East-west Gas Pipeline Project Construction Procedure for Cleaning, Gauging And Hydro testing of Pipelines Rev.: A1 China Petroleum Pipeline Bureau（CPP） Document No.: EWPL00-COS-PR-0014 7.3 Water Treatment If the sources don?t accord with the Specification about test medium, water treatment equipment shall add to the filling system. The full filling system is shown below. 7.4 Preparations for hydrostatic test 7.4.1 Site layout
The arrangement and the layout of the test head, main equipment and the devices involved in hydrostatic test are shown in the Figure-5 .
Figure-5
7.4.2 Equipment, devices and instruments for pressure test All equipment and devices involved in hydrostatic test such as:
-Test heads
-Temporary pipe fittings and valves -Pig signalers (if required)
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East-west Gas Pipeline Project Construction Procedure for Cleaning, Gauging And Hydro testing of Pipelines Rev.: A1 China Petroleum Pipeline Bureau（CPP） Document No.: EWPL00-COS-PR-0014 shall be hydrostatically tested for at least 4 hours equivalent to 1.25 times of the pipeline strength test pressure before putting into use. All the test records shall be submitted to Engineer-in-Charge prior to water filling activity. The welding between the test head and the trunk line and the NDT shall be carried out in accordance with the relevant project document. All instruments such as:
-Dead-weight testers -Pressure gauges -Flow meters
-Pressure and temperature recording instruments and transmitters -Thermometers and thermocouples
shall have been calibrated. Calibration certificates shall be submitted to Engineer-in-Charge prior to water filling operation.
Prior to pressurization, test engineer shall calibrate all pressure gauges with a dead-weight tester. Pressure gauges and dead-weight tester are connected to the same needle valve which has one inlet and two independent outlets. 7.4.3 Pig for filling
The pig shown as below is used for water filling and dewatering. Three pigs will be preplaced in the initial test head, two for water filling and one for dewatering. Each pig is equipped with 4~6 scraper/seal discs and two guide/support discs. The discs are made of urethane.
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East-west Gas Pipeline Project Construction Procedure for Cleaning, Gauging And Hydro testing of Pipelines Rev.: A1 China Petroleum Pipeline Bureau（CPP） Document No.: EWPL00-COS-PR-0014
Figure-6
7.4.4 Test heads
The temporary test heads will be fabricated and welded accordingly to welding procedure The temporary test heads shall be tested according with Company specifications and Engineer-in-Charge shall witness the test head testing. The test pressure will be 1.25 times the maximum test pressure of the test section that the test head shall be connected to.
The Test head acceptance certificate shall be signed by Pertinent test engineer and Engineer-in-Charge. 7.5 Filling
After acceptance of gauging run, water filling shall commence. For this purpose, pre-tested test headers loaded with three numbers of batching pig shall be welded to the test section. Un-inhibited water equal to 10% of the volume of test section shall be introduced ahead of the first pig. The first batching pig shall be launched using un-inhibited water equivalent to 1.5km length of the test section. Then the second pig shall be launched using inhibited water till the second pig is received at the other end. The water current shall be maintained about 400m/hr during filling operation. The Contractor shall continuously monitor the volume and pressure and, at approximately thirty minute intervals, the temperature of the fill water during the filling operation. When it has been confirmed that the filling pigs
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East-west Gas Pipeline Project Construction Procedure for Cleaning, Gauging And Hydro testing of Pipelines Rev.: A1 China Petroleum Pipeline Bureau（CPP） Document No.: EWPL00-COS-PR-0014 have arrived in the receiving test head, maintain water flow until the exhausting water is clean, to the satisfaction of Engineer-in-Charge. After water filling, it is better that the pressure in the filled pipeline is up to 20barg. In this way, time for pressurization will be reduced and less water will be needed. The thermal stabilization and pressurization operations can commence subsequently. The Figure-5 shows the arrangement and connection of the section during filling.
If the sections locate in area that lack source, the testing water shall be supplied by tested pipeline. Water will be pushed by a plate pig is drove by compressed air.
Figure-7
7.6 Formation of Backpressure
When the water filling pig propelled by water rushes down from the top of the hill, the air in front of the pig will get into the water easily if the pig runs with an accelerating speed, as is shown in Figure-8.
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