What should be the appropriate outlet pressure of the boiler feed pump in a hydrogen production plant?

There is an existing hydrogen production plant capable of producing 3,000 cubic meters of dry gas per hour. The outlet pressure of the boiler feed pump (a multi-stage centrifugal pump) is gradually decreasing; it was originally 43 kilograms per square centimeter, but now it is 38 kilograms per square centimeter, with the pump operating at 40% load； The steam outlet pressure from the drum is 30 kilograms. Questions: 1. What is the reason for the low pressure? The pump is experiencing cavitation (the current is higher than before, and the opening degree of the pump’s outlet valve has also increased). 2. If the pressure at the pump’s outlet is reduced, what should be the lowest appropriate level, as long as water can still be pumped? A pressure of 35 kg is already sufficient. 3. What is the load on the water pumping units of other companies? How is low load achieved? By adding a variable frequency drive, using impeller cutting, or reducing the number of stages? Initially, the pressure was 43 kg, with a head of around 420 m. In fact, the pressure in the steam drum is 3.0 Mpa; the pump’s outlet head needs to be 320 m, plus an additional 20 m due to height differences. Leaving some margin, a head of 350 m is sufficient. A too high head can also cause cavitation in the pump. Additionally, reducing the inlet temperature (the deaeration temperature must be above 100°C, and this cannot be changed as it would also result in increased energy consumption), as well as increasing the inlet pressure (by enlarging the inlet pipe diameter, reducing the number of inlet elbows, or increasing the height of the deaerator), are all effective methods. Your situation is similar to mine; I think the most effective approach is to remove one or two stages of impellers, or to use variable frequency controls to reduce the head.