Torque Requirements for Bolts on Steel Flanges 6

[DANGER]

Is there a reference for determining the amount of torque required to properly tighten carbon steel and stainless steel bolts and nuts when connecting carbon steel flanges for pipe of various diameters for pipe under pressure? What are the important parameters to be considered?

 

[omer2000]

hi
it is depend on grade of material(material quality) and bolts size
thanks

 

ASME PCC-1, Guidelines for Pressure Boundary Bolted Joint Assembly, a relatively new ASME standard, provides good guidance on this issue. It depends upon things like bolt size, lubrication, whether the bolts are coated, and if it is a first use of that type of bolts, etc. Torque goes into tensioning and overcoming friction. Target bolt tension values can vary depending upon circumstances, but 50,000 psi bolt stress is a commonly used target.

 

[MJCronin]

Danger, (very hip handle...)

As a matter of practicallity, what many large engineering firms (the Bechtels and the Fluors) have done is establish standard "torque tables" for various sizes of studs and for variuos types of materials. This table is sent to the piping contractor for his use in piping erection.

The standard tables are typically for "alloy steel" and "carbon steel" studs and machine bolts. Most projects are able to use just A36/A307 material (carbon steel)and A193 B7 (alloy steel) for almost all applications.

The tables are based upon work published by Crane in a valve catalog in the mid 1960s. Flexitalic ( and other gasket manufacturers also published the same information and referenced the Crane source....

See:

http://www.sealsolutions.com/techinfo/

Good Luck!!!

MJC

 

[stanier]

In critical applications it is better to measure the strain imposed on the bolt not the torque of the nut. This gives an accurate value for the compression of the gasket and hence the integrity of the flanged joint. Hydaulic tensioners can be used to elongate the bolt a known distance and thus the flange seating pressure is controlled.

Friction on the bolt thread can vary immensely due to tolerances, surface finish, corrosion, lubrication etc. Galvanising presents another problem as this is uncontrolled. When using stainless stell cold welding (galling) can occur.

 

[Deezul]

Danger Danger Warning Warning!! Sorry for that, Robbie the Robot's favorite warning or forecast and I couldn't help myself

Bolt torque, and flanges and pipe, easy!
"John H Bickford", from memory gives:
Tin = Fp.d.k ((lb.in, NOT! lb.ft) or (N.m)), where Tin = Torque input, Fp = Bolt preload, d = nominal bolt diameter, and k is a fudge factor depending on many variables. The most important of which is the Friction on the bolt/nut threads "which make the bolt work".

The wee calc above, gives an close approximation (10 to 20 percent (%)) to much longer and more detailed calc(s) and methods.

There are many! parametres! to be taken into account. Too many to list here anyway!

Go to the library and ask them for "John H Bickford" title on "Introduction to the design and behavior of bolted joints"


Kind regards

Deezul

 

[cgr]

I'd like to begin by apologizing for the length of this reply, but it all seems relevant...

The following is an excerpt from a recent edition of The Pressure News (published by ABSA at

http://www.absa.com)

"In general, flange connections consist of mating flanges, gaskets and the bolting elements. Failure to consider
each and every one of these elements when doing up a flange may result in premature failure, leakage,
environmental emissions and even worse, a serious incident. For standard ASME B16.5 flanges, the
standard determines the bolt circle diameter, the number of bolts in the flange and the allowable operating
pressure and temperature. There are also a number of flange face designs (e.g., raised face, flat face, ring joint, etc.) and surface finishes, and gasket designs (e.g., rubber, spiral wound, garlock, or any number of acrylics, Tufline, steel ring, etc.)
It should be noted that each component of a flange has a design parameter or limits that must be
considered whenever a flange is assembled.
- Flange material specification
- Rated allowable operating pressure and temperature.
- Gasket selection required for the flange rating.
- Gasket material suitabilty for the process contained.
- Bolt selection: material compatibility with the flange
material; loading and operating temperature
- Gasket loading for the gasket material and the flange design: torque values. (some owner/user companies may have standards that are different from the gasket supplier).
- Tradesman trained in installation (including bolting up) practice.
- Installation details communicated to the tradesman: gasket rating, material, torque values, etc.
- Checklist to ensure that all the requirements were met."

