Pressure vessel: pressure test of hydraulic test

Test medium  

1. Hydraulic test medium is generally clean water.

2. Using austenitic stainless steel pressure vessel pressure test：control the chloride ion content of the water not more than 25mg/L;

3. Using flammable liquids for hydraulic test: the test temperature must be lower than the flash point of flammable liquids.

Test pressure

1. PT = 1.15P[σ]/[σ]t

A: Steel, non-ferrous metal and glass-lined pressure vessels: 1.25.

B: Cast iron pressure vessels: 2.0.

C: Mobile pressure vessels: 1.5.

2. When pressure vessel components of different materials, the calculation of the pressure test should take the smallest of [σ]/[σ]t ratio of the component materials.

3. External pressure vessels and vacuum vessels: test the pressure resistance test with internal pressure, test pressure: 

pT = 1.25p

 4. Hydraulic pressure test pressure should be in accordance with the provisions of the drawings.

Test temperature

1. Carbon steel, 16MnR and normalized 15MnVR steel pressure vessel: the liquid temperature shall not be less than 5 ℃, other low-alloy steel pressure vessel, hydraulic test liquid temperature shall not be less than 15 ℃. If the plate thickness and other factors caused by the material without ductile transition temperature increases, the liquid temperature needs to be raised accordingly. Other materials system pressure vessel hydraulic test temperature according to the design drawings.

2. Ferritic steel low-temperature pressure vessel: the liquid temperature should be higher than the shell material and welded joints both Charpy impact test the high value of the specified temperature plus 20 ℃.

3. According to the characteristics of the region's high humidity, in order to prevent the test metal wall condensation which affects the observation, do the hydraulic test in the summer, the hydraulic test liquid should first be stored in the hydraulic test water tank, the test liquid temperature reaches to room temperature before use.

Test method

1. The interior of the container should be cleaned before filling. Set the gas discharge outlet at the highest position of the container so that the internal air is exhausted outward when the container is filled with liquid. Only when the gas is exhausted, it is allowed to close the container for pressure test work. During the test, the vessel observation surface should be kept dry.

2. The test should be carried out slowly when the pressure is raised or lowered. When the temperature of the pressure vessel is close to the liquid temperature, slowly ramp up the pressure to 10% of the test pressure, and not more than 0.05MPa, maintain 5-10 minutes, and the test system and all the welds and connections of the container for the first check to confirm that there is no leakage before continuing to ramp up the pressure. 

After checking that there is no problem, continue to increase the pressure to 10% of the test pressure, keep it for 5-10 minutes, and carry out the inspection of the test system and all welds and connection parts of vessel again to confirm that there is no leakage before continuing to increase the pressure. 

When the pressure is increased to 50% of the test pressure, carry out the initial inspection. If there is no leakage and no abnormality, continue to pressurize to the design pressure at a rate of 0.1MPa/min. At this moment, the pressure should be stopped for inspection, and be sure that the seal is fine without leakage or abnormalities before continuing to the test pressure with a rate of 0.1MPa/min.

Holding the pressure for 30 min during testing pressure, then the pressure is reduced to 80% of the specified test pressure and held for enough time to conduct a comprehensive inspection of all welded joints and connection parts.

The pressure should be kept constant during the inspection, and continuous pressurization should not be used to maintain the test pressure.

Test pressure should be completed by slowly releasing the liquid in the container (the rate of pressure reduction is not higher than 0.3MPa / min). Shall not release suddenly. Pressure vessel hydraulic test process shall not be under pressure to tighten the bolts or external force to the pressurized components.

Pressure resistance test qualification standard

No leakage.

No visible deformation.

No abnormal ringing during the test.

The limit of the specified value of tensile strength≥540MPa material, no cracks on the surface after NDT spot checks.