Technical assistance: Issue with the flow meter at the outlet of a plunger-type metering pump
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A plunger-type metering pump is installed on site; there is a damper at the pipeline outlet but no buffer tank. On the outlet pipeline, there is a metal tube rotameter. If all valves are opened and the pump is started, the indicator of the rotameter swings up and down and cannot operate stably. If the flow rate is adjusted using the valve at the outlet of the flow meter, the flow meter will remain stable within a certain range. However, during actual production processes, the valve needs to be adjusted repeatedly, which prevents the flow meter from operating stably over an extended period of time. Help, is there any way to stabilize the flow rate inside the pipeline? If the Kroni KPT series is used, can a constant current valve at the inlet be used?
A buffer pack can be installed at the pump outlet to provide buffering effect.
A buffer tank is installed at the pump outlet; the metering pump is controlled using frequency conversion. If a low flow rate is required, the plunger’s stroke can be reduced while increasing the frequency to raise the speed. Using an outlet valve to control a metering pump can easily lead to pressure buildup, causing the pump to stop automatically. This is how we control it on-site, keeping the traffic fluctuation within 3 units.
The pump is controlled by an inverter; for example, the pump’s maximum flow rate is 2000 l/h, and now the flow rate needs to be controlled at 500 l/h. We have a frequency of 50HZ and a plunger stroke of around 35%; in this case, if no pressure is applied at the outlet valve of the flow meter, the flow meter experiences significant fluctuations. We have buffers on our pipeline. According to the procedures on your end, should we increase the pump frequency and reduce the plunger stroke, or should we add a buffer tank? Now the flowmeter is fluctuating across its full range. Thank you! It would be better for communication if there were a QQ account or something similar
For example, the maximum flow rate of the pump is 2000 l/h, and now it is necessary to control the flow rate at 500 l/h. We set the frequency at around 45 Hz, then adjust the plunger stroke so that the flow meter shows around 500 L/h; if there are fluctuations in the flow rate, we fine-tune it using variable frequency. Once the flow rate reaches 500 L/h, if the flow meter shows significant fluctuations, we will add nitrogen to the outlet buffer tank; the nitrogen in this buffer tank needs to be replenished whenever there are fluctuations in the flow rate. We have two factories, and in both cases metering pumps are used for feeding the raw materials. Previously, the flow meters showed significant fluctuations, resulting in inaccurate amounts of material fed; but now, with the addition of buffer tanks, the performance has become very stable. What’s most important is that the nitrogen in the buffer tank plays a role
Are you using a buffer on the pipeline, the type with diaphragms, or a buffer tank? The nitrogen pressure in our buffer is currently 0.5 MPa, while the pump pressure is set at 1.0 MPa.
The buffer tank is simply an empty tank with nothing inside; nitrogen comes into direct contact with the material. There is no back pressure at the outlet of our metering pump, so we can’t determine the pressure.