ASME Section VIII Gasket Factors

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The ASME Code for Pressure Vessels, Sec. VIII, Div. 1, App.2, is the most commonly used design method for gasketed joints.  An integral part of the ASME code centers on two gasket factors:  M and Y.  The factors were originally determined in 1937, and even though there have been objections to their specific values, they have remained essentially unchanged to date.  The values are only suggestions and are not mandatory.[1]



Contents

M Factor

The m factor, often called the gasket maintenance factor, is used in the calculation of the required bolt load of a pressure vessel under operating conditions. The calculation: Wm1= H + Hp = 0.785G2P + (2b x 3.14GmP) gives the required bolt load to seal the flange at operating conditions, and is compared to Wm2=3.14bGy; the higher of the two values is then utlized to calculate the minimum required bolt stress to properly seal the flanged joint.[3]

Y Factor

The y factor is the minimum seating stress associated with particular gasket material and is concerned only with the initial assembly of the joint.


Bolt Loads

The following is important information specified by ASME Section VIII for choosing the appropriate bolt loads required for a successful gasket sealing in any application.[2]

General Requirements
  • Operating condition (m factor) and gasket seating (y factor) values
  • Loads must be determined for the most severe conditions
  • The minimum gasket contact width for sheet and composite gaskets


Flange ID

Gasket Contact Width

24in(600mm) < ID <= 36in(900mm)

1in(25mm)

36in(900mm) < ID < 60in(1500mm)

1.25in(32mm)

ID >= 60in(1500mm)

1.5in(38mm)


Design Conditions
  • Operating conditions requires finding the minimum load required to create a seal under normal conditions
  • Gasket seating requires finding the minimum seating stress for the gasket to make a seal


Require bolt loads
  • The required bolt load necessary to maintain a seal to resist hydrostatic end force (m Factor)
  • The minimum initial load required to seat the gasket without any system pressure
  • The bolt loads required for self-energizing gaskets


Total Required and Actual Bolt Areas
  • The total cross-sectional area of the bolts are required for both operating conditions and gasket seating


Flange Design Bolt Load
  • The maximum bolt force before the flange becomes damaged


Gasket M & Y Factors

Gasket Type
 M Factor
 		Y Factor (psi)
Kammprofile

Ring joint

  • Iron or soft steel
  • Monel or 4% - 6% chrome
  • Stainless steel and nickel-base alloys


  • 5.50
  • 6.00
  • 6.50


  • 18,000
  • 21,800
  • 26,000
Compressed synthetic fiber (CSF)

Compressed asbestos fiber (CAF)

  • 1/8" thickness


  • 2.00


  • 1,600

Elastomer

  • < 75 duro
  • > 75 duro


  • 0.50
  • 1.00


  • 0
  • 200
Self-energizing
  • 0
  • 0
Elastomer with cotton fabric insertion
  • 1.25
  • 400

Elastomer with mineral fiber fabric insertion

  • 1-ply
  • 2-ply
  • 3-ply


  • 2.25
  • 2.50
  • 2.75


  • 2,200
  • 2,900
  • 3,700
Vegetable fiber
  • 1.75
  • 1,100

Spiral wound

  • Carbon steel
  • Stainless, Monel, and nickel-base alloys



  • 2.50
  • 3.00



  • 10,000
  • 10,000

Corrugated Metal, mineral fiber inserted, or corrugated metal, jacketed mineral fiber filled

  • Soft aluminum
  • Soft copper or brass
  • Iron or soft steel
  • Monel or 4% - 6% chrome
  • Stainless steels and nickel-based alloys


  • 2.50
  • 2.75
  • 3.00
  • 3.25
  • 3.50


  • 2,900
  • 3,700
  • 4,500
  • 5,500
  • 6,500

Flat metal, jacketed mineral fiber filled

  • Soft aluminum
  • Soft copper or brass
  • Iron or soft steel
  • Monel
  • 4% - 6% chrome
  • Stainless steels and nickel-base alloys


  • 3.25
  • 3.50
  • 3.75
  • 3.50
  • 3.75
  • 3.75


  • 5,500
  • 6,500
  • 7,600
  • 8,000
  • 9,000
  • 9,000

Klingersil C-series compressed non-asbestos gasket materials

  • Sealing liquid, thickness <= 1/16"
  • Sealing liquid, thickness > 1/16"
  • Sealing gases, thickness <= 1/16"
  • Sealing gases, thickness > 1/16"


  • 2.75
  • 6.40
  • 2.75
  • 6.40


  • 2,000
  • 2,900
  • 3,700
  • 5,000

Garlock Blue-Gard 3000

  • Thickness <= 1/16"
  • Thickness > 1/16"


  • 4.20
  • 5.20


  • 3,050
  • 4,400

Gylon 3504

  • Thickness <= 1/16"
  • Thickness > 1/16"


  • 3.00
  • 2.50


  • 1,650
  • 3,000

Durlon 9000

  • Thickness <= 1/16"
  • Thickness > 1/16"


  • 2.20
  • 4.60


  • 1,937
  • 1,639

















































References

1.  Daniel E. Czernik, "Gaskets Design, Selection and Testing", McGraw-Hill, 1996, pg. 46, ISBN 0-07-015113-X

2.  ASME Boiler and Pressure Vessel Committee, "2007 ASME Boiler & Pressure Vessel Code - Section VIII, Division 1", The American Society of Mechanical Engineers, 2008, pg. 347-368

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