Pipe wall thickness sizing 3

[Simba12345]

Hi,

I am doing the calculations for selecting pipe wall thickness using asme b31.3.

the pipe application will be the transfer of high pressure water from a plunger pump to spray bars with atomizing nozzles. the pump has a PRV that operates at 250 bar and saftey valve is set at 290 bar.

the customer wants to use stainless steel pipes.

I am using formula (3a) "304.1.2 Straight Pipe Under Internal Pressure"

it is a seemless pipe with material grade is TP316L spec no A312. (alowable stress is 16700 psi)

working temperature 20-30 C.

1st question is that what design pressure do i use? 250, 290 or higher?

I have done the calculations using 300bar as the desing pressure and the biggest pipe OD that i could find to work was 1 inch pipe sch80s with OD of 1.315.

Follow up question, how are the bursing pressures in ASTM a312 stainless steel pipes chart calculated? when should that chart be used.

difference between desing pressure and bursting pressure?

sorry i have been looking at all the different information and am a bit confused.

 

[GBTorpenhow]

Design pressure should be at least the relief valve set pressure of 290 bar.

Design pressure is the maximum working pressure for your particular system, this determines the wall thickness etc. requirements for the piping per the relevant piping code.

Burst pressure listed in an ASTM spec is probably the pressure that will theoretically cause failure given the minimum tensile strength pipe per grade/size/thickness. This does not consider the relevant piping code (is likely far less conservative), and can be disregarded or considered as reference information only as the piping code should limit you to pressures well below the burst pressure.

 

[EngrPaper]

Confirming the above on a design pressure at a minimum of 290. Design pressure, and its coincident design temperature, are the physical scenarios the pipe will experience that result in the greatest wall thickness/rating. Burst pressure is not a factor.

 

[LittleInch]

Design pressure is set by the client or process engineer or is written into a piping schedule.

You should not / cannot be guessing or assuming this - this is a key fundamental design issue which needs to be clearly stated in a design basis or data sheet.If the rest of the system is designed to lets say 400 bar, but your pipe is only designed to 290, then you've got a problem.

A quick look tells me that people do make SS pipe in Sch 160S or XXH wall thickness at 1" and above. So ther eis no limit.

As others say, the "burst pressure" is meaningless in terms of design and I don't know why anyone would publish this as you would well into the plastic zone of a metal before this and the results are very indeterminate. So I would never use this chart.

 

[mfgenggear]

I am not an expert at piping , how ever I use to manufacture, ndt and hydrostatic test.
manufactured pipe would be tested to 1000 psi, verify for leaks and integrity.
surly this will depend on the material certification.

 

[EdStainless]

You said that 1 sch80 would work, did you calculate that with the 0.156" minimum wall?
You need to account for tolerances.
You can get larger and heavier pipe.
Burst pressure just provides a frame of reference.
Your design pressure should be <1/3 of the burst.
Often design turns out to be 1/5 of the burst.
It depends on materials and sizes.

 

[mfgenggear]

Some where in the specifications raw pipe manufacturing required min burst pressure with nitrogen. So there was a safety factor. One time test for a lot of pipe.

 

[GD2]

Hi,

I am doing the calculations for selecting pipe wall thickness using asme b31.3.

the pipe application will be the transfer of high pressure water from a plunger pump to spray bars with atomizing nozzles. the pump has a PRV that operates at 250 bar and saftey valve is set at 290 bar.

the customer wants to use stainless steel pipes.

I am using formula (3a) "304.1.2 Straight Pipe Under Internal Pressure"

it is a seemless pipe with material grade is TP316L spec no A312. (alowable stress is 16700 psi)

working temperature 20-30 C.

1st question is that what design pressure do i use? 250, 290 or higher?

I have done the calculations using 300bar as the desing pressure and the biggest pipe OD that i could find to work was 1 inch pipe sch80s with OD of 1.315.

Follow up question, how are the bursing pressures in ASTM a312 stainless steel pipes chart calculated? when should that chart be used.

difference between desing pressure and bursting pressure?

sorry i have been looking at all the different information and am a bit confused.

The Safety valve is set at 290 Barg which is equal to the MAWP or Design Pressure of the Pump. Pump manufacturer has set it based on the design of the pump.

