khaldacompany
Petroleum
if i have 20" sch 60 , its nominal thickness is 20.6 mm and i measure it find it 25mm . why its thickness be increased its nominal hickness
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
about manufacturer's tolerance of the wall thickness of pipes,fitting
- Thread starter khaldacompany
- Start date
- Status
khaldacompany
"why its thickness be increased its nominal hickness"
Because to routinely achieve the exact nominal thickness to within even typical machine shop measurement techniques would be prohibitively expensive.
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:
"why its thickness be increased its nominal hickness"
Because to routinely achieve the exact nominal thickness to within even typical machine shop measurement techniques would be prohibitively expensive.
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:
gr2vessels
Mechanical
khaldacompany,
Most likely the 20" sched 60 pipe is not what you have specified, but it is a higher schedule like Sched. 80, with some undertolerance. The maximum tolerance for sched 60 pipe wall thickness would only allow for 20.61 x 1.125 = 23.19 mm, much less than 25 mm you have measured, I assume. If the pipe came with a certification claiming sched 60, when it is obviously a higher schedule, I would question the rest of the details also, including the composition and other relevant details. It sounds like a typical Chinese delivery...
cheers,
gr2vessels
Most likely the 20" sched 60 pipe is not what you have specified, but it is a higher schedule like Sched. 80, with some undertolerance. The maximum tolerance for sched 60 pipe wall thickness would only allow for 20.61 x 1.125 = 23.19 mm, much less than 25 mm you have measured, I assume. If the pipe came with a certification claiming sched 60, when it is obviously a higher schedule, I would question the rest of the details also, including the composition and other relevant details. It sounds like a typical Chinese delivery...
cheers,
gr2vessels
DiplingAndre
Petroleum
First Question must be the Spec/Standard acc.the pipe is produced!
When the pipe is produced for e.G. acc. ASTM A 358 then you don't have a over tolerance.
You can only argue with the tolerances of the plate.
When the pipe is produced for e.G. acc. ASTM A 358 then you don't have a over tolerance.
You can only argue with the tolerances of the plate.
The following may be the reason:
(1)Most pipe specs, ASME B16 in particular, give a manufacturing tolerance of +/- 12.5%
(2) It coud also be that you did not identify the schedule of the pipe correctly.
(3) Most impotantly, the calibration of the tool used in carrying out the measurement might not have been correct or the tool might have been calibrated using a material having a grade different from that of the pipe and/or under a different environmental condition(temperature).
If the measuremnt was carried out using a UT set, the temperature of the material and that of the surrounding will have a significant effect on the measurement result.
Also the operators skill have effect on the end result(especiall ability to align probe properly).
Another thing that could affect the result is the measuring range of the instrument and its operating conditions.
(1)Most pipe specs, ASME B16 in particular, give a manufacturing tolerance of +/- 12.5%
(2) It coud also be that you did not identify the schedule of the pipe correctly.
(3) Most impotantly, the calibration of the tool used in carrying out the measurement might not have been correct or the tool might have been calibrated using a material having a grade different from that of the pipe and/or under a different environmental condition(temperature).
If the measuremnt was carried out using a UT set, the temperature of the material and that of the surrounding will have a significant effect on the measurement result.
Also the operators skill have effect on the end result(especiall ability to align probe properly).
Another thing that could affect the result is the measuring range of the instrument and its operating conditions.
- Status
Similar threads
- Question
- Question