System One Pumps Selecting Centrifugal Pumps S1-201

System One Pumps Operating Parameters Head/Capacity Temperature Viscosity Density Vapor Pressure Solids Content Chemical Compatibility Multiple conditions

The system controls the pump. Remember… The system controls the pump.

System One Pumps Head/Capacity THE SYSTEM THE PUMP As the rate of flow is increased through the system, friction losses increase. The losses increase discharge head and reduce suction head. This increases Total Dynamic head (TDH) as flow is increased. The pump is a machine that is capable of producing a maximum amount of head at shutoff. As more of the pump’s energy is diverted to producing flow, less head is produced by the pump.

System One Pumps Head/Capacity 2 THE SYSTEM THE PUMP The positive relationship between flow and head is the basis for the upward slope of the SYSTEM CURVE. The tradeoff between head and flow is the basis for the downward slope of the HEAD/CAPACITY CURVE for the pump.

System One Pumps Head/Capacity 3 THE SYSTEM THE PUMP The system often changes. Open/close a valve. Add/remove restrictions. Levels in tanks change. Filters get clogged. Things get moved around. The pump is usually fixed. Impeller trim is set at assembly (can only be changed by disassembly or increased with new impeller.) Motor speed is fixed (unless VFD is employed.)

System One Pumps Temperature THE SYSTEM THE PUMP It can change the density, viscosity, and vapor pressure of the pumped fluid, thus changing the shape of the system curve. The above factors can also impact NPSHa. It can exceed the design limits of the pump or impact material selection. It can reduce lubricity of the pumped fluid. It can trigger the need for certain options. It can impact required clearances.

System One Pumps Viscosity THE SYSTEM THE PUMP Increases friction head Increases required pipe size. Or is the cause of problems if size is not increased. May or may not be constant in the system compared to at rest. Shifts head/capacity curve down. Shifts power curve up. Reduces efficiency. Above 500cps has large impact on efficiency. About 1000cps is practical limit.

System One Pumps Density THE SYSTEM THE PUMP Used to calculate head if only pressure is given. Impacts velocity head. No impact on head/capacity. Impacts power requirements proportionally.

System One Pumps Vapor Pressure THE SYSTEM THE PUMP Can be important factor in determining NPSHa. Often not given in data Need to know VP if other factors point to low NPSHa. Need to know VP if fluid is unfamiliar. Need to know VP if temperature is high. Pump will cavitate if NPSHa is less than NPSHr. In severe situations, can vapor lock the pump so nothing gets pumped.

System One Pumps Solids Content THE SYSTEM THE PUMP Clogging will change shape of system curve. Abrasives may damage components, changing the shape of the system curve. Strainer can effect NPSHa. Solids must fit through the smallest passage. Abrasives may impact material choice. Abrasives may dictate slower running speed. Can build up in close clearances or can jam the pump causing damage.

System One Pumps Chemical Compatibility THE SYSTEM THE PUMP Material selection. Corrosion can reduce pipe diameter, thus changing the shape of system curve. Material selection. Seal selection. Seal support system selection.

System One Pumps Multiple Conditions THE SYSTEM THE PUMP Can be on one system curve. (Different flow through the same system.) Usually not on same system Curve. (System has been changed.) If on same system curve, a variable speed drive may allow multiple conditions with one pump. If not, may not be possible with one pump and bypass loops, control valves, and/or VFD may be required.

System One pumps Using Curves

The system controls the pump. Remember… The system controls the pump.

System One Pumps The System Curve Shape is determined by physical elements of the system and the pumped fluid. Always parabolic. Determined by any two points on curve. Operation can only be on curve unless system is changed.

System One Pumps The Head/Capacity Curve Shows tradeoff between head and flow. Each curve is for a fixed pump speed and impeller diameter. The pump can only operate on the H/C curve unless speed or diameter is changed.

System One Pumps The Rated Duty The pump must operate somewhere on the H/C curve. The system controls where on the H/C curve the pump will operate. The actual duty is at the intersection of the two curves.

System One Pumps Selection Example 135 GPM (30.7 m³/hr) 42 ft TDH (12.8m) 68° F (20° C) 1 cps S.G. = 1 No Solids Water Design Flow, Confirm Units Maximum at design flow Maximum, Rated, Minimum Through pump, not at rest At rated temperature If present, get size, hardness, concentration Get name of fluid to verify other data and make material selection.

System One Pumps Curve 1

System One Pumps Curve 2

System One Pumps Curve 3

System One Pumps Curve 4

System One Pumps Curve 5

System One Pumps Curve 6

System One Pumps Curve 7

System One Pumps Application Information to Pump Datasheet

System One Pumps A Quote for Your Quotes: “Default values have been used for all data not provided to Blackmer. Please review Pump Performance Datasheet to confirm that default values used are reasonable for the intended service.”

System one pumps General Arrangement Drawings

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