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Mill hydro test pressure per ASTM A530 for A106 pipes

Mill hydro test pressure per ASTM A530 for A106 pipes

(OP)
What seems to be the intend of the hydro test specified through the below, Is it not a strength test. At 2500 psi, it does not seem to be.

"22. Hydrostatic Test Requirements
22.1 Except as provided in 22.2 and 22.3, each length of
pipe shall be tested by the manufacturer to a hydrostatic
pressure which will produce in the pipe wall a stress not less
that 60 % of the minimum specified yield strength for carbon
and ferritic alloy steel pipe, or 50 % of the specified minimum
yield strength for austenitic alloy steel pipe. The test pressure
or stress shall be determined by the following equation:
P 5 2St/D or S 5 PD/2t (3)
where:
P = hydrostatic test pressure in psi or MPa,
S = pipe wall stress in psi or MPa,
t = specified nominal wall thickness, nominal wall thickness
corresponding to specified ANSI schedule number,
or 1.143 times the specified minimal wall thickness,
in. [mm], and
D = specified outside diameter, outside diameter corresponding
to specified ANSI pipe size, or outside
diameter calculated by adding 2t (as defined above) to
the specified inside diameter, in. [mm].
22.1.1 The hydrostatic test pressure determined by the
equation shall be rounded to the nearest 50 psi [0.5 MPa] for
pressures below 1000 psi [7 MPa], and to the nearest 100 psi
[1 MPa] for pressures 1000 psi [7 MPa] and above. The
hydrostatic test may be performed prior to cutting to final
length, or prior to upsetting, swaging, expanding, bending, or
other forming operations.
22.2 Regardless of pipe-wall stress-level determined by Eq
3, the minimum hydrostatic test pressure required to satisfy
these requirements need not exceed 2500 psi [17.0 MPa] for
outside diameters (see D in 22.1) of 3.5 in. [88.9 mm] or less,
nor 2800 psi [19.0 MPa] for outside diameters over 3.5 in.
[88.9 mm]. This does not prohibit testing at higher pressures at
the manufacturer’s option or as provided in 22.3.
22.3 With concurrence of the manufacturer, a minimum
hydrostatic test pressure in excess of the requirements of 22.2
or 22.1, or both, may be stated on the order.
22.4 The test pressure shall be held for a minimum of 5 s,
without resultant leakage through the pipe wall. For welded
pipe, the test pressure shall be held for a time sufficient to
permit the inspector to examine the entire length of the welded
seam."

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

It is a leak test, not a strength test.
You can't use hydro as a nondestructive strength test, if you use high enough pressures to verify strength you will be deforming the product.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

(OP)
The post fabrication hydro test of 1.5 times the design pressure can bring the resultant stress close to the yield stress.

Why is that the mill test pressure required much lesser. The term 5 in the formula is not understood.

Is a strength test a destructive test that will deform beyond the elastic limits?

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

The above internal pressure is to check for manufacturing defects which can result in through-wall leaks. It is a high pressure leak test.

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

(OP)
metengr, The mill test is at a stress of 60% of SMYS. This is nearly the allowable stress of 2/3 Sy. The pipe will only see a test pressure of 1 x design. My question is why is that a leak test of 1.5 times is required for post fabrication leak test per ASME B 31.3. The ASTM mill test is to test through wall leaks of a seamless pipe. Does it not be atleast equal to the post fabrication test pressure?

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

Ah, ok now I understand your question. ASTM and ASME are two different codes and standards bodies and, as such, do not always agree. In this case, the construction code governs with 1.5X MAWP because it is a completed, fabricated assembly hydrostatic test, and not just for pipe sticks.

RE: Mill hydro test pressure per ASTM A530 for A106 pipes

(OP)
Irrespective of what code they may be, is it not logical to think that a pipe that has passed a mill leak test should not leak a higher pressure leak test for a through the thickness defect during a leak test after fabrication. Moreover, ASTM materials are listed materials within the ASME B31.3.

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