Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
c:\fateh\standard\stad-eqp.wp
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE Hydrostatic Testing of Onshore Cross- SPECIFICATION NO. PAGE 8 OF 17
country Pipelines
MEC/S/05/62/03 REVISION A
7.6 Thermal Stabilization
After a check has been made to confirm if the pressure has attained at least 1 bar (g)
on the highest section, thermal stabilization can be started.
Thermal equilibrium between the pipeline and environment shall be checked through
the thermocouples installed on the pipeline.
Temperature readings shall be made at 4 hours-intervals. Thermal stabilization shall be
considered to have been achieved when a difference not higher than 1°C is attained
between the average values of the last two readings. Thermal stabilization completion
shall be approved by COMPANY.
7.7 Pressurisation
Pressurisation shall be performed in the presence of COMPANY at moderate and
constant rate not exceeding 2 bars/min. One pressure recording gauge shall be
installed in parallel with the dead weight tester. Volume required to reach the test
pressure shall be recorded periodically throughout the pressurization as follows:
- each 5 bar increments up to 80% of test pressure as recorded by the dead
weight tester;
- each 2 bar increment between 80% to 90% of test pressure as recorded by the
dead weight tester;
- each 0.2 bar increment between 90% of test pressure to full test pressure as
recorded by the dead weight tester.
The pressurizing shall be cycled according to the following sequence:
a) Pressurize to 50% of test pressure, hold pressure for 1 hour.
b) Drop pressure to static head of test section at test head.
c) Pressurize to 75% of test pressure, hold pressure for 1 hour.
d) Drop pressure to static head of test section at the test head.
e) Pressurize to test pressure.
During the pressurization to each test pressure, two tests shall be carried out for the
calculation of air volume in the pipeline under test.
In case, during the hold pressure periods indicated above, a decrease in pressure is
observed, the operations shall not be repeated more than twice, after which the line
shall not be considered capable of test, until the CONTRACTOR has isolated and
eliminated the cause for the lack of water tightness.