Impeller double suction

Q)nvcrt to a pump with a double suction impeller. Double suction impeller pumps are for low NPSH applications. 

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. 

According to HI convention, for double-suction pumps, Q is half of the total pump flow, ie, taken per impeller eye. The value of S is calculated at the best efficiency point (BEP) at maximum impeller diameter. 

Motor running backward or impeller of double suction design is mounted backward. Discharge pressure developed in both cases is about one-half design value. 

Use a double. suction impeller. Convert an end suetion centrifugal pump into a split ease horizontal design. 

Howe er, most conventional pump impellers receive the fluid into the impeller eye, at the center or inside diameter of the impeller. There are single suction impellers, and dual or double suction impellers with two eyes, one on each side. Dual suction impellers are mostly specified for low NPSH applications because the eye area is doubled (it ean reeeive twice as much fluid at a lower velocity head). Dual suction impellers arc mostly found on split case pumps where the shaft passes completely through the impeller. But they can afso be found mounted onto the end of the shaft in some special pump designs. 

Where N = the speed of the pump/motor in revolutions per minute Q = the sc]uare root of the flow in gallons per minute at the Best Efficiency Point BKP. Eor double suction impellers, use I/2 BEP flow. H = the discharge head of the pump at the BHP. 

Figure 3-4. Centrifugal Pump, double suction single-stage impeller. (Courtesy Allls-Chalmers Mfg. Co.)...

Enclosed double-suction Impeller with sealing rings on both sides. (Courtesy The Deming Co.)... 

Pulpy solids such as paper stock Single suction. Double suction only used on very slight solids concentrations and then with special end clearance wearing fits. Closed. Open type used to be standard but change to end clearance wearing fits made closed impellers better suited. 

Pump impellers are further classified as to the inlet flow arrangement such as single suction (which has a single inlet on one side) and double suction (which has a double inlet on each side of the impeller). 

IMPELLER, hydraulically balanced — double suction enclosed type for better performance under critical suction conditions. 

Double suction, 166, 167 Efficiency, 200 High speed, 169 Illustrations, 161, 164 Impellers, 164, 170 In parallel, 177, 178 In series, 176, 178 Liquid horsepower, 200 Materials of construction, 211 Mixed flow, 169 Multistage, 167 Operating curves, 180 Packing, shaft, 170... 

Single/Double suction Vertical/Horizontal mounting Impeller type ... 

Figure 7.9. Some types of centrifugal pumps, (a) Single-stage, single suction volute pump, (b) Flow path in a volute pump, (c) Double suction for minimizing axial thrust, (d) Horizontally split casing for ease of maintenance, (e) Diffuser pump vanes V are fixed, impellers P rotate, (f) A related type, Ihe turbine pump.

Double suction two incoming streams enter at the eye of the impeller on opposite sides, minimizing axial thrust and worthwhile for large, high head pumps [Fig. 7.2(b)]. 

Number of stages Single/double suction Operating efficiency Vertical/horizontal mounting Rotational speed Impeller type Impeller diameter Construction materials Casing... 

The regenerative pumps (1) consist of two double-suction impellers, each with a diameter of 0.036 m in series to increase the total pump head. All pumps are equipped with speed control and differential pressure sensors. The mixed phases enter the fluid cyclone (2) of 0.020 m diameter with a tangential tube entry. The underflow of the cyclones is connected to a small storage tank (3) with level con-... 

What is the upper limit of specific speed and capacity of a 1750-r/min single-stage double-suction centrifugal pump having a shaft that passes through the impeller eye if it handles clear water at 85°F (302 K) at sea level at a total head of 280 ft with a 10-ft suction lift What is the efficiency of the pump and its approximate impeller shape ... 

FIG. 10-42 Two-stage pump having double-suction impellers. 

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