1.Test content
A. Normal temperature leakage pressure test
B. Low temperature leakage pressure test
2.Normal temperature leakage pressure test
According to API598 specification to complete the leakage pressure test of the valve at room temperature.
test.
3. Low temperature leakage pressure test
A, low temperature medium: liquid nitrogen!
B, the test temperature: -196 ° C ° C
Test conditions: before the low-temperature test, should be completed in accordance with API598 shell strength, shell leakage, seat leakage and other pressure test at room temperature; valves and test equipment should be kept dry, dust-free, grease-free; valves should be thoroughly cleaned each component, remove grease; the connection bolts should be in accordance with the specified value of the torque for fastening.
D. Test device
As shown in the figure below, prepare blind flange, pipeline, pipe fittings, helium pressure gauge, valve, liquid nitrogen tank, thermometer, etc.
E. Test method
a. Immerse the valve in a liquid nitrogen tank, but the valve cover and packing gland are located outside the liquid ammonia.
b, keep the valve immersed in liquid ammonia to enough time to ensure that the temperature of the valve body is stable and balanced, with electric couplings on the valve body temperature measurement of various monitoring points.
c, at low temperatures, first of all with ammonia on the valve to do the pressure test test to ensure that the valve is in a good state of sealing, the test pressure for the maximum valve seat test pressure.
d, open and close the valve 20 times, and measure the torque required for the first and last switch.
e, gradually increase the pressure, has reached the maximum allowable working pressure of the product at 20 ℃ (if the valve manufacturer provides a step-by-step pressure value-added in accordance with the manufacturer's requirements, please perform); flowmeter leakage shall not exceed the standard value.
f, keep the valve open, close the needle valve, let the valve body to keep checking the packing gland, valve seat test pressure (keep 15 minutes), the body, the left and right body connections sealing, there should be no visible leakage. After the completion of the test pressure, the pressure should be slowly relieved, discharge the vent valve open.
h, take out the test valve placed in a clean, dust-free atmosphere and finishing the test process materials and equipment.
4.Precautions
A. Cryogenic frostbite protection: the operation involves the use of deep-cooled gas below zero degree, care should be taken to prevent personnel from suffering from cryogenic frostbite due to direct contact with the wave body as well as the cryogenic pipeline; the pressure test personnel must be equipped with overalls, working shoes, and antifreeze gloves. During the pressure test operation, leakage points should be checked in time; all personnel should be informed of the danger of cryogenic frostbite and the measures to be taken in case of cryogenic frostbite.
B. Helium Emission: Gaseous helium is a non-toxic, colourless and odourless gas. At average temperature, nitrogen is lighter than air, but helium can also asphyxiate when the concentration of helium is too high and replaces oxygen. People can not detect the change of gas and oxygen concentration, so it is not allowed to empty helium in closed areas or poorly ventilated locations.
C. Gas pressure safety: gas tightness test is dangerous, so the danger zone should be designated, and personnel should be responsible for guarding and hanging warning signs to prohibit the entry of unrelated personnel, and the pressure and pressure should be raised and lowered slowly to make the test pressure system to achieve equilibrium. During the pressure rise and fall, the pressure rise and fall must be paid close attention to, and overpressure is not allowed to happen.