d) The spring pressure rating of the safety valve shall be in accordance with the requirements of the commissioning pressure.
e) The operating temperature of the safety valve shall meet the requirements of the working medium temperature.
f) The maximum actual discharge of the safety valve should be slightly greater than the maximum medium flow of the pressure source.
g) When the medium temperature exceeds 200 °C, it is better to use a safety valve that has isolation measures for the spring box.
h) The connection and size of the safety valve shall comply with the requirements of the field equipment.
i) Lever-type safety valves shall have means to prevent the weight from moving by itself and guides that limit the lever.
j) Adjustable parts of the safety valve shall have holes for easy sealing or locking.
3. Safety valve calibration
a) The safety valve must be verified before it can be installed and used.
b) Safety valve in use, verified at least once a year.
c) After the verification is passed, the safety department will record the repair contents into the safety valve repair and verification technology file card. The inspection performer and the repair personnel must sign the file card.
d) A qualified safety valve shall be sealed or locked by an authorized person (or quality inspector). And fill in the verification data and signature on the verification card.
e) The boosting speed should be slow when verifying the safety valve to prevent the pressure reading from being inaccurate.
f) Verify the pressure gauge for the safety valve with an accuracy of 0.5 or higher.
g) The pressure point of the pressure gauge for inspection shall be such that the actual pressure in the inlet cavity of the safety valve can be obtained.
h) Calibration pressure gauges are often subject to strong vibration and large pressure fluctuations. They should always be calibrated with a standard meter to avoid errors.
i) The maximum range of the calibration pressure gauge shall be 1.5 to 3.0 times the working pressure, and the index of the pressure gauge shall be less than 1% of the maximum range.
j) The opening pressure deviation is specified: when the opening pressure is ≤1.0MPa, the allowable deviation is 20KPa, and when the opening pressure is >1.0MPa, the allowable deviation is ±2% of the opening pressure.
k) When the calibration value is approved, at least two consecutive data can be coincident, and the safety valve is not allowed to be tapped.
l) The sealing pressure must be tested after returning to the seat. When the working pressure is higher than the working pressure of the equipment, it will be qualified if it is not lowered for 5 minutes.
4. Safety valve installation
a) The safety valve that has passed the inspection and is sealed shall be installed.
b) The safety valve must be fitted with a discharge pipe and led to a safe and reliable place.
c) When no liquid is allowed in the discharge pipe of the safety valve, a drain pipe shall be installed at the lowest position of the discharge pipe, and the terminal shall be led to a safe and reliable place or recovery system.
d) The safety valve should not be shaken during handling and installation, and it must not be installed with force.
e) The seal should not be damaged during installation and recalibrated if damaged.
f) The safety valve must be installed vertically. The container or pipe with gas and liquid coexistence should be installed at the position of the gas phase interface. The safety valve should not be equipped with any valves between the equipment. However, for containers containing flammable, toxic or viscous media, a shut-off valve may be installed to facilitate cleaning and replacement of the safety valve; however, the structure and diameter of the shut-off valve shall not impede the normal function of the safety valve. During operation, the shut-off valve should be fully opened and then sealed.
g) Do not connect all media outlets on the connection between the safety valve and the equipment.
5. Management of safety valves
a) The engineering department shall serially assign the safety valves to them and use steel nails on the valves (including the backup valves) to avoid confusion.
b) The Engineering Department shall establish a safety valve account and a safety valve repair file card.
c) The engineering department shall designate personnel to conduct unified management of the inspection, maintenance and spare parts planning of the safety valve, and organize the periodic verification of the safety valve.
d) The operator shall check the safety valve at the same time as the equipment is inspected according to the time required for the inspection. The inspection contents include: whether the fastener is loose; whether there is leakage; whether the seal is intact; for the lever type safety valve, it should also check whether there is any obstacle that affects the normal opening.
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