Piping Engineering / Design Blog.


Hydrostatic Test Vents and Drains –Guidelines

Posted by Antony Thomas at Tuesday, June 07, 2011

Hydrostatic test vents and drains –Guidelines

This post provides guidance for designing test vents and drains for piping systems subject to hydrostatic testing. Pneumatically tested systems do not require venting and draining for testing.

Test vents and drains are required only when the high and low points in the section of the line to be tested are not free venting and draining.  The number of test vents and drains shall be minimized. They are to be provided only if there is no other means of venting and draining the line, such as process vents and drains or appropriate instrument connections.

Test vents are not required for lines 1 ½” and smaller. Test drains are required on all lines. Valves are normally not required.

Test vents and drains shall be installed at the piping high and low points respectively. The branch shall be as short as possible. The branch shall be braced if bracing is called in standard support drawing. Vents and drains shall be closed with a blind flange or a threaded cap/plug as provided in the relevant piping class.

Normally size of test vents and drains shall be:
-          ½” for line size up to 14”
-          1 ½” for line size 16” and larger.

But it will be vary depends on the fluid, project and client.

Drain point location shall allow sufficient space underneath for temporary installation of draining facility to discharge testing liquid.

This guide states the minimum requirements to be met when developing piping design.



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Hydrostatic Test

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