Regarding the selection of centrifugal pumps (for heating water)
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As shown in the diagram, the process conditions are as follows: the inlet pressure of the pump is around 11 kilograms, while the outlet pressure is around 15 kilograms. The water temperature ranges from 20 to 190 degrees, the maximum flow rate is 45 cubic meters per unit time, and the head is 45 meters. Initially, it was planned to use a canned motor pump, but considering the management’s desire to save money, a centrifugal pump was chosen instead. The figures shown in the diagram come from the data sheet provided by the design institute; however, our equipment specialists say that such pumps are not very suitable. I would appreciate it if experts could help determine whether this choice is appropriate Thank you! Are there any other suggestions?
The inlet pressure is too low; theoretically, cavitation can occur at the extreme temperature, so it is recommended to increase the inlet pressure； Plan 21 isn’t good either; Plan 23 is the best ； The data sheet provided by the design institute is also fine; the centrifugal pump can be used, and an auxiliary cooling system is sufficient for the design
The original poster has provided limited information; I’m not sure from what perspective your technicians claim that ordinary centrifugal pumps are not good In terms of process parameters, ordinary centrifugal pumps are more than sufficient; it is only necessary to pay attention to the material, sealing, and flushing. 1. The materials can be selected with reference to Appendices G and H of 610. 2. Mechanical seal: A single-face C-type mechanical seal will suffice. 3. Flushing system: As mentioned for Building 2 and Building 3, use 23 for flushing.
This is because the pressure for our imports is applied to the return water using medium-pressure steam; the maximum pressure of this steam is 12 kilograms, though 11 kilograms is already considered a relatively high pressure. Then can cavitation at the critical temperature be addressed by leaving enough cavitation margin? Then, compared to 21 and 23, what are the advantages of 23? Thank you!
What the teachers upstairs mentioned, 21/23, refers to the machine seal flushing method
Is it because 23 offers better flushing and sealing that everyone tends to choose it?
First, Annex A of API 682 recommends using Plan 23 because the water temperature exceeds 80°C. Secondly, footnote c provides a more detailed explanation: due to temperature constraints, the sealing elements in Layout 1 and Layout 2 need to be cooled. If cooling is not available, it is recommended to use O-rings made of FFKM material. It is recommended to use the 23 flushing scheme; based on field experience, this scheme is less likely to cause scaling and blockages due to circulation within the sealed chamber compared to the 21 flushing scheme. Nevertheless, because the 23 flushing scheme is more complex and expensive, users prefer to use the 21 flushing scheme. Alternatively, due to the absence of a circulating cooling water system, the 21 flushing scheme with finned air coolers is employed (the air cooling approach is more effective for the 21 flushing scheme when there is a large difference between the temperature of the process medium and that of the air). If a suitable flushing medium is available, the user may opt for the 32 flushing scheme, especially when the flushing fluid is intended to be injected into the process medium itself (such as fresh water). ... The parts in red in the text should be able to answer the original poster’s question.