Bolt Torque and Bolt preload query

[Danmecheng]

Hi All,

Currently going through a series of HX to calculate and verify torque values for girth flanges for an upcoming shutdown and pretty much doing a quick design sense check using the Appendix 2 calcs to determine the design minimum then following the guidance in PCC-1 appendix J , K and O to get the final assembly values. However when calculating the bolt preload to ensure the integrity of the bolts i.e. (tensile stress area x % utilisation x Minimum yield strength) can I ask for the yield strength value do you all normally use the yield strength for the bolt based at ambient temperature conditions or operating temperature conditions ?

I know standard practise is to applying between 40-70% yield and I like to use a utilisation of minimum 50% Yield but if you look at some of the exchangers the operating temp can be nearly 500°C so quite a difference in yield values compared to that of ambient condition so I assume it would be best to use operating conditions as to not over stress the bolt when it reaches its operational temp

This has caused abit of discussion in the office and keen to hear your thoughts on this and what you normally do ? I quite often use table Y1 of BPVC Section 2D to obtain the yield values at operating temps and find it quite good for this ?

Cheers

Dan

 

[r6155]

​

@ Trestala
It's obvious you have no experience in manufacturing or inspection.
.I'm sure you've never prepared an inspection plan or performed pressure tests, leak tests, or other tests.
Hence, your comment is ridiculous.

And......what is your help to the (OP)?

 

[XL83NL]

​

@ Trestala
It's obvious you have no experience in manufacturing or inspection.
.I'm sure you've never prepared an inspection plan or performed pressure tests, leak tests, or other tests.
Hence, your comment is ridiculous.

And......what is your help to the (OP)?

r, please provide some technical basis or background for your side of the story.
So far its the old song going on all bolt torque threads where you comment on: you mention elongation should be used, but never provide a reasonable or viable argument for your side of the story. Please do that THIS TIME or STOP POSTING THIS NONSENSE in future bolt torque threads.

 

[r6155]

@XL83NL
I already responded on Sunday at 7:32 PM.
You're too comfortable and don't read ASME PCC-1.
If you don't understand it, I can't do anything else.

 

[XL83NL]

@XL83NL
I already responded on Sunday at 7:32 PM.
You're too comfortable and don't read ASME PCC-1.
If you don't understand it, I can't do anything else.
I'm not your private tutor.

Ive read it. Now post which sections underline your statements, to prove you’re right (why does it feel I’m talking to a Trumpist?)

 

[Trestala]

It's obvious you have no experience in manufacturing or inspection.

You have no information on my background and experience. Better be professional on this forum.

And......what is your help to the (OP)?

I helped by disputing your claim that you failed to justify technically. No one uses vernier calipers during fabrication and on-site for flanges. We've used UT measurements alongside hydraulic tensioners. Torquing is extensively used on site and during fabrication. No one will bother measuring elongation on the hundreds of thousands of bolts on a plant if that can be addressed by proper torquing or hydraulic tensioning pressure conversion charts.

 

[r6155]

Control of the bolt stress is possible by means inherent in the procedure especially if effective thread lubricants are employed, but in all cases the bolt stress can be regulated within reasonable tolerances by measuring the bolt elongation.

You need to read more, over and over again. Or take a training course.
I'm not your private tutor.

 

[GD2]

Hi All,

Currently going through a series of HX to calculate and verify torque values for girth flanges for an upcoming shutdown and pretty much doing a quick design sense check using the Appendix 2 calcs to determine the design minimum then following the guidance in PCC-1 appendix J , K and O to get the final assembly values. However when calculating the bolt preload to ensure the integrity of the bolts i.e. (tensile stress area x % utilisation x Minimum yield strength) can I ask for the yield strength value do you all normally use the yield strength for the bolt based at ambient temperature conditions or operating temperature conditions ?

I know standard practise is to applying between 40-70% yield and I like to use a utilisation of minimum 50% Yield but if you look at some of the exchangers the operating temp can be nearly 500°C so quite a difference in yield values compared to that of ambient condition so I assume it would be best to use operating conditions as to not over stress the bolt when it reaches its operational temp

This has caused abit of discussion in the office and keen to hear your thoughts on this and what you normally do ? I quite often use table Y1 of BPVC Section 2D to obtain the yield values at operating temps and find it quite good for this ?

Cheers

Dan

Dan,
The key to keeping the appropriate bolt preload at both ambient (installation) and operating condition (500C) is to determine the bolt stress (Sb_sel) is as per Appendix-O. O-4.2 will take you through all the checks at both ambient and operating conditions for the flange assembly - bolt, flange and gasket.
If you look at the assembly with a hot process, for an uninsulated flange assembly, typically the flange and the gasket will be exposed to 90% fluid temperature and bolting to 85%.

 

[GD2]

Hi All,

Currently going through a series of HX to calculate and verify torque values for girth flanges for an upcoming shutdown and pretty much doing a quick design sense check using the Appendix 2 calcs to determine the design minimum then following the guidance in PCC-1 appendix J , K and O to get the final assembly values. However when calculating the bolt preload to ensure the integrity of the bolts i.e. (tensile stress area x % utilisation x Minimum yield strength) can I ask for the yield strength value do you all normally use the yield strength for the bolt based at ambient temperature conditions or operating temperature conditions ?

