Liquefied gas tank testing steps
In order to avoid the explosion of mixed gas before the tank is put into production or when the shutdown is over, it is necessary to carry out the replacement work before the above operations.
1, N2 replacement
1.1 Open the tank vent valve to vent the liquefied gas remaining in the tank. When the pressure drops to about 5000 Pa, close the vent valve. So that the pressure inside the tank is maintained at 3000 ~ 5000Pa (in this particular emphasis should be placed on the tank to prevent zero pressure or negative pressure).
1.2 Open the N2 cylinder valve, decompression valve after decompression, into the replacement pipeline, a nozzle in front of the exhaust port, the air line to exclude. After sampling analysis, when oxygen content <1% is qualified, close the exhaust valve.
1.3 open a nozzle at the valve so that N2 into the tank, in order to minimize the dilution of the mixing effect of replacement, and as little as possible to agitate the tank of the original gas, the general should be replaced tube diameter as much as possible to shorten Replacement time, and control the speed of N2 in the tube to 0.6 ~ 0.9m / s is appropriate.
1.4 open b nozzle mouth valve replacement operation, the operation should control the valve opening, the pressure inside the tank is always maintained within the range of 3000 ~ 5000Pa.
1.5 Timed measurement and recording b Liquefied gas and oxygen content at the nozzle, according to the two contents of the situation, adjust the discharge valve opening and replacement time.
1.6 sampling port sampling, when the liquefied gas content below the lower limit of the explosion limit, and the oxygen content of less than 1% index, the replacement of the tank N2 is qualified (based on two test results), and by the relevant inspection unit confirm.
2.1 using the blower b nozzle will be sent to the tank, N2 purged by a nozzle, so that maintenance personnel can open the tank overhaul.
2.2 purge process should be regularly detected a nozzle at the oxygen content, when the oxygen content reached 21% indicator, the tank replacement operation that is qualified air.
Into the tank overhaul
3.1 After opening the tank should once again oxygen content and liquefied gas content of the test, the two indicators should be qualified before entering the tank.
3.2 Because residual liquefied gas in tank wall rust layer can not be completely replaced, it is still volatilized continuously after purging. Therefore, the combustible gas content should be monitored at any time during operation.
3.3 into the tank staff should be equipped with anti-virus respirator, respirator intake end should be outside the tank.
3.4 tanker should be equipped with seat belts, seat belts should be at one end of the tank.
3.5 tank personnel should keep in touch with the guardian of the tank at any time, contact the tanker should be immediately pulled out to check the cause.
4. Overhaul N2 replacement
4.1 Close the manhole of the tank and other valves opened during overhaul, inject N2 into the tank through a nozzle and open the nozzle b of the nozzle to allow the air to escape.
4.2 through the test, CNC milling machine, when b nozzle exhaust gas oxygen content below the lower limit of the liquefied gas explosion limit, close the b nozzle valve.
4.3 continue to fill the N2 storage tank to maintain the pressure of 3000 ~ 5000Pa, nitrogen seal.
After the overhaul of liquefied gas replacement
5.1 Connect liquefied gas tank car, by a nozzle into the tank into the liquefied gas.
5.2 open b nozzle valve and control the opening of the valve so that the storage tank to maintain 3000 ~ 5000Pa (in this case should pay special attention to prevent zero or negative pressure tank).
5.3 When the tank after the replacement of all N2, liquefied gas replacement is qualified, the tank can be put into normal operation.