Chemical diagram legend

The vent manholes on industrial storage tanks are generally represented using the following symbols: 1. Manhole: First, a circular mark is used on pipes and equipment to indicate a manhole. For storage tanks, manholes are generally provided on both the bottom and sides, so circular marks need to be indicated at the corresponding locations. 2. Pressure release device: Above the manhole, the pressure release device is indicated by an arrow and a rectangle. The arrow pointing to the rectangle indicates that the pressure inside the tank gradually increases; when it reaches a certain set pressure, the pressure release device automatically opens to release the pressure, thereby preventing the tank from exploding due to excessive pressure. The specific parameters of the pressure release device and other information are indicated within the rectangle. 3. Safety valve: Next to the pressure release device, the safety valve is indicated by a double arrow. The safety valve can have its release pressure set manually; when the pressure inside the tank exceeds the set value, the safety valve opens automatically to release some of the pressure, thereby preventing an explosion caused by excessive pressure inside the tank. Through the legend above, we can clearly see the vent manholes of the storage tank and the corresponding safety devices, as well as how to represent them in a PID flow diagram. .