Flange bolt loads with wear insert / orifice plate
Flange bolt loads with wear insert / orifice plate
(OP)
Hi,
I was just wanting to have a quick discussion regarding clamping of either a flange wear insert or orifice plate in between two flanges and the effect of this on bolt loads due to there being 2 gaskets and a steel plate in between rather that just a single gasket. Following from that too, a butterfly valve that is clamped in between (hence the wear insert) which makes that 3 gaskets that are being clamped (see drawing) on a set of bolts.
Does this change the gasket factor (m) or Design seating stress (y) from ASME VIII Div 1, appendix 2? What I was thinking is that the bolts will be doing up over a longer distance but the resistant still should be the same hence if all the gaskets are the same then m & y should be too. That is unless you assume the wear insert is another gasket material rather than ignoring it.
Cheers
I was just wanting to have a quick discussion regarding clamping of either a flange wear insert or orifice plate in between two flanges and the effect of this on bolt loads due to there being 2 gaskets and a steel plate in between rather that just a single gasket. Following from that too, a butterfly valve that is clamped in between (hence the wear insert) which makes that 3 gaskets that are being clamped (see drawing) on a set of bolts.
Does this change the gasket factor (m) or Design seating stress (y) from ASME VIII Div 1, appendix 2? What I was thinking is that the bolts will be doing up over a longer distance but the resistant still should be the same hence if all the gaskets are the same then m & y should be too. That is unless you assume the wear insert is another gasket material rather than ignoring it.
Cheers





RE: Flange bolt loads with wear insert / orifice plate
I should keep the bolt loads the same, but if any different, only just slightly lower.
RE: Flange bolt loads with wear insert / orifice plate
Please explain the need, value and source of "a flange wear insert"
Sometimes its possible to do all the right things and still get bad results
RE: Flange bolt loads with wear insert / orifice plate
Gaskets in parallel result in stiffness equal to the inverse of the sum of the inverses of the single gasket stiffness (1/Y1 + 1/Y2 + ...)^-1.
As a bare minimum, I would suggest something other than a spiral-wound gasket; they tend to fail rather catastrophically when bolt load is lost.
RE: Flange bolt loads with wear insert / orifice plate
XL83NL, thanks for your comments, along the same thoughts of mine.
Pennpiper, the wear insert is to protect the flange against erosion caused by the fluid passing through the butterfly valve when it is not fully open as in the picture.
TGS4, thanks for your comments, this is currently a working joint which is having leakage issues, I have been doing some background work on it to make sure stresses in the flanges are within the allowables but the client is responsible for the tightening procedures etc we have just recommended they use ASME PCC-1 as a guide to help cut down their maintenance issues. You are saying with your gasket stiffness equation that if I have 3 gaskets the same in series then the overall stiffness is 1/3 of a single gasket? And with the thickness increasing by 3 the force required by the bolts is basically the same looking at a simple F = kX equation?
So from all this am I safe to assume that in this example, 3 gaskets the same in series will have the same m & y values when looking at the joint overall, and with an extra piece of steel (wear insert) thrown in the sandwich I can ignore this for my calculation?
RE: Flange bolt loads with wear insert / orifice plate
If you choose not to get an expert in the field involved, at least consider using the EN-1591 calculations approach. Much more appropriate.
RE: Flange bolt loads with wear insert / orifice plate
You wrote:
"the wear insert is to protect the flange against erosion caused by the fluid passing through the butterfly valve when it is not fully open as in the picture."
Just where did this cockamamie idea come from? If this was really a problem it would have shown itself decades ago when Butterfly Valves were first invented and used in process plants around the world.
I suspect that you have been swindled by a slick salesman who saw an opportunity to make a fast buck. I would bet this is another idea from "Beauregard Gustafson" (http://pipingdesigners.com/contents/blog/130-blog-...).
Sometimes its possible to do all the right things and still get bad results