The Width of Gasket

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ha.izadi Participant Join Date: Aug 2011 Posts: 4	The Width of Gasket 10/09/2011 10:00 AM
	I have bought a non-metal gasket for a ANSI flange with the following specifications: Size: 12 inch Class: 150 Type: Welding neck The width of gasket is lesser than the ANSI standard. It is half of the standard. One of my coworker said that "whatever the width of gasket be lower, the sealing of flanges will be done better". Now, experimentally this subject is correct. Could I know the opinion of others about this subject??
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#4 "Re: The Width of Gasket" by Mukesh0861 on 10/09/2011 10:20 PM (score 2)

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#3 "Re: The Width of Gasket" by blackpanic73 on 10/09/2011 5:54 PM (score 1)

asd23789 Commentator Join Date: Jun 2011 Posts: 63	#1 Re: The Width of Gasket 10/09/2011 10:59 AM
	Dear ha.izadi 1) It is a non-metal gasket 2) It is a class 150 Flange. 3) The MOC of the flange is Steel. Pls confirm 4) The standard you are referring to is ASME B16.21? now the gasket ID considering above 4 points as true will be pipe OD that is 323.8 mm. Hope this helps. __________________ The light of blindness of knowledge is yet to reach me, forget being clever.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#2 Re: The Width of Gasket 10/09/2011 1:20 PM
	IIRC, if the flanges are flat-faced rather than raised-face, a full-face gasket is needed. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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blackpanic73 Commentator Join Date: Sep 2011 Location: neighbor of the best country in the world Posts: 65 Good Answers: 2	#3 Re: The Width of Gasket 10/09/2011 5:54 PM
	Dear hi. Izadi Greeting to you For any gasket it has two values of outside diameter - The first value called (maximum outside diameter) which has dimensions are manufacturer's dimensions for «self-centering» gaskets compatible with flanges and nuts/bolts (diameter of circle tangent to bolt holes) that is the limit of this value. - The second value called (normal diameter) which has dimensions are those of raised faces of flanges. By applying these dimensions you can calculate the range of allowable width of gasket which under change. For gasket 12 inch 150 # O.D. max. = 405 mm . O.D.nor. = 381 mm (raised face). I.D.min. = 324 mm The minimum width of gasket = ((O.D. nor.) - (I.D. min.)) /2 = 28.5 mm The maximum width of gasket = ((O.D. max.) - (I.D. min.)) /2 = 40.5 mm check all dimenions of any gasket with the dimensions of flanges you need ASME B 16.5 FOR FLANGES. and MSS SP-44 - 1996 for gaskets dimensions or tables of trovay - cauvin __________________ enlightenment is blessing and self-denial is a good recipe
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Mukesh0861

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Join Date: Dec 2010

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Re: The Width of Gasket

10/09/2011 10:20 PM

Class 150

Size NPS	Inner Ring	Sealing Element		Outer Ring
Size NPS	Inside (A) Diameter	Inside (B) Diameter	Outside (C) Diameter	Outside (D) Diameter
1/4*	-	0.50	0.88	1.75
1/2	0.56	0.75	1.25	1.88
3/4	0.81	1.00	1.56	2.25
1	1.06	1.25	1.88	2.63
1-1/4	1.50	1.88	2.38	3.00
1-1/2	1.75	2.13	2.75	3.38
2	2.19	2.75	3.38	4.13
2-1/2	2.62	3.25	3.88	4.88
3	3.19	4.00	4.75	5.38
3-1/2*	-	4.50	5.25	6.38
4	4.19	5.00	5.88	6.88
4-1/2*	-	5.50	6.50	7.00
5	5.19	6.13	7.00	7.75
6	6.19	7.19	8.25	8.75
8	8.50	9.19	10.38	11.00
10	10.56	11.31	12.50	13.38
12	12.50	13.38	14.75	16.13

From the above table it is clear that sealing element width is not equale to the width of the raised face of the flanges. However with inner guide ring the ID of th gasket become equile to pipint ID and outer guide rings OD is compatible with inside diameters of the bolt holes so that gasket is centred automatically by the bolts.

Gaskets seal the flange jonts after getting crushed between the two flanges. Therefore the width of the gaskets are calculated by the maximum crushing load which can be imparted by the flange bolts on the gaskets. That is the reason for 150# rating flange gasket width is smaller then 300# rating gaskets. If we used wider gaskets, the crushing load generated by the bolts will not be able to crush the same and the softer material of the gasket will be exposed to the piping fluid which may cause leakage. Practically this do not happens and wider sealing face gaskets do holds well but theoritically gasket width should not be more then the designed for the standard flanges.

I hope this help in understanding.

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munirathnam Participant Join Date: Oct 2011 Posts: 1	#5 Re: The Width of Gasket 10/10/2011 4:58 AM
	ANSI standanrd gasket thickness was defined calculating the following parameter. 1. Type of fluid/liquid flowing throught the pipe. 2. pipe stresses.
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ha.izadi Participant Join Date: Aug 2011 Posts: 4	#6 In reply to #5 Re: The Width of Gasket 10/10/2011 7:17 AM
	Dear Sir Thanks a lot for your kind cooperation. My question is related to the width of gasket, but your text is about the thickness of that.
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Mukesh0861 Power-User Join Date: Dec 2010 Posts: 377 Good Answers: 20	#7 In reply to #6 Re: The Width of Gasket 10/10/2011 10:03 PM
	You can understand that as the width of the gasket will increase it will need more force from the flange boltings to get compressed to the required level so that it can hold the fluid inside the flange joint. Every flange is designed such that its bolts impart sufficient load on the gasket to hold the leakage for particular width of gasket depending upon rating and size.
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