Belleville Washers in Steam Applications 1

[engineeringguy]

Our client has requested that Belleville washers be used on their flanges for steam applications. Their reasoning is that improper torquing practices can cause the flanges to leak.

I am sure this has been done and I've seen discussions on this board regarding this and have read the white papers at Solon and key belleville.

My question:

- Has the use of belleville washers been examined by ASME/API and if not, is it in the spirit of the existing codes?

I get really nervous over using something like this because it seems to be doing the job of the bolt preload. Any thoughts?

http://www.piping-designer.com

 

[insult2injury]

That's exactly what's used for live loading valve packing to avoid excessive leakage over the life of the valve/packing.

I2I

 

[C2it]

Are you intending that your belleville washer will be crushed flat by the bolt preload ? If not you are introducing flexibility in the joint that was not anticipated in the design process. You may have leakage or gasket blowout due to piping forces and moments. I have not seen a reference to belleville washers for flange bolts in any code. The EN1591/EN 13445 code includes the facility to use over-length bolts with packers, to add elasticity in the bolt.

 

[MJCronin]

e-guy

This is one of severak major vendors:

Key Bellevilles, Inc.
100 Key Lane, Leechburg, Pennsylvania 15656-9531
Phone: 724.295.5111 Toll Free: 800.245.3600
Fax: 724.295.2570 Toll Free: 800.847.1672

They seem to have bolting tables developed and example applications that include pipe flanges to valves.

I would contact them and ask questions.

Why are good-old ANSI flanges no longer suitable for steam systems ?....Bolt-em up and forget them

The use of bellvilles on valves to supply a "live load" to packing has been around for many years. But these packed valves would have required periodic adjustment anyway. The belleviles make the adjustment less frequent

Have you explained to the client that there will be extra expense in installation, inspection and periodic testing of bellvilles on piping flanges ? How about the applications where the bellevilles will physically not fit ?

I do not believe that ASME B31.1 or B31.3 have any statements regarding belleviles on pipe flanges.

I also do not truly understand what is really gained by the use of these devices on pipe flanges. Steam piping flanges are not locations where a properly installed system typically leaks...!!!

-MJC

 

[engineeringguy]

Thank you for your answers. I want to explain to the client that the whole point of preloading the bolts is to keep them under tension and the procedure should be changed (or enforced) instead of adding additional mechanical components to the system.

http://www.piping-designer.com

 

[sjrfc2]

I always thought the reason for the bellevilles on flanges was to retain load during operation. During operation if you have gasket creep you have the potential to lose the elastic load in the bolts very quickly. The bellevilles give you the benefit of higher load over a greater gasket deformation. This might be especially desireable for applications that go through high temperature transients.

They have lines of bellevilles that are designed to go flat for a specific bolt preload. I always thought that was a nice feature. Keep in mind the springs go through a permanent set the first time they're compressed so you'd want to discuss that with the supplier and how they should be ordered.

I know that I saw them on rocket motors at Cape Canaveral. I know that Velan uses them on pressure seal valves for steam. This is where pressure seats the bonnet seal and any deformation would result in lower bolt load. Bellevilles are also used on boiler gage glasses by the manufacturer's. One of the complaints I've seen with the gage glass springs was that they cracked in service. I've also seen them spec'd to address gasket creep in boiler handholes, again a pressure seated application that had the potential for a lot of deformation due to high temps, tansients and repeated loading.

 

[LarryV]

I've used Belleville washers in very high vibration environments to maintain bolt pre-load and prevent the nuts from backing off due to vibrations. The use of Belleville washers normally isn't a Code issue, but an operations or maintenance issue (how often do you want to have maintenance crew retighten the flange bolts in these high vibration environments?).

 

[MJCronin]

To all..

Avoid all flanged joints in very high vibration environments...

-MJC

 

[rngrrix]

My experience with Bellevilles is primarily in boiler and valve applications. I think there would be little value in piping systems unless there is a unique characteristic. To simply install them to avoid installation quality concerns would speak ill of the QA/QC aspects of the job. My recommendation would be to focus efforts on QA/QC instead of spending money on a band-aid that may not provide any benefit.