Engineering Design of DCS System for Liquid Air Separation Plant

1. Before filling with pearlite, the water accumulated on the foundation surface of air separation unit must be removed, dried with hot air, and all manholes shall be closed. 2. When filling pearlite, all containers and pipes in the cold box should be inflated and kept at 50kPa pressure, then slightly open the valve of each meter pipeline, and all thermometers should be electrified to check whether the thermometer cable is damaged during the filling process. 3. The filled pearlite shall not be mixed with combustibles. 4. When filling with pearlite, coarse mesh or pearlite pouring device should be set at the manhole on the top of the cold box to prevent whole bag pearlite from entering the cold box. 5. After the pearlite is filled, the manhole shall be sealed.

In the process of operation, especially in the start-up and shutdown of the air separation unit, one-way force should be avoided on the instrument. During the start-up of the equipment, close the high pressure and low pressure valves firstly, then open the balance valve, and then slowly open the high pressure (or low pressure) valve, so that the measured medium can enter the positive (negative) pressure chamber of the transmitter. If the liquid is to be measured, the gas in the positive (negative) pressure chamber should be discharged from the upper vent. If the gas is measured, drain the liquid accumulated in the positive (negative) pressure chamber from the lower drain screw hole. After discharging the gas (liquid), close the balance valve, and then open the valve on the other side. When the equipment is shut down, the high pressure (or low pressure) valve should be closed first, then the balance valve should be opened, and then the valve should be closed on the other side. Someti