessary to pass on RTJ?

I somehow should substantiate for AI. Whether there is a literature where this question within the limits of ASME is observed?