Impellers open type

Milk-of-lime transfer pumps should be of the open impeller centrifugal type. Pumps having an iron body and impeller with bronze trim are suitable for this purpose. Rubber-lined pumps with rubber-covered impellers are also frequently used. Makeup tanks are usually provided ahead of centrifugal pumps to ensure a flooded suction at all times. Plating out of lime is minimized by the use of soft water in the makeup tank and slurry recirculation. Turbine pumps and eductors should be avoided in transferring milk of lime because of scaling problems. 

Figure 3-2. Cut-a-way section of single-stage pump. Part 1 (above) enclosed type impeller. Part 2 (lower left) open type impeller. (Courtesy Peerless Pump Div. FMC Corp.)...

Wearing plates With open type impellers or end clearance wearing fits, these perform the same purpose as wearing rings do with radial clearances. 

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. 

Note Integral gear pumps are frequently utilized in low specific speed applications, where efficiency is optimized with open type impellers. 

Open-type turbines This kind of turbines is also called full-blade turbines (Figure 3.17). The blades are vertical (parallel to the axis of the drive shaft) and could be straight or curved. They are cost-effective impellers for operations veiy near the floor of a tank for agitating the... 

Figure 7.10. Some types of impellers for centrifugal pumps, (a) Open impeller, (b) Semiopen impeller, (c) Shrouded impeller, (d) Axial flow (propeller) type, (e) Combined axial and radial flow, open type, (f) Shrouded mixed-flow impeller, (g) Shrouded impeller (P) in a case with diffuser vanes (V). (h) Turbine impeller.

FIGURE 4.4 Various types of pump impellers (a) axial flow (b) open type (c) mix-flow type and (d) shrouded impeller. 

The sani-open impellers have only one wearing ring. For liquids having comparatively high viscosity like molten sulfur a semi-open type impeller is usually preferred. These impellers are non-clogging and easy to clean whenever the pump is removed for maintenance. The frontal clearance, i.e., the distance between the suction plate/cover face and the impeller is very important when using a semi-open impeller. An increase in the frontal clearance drastically reduces the head or flow of the pump. 

Circulation pump capacity, head, impeller design (shonld be semi-open type if more suspended solids or ciystals will be present in the solution), power consumption, shaft seals to be informed by vendor. This will depend on the length of the tubes, flow velocity, density of the solntion and whether boiling will be allowed or not allowed in the tnbes. 

Entrained liquids and solids also can affect operating life. When dirty air must be handled, open-type impellers should be used. An open design provides the ability to handle a moderate amount of dirt or other solids in the inlet-air supply. However, inlet filters are recommended for all... 

A semi-open impeller has exposed blades, but with a support plate or shroud on one side. Some people prefer the name semi-enelosed. These types of impeller are generally used for liquids with a small percentage of solid particles like sediment from the bottom of a tank or river, or crystals mixed with the liquid (Figure 6-17). 

Figure 3-15. Impeller types. Open impeller for corrosive or abrasive slurries and solids. (Courtesy Goulds Pumps, Inc.)...

The manufacturer must know if the suction side of the pump is associated with v acuum equipment, or is to lift the liquid. This can make a difference as to the type of impeller suction opening he provides. If the system operates intermittently it should be noted. A piping diagram is often helpful in obtaining full benefit of the manufacturer s special knowledge. 

This dispersion of the gas passes through several stages depending on the gas feed rate to the underside of the impeller and the horsepower to the impeller, varying from inadequate dispersion at low flow to total gas bubble dispersion throughout the vessel. The open, without disk, radial flow type impeller is the preferred dispersing unit because it requires lower horsepower than the axial flow impeller. The impeller determines the bubble size and interfacial area. 

Figure 12-46F. Open radial blade impeller, Type R. (Used by permission Bui. Centrifugal Compressors Single Stage. A C Compressor Corporation.)...

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