The metering pump damaged the pressure gauge
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It’s my first time dealing with metering pumps; I learned about their working principle online. There are 2 metering pumps installed in the system, and 4 pressure gauges have already been damaged. The nameplate on the first metering pump indicates a pressure of 0.6 MPA; it serves as a power pump for the return flow of light oil from the oil-water-gas separation tank at the top of the vacuum distillation tower, as well as for the flow exiting the system. The flow control for the reflux from the distillation tower is connected to the temperature at the top of the tower, while the flow control for the flow exiting the system is linked to the oil level in the separation tank； The second metering pump is an alkali pump. Question 1: Almost all of the fluid pumped by the first pump flows out through the pipe leading out of the device, with very little returning. By making slight adjustments to the reflux control valve, the pressure at the outlet of the metering pump increases; it can reach 3MPA in an instant, with a stroke volume of 40%. Eventually, no other choice remained than to set the stroke volume at 30%. How can the outlet flow rate of the metering pump be controlled – by adjusting the stroke volume or by adjusting the opening degree of the outlet valve? ； How can the pressure buildup risk associated with cascade control be avoided? Question 2: The alkali pump has also damaged one gauge; the pointer of the high-range pressure gauge currently in use will not return to its position even when the pressure is at 0.5 MPA. When the stroke was adjusted to 40%, the pressure at the pump outlet reached around 0.3–0.4 MPa. When the pump was started the next day, it was found that the pressure gauge had been damaged; likely, an instantaneous high pressure during operation caused the gauge to break. I was wondering if anyone has any experience that could be shared regarding the operation of metering pumps. Thank you!
This post was last edited by zwp997 on 2015-8-17 21:37. Should an anti-pulse device be added? How about connecting a pressure gauge after the pulse generator? A metering pump is a type of positive displacement pump; it is not possible to control its flow rate using the outlet control valve, as this may damage the pump. Such pumps should be adjusted by modifying the stroke length.
A 20mm pipe isn’t worth having pulses added to it
The flow rate of the metering pump is controlled by speed and stroke
Pulse is present in metering pumps, so it’s correct to install a damper. For metering pumps, which are pressure boost pumps used to regulate flow, the stroke should be adjusted using a handwheel.
Pump meters belong to the category of positive-displacement pumps. There are two ways to regulate the flow rate: Method 1 involves adjusting the number of strokes per unit time, which requires an inverter-driven motor; Method 2 involves adjusting the stroke length. As suggested by the original poster, it is advisable to install a buffer tank at the outlet. During the discharge stroke, the pressure at the outlet of the pump is very high for a brief moment.
First, check the operation – the pump’s outlet must remain fully open. Second, a needle valve can be installed at the base of the pressure gauge; it should be closed before starting the pump and opened once the pump is operating properly, in order to prevent sudden overpressure that could damage the pressure gauge~~
First of all, metering pumps cannot have their flow rate adjusted using an outlet control valve; the flow rate is controlled by adjusting the pump’s stroke. Under these operating conditions, I think a metering pump is not the right choice. Without replacing the pump, it is possible to implement split-range control on the return and discharge control valves: when the return control valve is closed, the discharge control valve is opened, thereby ensuring that the pump does not experience pressure buildup due to the closure of the control valves. Another method of operation is: if your metering pump has its stroke controlled from the control room, open the valve that controls the discharge volume fully, and implement a cascade control system between the pump’s stroke and the liquid level. If the liquid level is high, the pump automatically increases its stroke; since your discharge control valve is fully open, the pump will not experience pressure buildup even after increasing its stroke.
Open the inlet and outlet valves of the pump fully, set the stroke to the minimum, and adjust the stroke after starting the pump
Adjusting the stroke only affects the flow rate; it does not address the maximum hydraulic pressure at the outlet. As long as there is pressure buildup, damage will occur. It is necessary to check for any misoperations or situations where the pipeline valves are opened too slightly. If needed, a safety valve can be installed – by connecting its outlet to the pump’s inlet, the pressure gauge will not be damaged
1. The range selected for the pressure gauge should be appropriate; generally, the normal display value should fall between 1/3 and 1/2 of the full range； 2. Metering pumps are positive-displacement pumps; when the pressure is too high, buffer devices such as buffer tanks or accumulators need to be installed on the outlet pipeline ； 3. Also, check whether your piping system is unobstructed; if the outlet of a positive-displacement pump is blocked or not clear, it can cause the equipment to explode. It’s similar to inflating a bicycle – if you do it too forcefully, the tire might burst: lol.