I know standard practise is to applying between 40-70% yield and I like to use a utilisation of minimum 50% Yield but if you look at some of the exchangers the operating temp can be nearly 500°C so quite a difference in yield values compared to that of ambient condition so I assume it would be best to use operating conditions as to not over stress the bolt when it reaches its operational temp

This has caused abit of discussion in the office and keen to hear your thoughts on this and what you normally do ? I quite often use table Y1 of BPVC Section 2D to obtain the yield values at operating temps and find it quite good for this ?

Cheers

Dan

Hi Dan,
The key to find your answer is follow Appendix O and determine Sb_sel following Joint Component Approach O-4.2.
Integrity of a flange joint is dependent on integrity of all the assembly components - the flange, gasket and bolt. Para O-4.2 is a stress check for all the components both at installation and operating conditions. The check is done for all the components.
Once the Sb_sel is determined, assembly bolt torque can be easily found.
What will you do if the flanges are SS and operates at 500 C in which case the YS will drop significantly? Will you still go the bolt material rule? You need to assess the joint as one assembly and not on bolt alone.

 

[r6155]

The problem is the lubricant for 500 C if torque is used.

 

[A8yssUK]

I always miss the good arguments.... FYI I am a flange gasket expert, I've seen and tested every conceivable way to apply load to a gasket..

Franky r6155 is right, but so is XL83NA etc... hence why the PCC-1 allows for torque control of flanged joints. In a perfect world all the joints would be hydraulically loaded with a nice calibrated load cell under each bolt

Also, the bolting friction factor at 500°C is irrelevant, as you are torquing at room temp...

I would answer the OP, but I assume they ran off at least 2 weeks ago

but please @r6155 You state that using the same torque values for long and short bolts is crazy, could you point me to a direction as for why ?

 

[r6155]

@ A8yssUK​

If you are a flange gasket expert, then why not read ASME PCC-1 2022?.The answer is here.
You said: “Also, the bolting friction factor at 500°C is irrelevant, as you are torquing at room temp.”

The lubricant is present at 500 C, did you consider that corrosion could occur?

 

[mfgenggear]

You have no information on my background and experience. Better be professional on this forum.

I helped by disputing your claim that you failed to justify technically. No one uses vernier calipers during fabrication and on-site for flanges. We've used UT measurements alongside hydraulic tensioners. Torquing is extensively used on site and during fabrication. No one will bother measuring elongation on the hundreds of thousands of bolts on a plant if that can be addressed by proper torquing or hydraulic tensioning pressure conversion charts.

Please advise the procedure for hydraulic tensioning. I did not know it existed.

 

[mfgenggear]

Yes I agree with those
It really matters on the application and intent.
There situations high stress high load elongation is required. However if torquing is satisfactory
And is more cost effective well it's more cost effective.

 

[XL83NL]

@ A8yssUK​

If you are a flange gasket expert, then why not read ASME PCC-1 2022?.The answer is here.

You keep on saying and saying this r, not only in this post, but also several other posts. Yet, you never provide a decent argument. When questioned, you mention you're not a tutor. That may be true, but nog giving answers means you don't seem to be competent either.

You said: “Also, the bolting friction factor at 500°C is irrelevant, as you are torquing at room temp.”

The lubricant is present at 500 C, did you consider that corrosion could occur?

There are plenty good anti-seizes that work at (and far above) 500 C. Nothing special. True, corrosion should be considered during selection of applicable anti-seize ..

 

[r6155]

I'll show you the way to learn how to assemble bolts.
If you don't put in the effort to understand the basic principles, I can't do any more for you.
You need to study further to understand it without help.
I don't care what you think of me.

 

[mfgenggear]

I'll show you the way to learn how to assemble bolts.
If you don't put in the effort to understand the basic principles, I can't do any more for you.
You need to study further to understand it without help.
I don't care what you think of me.

We are human beings and have we pride.
I don't have access to specifications.
If you provide a screen shot of the specification I would be grateful

 

[r6155]

Joints assembled with strong, long bolts are MORE FLEXIBLE than those assembled with short bolts, and two-flange joints are more flexible than single-flange joints. A more flexible joint will withstand more abuse, such as differential thermal expansion loads. Stronger bolts also permit higher assembly loads if needed.

 

[mfgenggear]

Joints assembled with strong, long bolts are MORE FLEXIBLE than those assembled with short bolts, and two-flange joints are more flexible than single-flange joints. A more flexible joint will withstand more abuse, such as differential thermal expansion loads. Stronger bolts also permit higher assembly loads if needed.

That makes sense. Longer bolts will have more % of elongation. Thus measuring the preload more exact. Give me more.

 

[mfgenggear]

well learning is a continuous improvement
we can never say we know it all.
torque vs elongation is been hashed out
over and over.
this video details the questions of shear loads, tensile loads or both.
I have learned much from engineer's posting on this platform.
this one video touched on it
and it's very important subject concepts

 

[r6155]

Be careful with this video: studs are not mentioned.
I've never used bolts on pressure vessels; I use studs.
There are many examples using bolts on block flanges (Figure UG-34 (p), Figure UG-40 (a-1), (a-2)): INCORRECT