The two metering pumps, one large and one small, are connected in parallel. How do I start them?

1. The outlet pressure is 2 MPa; to avoid interference with each other (as interference can cause vibrations that lead to pipeline damage), the backpressure valves of both the large and small pumps should be designed to operate at a pressure of over 4 MPa (more than twice the outlet pressure). 2. The pulsation of a single pump can be reduced by using appropriate buffers; if possible, multi-pump systems can be employed to lessen pulsation-induced resistance. A higher frequency along with shorter stroke lengths can also help reduce this resistance (the only downside of a higher frequency is that it shortens the lifespan of the moving parts). 3. The order in which the pumps are started does not matter; the two pumps can be treated as separate units, and frequency conversion or shutdown has little impact on them. Note: Two pumps of different sizes are connected in parallel for chemical dosing; this configuration is typically used in precise dosing processes where the larger pump handles coarse adjustments and the smaller pump makes fine adjustments. (It is recommended to use flow meters in such setups.) If the need to add more pumps arises simply because the initial pump was undersized, it is recommended to simply select a larger pump as a replacement and upsize the piping.

Thank you for answering the questions. Still have questions. 1. The backpressure valve is designed for 4 MPa. Does this mean that the design pressure is 4 MPa? What considerations went into this? Shouldn’t the back pressure determine the pump outlet pressure? 2. A pulse damper has been installed, but considering that the two pumps will be started at staggered times, it is believed this will further reduce the pulsation. 3. If the large pump is turned on first and then the small pump, will the starting current of the small pump be relatively high? Because it is equivalent to a higher initial back pressure before startup, compared to starting at a lower outlet pressure. Thank you again.

1. You said the pump outlet pressure is 2 MPa – is this the maximum backpressure value among the pump’s performance parameters? Or is it the pressure value under actual operating conditions? I interpret it as the pressure value under actual operating conditions. 2. The backpressure should be more than twice the actual operating pressure value (4 MPa); its purpose is to ensure no interference. Specifically, each of the two pumps is equipped with a pulsation damper and a backpressure valve (with a pressure gauge). First, pump A is turned on; under actual operating conditions, the pressure is 2 MPa. When the pump starts, the pressure gauge..

1. You said the pump outlet pressure is 2 MPa – is this the maximum backpressure value among the pump’s performance parameters? Or is it the pressure value under actual operating conditions? I interpret it as the pressure value under actual operating conditions. 2. The backpressure should be more than twice the actual operating pressure value (4 MPa); its purpose is to ensure no interference. Specifically, each of the two pumps is equipped with a pulsation damper and a backpressure valve (with a pressure gauge). First, pump A is turned on; under actual operating conditions, the pressure is 2 MPa. The backpressure valve is then adjusted so that the pressure gauge indicates a value above 4 MPa. At this point, the backpressure exerted by the valve is equal to the total pressure (>4 MPa) minus the actual operating pressure of 2 MPa, resulting in a backpressure value of >2 MPa. The same procedure applies to pump B. At this point, the two pumps function as separate units, with the backpressure valve of pump AB preventing any interference between the fluids. 3. If the 2 MPa you refer to is the maximum back pressure value as a performance parameter of the pump, it is necessary to know the actual pressure under operating conditions at the outlet (which must be < 1 MPa); other operations follow those shown in point 2.

I guess you guys work with hydraulic systems. The backpressure valves are installed before each pressure-using point, ensuring that each point operates under different pressures. Our system requirements don’t match ours. There is no back-pressure valve design; there’s only a pressure relief valve at the equipment outlet, which is sufficient to maintain the inlet pressure of the equipment.