Performance of a Centrifugal Pumps largely depends on a correct specification and selection.

IMPORTANCE OF CENTRIFUGAL PUMPS SELECTION

The best selected pump for any duty condition may be most Hydraulically fit or with best efficiency but it may not be most suitable or cost efficient. The selection criteria must include maintainability and reliability as a foremost factors.Engineers overlook systems where the centrifugal pumps has to be used and lack of experience often results in under performing and oversized or wrong pumps with higher operating costs .Considering pump as a plug and play device will always add cost burden to the process.

SELECTING A CENTRIFUGAL PUMPS

Selection can be divided into technical and commercial considerations. Various steps are taken before concluding on the pumping equipment.

STEPS

1. Complete analysis of the system

A complete system analysis is necessary before proceeding with the centrifugal pumps selection . An engineer should consider following points

• Net Positive Suction Head (NPSHA) : Pump failures are often mistaken on number of unrelated causes and often NPSH is never examined. NPSHa or NPSH available should always be 1.5 m more than NPSHr or NPSH Required which has to be specified by Pump manufacturer. Difference less than 1.5 m will lead to Cavitation and may lead to complete failure of the pump.
• Fluid Type and Specification : The Nature of fluid is very important to know before selecting a pump. Impeller Design, Metallurgy of the pumps and type of pumps are largely dependent on the specification of the fluid. Few Considerations to be taken care are Solids to be handled, Temperature of fluid, Corrosive and abrasive nature of fluid , toxicity of fluid and we should check if the fluid is highly flammable .
• Criticality of the application : In case of application critical to the system a spare pump is necessary and is installed on the common header. The pump is of identical duty parameter and is used if one pump fails prematurely .
• Sealing requirement : Mechanical seals are used where leakage is not permitted . The reason for Zero tolerance can be hazardous liquid or it may be commercial motives .
• Construction Requirement : Various types of pumps are available in the market for numerous services. Some of the types are Cantilever Type Vertical Sump Pumps, Split Casing Pumps, End Suction , Torque Flow, Vertical Mixed Flow, Horizontal Mixed Flow ,Multi Stage Pumps etc. Right pump should be selected as per the space constraint , liquid to be handled and other commercial factors. Lubrication type of the pump is also critical in many cases where clean water is not available and oil lubricated pumps are desired. Cyclone separators shall be used .
• Efficiency  : Pump is one of the biggest consumer of Energy and therefore one should look for highly efficient system . In a continuous duty process plants it can save 1000’s of KiloWatt of Energy and in turn reduces the Power Bill and eventually help reduce CO2 Emission. But one should keep in mind a pump with highest efficiency does not mean high suitability for that particular application .
• Drivers : Pump can be driven using Steam Turbine, Diesel Engine and Electric Motor . It should be mentioned to the Pump Vendor .
•  Pumps in Parallel operation : Pumps in parallel operation should be analysed throughly. As all pumps have different hydraulic characteristics, system curves should be drawn for parallel operation and analysed properly

2. Commercial Considerations

• Capital Costs : Often buyers purchase oversized pumps with various misconceptions. Unnecessary safety margins are added and thus resulting in huge Capital Cost.I most of the cases discharge valve has to be throttled and resulting in increase Energy Cost.
• Operating and maintenance costs : A pump lower in capital cost does not always guarantee low operating cost . Unreliable pumps can increase downtime, burden on inventory of spares and increased power consumption .
• Efficiency : More efficiency means higher energy saving. Though energy efficiency should be one of the primary consideration , but it should not be the only consideration.For example a Torque Flow Pump with about 50% Efficiency is more suitable for fibrous and high solid content than a one size bigger Semi open impeller pump with efficiency over 70%. Though it has Lower efficiency , but it is almost maintenance free with negligible spare part cost. Saving on Maintenance ,operation and spare part cost is much more than more energy consumed in the process.
• Other Factors : Other Factors may include Service history and capabilities of the Vendor, Spare part cost and availability , proximity to the service center etc.

All pump systems vary in their size, type and operational requirements. Seek the help of an expert to assist you ensuring that your pump is energy efficient to improve your outputs and reduce energy consumption. We at Sintech pumps #1 centrifugal pumps suppliers in India to fulfill all your Industrial  pumps needs. We are available on www.sintechpumps.com or you can call us on +91 120 4176000. For more information on Pumping Systems please feel free to contact Mr Sahil Dhingra at sahil@sintechpumps.com