Nominal size and wall thickness of the pipe
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This post was last edited by Aarontong on 2015-12-25 at 13:34. The wall thickness values listed in the pipe material grade tables confuse me. I’ll use B36.10 and B36.19 as examples here: it’s a stainless steel pipe, seamless, with an allowable stress of 110 MPa and a design pressure of 5 MPa. Algorithm 1: Use the formula selected based on the table number: Sch. = P/t × 1000. The value obtained through this calculation is 45, and the grade specified in the material table is Sch60S. However, within the specified diameter range, neither B36.10 nor B36.19 has this table number. Algorithm 2: Use the formula for calculating the wall thickness of straight pipes under internal pressure; there’s also an Excel version available on the forum at http://bbs.hcbbs.com/thread-1370178-1-1.html. By applying certain negative deviations and tolerances and checking the wall thickness table, the resulting value is still less than that corresponding to Sch40S. Clearly, this wall thickness does not take into account the pressure resulting from a 1.5 times hydraulic test. So I’m asking the experts: how exactly should the actual wall thickness of a pipe be determined?
:Lol, the better approach is to choose the second one. . After calculating, round up. . .
How should pressure test verification be carried out? Should the wall thickness be calculated using 1.5 times the pressure, plus the negative deviation, and then the larger value taken?
A pressure test is something related to pressure testing. . It has nothing to do with strength calculation, right?
When conducting pressure testing, 1.5 times the pressure should be used; otherwise, there’s a risk that it won’t hold up, right?:L
In the strength calculation, it is necessary to verify whether the material can withstand the test pressure; the allowable stress of the material must not exceed 90% of its ultimate stress. Otherwise, recalculation is required
Thank you, are there any specific guidelines mentioned for this?
Because a portion of the wall thickness actually represents allowances, such as corrosion allowance and erosion allowance, in addition to the negative deviations resulting from processing. Since the test pressure is 1.5 times the design pressure, it is definitely not sufficient if these allowances are not taken into account. . . However, since there is definitely some deviation in pipe processing, and the new pipes are not corroded, should a negative deviation also be added to the checked wall thickness?
Dear expert, may I ask what the verification standard is?