For the piping, you need to first determine what should be the design pressure. This will be based on the MOP you need. If the PRV had been set at MOP (PRV may be set at just one set of operating pressure , not necessarily MOP), the design pressure will be say 250 Barg + 10 Barg = 260 Barg. You can else do a back calculation from the spray nozzle bar (check the rating of the bar) to determine MOP.

Determine pipe wall thk based on this pressure. You might get appreciable cost savings if you run a long piping.

You might have to install another PSV for the piping section set at 260 Barg.

Once you have determined the Wall thickness, you can determine the Burst Pressure using the hoop stress equation with SMTS (Specified Minimum Tensile Stress) value of the pipe material at test condition.
P=[2(SMTS)t]/D.

 

[Snickster]

I have performed calculations for 1" to 1 1/2" Sch 80 to XXS for safety relief valve set point of 290 barg attached. For non-threaded pipe Sch 80 is satisfactory for 1" but not for 1 1/4" & 1 1/2". For threaded pipe XXS is required due to thread allowance. Calculation did not consider a corrosion allowance.

At the right of the calculation there is indication if the wall thickness is satisfactory for threaded or SW/BW.

 

[Simba12345]

thank you all for the great explanations and for your time i really appreciate it. Definetly helped clear a lot of thing.

 

[Asisraja D]

Hi
i have tried your calculation in my excel sheet as per 304.1.2 straight pipe under internal pressure

i get the values of minimum wall thickness tm=7.95mm for 1" Grade TP316L Spec.No A312. I Took 300 bar as design pressure.

 

[Snickster]

Hi
i have tried your calculation in my excel sheet as per 304.1.2 straight pipe under internal pressure

i get the values of minimum wall thickness tm=7.95mm for 1" Grade TP316L Spec.No A312. I Took 300 bar as design pressure.

If you use 290 barg, S value=16.7 and zero corrosion allowance you will get 0.15 inch min. wall just like my calc. - without thread allowance.

 

[LittleInch]

A few things.

1) Don't mix units like you've done. Use the exact units written in B 31.3.
2) Why have you added 3mm CA for a stainless steel pipe?
3) S value for you is not 20 ksi, but 16.7

wt with 0mm CA is now 0.155 in, within the wt for sch 80S

That spreadsheet is set up for A106 c Stl pipe.

 

[Asisraja D]

That spreadsheet is set up for A106 c Stl pipe.

yes. i prepared it for CS but we can use it for SS too if we give the correct data.

S value for you is not 20 ksi, but 16.7.
You are right. i corrected it now.

then it is 0.155 inches (3.939mm).

Thanks for correcting me.

 

[Asisraja D]

LittleInch
i have an doubt. i got 0.155 inches calculated wall thickness and if i select sch 80 then it shows 0.179 inches which one would i choose for purchasing ? can you bit explain me about the usage of the calculation ?

​

 

[LittleInch]

In theory you can specify any thickness you want, but in reality everyone supplies the wall thicknesses listed in ASME B 36.10/19. Not that some wall thicknesses are more common than others, but Sch80S should be commonly available so you usually just choose the next size up from your calculated thickness. In this case 0.179" / 4.55mm

NOTE. stainless schedules are different to B 36.10M - Use ASME B 36.19 or just google it. In this case the wall thicknesses are the same, but it is called schedule 80S

e.g. https://www.engineeringtoolbox.com/steel-pipes-dimensions-d_43.html or

https://vmsteel.com/wp-content/uploads/2020/04/wall_thickness_table.pdf

This is usually where you use the much thinner walls like sch 5S or 10S, which no one uses in Carbon steel as its too thin.

Contrary to my previous post, I think no one makes anything thicker than sch 80S in stainless in standard form. If you pay for it you can probably get anything, but it will cost a fortune, especially for a short length.

 

[Asisraja D]

LittleInch​

Thank you.

 

[Snickster]

That spreadsheet is set up for A106 c Stl pipe.

yes. i prepared it for CS but we can use it for SS too if we give the correct data.

S value for you is not 20 ksi, but 16.7.
You are right. i corrected it now.

then it is 0.155 inches (3.939mm).

Thanks for correcting me.

It is 0.15 inches if you use 290 barg instead of 300 barg.

 

[EdStainless]

You go to the specification that you will use for the pipe, such as A312.
And then look at the allowed tolerances.
And you see that the under tol is 12.5%.
So if you order 0.179" nominal wall you will have a 0.156" minimum wall.
We used to custom make welded pipe and tube to all kinds of wall requirements.