Hydrostatic pressure test methods and procedures of LSAW steel pipe

The hydrostatic testing of large diameter Longitudinal Submerged Arc Welded (LSAW) steel pipes involves several critical steps to ensure the integrity and performance of the pipes. Here is a detailed explanation of the process.

Hydrostatic Testing Procedure of LSAW Steel Pipe

Sealing and Initial Water Injection

End Sealing: The test begins by sealing both ends of the LSAW steel pipe using specialized sealing devices.

Low-Pressure Water Injection: Low-pressure water is injected into the pipe, with air being expelled through an exhaust valve during the filling process.

Pressurization

High-Pressure Water Injection: Once the pipe is filled with water, a high-pressure water injection device boosts the pressure inside the pipe to the required test level.

Dwell Time: The pipe is maintained at the predetermined test pressure for a specific duration. During this time, any leaks or deformations are monitored.

Decompression and Inspection

Pressure Release: If no leaks or deformations are detected during the dwell time, the pressure is gradually released.

End Seal Removal: The end seals are removed, and the low-pressure water is discharged from the pipe.

Visual Inspection: The pipe is then moved to a visual inspection station to check for any suspicious penetrations or defects.

Recording

Automated Recording: The entire pressure testing process, including the pressure curve, is automatically recorded according to the standard pressure testing procedures.

Pressure Testing Steps

Test Pressure Parameters

Minimum Pressure: The hydrostatic test pressure for longitudinal seams should not be less than 0.80 MPa. If the working pressure is less than 0.80 MPa, the test pressure is set at 0.80 MPa.

Consistency: The test pressure must not be altered during the test.

Leak Detection

Initial Water Filling: After the initial filling, all connection points (including attachments) are checked for leaks, which must be resolved before proceeding.

Segment Lengths

Maximum Length: The maximum length for pressure testing a segment of pipe is 1000 meters. For sections with fittings, the maximum length is 500 meters. Different material segments should be tested separately.

End Inspection

Secure Ends: The pipe ends must be securely inspected to ensure they are solid and reliable. Support facilities must remain intact, and valves should not be used as sealing plates during the test.

Pressure Measurement

Measurement Devices: Mechanical devices with a metering accuracy of not less than 1.5% (maximum permissible error does not exceed 1.5% of full scale) should be used. The scale range should be 1.3 to 1.5 times the test pressure, and the dial diameter should be at least 150 mm.

These meticulous steps ensure that the LSAW steel pipes meet stringent quality standards, guaranteeing their reliability and safety in various applications.