Development headings

For double suction pumps, using the HI convention, is taken as the total pump flow, although some pubHcations use half-flow, ie, flow per impeller eye. For multistage pumps, the developed head must be taken per stage for the NS calculation. By definition (eq. 9), high head, low flow pumps have low specific speed low head, high flow pumps, such as turbine and propeller pumps, have high specific speed. 

Eff. = Pump percentage efficiency F = Developed head, ft G = Flow, GPM... 

F = Factor for fractionation allowable velocity or packed column packing factor or pump developed head, ft. 

An approximate method to estimate pump efficiencies is based on the following formula. The expression is valid for flows between 100 and 1,000 gpm, and for developed heads between 50 and 300 ft. 

Flow rate Developed head Operational mode l20 - 240kg/s 1,2-1,8 MPa standby ... 

No. stages from (6) must develop head from (5) or determine average head/stage = Hp/no. stages = head/stage, ft-lb/lb or ft, per stage From the Fan Laws, H N. ... 

This shows that the pump head is determined primarily by the size and speed of the impeller and the pump efficiency, independent of the flow rate of the fluid. This is approximately correct for most centrifugal pumps over a wide range of flow rates. However, there is a limitation to the flow that a given pump can handle, and as the flow rate approaches this limit the developed head will start to drop off. The maximum efficiency for most pumps occurs near the flow rate where the head starts to drop significantly. 

Characteristic curves are plots or equations relating the volumetric flow rate through a pump to the developed head or efficiency or power or NPSH. 

Mixed flow develops head by combined centrifugal action and propeller action in the axial direction, suited to high flow rates at moderate heads [Fig. 7.3(e)]. 

Of the Elgin State Hospital patients who received injections of radium-226 (see Section 2.2.4), two patients developed bone sarcomas, four developed head carcinomas, and a seventh patient had both types of malignancy (statistical significance was not addressed) (Gustafson and Stehney 1985). 

In the assessment of human development, head circumference appears to be a... 

A centrifugal pump delivers 100 gpm of water at 60°F when the impeller speed is 1750 r/min and the pressure drop across the pump is 20 psi. If the speed is reduced to 1150 r/min, estimate the rate of water delivery and the developed head in feet if the pump operation is ideal. 

Pumping is a unit operation that is used to move fluid from one point to another. This chapter discusses various topics of this important unit operation relevant to the physical treatment of water and wastewater. These topics include pumping stations and various types of pumps total developed head pump scaling laws pump characteristics best operating efficiency pump specific speed pumping station heads net positive suction head and deep-well pumps and pumping station head analysis. 

The literature has used two names for this subject total dynamic head or total developed head (H or TDH). Let us derive TDH first by considering the system connected in parallel between points 1 and 2. Since the connection is parallel, the head losses across each of the pumps are equal and the head given to the fluid in each of the pumps are also equal. Thus, for our analysis, let us choose any pump such as the one with inlet g. From fluid mechanics, the energy equation between the points is... 

If values of ft), Q, and H are taken from the characteristics curves at the best operating efficiencies and substituted into Equation (4.43), values of specific speeds are obtained at these efficiencies. Eor example, from Eigure 4.8 at a <2 of 0.16 mVs, the best efficiency is approximately 66% corresponding to a total developed head... 

Total dynamic head or total developed head— The head given to the pump... 

Total developed head requirement— The equivalent head loss corresponding to... 

Developed pressure, equivalent to total developed head Power to fluid. 

Rate of discharge Total dynamic or developed head Total developed head requirement Velocity... 

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