On-site issues with turbine flowmeters!
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This post was last edited by batawfn on 2024-6-3 at 14:08. There is a water heating tank on site; the height of the tank is 440 MM, and the width is unknown, but it’s probably not very large. The pump supplies water to the water tank; the water is pure water. The normal flow rate is 0.5–1.5 M/H, which is quite low, and the normal pressure is 0.2–0.3 MPa. On the pipeline, there is a turbine (DN40) first, followed by a pressure transmitter, with the control valve located about 2 meters further along. 1. The pump never stops running during operation. 2. Keep the liquid level in the water tank at 220 MM; the water tank is used to heat the air. 3. When the water level in the tank drops below 220 MM, the control valve opens. The control valve closes when it exceeds 220 MM. 4. With this process, the control valve is closed, but the pump continues to supply water; the pressure inside the pipeline rises to around 2 MPa, which is the maximum pressure. The control valve is opened. When water passes through the turbine instantly, the flow rate indicated by the turbine flow meter exceeds the meter’s range significantly, which can lead to damage of the turbine shaft or even breakage of the impeller. 5. The above steps need to be performed frequently. One round trip takes about 1 minute. 6. The manufacturer insists that it is a problem with the turbine; I hope someone from Haichuan can explain things to them properly. I can’t explain it any further.
After HaiChuan entered the post, the version looked very uncomfortable to read. Can it be changed?
Is a pump pressure of 2 MPa still required to supply water? 0.2-0.3 MPa is sufficient; our circulating water pressure is also below 0.5 MPa, and the same applies to tap water. This pump must not be used only to supply water to the tank, so it needs to stay on all the time. Add a stop valve in the middle of the water supply to the tank to reduce pressure, or use a pressure reducing valve. Such high pressure is generally beyond the capacity of flow meters that lack special design, especially when the water hammer effect is so pronounced. Is the CV value of the control valve chosen appropriately? It seems to be too high; as soon as it is opened, the flow rate becomes very large. It is sufficient for the control valve to achieve a flow rate similar to that of water when it is open at 40%. This prevents the control valve from opening and closing repeatedly. Instead, once the control valve reaches a certain opening degree, dynamic equilibrium is achieved and the liquid level remains at the set value. Just use a cut-off valve directly.
1. Why can’t the pump be stopped? Is it just by forcing it in, with no return pipeline or anything? 3. Why should the control valve be opened or closed? Can’t it be regulated using a single-loop PID for the flow rate? 4. 220mm, 20 kilograms of pressure? Is the head selection appropriate? Why is a turbine used in this process? There’s no need to worry about electromagnetism! 5. Why is it so frequent? Are the parameters not set correctly?
Without altering the manufacturer’s operating methods or the equipment, a damper (accumulator) with a capacity of over 50 liters is installed between the flow meter and the so-called control valve (which appears to be a on/off valve), and then a 1.5 mm orifice plate for flow restriction is placed downstream of the damper. This helps to minimize the pressure difference in the pipelines before and after the instrument during operation, thereby reducing the impact on the instrument. If it is possible to change the way the equipment operates, the pump should be stopped when the pressure at its outlet is above the HH value, and started again when it is below the LL value; an optimal water tank level is within the range of 200–240 mm.
It is reasonable to start the pump and open the valve at a low liquid level of 200 mm, and to stop the pump and close the valve at a high liquid level of 300 mm. A control scheme that involves frequent starting of the pump when the liquid level is above 220 mm or below 220 mm, without taking into account the difference between high and low liquid levels, is unreasonable.
Turbine flowmeters are not recommended when the flow rate is unstable. Or it is installed on a fluid-stable pipeline.
Yes, typical start at low liquid level and stop at high liquid level.
Variable frequency can be considered; when selecting a flow meter, the operating conditions must be taken into account
Everything that needed to be said has already been mentioned above. First of all, the setpoint range for the level interlock control is too narrow. Moreover, this isn’t a control valve at all; if a control valve is intended to be used, it’s recommended to choose one of the equal percentage type. Additionally, the pressure buildup is too high, and such frequent opening and closing actions cause water hammer effects that no flow meter can withstand.