Help for Calculate C on Miter Bend Formula

[jafary64]

I have a question for how to find or calculate C “C = Sum of mechanical, corrosion, and erosion allowances” on attached file.
I know it is on ASME “304.2.3 Miter Bends” but how to reach c: 0.05905512 in
Can anybody help me & explain it?
Thanks a lot

 

[XL83NL]

Normally, c is a given value. Based on formatting, if yellow is input, c is a given value in advance.
Refer to 304.1.1 how c is determined. If the pipe requires 12/5% tolerance on wt, you already have a c of 0.0469 in.

I would ask the engineer who made this calc, how he ended up with 0.059 in.

Huub
- You never get what you expect, you only get what you inspect.

 

[LittleInch]

First off,

Who in gods name still makes mitre bends for pipe with a design pressure of 124 psi??

These things should be consigned to the annals of history IMHO. Or used as HVAC ducting.

This calculation is where someone has gone rather berserk in transposing what is nominal thickness etc in one set of units into another one. He should have gone 0.05" or some other nominal thickness in inches. So 0.59..... is actually 1.5mm. Basically a "standard" corrosion allowance commonly used. You'll probably find it in the piping class.

Never tried these, but why is one of the calcs saying 77psig when the DP is 124?? And it's still ok??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jafary64]

XL83NL (Mechanical)18 Oct 24 12:24
Normally, c is a given value. Based on formatting, if yellow is input, c is a given value in advance.
Refer to 304.1.1 how c is determined. If the pipe requires 12/5% tolerance on wt, you already have a c of 0.0469 in.

I would ask the engineer who made this calc, how he ended up with 0.059 in.
Huub
- You never get what you expect, you only get what you inspect.

Hi
Thanks for your reply I see 304.1.1 and it says " c = sum of the mechanical allowances (thread or
groove depth) plus corrosion and erosion allowances. For threaded components, the nominal
thread depth (dimension h of ASME B1.20.1, or equivalent) shall apply. For machined surfaces or
grooves where the tolerance is not specified, the
tolerance shall be assumed to be 0.5 mm (0.02 in.)
in addition to the specified depth of the cut." I want to know 0.02 inch on ASME or 12.5% that you say which one more correct ?

 

[jafary64]

LittleInch (Petroleum)18 Oct 24 12:48
First off,

Who in gods name still makes mitre bends for pipe with a design pressure of 124 psi??

These things should be consigned to the annals of history IMHO. Or used as HVAC ducting.

This calculation is where someone has gone rather berserk in transposing what is nominal thickness etc in one set of units into another one. He should have gone 0.05" or some other nominal thickness in inches. So 0.59..... is actually 1.5mm. Basically a "standard" corrosion allowance commonly used. You'll probably find it in the piping class.

Never tried these, but why is one of the calcs saying 77psig when the DP is 124?? And it's still ok??
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Hi My friend
thanks for your attention
this line is for cooling water of sea and if you see bellow link you will be more familiar how to calculate 77 psig.

https://makepipingeasy.com/miter-elbow-or-miter-bend-design-calculations/

 

[LittleInch]

I want you to explain it.

And comment on the answer about C

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jafary64]

LittleInch (Petroleum)19 Oct 24 07:26
I want you to explain it.

And comment on the answer about C

Hi My friend
I will be appreciative for your attempt
God bless you

 

[goutam_freelance]

In my view, these values should be based on the experience of the contractor who is designing and manufacturing and of the client using the same.

For an outsider, it is very difficult to calculate or predict, though some guidance may be available in codes and standards.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[LittleInch]

C in this case is a nominal 1.5mm corrosion allowance. That's it. Nothing else to see here.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jafary64]

C in this case is a nominal 1.5mm corrosion allowance. That's it. Nothing else to see here.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Corrosion allowance is a one part of required data for calculate C according to 304.1.1 ASME B31.3

 

[LittleInch]

Then they've clearly decided the other bits are zero other than corrosion allowance.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[FMJalink]

Hi jafary64,
To my experience the actual corrosion allowance for chemical attack etc has to come from the owner/user, licencer or material expert knowing the substances going through the bend taking temperature and required lifetime in account.
Mitered bends I normally see only in case of special materials of construction or when something does not fit in an existing situation. With special materials as e.g. Titanium grade 7, the (chemical) corrosion allowance normally is as low as acceptable as such a material is expensive.
Success

 

[GBTorpenhow]

Refer to 304.1.1 how c is determined. If the pipe requires 12.5% tolerance on wt, you already have a c of 0.0469 in.

It's something of a fine distinction as it all comes out of the nominal wall thickness in the end but manufacturers minus tolerance on wall thickness is baked into T and is separate from the c allowances.

I want to know 0.02 inch on ASME or 12.5% that you say which one more correct?

As you are apparently using standard 0.375" WT pipe, neither is relevant to c. The 0.02" referenced is just a default tolerance to use for machined surfaces or grooves where the tolerance is not specified. You have no threads and no grooves or machined surfaces so c is just erosion and corrosion allowance.