Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF: RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE Flushing and Testing SPECIFICATION NO. PAGE 6 OF 9
MEC/S/05/62/11 REVISION 0
Open ends of piping system where blanks cannot be used, such as pumps,
compressors, turbines or wherever equipment or pipe spool have been
receivered or disconnected prior to hydrostatic testing, shall be blinded – off by
using standard blind flanges of same rating as the piping system being tested.
Pressure gauges used in testing shall be installed as close as possible to the
lowest point in the piping system to be tested, to avoid overstressing of any of
the lower portion of the system. For longer lines and vertical lines, two or more
pressure gauges shall be installed at locations selected by the
Engineer-in-charge. For lines containing check valves any of the following
alternatives shall be adopted for pressure testing. Wherever possible pressurise
up-stream side of valve.
Replace the valve by a temporary spool and re-install the valve after testing.
Provide blind on valve flanges and test the upstream and downstream of the line
separately and remove the blind after testing. All these flanges, temporary
gaskets shall be provided during testing and shall be replaced by permanent
gaskets subsequently. For check valves in lines 1-1/2" and below, flapper or
seat shall be removed during testing (if possible). After completion of testing the
flopper/ seat shall be refitted.
Gas lines when hydrostatically tested shall be provided with additional temporary
supports during testing as directed by Engineer-in-charge.
Piping which is spring or counter – weight supported shall be temporarily
supported, where the weight of the fluid would overload the support. Retaining
pins for spring supports shall be removed only after testing is completed and test
fluid is completely drained.
When testing any piping system, air or steam of approximately 2 kg/cm 2 (g) may
be used as preliminary test to detect missing gaskets etc. as this avoids the
necessity of purging the gas to make repairs. However, this method may not be
used for this purpose, if the steam temperature is more than the design temp. of
the line.