There are numerous problems in pumping small amounts of liquid (e.g., chemicals for water treatment) with conventional piston or diaphragm pumps. This is usually accomplished by the prior art pumps by using either a small diameter piston or a diaphragm having a very short stroke.Instrument Manifolds Accurate adjustment of short stroke diaphragm mechanisms leads to complex design problems. On prior art small diameter piston units, the pumping accuracy has been sacrificed in order to obtain reliable priming and/or a variable output. Some pumps bypass a portion of the output back to the supply container; these units usually have a volumetric output which varies inversely with system pressure. Some success has been had with more complex designs for bypassing a portion of the output; however, by adding more components the overall accuracy is diminished and the cost increased.

A pump designed to deliver minute quantities of liquid should meet the requirements discussed briefly below.Forged Steel Valves The pump is required to self prime against full rated output pressures at all settings. When the output is feeding a pressurized system or the stroke of a piston is reduced to obtain low output, the compressability of gasses makes priming impossible unless a means of discharging the gasses is provided. This degassing also ensures against the loss of prime during operation of the pump. The pump must self-degas to ensure against changes of output. When gases develop in the pumping chamber, the discharge volume drops by the rate of gas build-up in the cylinder area. This means, even though the gas accumulation is not sufficient to break the prime, it will change the output volume of the pump.WATER POWER CONTROL VALVE The pump is required to remain operable with slight leakage of check valves due to precipitants from the liquid being fed. The pump is further required to run dry without damage to dynamic seals. No prior art pump presently known sufficiently meets these requirements.

MORE NEWS

2011-12-16

Back