Vacuum Systems with Pump
The operation of liquid ring vacuum pumps can be carried out in three ways:
- Without any recirculation (see Vacuum Pumps section).
- Partial recirculation
- Total recovery
In the case of the partial recirculation, the sealing liquid enters and leaves the pump as no recirculation case. After that, a part of the sealing liquid from the separator tank is recirculated to the pump and the remainining is drained. On the other hand, fresh sealing liquid is added to the system, as much as necessary to maintain the proper temperature, that is essential for the proper performance of the pump. This type of arrangement is used when sealing liquid conservation is important (the consumption of fresh water can be reduced up to 50% i, and if another liquid is used, the consumption can be reduced more than 50% depending on the vapour pressure and fluid temperature).
In the case of total recovery, there is a total recirculation os the sealing fluid. In this case, a heat exchanger (plates or shell and tubes) is added to the system in order to dissipate the heat of compression and condensation from the sealing liquid before being reintroduced into the pump. For long periods of operation and high suction pressure values, and when the system (exchanger, piping, valves, …) has an excessive pressure drop, it may be required a recirculation pump.
Additionally, there are other possibilities of vacuum systems with pump:
- Hybrid Vacuum Systems
- Total recirculation systems with air ejector
- Oil total recirculation systems
Total Recirculation with Air Ejector
An air ejector is used before the pump to reach suction pressure values lower than 33 mbar a, about 10 mbar a depending on service liquid temperature.
Oil Total Recirculation
The liquid ring fluid is oil, which is cooled before entering into the pump, with a heat exchager.