API standard 650 self-anchored tanks cover plates

All welded seams in the API standard 650 self-anchored tanks bottom, and complete penetration and complete fusion sidewall-to-bottom welds, shall be inspected by means of a vacuum box test as described in Q.8.2.1. Sidewall-to-bottom welds not having complete penetration and complete fusion shall be inspected by means of either a vacuum box test of the inside weld as described in API 620 specification Q.8.2.1, or where approved by the Purchaser, a direct pressure solution film test as described in Q.8.2.2.

For floating roof API 650 tanks, the net working capacity is the liquid volume contained between the API standard 650 self-anchored tanks maximum operating level (300 mm below rim for metallic type seals and 600 mm below rim for fabric type seals) and the minimum operating level (API 650 tanks roof supports clearing the tank bottom by 25 mm while set at the operating position).

Under the condition of static storage without receiving and sending operation, the temperature of gas space, evaporation rate, depth and pressure of vapor in the API standard 650 self-anchored tanks will change with the change of temperature and pressure in a day. The oil loss caused by the process of discharging oil vapor and inhaling air gas is called "small breathing" loss, which is also called static storage loss of oil tanks.