The capacity of the BOG compressor is determined according to the maximum BOG production in the storage tank. After the BOG compressor is selected, its capacity is constant. If the amount of air sucked is greater than the amount of BOG generated in the tank, the tank pressure will drop. When the tank pressure drops to a certain level, in order to compensate for the lack of air volume at the BOG compressor inlet, the following two measures can be taken:
1. The secondary outlet gas phase of the BOG compressor returns to the inlet flash tank D~2, and the control loop part of the valve PV-2 is controlled by the D-2 pressure P-2. Here, the set value of P-2 is 300KPa. If the pressure of D-2 is higher than this value, the valve PV-2 will be closed. If the pressure of D-2 is lower than this value, the valve PV-2 will be opened to return the gas phase.
2. The intake air volume can be reduced by unloading the BOG compressor inlet, that is, the BOG compressor capacity is reduced from 100% to 50%. For Diaphragm-type unloaders, the inlet air valve unloader operated by instrument air restricts the free movement of the valve plate, keeping the inlet air valve open. Since the inhaled gas is not compressed and is discharged back to the inlet. In this way, if one end of the double-acting cylinder (cylinder end or crankshaft end, generally the cylinder end) is unloaded, the capacity of the compressor becomes 50%, and if both ends are unloaded, it becomes 0%.
Lubricating oil can be called the blood of the compressor. It can lubricate various components, reduce wear and tear, reduce the temperature of components, and also play a role in sealing, vibration reduction, and rust prevention. The BOG compressor is equipped with a special lubricating oil pump, and the oil pump must be started before starting the compressor. To ensure the normal operation of the compressor, there are strict requirements for the pressure and temperature of the lubricating oil. The high oil temperature report value is set to 55°C, and the low oil pressure report value is set to 0.175MPa. If the corresponding indicators are exceeded, the system will Pre-alarm.