Max torque on flange gasket
Max torque on flange gasket
(OP)
I'm using 1/8" SBR red rubber gasket (various sizes) and I am having a difficult time finding out what the min and max clamping forces on the seal should be. I called the manufacturer and of course they were no help. We had a failed gasket and now our costumer wants a writen spec. So if anyone can help me find a website that would offer clamping forces of the gaskets or better yet the torque ratings for bolts, I'd appreciate it.





RE: Max torque on flange gasket
That being said, I was told many years ago (by someone I considered much more of a rubber expert than me!) that at least then many “red rubber gaskets” were composed of a very high percentage of some sort of “clay”. While I would not otherwise consider myself any sort of expert in cookie-cut red sheet rubber, I suspect it would follow that those rubbers would quite likely exhibit different physical properties, e.g. some lesser elongation or maybe even significantly greater compression set etc. (than for example some other engineered rubber pipeline seals with lesser or other fillers, e.g. such as those required for push-on and mechanical gasket seals by standards such as ANSI/AWWA C111/A21.11-07 American National Standard for Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings.)
Flanged gaskets other than “red rubber” are available, and also some with special sealing features from various vendors that may be arguably helpful maybe particularly with variations in bolting diligence/expertise and variable joint loadings (e.g. see gaskets described on page 8-3 at http://www.acipco.com/adip/products/Sect8.pdf).
While such molded gaskets and even with special sealing features may or may not be more expensive than sheet rubber, depending on factors such as size etc., I suspect in many common at least small piping sizes these molded gaskets are probably at least a little more expensive per each than red rubber basically stamped or otherwise sort of “cookie cut” from larger/bulk sheet.
With abject apologies to William Shakespeare (I think), perhaps “therein lies the rub” (so to speak), I wonder if this may in a sense be a case of one getting what one pays for?
RE: Max torque on flange gasket
Any time we have an problem they have been a great help.
RE: Max torque on flange gasket
The failure: The pipe flanges were seperated and the gasket had been torn due to over clamping. It did not leak, but the since it was torn, we believe it eventually would. We torqued the bolts to recommended torque value of the bolt (not considering the gasket). No we are re-assembling and I need to know the max value so this doesn't happem again.
The vender: They are no help because they can not give a min or max clamping value to achieve seal without damaging the gasket. The refer to manufacturer who then refers to material supplier. The material supplier says they do not test for that kind of thing and simply make the material per a standard. The state we should contact the company who stamps the gasskets. So as you can see, this is one big circle.
I can find values for brand name gaskets, but nothing for a plain red rubber gasket. I have found some generic min torque numbers and that is where we are starting at. During our proof pressure testing we are going to increase torque in 10 ft-lb incriments if leaks are found.
So that is my situation better explained. Any suggestions?
RE: Max torque on flange gasket
RE: Max torque on flange gasket
RE: Max torque on flange gasket
If you look in ASME Section VIII, there is a lot of material on gasket clamping, seating stress, flange face type, etc., all as needed to effect a seal.
You did not say what type flanges you have, whether they are spiral-finished, etc.
You probably don't want to hear this but it may be better to switch to a material for which there is a known required seating stress, e.g. Flexitallic or Garlock Blu-Gard. You can't go wrong with Flexitallic - they're cheap, you can buy them everywhere, good for all sorts of fluids, and you can calculate the required seating stress
RE: Max torque on flange gasket
Red rubber, all 60-70 durometer elastomers for that matter, should be assembled to a compressive stress range of 500 - 1500 psi. 500 psi as a minimum stress and 1500 as a maximum.
Do not use gasket seating values listed in ASME Appendix 2, as these are design stresses, not assembly stresses (there is a big difference).
Hopefully you are using the red rubber between flat face flanges. If you have raised face flanges you better select another material as you'll max out the smaller gasket contact area long before you develop any appreciable stress on your fasteners. If your flanges are FRP/Plastic, calculate your assembly torque at the low end of the min/max stress range.
RE: Max torque on flange gasket
RE: Max torque on flange gasket
RE: Max torque on flange gasket
The original query was about a torn gasket - - possibly perfectly OK for many years but torn on being dismantled ??
Regards CM
RE: Max torque on flange gasket