1. European standard tank port manhole cover structure of oil tanker: The manhole cover of oil tanker is mainly composed of a large cover, a small cover, an upper pressure plate, a lower pressure plate, and a built-in breathing valve. (as the picture shows)
2. The working principle of the European standard tank mouth of the oil tanker:
◎ Emergency exhaust: When the pressure in the tank is higher than the external pressure by 21-32KPa, an emergency exhaust will be performed to release the pressure in the tank to prevent damage to the tank. Its diameter is 252mr, and its maximum displacement is 7000L/min.
◎ Built-in breathing: When a certain pressure difference between the tank internal pressure j1 and the external pressure is formed, the breathing valve will automatically open to exhaust or breathe in to adjust the pressure difference in the tank. The maximum ventilation flow can reach 600L/min (one or two breathing valves can be installed according to user requirements).
◎ Positive pressure of breathing valve opening: 6-8KPa Negative pressure of breathing valve opening: -2—3KPa
◎ Dumping and overflow prevention: When the tanker accidentally dumps, the breathing valve will be automatically closed to prevent the oil from overflowing.
◎ Three spare openings: There are three auxiliary openings on the adult manhole cover, which can be used to install oil and gas recovery valves, anti-overflow probes, oil measuring holes or external breathing valves.
◎ Two-stage opening: When opening the upper pressure plate, the internal pressure will be released first, which plays a role of safety protection.