(1) PPR pipe inspection method Appearance inspection: u […]
(1) PPR pipe inspection method
Appearance inspection: uniform color, the inner and outer surfaces of the pipe should be smooth and flat, without dents, bubbles and other surface defects affecting performance. The pipe should not contain visible impurities and should be opaque.
Longitudinal retraction rate: The ppr pipe sample of the specified length was placed in an oven at 135 ± 2 ° C for the specified time. At 23 ± 2 ° C, the distance between the marked lines before and after the sample was placed in the oven was measured. When sampling, the minimum length of the sample is 200mm. Take a sample from each of the three pipes. Use a scriber to draw two circumferential markings on each sample with a distance of 100mm, so that one of the markings is at least 10mm away from one end. The oven temperature was then adjusted to 135 ± 2 ° C and the sample was placed in an oven so that it did not touch the oven wall or oven bottom. After the time required for the test is reached, the sample is taken out of the oven and placed flat on a smooth surface. When fully cooled to 23 ± 2 ° C, the maximum and minimum distance L between the two markings is measured along the bus. Finally, the arithmetic mean of the three-stage sample is obtained as the longitudinal retraction rate of the pipe.
Hydrostatic test: After the sample is adjusted by the state, it will remain leak-free and crack-free after a specified period of time under the specified constant hydrostatic pressure. When the sample diameter DN≤315mm, the free length L0 of each sample between the two sealed joints shall not be less than three times the outer diameter of the sample, but the minimum shall not be less than 250mm; when the pipe DN>315mm, the minimum freedom Length L0 ≥ 1000mm. Then, the state-adjusted sample is clamped by the clamp, connected with the pressurizing device, and the air in the sample is removed, and then used between 30s and 1min according to the material, size and pressure equipment of the sample. Apply the test pressure to the set pressure value evenly and smoothly as short as possible. When the test is completed, observe whether the sample is leaky or cracked. If it is, it is unqualified. If it is not, it is qualified.
Simple beam impact test: sampling on ppr pipe of the same specification, the pipe with outer diameter less than 25mm is the whole pipe section of (100±2)mm length; the pipe of 25mm≤ outer diameter <75mm, the sample is along the longitudinal direction Cutting; tubes with an outer diameter of ≥75 mm, the specimens were cut in the circumferential direction and the longitudinal direction, respectively, for a total of 10 samples. The sample was placed in a low temperature freezer at 0 ± 2 ° C for one hour. After the sample freezing time is cut off, it is taken out of the drop hammer impact test machine for impact test. Before the test, first replace the appropriate pendulum according to the impact energy requirement, then press the “Start” button to raise the pendulum. After setting the height and stability on the spot, remove all obstacles in the pendulum ring of the woodboard machine. Turn the dial pointer to the maximum hit energy scale. Press the “Test” button, the drop hammer impacts the sample, and when the pendulum stops swinging, record the impact energy. After the test is completed, the operator is hung back to the original position and the sample is observed for damage. If the damage rate is less than 10%, it is acceptable.
(two) ppr pipe inspection precautions
Note on longitudinal retraction rate: The test time should be from the temperature of the oven to the test temperature. The oven test temperature is 135 °C; the line drawn by the scribe should be clear to prevent the line drawn at high temperature from being unclear.
Hydrostatic test precautions: The sample should be hung in a constant temperature controlled test environment. During the whole test, the average temperature difference is ±1 °C and the maximum deviation is ±2 °C. If the sample breaks, record it. The type of failure is ductile failure or brittle failure; if the specimen is damaged at a distance of less than 0.1L0 from the sealing joint, the test result is invalid, and the specimen should be retested (L0 is the free length of the specimen).
Precautions for the simple beam impact test: When measuring the sample size and measuring the remaining thickness at the notch, the arithmetic mean should be taken at each end of the notch to the nearest 0.02 mm; the energy required for the failure of the sample should be selected. Pendulum, so that the energy consumed is 10%-85% of the total energy of the pendulum; adjust the zero point of the energy dial before the test starts, so that it is in contact with the active needle when the pendulum is in the starting position, and the air strike test is performed to ensure The total friction loss shall not exceed the specified value; the impact value of the sample without damage shall not be taken as the value, and the sample may be completely destroyed or partially destroyed; if the temperature difference is less than or equal to 5 ° C, the sample is taken out from the pretreatment environment, The impact should be completed within 60s. If the temperature difference is greater than 5 °C, the impact should be completed within 10 s after the sample is taken out of the pretreatment environment.