MSHA - Code of Federal Regulations - 30 CFR 7.307
30 CFR § 7.307
Static pressure test.
(a) Test procedure. (1) The enclosure shall be internally
pressurized to a minimum of 150 psig and the pressure maintained for a
minimum of 10 seconds.
(2) Following the pressure hold, the pressure shall be
removed and the pressurizing agent removed from the enclosure.
(b) Acceptable performance. (1) The enclosure during pressurization
shall not exhibit--
(b)(1) (i) Leakage through welds or casting;or
(b)(1) (ii) Rupture of any part that affects the
explosion-proof integrity of the enclosure.
(2) The enclosure following removal of the pressurizing
agent shall not exhibit--
(b)(2) (i) Visible cracks in welds;
(b)(2) (ii) Permanent deformation exceeding 0.040 inches per
linear foot; or
(b)(2) (iii) Clearances, in excess of those specified in this
subpart, along accessible flame-arresting paths, following any necessary
retightening of fastenings.
[57 FR 61197, Dec. 23, 1992]