Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
(OP)
Hello everyone,
I was wondering if belleville washers really work effectively.
1. All springs add or maintain force but how much compared to relaxation of bolts and gasket?
2. How is the variance of a torque wrench factored in on bolting them up(Given values of torque manufacture is different than actual)? In other words how much can you be off by and it still be effective?
Please respond with technical data, studies or calculations. My experience is they usually seem to work only because the flange is inspected more carefully, torque wrench is used, Flange make-up is more closely watched higher torque value is used or a new or better gasket is put in.
I was wondering if belleville washers really work effectively.
1. All springs add or maintain force but how much compared to relaxation of bolts and gasket?
2. How is the variance of a torque wrench factored in on bolting them up(Given values of torque manufacture is different than actual)? In other words how much can you be off by and it still be effective?
Please respond with technical data, studies or calculations. My experience is they usually seem to work only because the flange is inspected more carefully, torque wrench is used, Flange make-up is more closely watched higher torque value is used or a new or better gasket is put in.





RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Like these for example,
http://www.portlandbolt.com/technical/specificatio...
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Anything past that exceeds prices and does not make the gasket any more reliable.
Anything less makes the gasket less reliable (almost certain to leak over time) regardless of anything else done.
A metal-to-metal flat-face connection relying only on the force across each stud - as on a turbine head assembly or generator casing enclosing hydrogen gas? Follow the manufacturer's specific written procedure to every decimal place. Or it WILL leak. And you WILL pay to rebuild it to the turbine maker's specifications.
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
To be more specific I am talking about putting Belleville washers on the bolts of the body flanges on a ASME Section 8 Div 1 pressure vessel (Large piping rarely used on). I am not concerned with how to stop a leak but rather taking them off because they may or may not be needed to maintain a seal. I am familiar with ASME PCC-1, WRC 538, and WRC 510.
Here is the link if your looking to buy them http://www.ghxinc.com/ProductsServices/Fasteners/B...
I have read studies written by the companies selling Bellevilles but wonder if there is any third party studies to confirm or deny.
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Stretching the stud, then spinning on the nuts to the required position, then releasing the stretching force so the nut prevents further release of the stretched stud is the best way to get an accurate clamping force on the PV flange. Then, you "only" need to maintain that clamping force.
In your application, it is far better to use a positive clamping (anti-loosening) process such as Nordlock washers . An advertisement is from one typical sales page below.
They are expensive if used on every pipe flange, but reasonable i fyou are putting only on PV vessel flanges. Anti-loosening compounds are also available (both red (permanent) and blue (releaseable) locking chemicals are much less. Are you worried about chemicals degrading at the process temperature?
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Here is a link to an article which shows example calculations of Bellville washers in a flanged joint and a busbar joint.
http://www.sealing.com/fileadmin/docs/Using_Bellvi...
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
I can't see where Nordlocks would make a difference either. If loosening is only a matter of turns retention, they would help, but they won't help with tension retention, which is the goal in fastened, gasketed joints.
From a plain fastened, thermally cycled, pressurized joint design - I'd look at the gasket characteristics and determine hoe to make the fasteners about 1/10th the stiffness of the gasket to give some compliance, particularly for thermal transients.
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Some valve manufacturer's seem to make them standard items for valve stem packing gland bolts as well as pressure seal bonnet retainer bolts (especially with graphitic pressure seal rings).
If you visit the Rocket Garden at Kennedy Space Center in Florida you'll see them on rocket engines.
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
Piping Design Central
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
We used one on each side (studs) of the flange.
They were slightly different ratings. We torqued to just flatten the weaker of the two, leaving the stiffer one to allow for expansion.
They are a pain. They are expensive and you must use good hardened steel washers under them and make sure that they are free to scoot (add a bit of lubripate).
We had much better sealing when we used them, but I am not convinced that conscientious installation and periodic re-torquing wouldn't have done the same.
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P.E. Metallurgy, Plymouth Tube
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
I'd suggest you get hold of a report from a few years ago from:- ASME Standards Technology LLC, Called "Bolted Flanged Connections in Elevated Temperature Service" reference "STP-PT-036" which is interesting, but also concludes that using Belleville washers isn't much use on high temperature creep problems.
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact
RE: Belleville washers effectiveness on 6" to 60" flanges (pipe and HX) myth or fact