Problems with the PLAN21 centrifugal pump
Thread Content
Dear experts, one of the side-line pumps in the pressure relief unit at my company is equipped with a mechanical seal of the PLAN21+53B type. In the 21 system, the upper water pipeline of the cooler tends to get hot, and vaporization of water often causes erosion in those pipelines. The medium pumped away is mainly diesel components at 130–370°C, with a temperature of around 150°C. The manufacturer’s current explanation is a lack of water supply, but all other pumps that use circulating water are connected through the same pipeline. I would appreciate it if the experts could provide some insights and suggestions for improvement. Thank you.
Check whether the inlet pipelines of the heat exchanger are fouled and blocked; if there is severe scaling on the shell side of the heat exchanger, clean it regularly and improve equipment maintenance. Technical upgrades can also be carried out by installing another coil-type heat exchanger, allowing one of them to be cleaned while the system is in operation
Reduce the flow of cooling water to the other pumps. It’s also necessary to check whether the cooling water comes from a main pipe and is then distributed to each pump; after entering each pump, it splits into several streams that go to the bearing housings, heat exchangers, and other components. As can be seen from the photos, there are many 90-degree elbows in the cooling water system. It is necessary to reallocate the water inflow amounts according to Layout 1 in order to reduce pipeline losses 2. 3. Remove scale. If that doesn’t work, install a pneumatic diaphragm pump to increase the water pressure (since it’s not possible to run cables and motors on-site), or discharge the water on-site or use a thicker water inlet pipe
It is recommended to connect the bearings’ water streams together before feeding them into the heat exchanger; doing this for each pump can **increase the water flow rate**. Remove the pressure difference of the inlet and outlet main pipes at the same time
The return water temperature isn’t low; it’s indeed due to insufficient water supply or too low cooling capacity. :P: It is recommended to check first whether the cooling water flow is set at the maximum level ； If it’s not already at full capacity, increase it as much as possible while keeping a close eye on the situation ； If the cooling water flow has been set to its maximum level, check the condition of the cooler: (1) If there is a blockage in the water circuit, replace the cooling water as soon as possible (desalinated water is preferred); if there is a blockage in the oil circuit, analyze whether the oil is too viscous or contains too many impurities and take necessary actions ； (2) If there is no blockage, it is recommended to replace it with a cooler with a larger heat exchange area.
Increase the water flow rate, disconnect the outlet and check the flow volume; if the valve is fully open but the flow is very low, reverse the hose connection so that the outlet becomes the inlet and use it for flushing for a while, or switch from option 21 to option 23.
From the position of the circulating water interface in the heat exchanger, it doesn’t seem like there’s any reversal in the connections. If the inlet and outlet pipes are connected correctly, then a valve should be installed at the return port of the oil cooler for draining water; by doing this, one can check two things: first, the water flow rate, and second, whether the temperature of the inlet pipeline can be reduced. If that’s possible, it means there’s an issue with the return pipe of the pump. If that still doesn’t work, or if the water flow rate is low, then it’s possible that the oil cooler is blocked, or there’s a blockage in the inlet pipe branches. It’s necessary to check each step carefully. It’s also possible that there’s an air blockage inside the water chamber of the oil cooler, or in the return water stream; in all such cases, the problem is still caused by poor circulation of the circulating water.
Insufficient heat exchange leads to high water temperature; check whether the heat exchanger is clogged or scaled, clean it, and then see if there’s an improvement.