WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
(OP)
I'd like to determine pipe wall thickness, may I know I should consider design conditions like design pressure, design temperature only or should I take hydro test (1.5 times design pressure) pressure in order to determine the pipe wall thickness?
This is to be used in skid fabrication were hydro testing will be done for 24 hrs @ 1.5 times design condition.
On which criteria we have select suitable wall thickness?
This is to be used in skid fabrication were hydro testing will be done for 24 hrs @ 1.5 times design condition.
On which criteria we have select suitable wall thickness?





RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
Use formula provided in 304.1.2 and Table A-1
Code also says piping should be designed for bending stress and other dynamic loads apart from internal pressure
Kindly go through the ASME B 31.3
After designing as per code, now check the pressure of Hydrotest and compute values and verify, if your design can not able to withhold hydro pressure, design for hydro pressure as well
Raghav
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
Yes I am designing as per ASME B31.3 process piping (formula provided in 304.1.2 and Table A-1) From my previous experiences many suggested me WT is determined only using design parameters like design pressure & temperature & not hydro test pressure. So now i am totally confused.
My inputs are material: API 5L GR.X42 pipe, design pressure 92 bars, temp 80 deg C, Line size: 48 inches, used to make Meter Skid in refinery. Corrosion allowance taken is 3mm. As per ASME B31.3 taking design pressure WT obtained is 42.6mm, By taking hydro test pressure WT obtained is 58mm, so which thickness is correct? & to perform hydro testing for 24 hrs for whole skid.
Please suggest.
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
The esteemed gentlemen above may have confused the issue a little as you did not give all the information in the first post (design code is very important in these discussions).
To determine wall thickness to B31.3 you use design pressure as this is what it says in the code. The code already allows for the test pressure without breaking the pipe therefore although 24 hours seems a little excessive.
They are correct to point out that wall thickness to resist hoop stress is the first step and you need to check that the combination of pressure, temperature expansion /contraction stress and any bending stress do not exceed the allowable combined stress, especially when you add supports into the mix. Hydrotest loads are also calculated but use a different maximum allowable stress value to the normal operating mode. This is all normally done by the stress engineer. In the majority of occurrences the wall thickness to resist hoop stress from internal pressure is the one you end up with plus any corrosion allowances.
The worst case is normally gas lines where the pipe is designed to normal operating with gas, but then when you fill it with water and pressurise, it can fail / exceed the allowable stress for hydrotest.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
first question - Yes it will
second - If you look at 5L you'll find that for welded pipe above 15mm wt, you go down to +/- 1.5mm for wall thickness tolerance. B31.3 appears to add manufacturing tolerance to the calculated thickness tmin (304.1.1), but either way it's not much at this sort of thickness.
As zdas04 says, you need to find someone to make this.
Can't work out why you're going for X42 instead of A106 B - you get no benefit for the extra SMYS - both have allowable stresses of 20,000psi and is probably a bit easier to get.
Latest edition of API 5L is now 45th, but appears to be nearly identical to the 44th version.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
RE: WALL THICKNESS BASED ON DESIGN CONDITIONS OR HYDRO TEST CONDITIONS
If you're designing to a pipeline code then you get some decent benefit from higher SMYS pipe / materials, but very little/none from the same material when you use B 31.3.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way