I was recently involved in a project where excessive torque was used resulting in over-compression of the spiral-wound gaskets. The resulting corrective work wreaked havoc with both the budget and schedule of the entire project, so in my opinion these are all important parameters for consideration when trying to determine bolt torque requirements.

Regards,

 

[MJCronin]

cgr,

Are you sure that you posted the correct link ?

I tried "

http://www.absa.com"

and it got me into some kind of wierd banking seminar, then froze my machine up.....I was creeped out...

The last time I had that kind of creepy feeling was when I dated that one-legged female accountant....back in '82

 

[stanier]

Try the klinger website and download their 'expert" gasket software. You can determine the bolt torque based upon pressure, friction factor, type of gasket, # & size of bolts. OInly drawback is they dont include SWMA as yet but your local Klinger rep will give the information.

Another approach is to caclulate the load required on the gasket and use hydraulic tensioners to achieve the load. Then simply tighten the nut up to the flange face with minimum torque. Takes the guess work out of it. I have seen Shell do this on critical service.

Sharing knowledge is a way to immortality

 

[jte]

MJCronin-

Try

http://www.albertaboilers.com/newsletter/v08i1/v8-iss1-net.pdf

jt

 

[cgr]

sorry MJCronin

shoulda been

http://www.absa.ca

apologies

 

[denniskb]

While this may cross over some of the responses above I would like to ask a simple question.

"What axial tension (e.g. % of SMYS or% of SMTS) should be applied to a B16.5 flange stud bolt when tightening it and what code or reference determines this?"

Table A-2 of B31.3 states allowable design stresses for stud bolts and the usual B7 gets a design stress of 25 ksi. This works out at less than 25% of SMYS (it is actually 20% of SMTS).

Various other codes and references recommend stressing bolts to anything from 33% to 75% of SMYS.

How come none use the value from B31.3 - OK that was two questions but I had to ask!

Dennis Kirk Engineering

http://www.ozemail.com.au/~denniskb

 

[magyar]

calculation torque for any bolts possibly with program
calculation from :

http://www.cedarhouse.co.uk/

Program name : Bolt Torque

 

[denniskb]

One more question to add to or clear up my confusion.

I have calculated the effective stress area using
Deff = Dmaj - 0.9743 / N
which I obtained from several reputable sources.

When I look at some of the tables around I find different effective diameters listed. One of these (Flexitallic) appears to use
Deff = Dmaj - 1.296 / N

Can anyone explain why there is more than one commonly used method and which one is "correct"?

Dennis Kirk Engineering

http://www.ozemail.com.au/~denniskb

 

[bvi]

Don't get confused between allowable stress and desired stress in the bolts achieved by torquing. They are two different things. The allowable stress is used for sizing bolts. The desired prestress is higher, 50,000 psi is a typical value. For information published by ASME on this subject, see Section VIII, Div 1, Appendix S, and better yet, ASME PCC-1, Guidelines for Pressure Boundary Bolted Flange Joint Assembly. PCC-1 also gives torque tables based on acheiving a 50,000 psi prestress, and has a lot of other useful information related to bolted flange joint assembly.
PCC-1 is available in the publications section of the ASME website.

 

[unclesyd]

Code Calculations for a specific flange, pressure, temperature, gasket type/material, etc. is very laborious. A good flange program would be a great help if one understands the basics of flange design. There are manufactures tables for the standard pipe flanges using a predetermined bolt stress, 25000,30000,,50000 psi. Most gaskets manufactures have tables as to what stress is recommended to properly seat each specific gaskets.
If one knows the desire bolt stress the following site has a download able program that will give different tightening values for a specific flange size, type, and class. The program defaults to a specific value for bolt stress, but this value can be changed.

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

An interesting note is this program defaults to bolt stress of 50000 PSI. I have some old flange books that use a bolt stress of 25000 PSI. The friction factor can also be changed.

Another site that might be of interest is:

http://www.boltscience.com

This site offers a lot general information on bolted joints and give on a little in site on seat a gasket.

As mentioned above the book by Bickford is very good.