MIL-V-1558B
4.2.1 Sampling for qualification.
One class B valve of each type shall be submitted
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for the examination and tests specified in 4.5 and 4.6. Qualification approval of the 2 inch
size will include qualification of the 2 inch size and under. Qualification approval of the
6 inch size will include qualification of the 2-1/2 through 16 inch size.
for quality conformance inspection
4.3 Sampling
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4.3.1 All valves of the same size, type, class and operating mechanism presented at
one time shall 9be considered a lot for the purpose of quality conformance inspection.
4.3.2 Sampling for visual and dimensional examination. A random sample of valves
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shall be selected from each lot in accordance with tabl e II for the examination specified
in 4,4.1. Any valve in the sample containing one or more visual or dimensional defects
shall be rejected, and if the number of defective valves in any sample exceeds the accept-
ance number for that sample the lot represented by the sample shall be rejected.
Table II - Sampling for visual and dimensional examination
AQL (approx. ) = 1.5 percent defective.
4.4 Quality conformance inspection.
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4.4.1 Examination.
Each valve selected in accordance with 4.3.2 shall be subjected to
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the visual and dimensional examination specified in 4.5.
4.4.2 Tests.
Each valve in the lot shall be subjected to the tests of 4.6.1 through
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4.6.1.2.
4.5 Visual and dimensional examination. Valves shall be examined to determine com-
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pliance with the requirements of this specification as to material, workmanship and dimensions.
4.6 Tests.
4.6.1 Hydrostatic tests.
4.6.1.1 Assembled valves shall be tested hydrostatically with water to a pressure of
300 p.s.i. for strength and porosity with the valve open, Leakage, sweating, or visible
deformation at any point on the surface shall be cause for rejection of the valve.
4.6.1.2 Valves shall be tested hydrostatically with water for tightness on seat as
follows. Leakage under these tests shall be cause for rejection.
Class A valves:
(a) With 150 p.s.i. under the valve discs and 150 p.s.i. operating pressure
on the valve diaphragm, with the opposite side open for examination.
(b) With 150 p.s.i, over the disc and 150 p.s.i. over tthe diaphragm, with
the opposite end open for examination.
Class B valves:
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Same as class A except 250 p.s.i.
4.6.2
Control valves (main valves, pilot valves, and electrical or mechanical opera-
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tion) shall be tested for ease and speed of operation within the pressure range of 50 to
150 p.s.i. for class A valves and 50 to 250 p.s.i. for class B valves.
4.6.3 The main valve diaphragm shall be subjected to an accelerated life test consist-
ng of repeated opening and closing of the valve for not less than 2,500 cycles without
failure of the diaphragm. Reliability under repeated operations shall be determined.
4.6.4 A typical assembled unit shall be shock-tested in accordance with MIL-S-901,
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for grade A, class I, type A equipment.
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