Selection of pumps for low flow rates and high head
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Experts: My installation is equipped with two cooling water pumps that feature low flow rates but high head pressure. The net positive suction head available in this system is quite low, at only 2 meters; the design team believes that it is not possible to increase this value further. The current situation regarding product selection is as follows: 1. For a major domestic manufacturer of high-speed pumps, the required net positive suction head cannot be met; the minimum value that can be achieved is 3 m. 2. A certain centrifugal pump manufacturer chose the BB3 pump with a 13-stage impeller; it requires a net positive suction head of 1.4 meters, which just meets the requirements. However, I still feel that this isn’t very reliable. Do anyone have any better suggestions? The image below is the data table from HaiChuan Pump Friends Circle
If a horizontal multi-stage centrifugal pump is used, then the pump suggested by the manufacturer already boasts very high performance. I have checked the performance curves of the pumps produced by our company; for BB4-type pumps with 50–220 parameters and 11 stages, at an operating capacity of 33 m3/h and a head of 689 m, the required net positive suction head is 1.7 m. This shows that the parameters provided by the manufacturer are accurate. It can meet the requirements for flow rate, head, and also the net positive suction head requirement.
Still need to dig holes, it’s troublesome\ud83d\ude04, thanks
Thank you\ud83d\ude0a
Thank you for your helpful assistance; I guess this pump will have to do
The design institute tells you that for your flow rate and head requirements, pumps of type BB4 or BB5 would work, but cavitation issues will be difficult to overcome. This is steam condensate, so it is at a near-saturated state; therefore, the NPSHa is only 2 meters. Based on my experience, the head is on the high side. According to API610 11th edition, section 6.3.9, although your head is less than 1000, I still recommend choosing a radially split design rather than the axially split BB3 design. Furthermore, even if you choose too many BB3 series components and the size of each wheel is small, such a length-to-diameter ratio is inappropriate, resulting in unreliable operation. Moreover, it is likely that the manufacturer added inducer wheels or a double-suction design in order to achieve a cavitation margin of 1.4; this makes the operation of multi-stage pumps unreliable as well. With such low cavitation and high head, I recommend using a tubular belt pump mounted at the bottom, which can meet your requirements. If satisfied, please leave a positive review.
Thank you for your reply. I was also worried about unstable operation, so I used an impeller of grade 13; moreover, the pump manufacturer is not a well-known brand, which makes me concerned that problems might arise during operation.