Hydrostatic Testing of Piping or Pipelines | Design and Engineering (2023)

This blog gives you brief information regarding, hydrostatic testing of piping or pipelines. This covers Scope of Hydrostatic Testing of Piping or Pipelines, test procedure, test duration, test pressure, equipment’s required for hydro test, acceptance criteria for hydro test, test reports etc.

In addition to above this covers basic information regarding minimum requirement of supply, works and operations to be performed by the Construction contractor for hydrostatic testing of cross country pipeline transporting high pressure.

Brief of Hydrostatic Testing of Piping or Pipelines:

Hydrostatic test to be performed on the entire length of the pipeline in accordance with approved Hydrostatic Test Diagrams for each test section. The length of each test section to be decided according to site requirements, but limited to a maximum of 1 KM. However the test gap between successive reach should not exceed one pipe length.

For pipeline sections which in Owner/Consultant’s opinion, once installed would require an inordinate amount of effort for repair in case of a leak, a provisional pre- test to be carried out after installation, such pre-tested sections to be tested again along with the entire pipeline.

Hydrostatic test to commence only after mechanical and civil works completion. i.e. after all welds have been accepted and the pipeline has been laid and backfilled according to the specifications. Hydrostatic test to include those sections, which have been previously tested, viz. Rail/ road crossings and major water crossings. The Construction contractor to perform all works required for hydrostatic testing.

The pipeline to be tested in accordance with the requirements of the applicable codes and requirements of this specification.

On successful completion of pretest the pipe section to be coated, laid in trenches and backfilled.

Final hydrostatic test to commence only after all mechanical and civil works are completed, i.e. all welds have been accepted and the pipeline has been laid and backfilled according to the specifications. Hydrostatic test to include those sections which have been previously tested. Interconnecting weld joints of pre tested lengths and portions of pipeline not previously tested to be kept exposed during the final hydrotesting.

The duration of hydrotest to be minimum 24 hours after stabilization.

It will be the responsibility of the construction contractor / to provide all facilities viz., pumps, water, bolts, gaskets, flanges, pipes, pressure gauges, etc. for the testing.

Vents and drains to be provided wherever necessary to avoid air trapping and for easy draining.

Water from the tested pipes to be drained to a location minimum 25 mts away from the trench. In no way to be this water flow in to the trenches.

Hydrostatic Testing Procedure:

Every construction company is preparing test procedure manual as a construction contractor, for Owner or client before starting hydro testing. This test procedure manual includes all temporary materials and equipment, as below.

For the systems to be tested, a diagram indicating lengths, elevations, all fittings, vents, valves, temporary connections, relevant elevations and ratings. The diagram to also indicate injection locations and intake and discharge lines.

Estimated amount of test water, water sources, including required concentration of corrosion inhibitor and additives, procedure for inhibitor injection and control of concentration.

Filling and flushing procedures, test medium, fill rates; line volume including a complete description of all proposed equipment’s and instruments, their location and set up.

The procedure adopted for cleaning and air removal.

Procedure for leveling and stabilization after filling and for pressurization and to allow for temperature stabilization.

Pressure testing procedure including a complete description of all proposed equipment and instruments, their location and set up, and proposed system for observation and recording of data during the pressure test.

Procedure for detection and location of leaks.

Procedure for dewatering the pipeline sections after testing, disposal of test medium including a complete description of all proposed equipment and instrument, their location and set up.

Safety precautions and procedures.

Forms for recording the test data.

Test Duration and Test Pressure:

The duration of hydrostatic test will be minimum 24 hours after stabilization and the test pressure to be 1.5 times the design pressure.

Equipment’s and Instrumentation required for Hydrostatic Testing:

The Construction contractor is furnishing all necessary equipment for performing the work as stated in the test procedure for cleaning, flushing, filling, leveling, stabilizing, testing and dewatering.

This includes, the following equipment’s and instruments.

Equipment’s for filling, cleaning and gauging.

Fill pumps

Variable speed positive displacement pumps equipped with a stroke counter to pressurize the line with a known stroke and capable of exceeding the maximum test pressure.

Two positive displacement meters to measure the volume of water used for filling the line. These meters to be provided with a calibration certificate not older than one month.

Portable tanks of sufficient size to provide a continuous supply of water to the pump during pressurizing.

Bourdon pressure gauges of suitable pressure range and accuracy.

Dead weight testers with an accuracy of 0.01 bar measuring in increments of 0.05 bars provided with a calibration certificate not older than one month.

