Functionality Of Pumps/Valves in Process Industry

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Thread Starter

Rushi Shroff

What is basic application of pumps in industry ? How they work together with valves? what are types of pumps? Are they connected with DCS as valves do?

Please give some insights about pumps/valves.
 
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Terry Whitworh

Depends on type of pump..Basic process has 1 type. This being a centrifugal style. When pump is dead headed the motor load drops. Full flow capacity load will climb to what is needed. The amount depends on size and head on the discharge. Valve sizing should always be full ported per pump curve. Meaning control valve should always let the pump full flow if needed. Some will try a VFD. If sized correctly and a quality check valve is installed on the pump they perform very well. I myself pervert the auto valve control. Again it is the type of process. A hydraulic system will use a positive displacement pump with a pilot operated relief valve. This will be used to set system pressure and protect the pump. One thing to remember about pumps they do not deliver pressure but they deliver flow. I hope this is some help.
 
Before you apply this advice, please read about the pump affinity laws here:

http://en.wikipedia.org/wiki/Affinity_laws

Centrifugal pumps deliver both flow and pressure. With an installed pump, the impeller diameter is a constant. If you locate a control valve downstream from the pump, and close the valve while the pump is running at constant speed, the head (pressure) developed by the pump will indeed increase. Using a VFD (Variable Frequency Drive) allows a flow control system to adjust the pump rotational speed to develop the amount of pressure needed to produce the flow required by the process as long as the pump and motor are properly sized. In this case, a control valve is not needed - the speed of the VFD can be regulated to control flow.

Dick Caro
Certified Automation Professional (ISA)
Buy my books at the ISA Bookstore:
Wireless Networks for Industrial Automation
Automation Network Selection
Consumers Guide to Fieldbus Network Equipment for Process Control
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