What are the reasons why a diaphragm metering pump has no pressure and cannot pump fluid?
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This post was last edited by z88m11f1 on 2016-8-5 at 18:17. We have a diaphragm metering pump from Cixi with a design pressure of 2.0 MPa; it stopped being used half a year ago due to production reasons (it had been working properly before). We now want to use it again – the materials, process, and pipelines remain unchanged. However, when starting the pump, it was found that the pressure and flow rate did not meet the process requirements. Upon inspection, it was discovered that the valve ball and valve seat were severely worn. Today's maintenance: After replacing the check valves at the inlet and outlet and the packing seals at the piston, a pressure and flow test was conducted with water, and both values were normal ； However, when switching to the material, there is no pressure or flow, and no sound of the valve ball hitting the valve seat can be heard either. So the inlet pipeline was disassembled, cleared, and cleaned; everything was normal. The inlet and outlet check valves were checked again and also functioned properly. When the pump was tested once more, it worked normally even when tested with water, and the sound of the valve ball hitting the valve seat could be heard ； However, even after switching to the material, there is still no pressure or flow, and no sound of the valve ball hitting the valve seat can be heard. The material is a potassium hydroxide solution at room temperature. Could someone experienced help take a look? There might be some issue somewhere........................ We suspect that the different materials of the valve balls used could be causing the difference in weight; we plan to replace the valve balls tomorrow.
Personally, I don’t think it has much to do with the ball valve; I’m not sure how the material and water are switched between each other. Make sure to check whether there are any leaks in the pipe leading to the material supply
The inlet is a three-way fitting: one end is connected to the material, and the other end is connected to water or another fluid used for cleaning the pipeline after the reaction is complete； Work is over now; I can find someone to take a photo tomorrow. . . . If there is a leak, one should be able to hear the impact sound of the valve ball against the valve seat
Yes, without liquid, there is only air, and the sound is clearer; with liquid, the sound is muffled. It is recommended to try using water in the feed pipe; if everything works fine, then it is likely a problem with the valve ball. Using a valve ball with a higher density than that of the material should solve the issue, and generally ceramic valve balls should not present this problem
Has anyone encountered this situation before? I’d appreciate some advice.................... There’s another question: since the material used in the metering pump is potassium hydroxide, what material would be best for the valve ball? Stainless steel? Ceramic? Or something else
If the valve ball is made of PTFE, what material should be used for the valve seat?
With potassium hydroxide, there’s usually no problem with PVC pump heads
Were you there when it was tested? How was the process?
What I want to say to the original poster is that the selection and installation of the company’s equipment were determined by the design institute at the beginning of plant construction. Moreover, you mentioned that the pump worked normally during its use before it was taken out of service, which indicates that the design and selection of this pump were correct and there were no issues with it. If the ball valve inside your metering pump is worn out, it indicates that the medium may be dirty and contain impurities, or there could be issues with the installation. In such cases, it is recommended to purchase original spare parts from the manufacturer itself; after all, different manufacturers use different designs and materials for their metering pumps. It is advisable to replace both the valve ball and the valve seat. Another thing to note is the need to replace the diaphragm, as it is the component responsible for carrying out the pumping action. Also, consider the process-related factors: whether the current values for parameters such as medium concentration and viscosity are the same as before or have improved. All of these can have an impact on the operation of the metering pump.