Hydrostatic and burst pressure test methods for thermoplastic pipes for liquid transportation

Plastic pipes are common fluid transport pipe materials in our daily life and are widely used in construction, municipal administration, industry and agriculture, such as building water supply and drainage, agricultural irrigation, etc. Currently, the common plastic pipes for fluid transport on the market are mainly divided into two categories: thermoplastic plastic pipes and thermosetting plastic pipes.

Currently, the commonly used plastic pipes for fluid transportation are mainly divided into two categories: thermoplastic pipes and thermosetting plastic pipes.

The plastic that has the characteristics of heating, softening and cooling hardening is called thermoplastic. Thermoplastic pipes are made from this type of plastic through extrusion processing in a pipe-making machine. Thermoplastic pipe types include polyvinyl chloride pipes, polyethylene pipes, polypropylene pipes, and polyoxymethylene pipes, etc.

Thermosetting plastics refer to plastics that can cure or have insoluble (non-melting) properties when heated or under other conditions, such as phenolic plastics and epoxy plastics. Among them, thermosetting reinforced plastics are those in which fibers and other fillers are added to increase the strength of the plastic. This not only improves the strength and heat resistance of the plastic but also reduces costs. Thermosetting reinforced plastic pipes are pipe products made from thermosetting reinforced plastics, such as fiberglass pipes.

Principle of Pressure Resistance Test for Plastic Pipes：

This test method is divided into two types: instantaneous burst test and hydrostatic pressure test.

The instantaneous burst test involves rapidly and continuously applying liquid pressure to a given section of plastic pipe sample, causing the sample to rupture in a short period of time. The pressure value at which the sample ruptures is read, and its circumferential stress is calculated.The pressure resistance test involves applying a specified constant internal pressure to a given section of plastic pipe sample over a designated period of time to observe whether the sample exhibits any signs of failure. The test pressure value and test duration are determined by the product standards of the pipe.

Preparation of plastic pipe pressure test specimens

1. There should be no visible cracks, scratches or other defects that affect the test results on the surface of the test specimen. Both ends of the specimen should be flat and perpendicular to the axis of the pipe.

2. Specimen length: Unless otherwise specified in the product standard, the effective length L of the specimen between two sealing joints should comply with ISO1167.

3. Number of specimens: Under the same test conditions, the number of specimens shall not be less than 5, or the number of specimens shall be determined according to the provisions of the product standard.

Experimental steps for the pressure test of plastic pipes

1. Install the sealing joints on the specimens, fill each specimen with liquid at the test temperature, remove the air in the specimens, and then pre-treat according to Section 4 of the test conditions and pre-treatment section.

2. Connect the specimens to the pressure device and support the specimens to prevent bending and deflection of the specimens due to the weight of the pipes and joints (the support should not cause longitudinal and radial restraint forces on the specimens).

3. Apply test pressure to the specimens

4. During the instantaneous burst test, apply pressure to the sample continuously, evenly and quickly, and start timing at the same time until the sample breaks. If the sample breaks in less than 60s, reduce the pressure speed and repeat the test until the sample breaks within 60-70s. Record the pressure and time when the sample breaks and the state of the sample's rupture.

5. During the pressure test, continuously and evenly apply the sample pressure to a given value, and then start timing. During the entire test process, keep the pressure constant, and after reaching the specified time, record the test results and the state of the sample's rupture.

6. When the damage occurs within a diameter length from the joint, if there is reason to confirm that the damage is caused by a defect in the sample itself, the sample is valid. Otherwise, take another sample and retest.