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I need to increase/decrease a chemical injection pump stroke adjustment for speed via DCS. I need to know if any pump vendor or anyone has experience in connecting electric actuator on the pump to the DCS (analog output) so that we can increase/decrease the pump stroke adjustment.

If the electric actuator can receive 4-20 ma, do we need to have two analog outputs from DCS for increase/decrease or is one analog output sufficient?

Please offer your advice. Thanks.

To all,

Milton Roy makes adjustable positive displacement pumps suitable for chemical injection. Only one analog output will be required.

http://www.miltonroy.com/corp/details/0,10294,CLI1_DIV39_ETI3654,0 0.html

Milton Roy is not the only game in town, there are many others.

Rob Barrese
ArcelorMittal Dofasco

One output is all that is need as it should control the speed of the pump and thus the stroke or at least thats how we control the LMI pumps.

If your metering pump is one of the smaller variety where the diaphragm is driven by a solenoid, another possibility is to drive it from a pulse train generated by the DCS.

Some of the pumps I work with have provision for a low voltage pulse input, others I have driven the coil directly using an interposing relay. By counting the pulses and multiplying by stroke volume you have a rough idea of the total flow and can calculate rate. This can easily be verified by timing to a graduated cylinder.

Hope you find this useful.

Regards,
Roy