When pipeline centrifugal pumps are connected in parallel, the outlet pressure of the pumps increases
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Initially, one centrifugal pump was in operation; due to insufficient heat transfer capacity, another centrifugal pump was connected in parallel to it. As a result, the outlet pressure of the centrifugal pumps increased by about twice, and the outlet flow rate also increased. I would like to ask whether the head pressure also increased (in other words, does the pressure at the pump’s outlet become higher?) ） ； If two pumps are connected in series, according to the principles of chemical engineering, the head pressure increases while the flow rate at the pump outlet remains unchanged. I’m not sure why; it seems that the fluid is first pressurized by Pump 1 and then again by Pump 2. Therefore, the outlet pressure of Pump 2 must be higher than that of Pump 1. With a constant diameter in the outlet pipeline, the flow velocity at the pump outlet should increase. Since the velocity per unit volume increases, the flow rate of the pump should also increase, right?
When two pumps with the same head are connected in parallel, the head remains unchanged while the flow rate increases； The pump outlet pressure increased after connecting them in parallel; one reason could be that the head of the two pumps is different, and the pipeline is not capable of handling the flow rate from both pumps.
I suggest you take a look at the parallel and series curves of the pump. Understand the concept of head. If you look closely at the curve, you’ll understand naturally. The parallel operation condition you described is in line with the curve: as the flow rate increases, the head also increases. In series, it should be like this: the head increases, but not by 2 times ； Run with a slightly higher traffic volume.
An increase in outlet pressure means that the flow rate of each pump decreases, while the total flow rate increases.
In parallel operation, one pump should be in use while the other serves as a backup; this is only possible when the pipeline cannot meet the flow requirements of two pumps, resulting in high static pressure