Minimizing the pipe stress on a pump’s suction and discharge connections is important. The pipe stress should be minimized to within the pump’s allowable, which will vary depending on the pump size and model. Minimal pipe stress can be achieved by making sure the piping is correctly supported upstream and downstream of the pump. When unbolted, the pumps suction and discharge piping should not spring out in any direction and a pry-bar shouldn’t be needed to connect or disconnect the pumps suction and discharge piping.
Soft foot is also an issue that needs to be checked. A liquid ring pump should be mounted on a machined flat surface and the feet shimmed level to make sure that the mounting is not putting any forces on the pump. The pump also needs to be bolted down to the base at each of its feet and the mounting hardware needs to be torqued down to prevent the pump from moving.
After the pump and motor have been mounted and the piping connected, a final shaft alignment needs to be completed. This alignment is often done with dial indicators or a laser alignment tool. The pump’s motor can be shimmed in order to make sure that the pump and motor shafts are aligned. The pump’s coupling is not designed to be a misalignment tool and should not be treated as such.
Liquid ring pumps can be supplied with a large variety of mechanical seal flush arrangements. While most pumps utilize service liquid to cool the mechanical seals, some flush arrangements depend on an external source of water for the mechanical seals. While an external source of water for the mechanical seals helps ensure good water quality, that source of water can cause other problems. If the mechanical seal flush is run while the pump is not in service, that source of water can eventually flood the system. If a pump is restarted flooded, it can damage or destroy that pump.
Some liquid ring pump skids are supplied with a service liquid recirculation pump, which is used to help circulate the service liquid back to the LRVP. When starting a system the liquid ring pump should be started before the recirculation pump. When shutting down a system the recirculation pump should be shut down before the liquid ring pump. This helps prevent the pump from being flooded with service liquid. Systems that do not use a recirculation pump and get service liquid from an outside source often use a solenoid valve which opens and closes with the start/stop of the liquid ring pump’s motor. This is for the same reason, so the pump is not flooded with service liquid prior to being put into service. As mentioned previously, if a pump is restarted flooded, it can damage or destroy that pump.