Regarding the issue of one pump in use and one as backup
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At the site, many pumps are operated in a one-in-use-one-backup configuration, with identical model specifications; however, often one of the pumps develops frequent faults, such as seal leakage. So, in a one-in-use and one-backup operating mode, what should be taken into consideration when in use? How should the pipelines be arranged? Valves and such? If the pump inlet diameter is DN40 and the outlet diameter is DN25, what size should the pipeline be? Wait, wait, wait? Welcome to provide guidance and exchange ideas; thank you.
Here, sometimes one pump performs well, but once we switch to it, the original backup pump does not work as well. So under normal circumstances, when it’s time for the regular switchover, we usually let the backup pump operate under load for a while, and then shut it down to serve as a backup.
The inlet size should not be smaller than that of the pump; it is usually 1-2 sizes larger. The outlet size also needs to take into account pipeline losses, and is generally 1-2 sizes larger as well.
1. The pump has a short service life, and the reason for this should be identified. Is it due to quality issues with the concurrent use, or are the applicable ranges of the materials and pumps beyond the specified operating conditions? It should be determined so that the right solution can be applied. 2. Connect the pumps in parallel; the pipe diameter can remain the same as before. The key is to install a check valve. For reference.
A procedure manual needs to be prepared. When starting the pump, one must pay attention and monitor the flow rate, and make adjustments as needed.
1. So, in a one-in-use-one-backup operation mode, what should be taken into consideration when in use? The standby pump should be rotated periodically, and it should be switched on regularly to operate under load. For guidelines on operation, refer to \"Pump Technology Q&A\" compiled by Zhou Guoliang and others. 2. How should the pipelines be arranged? For submersible centrifugal pumps, the inlet pipe should be lower at each step. Refer to SHT 3012-2011, Code for Design of Metal Piping Layout in Petrochemical Industries. 3. For valves, there are isolation valves, drain valves, and filters at the inlet, while check valves, isolation valves, etc. are available at the outlet. You may also consult SH 3122-2013, Code for Design of Process Piping Systems in Refining Units. 4. The diameter of the inlet and outlet nozzles of the pump is determined by the pump manufacturer. The diameter of the pump’s inlet pipe is determined based on the required net positive suction head of the pump. For pumps that transport subcooled liquids, the flow velocity can be higher, resulting in a smaller pipe diameter; whereas for pumps that transport saturated liquids, the flow velocity is generally lower. The diameter of export pipelines is usually determined based on the economic flow velocity, which is generally set at 1–2 m/s. References can be made to Appendices B and C of the SHT 3035-2018 Guidelines for Selecting Pipe Diameters in Petrochemical Process Units. All the standard forums I listed should have them; if you can’t find them, you can ask me for them.
Seeking information; hoping experts can offer guidance. zhouyadong1219@163.com
Many times, a very stable operation can become chaotic when switched to another mode of operation.
If you don’t do it regularly, you might lose proficiency; if you do it too often, mistakes can occur. So it’s necessary to find this middle ground; one can’t make decisions arbitrarily!
Regular switching is important; moving equipment suffers the most from being left unused for long periods, as problems are likely to arise when switching it passively. Generally, standby pumps and operating pumps are of the same model and specifications; it is best to switch between them from a operational management perspective (for example, every week or two), so that issues can be identified promptly. Additionally, if the issue of leakage from the mechanical seal is not due to poor quality, it is likely related to the pump not being suitable for the intended operating conditions. A better solution can be found by considering the selection of the appropriate pump; otherwise, frequent replacement of the mechanical seal incurs high costs and also affects operational efficiency.
Check the condition of the backup pump to determine whether warming it is necessary to prevent freezing, etc； The piping layout can be arranged according to standard practices ； Pumps should be used under specified conditions; these limits must not be exceeded, such as pressure, as well as the quality and pressure of the seal water