I would like to ask an expert about the connection issues between metering pumps and safety valves as well as backpressure valves.
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Details: A new setup has been installed in the factory – a regular diaphragm metering pump (50 L/h) is connected in parallel with a backpressure valve/safety valve (18615), and the flow then goes directly to the flow meter and onward to the downstream equipment. There are no devices such as pulsation dampers. Question: 1. Is this installation correct, and what is its purpose? 2. When the unit arrives, the inlet of the back pressure valve is on the top side (as indicated by the arrow on the back pressure valve); could it be installed upside down? 3. Is it installed in this position to act as a back pressure valve or a safety valve? 4. During testing, it was found that the flow rate was unstable with significant fluctuations. Is there any way to solve this?
The function of a safety valve is to prevent damage to the pump and pipeline leaks, which can occur due to overpressure at the outlet of the metering pump when the pipeline at the pump’s outlet becomes blocked or obstructed. For example: when the ball valve at the pump outlet is closed while the metering pump continues to operate, the pressure at the pump outlet will keep rising. Once it reaches the set pressure of the safety valve, the safety valve opens to release pressure at the inlet, thereby protecting the equipment and pipelines. The safety valve is installed correctly as indicated by the directions in the diagram. Since there is no pulse suppression device at the outlet of the diaphragm pump, the flow rate there is pulsatory in nature; as a result, the flow meter will show fluctuations in value. If high stability of the flow rate is not required, it can be adjusted using the flow control knob on the diaphragm pump. Otherwise, a pulse suppression buffer must be installed at the pump’s outlet, as shown in the diagram
Installing a safety valve in this way is definitely incorrect; generally, the pressure relief pipe is connected directly to the storage tank, and no other valves are allowed to be installed in between.
Ball valves are not allowed to be installed in front of safety valves
Thank you, boss. So what’s installed in this position serves as a safety valve, preventing damage to the pipeline in case the pump outlet or the valve at the back isn’t opened, right? The direction of the safety valve here is also correct. But there’s another issue: why does adjusting the nut of the safety valve here affect the flow rate of the metering pump? Tightening it increases the flow rate, while loosening it reduces it. Also, does a pulse damper need to be added in order to achieve stable flow as you mentioned? And if a damper is used, is it still necessary to install a backpressure valve on the main pipeline as well?
Well, so the outlet of the safety valve in that position shouldn’t go back to the pump inlet, but rather directly back to the storage tank, right?
Understood; ball valves cannot be installed at the outlet. Thank you
It is recommended to take a picture of the scene to take a look.
This is used to protect the pump; there are no issues with its installation
There is no ball valve installed in front of the safety valve; take another close look