Metering pumps can meter the feed reagents at very low flow rates where high pressures are built up. Flow rates as low as 0.001 ml/min normally do not attain a very large flow rates. Maximum attained flow rates in Eldex pumps is 80 ml / min. To attain higher flow rates, pressure conditions are towards lower side. Advanced software algorithms control motor speed based on piston position, achieving rapid fluid intake and smooth, constant fluid delivery, minimizing pulsation. Flow rates are determined by piston displacement (diameter, and stroke length) and motor speed.
While considering the metering pumps one must take into account the pressure generated which a pump needs to handle when dispensing the chemical feed in a reservoir or vessel or column. The Optos series model of Eldex pumps can handle up to 6000 psi at certain flow rates.
Material of Construction:
In case of metering pumps when the objective of pumps is to feed the reservoir, then feed reagent or chemicals come in contact with various parts of pumps like pistons, piston seals and liquid end assembly etc. Normally such pumps use PTFE seals, Sapphire pistons, with ruby balls and Liquid end assembly made up of SS316 to avoid most of the corrosive chemicals. But still to deal with some highly corrosive chemicals, instead of SS316, PEEK based or Hestelloy based Liquid end assemblies can be chosen. Eldex takes care of such adoptions if requested. One must ask for the compatibility chart with the supplier of pump for the material of construction of wetted parts and chemical or reagents used for metering.
Dampener to prevent pulsations:
Some pumps may be fitted with a pulse damper. The damper is a diaphragm type damper, where a diaphragm made of an inert material flexes against a compressible fluid (spiked with red dye), thereby absorbing pulses in fluid delivery. To maximize the damper’s efficiency, the system should operate against at least 500 psi. If your system does not normally generate such pressures and you wish to increase the efficiency of the damper, you can install a backpressure device, or some narrow ID tubing downstream of the pump.
Electronics to control the pump:
Pump is controlled from a series of menus and there is no need to remember esoteric control codes or command sequences. Advanced software algorithms should control motor speed based on piston position, achieving rapid fluid intake and smooth, constant fluid delivery, minimizing pulsation. There should be simplicity in electronic components.
Robust and Simple to maintain:
While selecting the pump one must take care that Pumps should be simple to operate and maintain. Eldex provides a fantastic user manual to maintain the pump and it is always recommended to keep Preventive Maintenance Kit for routine maintenance for replacement of seals and check valves. Also this is recommended to prime the pump heads, filter the solvents and in case a pressure problem occurs solvents must be degassed. If the pressures at end point are less than 500 psi then dampener should be removed.
Temperature of the feed in case of Eldex pump goes to 100 degC but to attainthe higher temperature pump doesn’t have any inbuilt option howevermany users wrap the heating element surrounding the SS316 body of Liquid End Assembly.
Written by Rakesh Arora, CEO, TechnoConcept India Pvt Ltd.
Image and information courtesy - www.eldex.com