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How to convert PPMw (by weight) to PPMv(Volume) for H2S & moisture(H2O) in gas mixture?
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Submitted Chris Haslego, Nov 21 2011 11:21 AM | Last updated Nov 21 2011 01:29 PM

Category:	Fluid Dynamics
Question:	What is the best way to control a positive displacement pump?
Keywords:	v1i16,pd,pumps,pump,positive,displacement,control,controlling
Answer:	When controlling a positive displacement pump, the very first thing to remember is this: YOU CANNOT CONTROL IT BY THROTTLING THE DISCHARGE! Trying to do so if fruitless and in most cases, you'll actually cause damage to the pump. The second thing to remember is this: YOU CANNOT CONTROL A PD PUMP BY THROTTLING THE SUCTION SIDE. It's important to get these two points out of the way. PD pumps are NOT centrifugal pumps, and they cannot be controlled in the same way as centrifugal pumps. O.K., now that we've addresses to you cannot control these types of pump, we'll move on to how you CAN control them.The recommended way to control a PD pump is via a recycle from the discharge line to the liquid source. The recycle line is fitted with a control valve. Essentially, the flow (and subsequent pressure) to the process is reduced by the flow that is allowed to recycle. This keeps the PD pump operating at a consistent flow and pressure, but allows for control of what continues to the process.
Links:	More of PD Pump Control