Based on API 650 Para 8.6 Vacuum Testing.
8.6.1. Vacuum testing is performed using a testing box
approximately 150mm (6in) wide by 750mm (30in) ling with a clear window in
the top, which provided proper visibility to view the area under inspection.
During testing, illumination shall be adequate for proper evaluation and
interpretation of the test. The open bottom shall be sealed against the tank
surface by a suitable gasket. Connection, valves, lighting and gauges as
required, shall be provided. A soap film solution or commercial leak
detection solution applicable to the condition shall be used.
8.6.3 A partial vacuum of 21 Kpa (3lbf/in², 6 in Hg) to 35 Kpa
(8 Lbf/in², 10 in Hg) gauge shall be used for the test. If specified by the
purchaser, a second partial vacuum test of 56 Kpa (8 lbf/in, 2/16 in.Hg) to
70 Kpa (10 lbf/in, 2/20 in.Hg) shall be performed for the detection of very
small leaks.
8.6.5 The vacuum box test shall have at least 50mm (2 in) overlap
of previously viewed surface on each application.
8.6.8. The vacuum shall be maintained for the greater of
either at least 5 second or the time required viewing the area under test.
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