API 650 duplex stainless steel tanks roof drain valves

API 650 duplex stainless steel tanks Liquid Relief ValvesA tank, which is likely to operate completely filled with liquid, shall be equipped with one or more liquid relief valves at the top of the roof, unless otherwise protected against overpressure. When such valves are, in effect, supplementary relief devices, they may be set at a pressure not greater than 1.25 times the design pressure. Because the relief valve at the pump, which provides the inflow of liquid to the tank, is set at a pressure greater than 1.25 times the design pressure of any tank that may be built under these rules, provision should be made for preventing overfilling of the tank by a self-closing float valve, by some practicable pilot-valve control, or by any other proven device.

The tank wall design of API 650 oil storage tank. Since there is no ventilation pipe directly connected with the outside on the top of the API 650 duplex stainless steel tanks tank, the ventilation between the inside and outside of API 650 oil storage tank is realized by the respiration valve. The constant pressure of the respiration valve is 0.3kPa, so the pressure on the top of the tank is 0.3kPa.

Treatment of API 650 duplex stainless steel tanks welding defects:
1. Lack of fusion: once found, it should be shoveled and grinded off before re welding.
2. Incomplete penetration: over standard defects shall be removed and re welded. When welding on both sides, the shallow side of the groove can be grinded and shoveled to expose the welding root on one side, and then the welding is repaired.
3. Slag inclusion: over standard defects shall be removed and re welded.
4. Crater: weld to full after grinding.
5. Air hole: if the internal air hole exceeds the standard, it shall be welded again after being removed by grinding shovel, and the surface air hole shall be removed by grinding wheel and then repaired.