How to use a pressure relief valve
Thread Content
The company has a multi-stage centrifugal pump with a capacity of 150 m3 and a head of 300 meters, which is used to supply water to the boiler’s water wall; after passing through the heat exchanger, the water returns to the tank. To maintain the pressure inside the water-cooling wall tubes, a pressure relief valve, also known as a pressure maintenance valve, is installed in the return pipeline between the heat exchanger outlet and the water tank. This valve helps to keep the pressure before it around 3 Mpa, while the pressure after the valve can be reduced to 2–3 kilograms per square centimeter. However, there is a problem: although the pressure relief valve helps to maintain the pressure before it, the flow rate decreases significantly due to the need to hold back that pressure. When the variable-frequency pump operates at 45 Hz, the pump heats up and cannot operate at full capacity. By reducing the pressure before the pressure relief valve to around 2 Mpa, the flow rate increases again, and the pump no longer overheats. I would like to ask: if we want to maintain a pressure of 3 Mpa before the valve, how should the flow rate be controlled to ensure that it remains at 150 cubic meters per hour? There are no bypasses in the entire system.
Is it a pressure relief valve? Isn’t the pressure before the valve related to the pump’s head? As I understand it, the pressure before the valve is regulated through interlocking control between the pump’s frequency converter and the pressure gauge after the pump. I’m not sure if my understanding is correct
1. It is unclear how the original poster matched the pressure relief valve selection with the pump’s performance curve. 2. By analyzing the pump’s performance curve, it needs to be determined whether the range of head variation within the water wall supply flow rate covers the required value of 3 Mpa. 3. Based on the description of the problem, it can be inferred that at a relief valve setting pressure of 3 Mpa, the pump’s flow rate decreases. This can be attributed to an increase in the pipe resistance at the pump’s outlet, which causes the pump’s operating point to shift to the left side of the curve; as a result, the pump operates at a low flow rate and its performance does not meet the required standards. 4. The pump’s flow rate of 150 m3 and head of 300 meters generally refer to parameters under rated speed. When the speed is reduced, the pump’s head will decrease at the same flow rate, and to achieve the desired head, it is necessary to reduce the flow rate. 5. In light of the above, it is necessary to verify the performance of the pump on-site and resume operation at line frequency in order to determine whether the selected pressure relief valve is appropriate