Two 48 hours recording pressure gauges with charts and ink gauges tested with dead weight tester prior to use.

Pressure recording charts.

Communication equipment suitable for a continuous connection between the beginning and the end of the test section and with the inspection team along the line, in accordance with the requirements of Local Authorities.

Hydrostatic Testing Procedures:

Equipment and/ or parts which need not or must not be subjected to the test pressure, or which must not be tested with water, must be disconnected or separated from the pipeline to be tested.

If the difference of minimum and maximum atmospheric temperature should cause thermal instability on the pipe section directly exposed to atmospheric condition, such above ground pipeline to be properly protected.

The water to be used for testing to be of good quality, not contaminated and free from mud and silt. Construction contractor to submit Laboratory test reports of water used for testing, if required. The river water may be used subjected to the degree of cleanness, the possibility of obtaining a pre determined salinity neutralization and the use of corrosion inhibitors. Construction contractor to provide corrosion inhibitors, oxygen scavengers and bactericides to be added to the test fluid. The Construction contractor to supply and install all temporary piping required for the testing.

Before filling operation, the construction contractor to clean the pipeline by suitable method to remove all mill scale, rust/ sand, debris etc. from the pipe section.

After cleaning the pipeline by suitable method the whole length of pipeline to be filled with water without inhibitor. Air vents to be kept closed at the start of filling to allow pressures to build up.

The pressurization to be performed in the presence of Owner/Consultant at a moderate and constant rate not exceeding 2 bars/min. One pressure-recording gauge to be installed in parallel with the dead weight tester. Volume required to reach the test pressure to be recorded periodically throughout the pressurization.

After the section has been pressurized test pressure to be held for a minimum of 24 hours after stabilization. After temperature and pressure has stabilized, the injection pump to be disconnected and all connections at the test heads to be checked for leakage. The pressure recorders then be started with charts in a real time orientation for continuous recording throughout the test.

Hydrostatic Testing of Piping or Pipelines | Design and Engineering (1)

Acceptance Criteria for Hydro Testing:

The hydrostatic test to be considered as positive if pressure has kept a constant value throughout the test duration, except for change due to temperature effects

If test section fails to maintain the specified test pressure after isolation, construction contractor to determine by search the location of leakage or failure. All leaks and failures within the pipe wall or weld seam to be repaired by replacement of entire joint or joints in which leakage or failure occurs. In those cases where leaks occur in circumferential welds, the Owner/Consultant to determine the method of repair.

Construction contractor to comply with instructions of the Owner/Consultant whether to replace a section of the pipe that includes the line leak or whether to repair the circumferential weld. This repair should, however, meet the requirements of specification for welding pipelines and testing. Where failures occur in pipeline field bends, bends to be replaced with same degree of bends. After completion of repairs, the hydrostatic test to be repeated in full as per this specification.

Normally All costs towards the repair is in account of constructioncontractor

Construction contractor to haul and stockpile all damaged and defective pipes to storage locations designated by the Owner/Consultant, all cracks and splits resulting from failure to be coated with an application of grease to preserve the characteristics of failure from corrosion. Joint of failed pipes to be marked with paint, with a tag indicating failure details, date and location of failure and pressure at which failure occurred.

Termination of Hydro Testing:

After the positive results of testing and all the data have been gathered, the test to be terminated.

All vents to be opened and the pipeline to be slowly depressurized at a moderate and constant rate.

Construction contractor to dewater the tested line as per the relevant standards. The dewatering procedure to be furnished by the construction contractor.

During dewatering, care to be taken to properly dispose the discharging water in order to avoid pollution, damages to fields under cultivation and/of existing structures and interference with the traffic.

Upon completion of the testing and dewatering operation, all temporary installation relating to the test to be removed. Subsequently the individual sections of the line already tested to be joined in accordance with the requirements of relevant specifications issued for the purpose.

Hydro Test Report:

A complete report signed by construction contractor to be submitted upon completion of the hydrostatic test for each test section.

This report to contain as a minimum.

The cleaning, flushing, filling and testing procedure used.

Schematic layout of cleaning, filling and testing facilities.-Instrument calibration certificates

Profile of the pipeline showing the test sites, instruments and injection connections

Pressurization and stabilization records

Pressure recording charts with appropriate information inscribed thereon.

Dead weight tester logs and recording.

Environmental data.

Depressurization logs and records.

Dewatering procedure and schematic layout of relevant facilities.

Dewatering logs and records.

Records and photograph of all leaks.

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