Seeking advice on screw pump issues
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Dear sea friends, I need help with issues related to screw pumps! Currently, two new screw pumps installed in the unit are experiencing flow rate issues. Specifically, they can achieve their rated flow rate at low back pressure (0.05–0.1 MPa); however, as the back pressure increases, the flow rate drops rapidly. When the outlet pressure reaches 0.3 MPa, the maximum flow rate is only 35 cubic meters, whereas the pump’s rated flow rate is 50 m3. The designed pressure of the pump is 0.7 Mpa, and the set pressure of the safety valve is 0.9 Mpa. Please share your opinions – have you experienced similar situations, and what are the solutions?
A screw pump is a positive-displacement rotary pump. Its output pressure is related to the profile of the screw. There is an issue with the selection of this pump. When the back pressure increases, since the outlet pressure of the pump is lower than the back pressure, the pump experiences liquid blockage and is unable to deliver fluid.
Recommendation 1: Verify the selection made at that time to confirm whether the screw pump was chosen based on the operating pressure. 2: Check with the manufacturer for the pump’s factory test records from that time. 3: A significant decrease in flow rate when pressure increases is likely due to too low viscosity of the medium, which leads to increased internal leakage and thus a reduced flow rate; it could also be caused by a damaged safety valve that opens prematurely, resulting in backflow. Based on our experience, screw pumps generally do not experience such issues. Screw pumps are positive displacement pumps, and their flow rate is directly related to their rotational speed; therefore, the flow rate does not vary significantly when the speed remains constant. The exact cause will need to be determined through on-site investigation
It’s likely that the gap between the screws has increased; the greater the pressure difference, the greater the internal leakage, and the lower the flow rate. . . The other one is related to the viscosity of the medium.
It is unacceptable for new screw pumps to experience such problems. I’m not sure whether the issue has been resolved yet. My suggestions involve considering the problem from two aspects: 1. The screw pump was not selected appropriately; the gaps between the screws, as well as between the screws and the sealing chamber of the pump casing, are too large, which leads to severe leakage even when pressure increases. Or is the pressure value at the safety valve of the screw pump not set properly? 2. Pipeline issues: please upload the pipeline installation diagram if possible.
The problem has not been resolved yet; the experimental platform works normally, but the system fails to function properly when reinstalled. We are currently checking the status of the process pipelines. Thank you
I’m not familiar with screw pumps. My suggestion is to have the manufacturer come over; it will help you solve the problem
I’m sorry, but I haven’t been to the forum for a long time. The issue has now been resolved; it was mainly because the manufacturer underestimated the leakage rate of the screw pump, and the flow rate design was too low, which led to an increase in pressure difference and a decrease in flow rate that wasn’t sufficient to meet the design requirements.
I’m sorry, could you explain it in more detail? 》I’m not quite sure what was the reason in the end