3 replies to this topic

[curious_cat]

I have  a positive displacement electrically operated metering pump that's been dosing pretty erratically: Specs. specify a +/- 3% tolerance whereas the feed tank currently shows 25% variation (as measured between successive time periods). 

 

What are typical items to troubleshoot?

 

The pump has a diaphragm coupled to a prime mover by an intermediate hydraulic fluid. Flow adjustment if by means of a manual screw and pump operates at 100 strokes per minute. Prime mover is a three phase induction motor. Pump has a pulsation damper on the discharge side and a strainer on the suction. Rated pressure is 3 barg on the discharge. 

 

The atmospheric pressure feed tank outlet is ~4 feet above the pump suction and is connected to it by 1 inch piping of ~20 feet length. The discharge piping is also 1 inch and goes to a reactor nozzle about 30 feet above the pump discharge. The target flow rate is ~400 Litres per hour. 

 

The fluid is  40% H2O2 at around 30 C ambient temperature. 

 

Any tips? 

[latexman]

Most diaphragm metering pumps require a minimum backpressure on the discharge side to provide repeatable performance.  Check the pump documents or ask the vendor about this.

[curious_cat]

Most diaphragm metering pumps require a minimum backpressure on the discharge side to provide repeatable performance.  Check the pump documents or ask the vendor about this.

 

Thanks for the tip! I didn't notice the requirement in the spec sheets that came with the pump but I've sent a message to the vendor.

 

This may be it. 

[curious_cat]

The discharge line has an orifice plate fitted quite close to the pump. I wonder if that was meant to provide the necessary back pressure.