Vessel Cover Gasket

[impeller1]

Hey Everyone,

I have an urgent problem here, basically, I've got a vessel with an operating pressure of 10 bars. The incorrect gasket was used to seal to top cover flange of the vessel (approx 3950mm in diameter). The correct gasket was now specified in terms of material, however, two different thicknesses were proposed from our local sales vendor. The OEM specified thickness is 200mm, however, 130mm and 320mm gaskets were proposed. Question I have is whether or not either of these can be used, and how do I verify this? My initial thoughts are that the thicker one can be used, but a higher bolt torque would have to be used in order to compress the gasket sufficiently?? Is there some calculation to determine this? I would appreciate any asssistance with this, thanks in advance.


Regards,
Timothy

 

[XL83NL]

a gasket 200 millimeter thick?

 

[gr2vessels]

I guess I've got a lot more to learn. I am trying to figure out how many extra tones of steel the flanges should have to confine a 320 mm thick gasket. I never heard something like that, but I tend to assume it was (too) early Monday morning for the supplier to advise that thickness. I have checked with my gasket supplier for any similar gasket and he told me to give up that stuff I am using...However, I am all eyes and ears for continuation.
Cheers,
gr2vessels

 

[marty007]

Hey Timothy,

Depending on the code of construction for the vessel, there should be guidance on the design of the flange.

Speaking from ASME VIII-1 experience, what you should look at are the m,y values of the proposed gaskets, as well as the gasket width.
[ul]
[li]y-value: This is used by ASME to calculate the required bolt load to properly seat the gasket[/li]
[li]m-value: This is used by ASME to calculate the required bolt load for the operating conditions[/li]
[li]Gasket width: This determines the bearing area over which you must generate the seating and operating compressive stresses on the gasket[/li]
[/ul]

If all of these values are lower for the new gasket compared to the old gasket, you should be fine. If however they are higher, you may want to have someone take a look at the code calculations.

With respect to gasket thickness, are there any nozzles with connected piping on the bolted cover? If so, you may get some mis-alignment if you use a thickness too much different than the original gasket.

Also, as XL83NL points out, 200mm thick? That doesn't sound right.

 

[racookpe1978]

What liquid or process fluid? What operating temperature and what operating cycle conditions?

This is "only" 150 psig (10 bar) and there could be no real problem at all. Or may be deadly problems.

A 200 mm gasket is not a gasket. Even a 20 mm gasket is a suspicious dimension. Almost all are 1/8 inch or 3+ mm.

 

[XL83NL]

1.3 (say 1.2), 2.0 and 3.0 mm are all standard gasket thicknesses. I guess the OP made a typo somewhere down the line on his early Monday morning

 

[GenB]

I use up to 6 mm on boiler hand hole and manhole testing. Neoprene like,
once compressed can hold liquid 30 bar at 10 C. and 10 bar at 125C. Thicker gaskets are not allowed. The question of impeller1 is beyond ASME boiler,PV Code. It seems impossible to use a gasket with those dimensions.

 

[impeller1]

Oh dear, Yes, Monday's are really the worst.. the gasket thickness is 2mm, sorry about that error, as glaring as it is.. anyway, yes, the process is nitrogen dioxide..so I can't afford for a gasket to go up there and fail at all.. 10 bars @ 490 deg. C.

 

[Ripz]

Oh Dear, Timothy. Oh, Dear.

 

[marty007]

Timothy,

Depending on the material of the gasket you are going with, different thicknesses come with different compression requirements and maximum PxT limits.

For example: Gylon 3510 has the following design factors:

1/16" & under:
[ul]
[li]PxT (max) [psig x °F]: 350,000[/li]
[li]"m" factor: 2.0[/li]
[li]"y" factor: 2350 psi[/li]
[/ul]

1/8":
[ul]
[li]PxT (max) [psig x °F]: 250,000[/li]
[li]"m" factor: 2.0[/li]
[li]"y" factor: 2500 psi[/li]
[/ul]

The only way to know for sure if your flanges will be okay would be to run through a flange calc (Appendix 2 or equivalent).

On a side note, at that diameter I would be very tempted to go with the thicker gasket if I had the choice and it passed the calcs. It would give you a better chance to make up for any flatness issues (more pronounced on a larger flange).

 

[gr2vessels]

Yes marty007, a minimum of 4.5-5.0 mm gasket, with SS insert;- perhaps alternatively Kammprofile Flexitallic. Probably m = 2 and Y = 2500 psi.

 

[SnTMan]

Was gonna say, a compositon gasket this size (trusting 3950mm not a typo ) is probably going to be multiple pieces, and defintely going to be a challange to handle w/o breaking. I'd go with a metallic with soft faces, graphite or teflon or some such. Kammprofile or maybe graphonic.

Regards,

Mike