ASME Flange Bolting Recommendation 4

[samctu]

Hello,

I'm looking for the recommend torque to put on an ASME flange. I can't seem to find it in ASME B16.5. Is there an industry standard that people go by or is there a chart that I can look up these values in?

Thanks,
Sam

 

[bvi]

Flange bolting recommendations are provided in ASME PCC-1, Guidelines for Pressure Boundary Flanged Joint Assembly.

 

[samctu]

Thank you bvi

I looked up ASME PCC-1 and from the abstract, I get the feeling it is for ring type joints only. Is there also a publication for raised face flanges or does this publication also apply to it?

 

[bvi]

It applies to raised face joints.

 

[NozzleTwister]

Another source of information for spiral wound gaskets can be found at the following link:

http://www.flexitallic.com/products/techsupport/literature.htm

Flexitallic Design Criteria, page 56.

NozzleTwister
Houston, Texas

 

[proinwv2]

Look at ASME VIII, Appendix S.

You may find it very interesting.

Paul Ostand

http://www.ostand.com

 

[UKCats]

my 2cents...

The purpose of flange torque is to compress your gasket within the limits of the bolts and flange. The last time I needed torque requirements, I contacted the gasket mfg.

 

[Shmulik]

You may free download a torque calculator at the following link:

http://www.welding-units.co.uk/start.htm

 

[tothepoint]

Be very careful with "recommended" torque values, as there is no one torque value for an ASME flange that takes all factors into consideration.
Assembly torque should consider the minimum and maximum stress for the gasket, the yield stress of the bolting (ASME PCC-1 suggests 50% yield for A193-B7 bolting), and finally the yield limits of the flange itself (integral flanges vs loose flanges have very different flexibility and thus allowable bending).

Gasket manufacturers are good at telling you what their gasket's require, yet they typically do not consider the min/max limits for bolting, nor do they consider the flange type. You need to hook up with a supplier that has the technical competency to help you with these analyses.

 

[LSThill]

TECHNICAL NOTE:

REVIEW PP25+PVRC+PRESENSTATION BY John Ludman, Randy Wacker, Kevin Kelleher, and Ed Perez May 24, 2005.

Optimizing Torque Values:
Why we did the work
How we did the work
What we learned
what needs to happen

Why optimize?
Existing Corporate Flange Assembly Standard based on single bolt stress value for “sheet” (20 ksi) and spiral wound (45 ksi) gasket
Poor sealing experience
Some flanges damaged (rotated)
Previous PVRC efforts shows need
W.E. Short - ASME PVP-Vol. 235 1992 - referenced PVRC initiative to study stress limits of 16.5 flanges (FEA)
Rodabaugh/Moore - ORNL-NRC-5 - a) ASME rules don’t adequately analyze ASNI flanges, need for limit analysis
Several sources of conflicting torque tables

Sources of Recommended Pre-load

Gasket Manufactures - consider gasket stress and bolting
PCC-1 - Similar to existing corporate standard, single bolt stress value (50 ksi)
ASME Flange Calculations (Appendix 2) - max allowable pre-loads were conservatively low (Rodabaugh/Moore Study-suggests 40 ksi bolt loads although ASME rules predict excessive stresses)
Pre-load required to achieve “tight” (T3) seal - only considers gasket, not optimal
Rule of Thumb - 40% of bolt yield strength (Bickford)

Optimal Pre-Load

Maximum pre-load that does not damage fastener, gasket or flange
Flange - consider stress and deflection (output only)
Gasket - consider mechanical properties
Fastener - assume high strength bolting only

“Tightness” is an output not an input

Conditions of Analysis

1) ASME B16.5 Flanges (Lap Joint, Weld Necks)
2) Design Conditions, pressure rating at 400 degrees F.
3) Diameters, 1/2” through 24”
4) Standard Pipe Sizes
5) Material A105
6) High Strength Bolting
7) Spiral Wound and Sheet gaskets (allowable compressive stress > 10,000 psi)

General Strategy
1) Established acceptable limits of stress (flange, bolt, gasket)
2) Adjusted fastener loadings to achieve flange stress limits
3) Compared resulting gasket stress to gasket stress requirements (T3 seal, manufacturer’s recommendations)


Lap Joint Flanges

Method
ASME, Division 1 Appendix 2 equations

Limits and Considerations
1) Bolt-up case only (pressure increases stress by ~ 12%)
2) Flange stress limited to 90% of hot yield (at bolt- up)
3) “Hub” not included in Appendix 2 calculations
Verification
1) Axisymetric Finite Element Modeling (considered hub)
2) Verified several sizes (proved method used was conservative)

Weld Neck Flanges

Limits and Considerations
1) Limit Flange stress to 90% Sy
2) Limit Hub stress to 1.7 x Sy
3) Yield (Sy) value at temperature
Verification
1) Elastic-plastic FEA analysis (for hub stress)
2) Verified bending stress in hub was “secondary”, use criteria of <2 Sy


Method
1) 3D Finite Element Modeling (AxiPRO, Paulin Research)
2) Gasket dimensions per ASME B16.20 (spiral wound) and ASME B16.21 (ring)
3) Reviewed output (flange stress and deflection) and adjust bolt load to approach limits

I could not add the rest of the pp.

E.C. Rodabaugh and S.E. Moore published a report “Evaluation of the Bolting and Flanges of ANSI B16.5 Flanged Joints ASME Part A Design Rules” sponsored by US Nuclear Regulatory Commission, We were referred to this report by Clyde Neeley. Available through National Technical Information Services (ORNLSUB29133)

This PP is available.

 

[LSThill]

Key Observations

Recommended pre-load based on single bolt stress value inadequate criteria for all flange combinations
Lap Joint flange design allows limited pre-load, tightness - new tables increase pre-load from 20 ksi
Use of 50 ksi bolt stress pre-load could overstress small size Class 150 (up to 1”) and 300 (up to 3”) weld neck flanges, damage gaskets in small sizes (over 20 ksi gasket stress)
Pre-loads of 60 ksi are recommended for some Class 150 flanges (3” and 8”)
The torque tables consider all elements of the flanged assembly (gasket, bolt, flange)


What’s Next?

Complete analysis for slip-on flanges
Class 300
Complete analysis of SS flanges
Consider additional flanges classes
Field observations
Higher pre-loads established for sheet gaskets
Lower pre-loads recommended for SW’s in small sizes and larger size
Work with PVRC Task Group to study topic across industry