Gasket Factors "m" and "y"`

Hi nbhabibkhan,

well basically m and y are the gasket factors which are used for flange designers only as specified in the ASME Boiler and Pressure Vessel Code Division 1, Section Vlll, Appendix2.

The m = maintenance factor which provides the additional pre-load needed in the flange fasteners to maintain the compressive load on gasket after internal pressure applied to a joint.

The y= minimum design seating stress on the contact area of the gasket that is required to provide a seal at an internal pressure of 0.14 bar Y=W/A_1, where W is total fastener force in N and A₁ is gasket area in mm².

Good luck

You are right, and these factors apply for design of non-standard flanges used in pressure vessels and heat exchangers designed in accordance with ASME BPVC.

Dear Sir

I have one doubt.In AEW type heat exchangers, the floating side gaskets used to be a O ring gasket made of Teflon. So in such case what values we should consider for m & y ?

Thanks

Praphulla

Dear Praphulla Phirke,

From ASME VIII, Division 1, Table 2-5.1, the self-energizing gasket types such as O rings, metallic, elastomer, other gasket types considered as self-sealing, all have m = 0 and y = o.

See the attached table: ASME_BPVC_VIII_D1-2009a Table_2-5.1

Dear brother

I am working on the designing of vent stack. Body flanges or connecting flanges are required in the middle of these stack (200ft height.). holding the weight above it and resisting the vortex shedding moment I have design considering flanges as base plates and calculations are as per Henry and Bednar.

Client requirement is that they want to design flanges using gasket factors m & y

what type of gaskets should we used in the vent stack and values m & y

design temperature is 400F

ASME can also refer stack or not?

thanks

what area of the gasket ? the cross sectional area ? the contact area ? what do you mean by A1 ?

I guess these factors are for the manufacturers and mechanical engineers only and process engineers wouldn't care about them. Metallurgically, we will see that the material is B7, 2H or B16 and matching grade nuts are used for the flowing temperatures. Am I right in my assumptions?

Regards;

Nadeem Butt

Yes.

B7 is just a grade of Stud Bolt material ASME SA293 (ASTM A293), there are a lot of another grades and also material.

2H is just a grade of Hex Nut material ASME SA294 (ASTM A294), there are a lot of another grades and also material.

During design of any flange, you have to select the proper bolt and nut material and calculate its size to withstand both pressure, temperature, and forces arise at two cases : Gasket Seating Condition and Operating Condition.

Thank you very much for clearing it up.

Regards;

Nadeem

what are prssure vessels exactly ?

Any vessel subjected to an internal pressure equal to or exceed 15 psi is called pressure vessel, the vessel can be subjected also to an external pressure. A lot of and variety of pressure vessels such as : boilers, dryers, accumulators, fractionation's, filters, .... etc.

thanks, so a pipeline is considered to be a vessel hence the codes ASME B&PV apply to it right ?

No. Piping as a pressure system (called pressure piping) is differ from pressure vessel. There are a special code for each piping or pipeline depend on its service, such as :

For piping : ASME B31.1 Power piping & ASME B31.3 Refinery piping.

For pipelines : ASME B31.4 Liquid Hydrocarbon and Ammonia & ASME B31.8 Gas Transmission and Distribution.

Note. ASME BPVC is a committee for Boiler and Pressure Vessel Code, where ASME B31 is the committee for Pressure Piping.