BOLTUPprocedure for high temperature service 1

[LupusLupis]

Hi people,
I've opened this thread because I did not find a proper discussion about this matter.

I have to prepare a Boltup procedure for an equipment in 304H Asme B31.3 with design temperature 760°C
pressure 350Kpa standard flange Asme B16.5 24" 300# with spiral wound gasket with thermiculite, bolt
material A193Gr.B8m (170Mpa/15Mpa allowable 20°C/760°c, mandatory).

The question is that client asked to comply with Asme VIII D.1 appendix 2 and wm1, wm2 have to be verified,
situation is as follow 140275kgf/170Mpa and 16734kgf/15Mpa respectively it means the bolt area required depend on operating
condition wm1, but which will be the tensioning at ambient temp. 20°C to each bolt wm1/nos.bolt or wm2/nos.bolt ????

If I use tensioning with presetting condition the stress will be too much high at operating > than allowable stress
of the bolt at 760°C =15Mpa.

 

[TGS4]

Appendix 2 is a DESIGN procedure only, and the values therein have no bearing on what should be done in practice. See Appendix S. Even at temperature, the allowable stresses have no indication of what bolt stresses should be used during operation.

I would recommend that you retain the services of a bolted flange joint specialist to assist you with this situation. Those temperatures need special treatment - more than can be provided free over the anonymous internet.

 

[racookpe1978]

"24" 300# with spiral wound gasket with thermiculite"

There are your requirements.

Now, I don't know "thermiculite" and so will NOT make assumptions about "thermiculite", but when I want to know how to bolt up a flange around a Flexitallic gasket, (or a soft rubber gasket or a permaflex gasket) I go to the Flexatallic website and look up the specific torque sequence and torque values for the gasket I am using.

Your bolting sequence and the intermittent torque values on the studs at each intermediate level are set BY the gasket material. NOT by ASME or the "code" .

 

[gasketguru]

This sounds like a cat cracker or similar application, which often give problems. - As has been suggested, your likely real bolt load is likely to be at least 1.5x to 2x the load you have calculated in order to get decent compression and operating stress on the joint. Experience suggests that the bolts won't be sufficiently strong and are the weak point here - you should probably be looking towards B17 / A660 / A286 / 1.4980 (whatever you want to call it...) as a bolt material, as this has a similar expansion to the flanges but a lot more strength than the B8's. (Also take into consideration the bolt temperature vs. flange temperature - your ASME calculation is lacking in this respect.) The next problem is how you measure the installed bolt load, as of course torque only measures turning power on the nut and if you use tensioners the load-transfer relaxation effects will be high as the clamp length vs. bolt diameter ratio is less than 4:1, so you will need to make allowances for the errors in the tightening method.