Pumping single stage

Vane compressors tend to be limited to low pressure service, generally less than 100 to 200 psi discharge. They are used extensively as vapor recovery compressors and vacuum pumps. Single-stage vane compressors can develop 27 in. Hg vacuums, two-stage compressors can develop 29.0 in. Hg, and three-stage compressors can develop even higher vacuums. 

Fig. 8. Single-stage between-bearings double-suction pumps (a) axially split design and (b) radially split design.

An axially spHt pump typically has a volute, and offers the advantage of easy maintenance because of quick upper-half casing and rotor removal that is similar to a single-stage version. The piping, attached to the no22les located at the lower half of the casing, remains undisturbed. 

Axial-Plow Propeller-Type. For high capacity, single-stage propeller-type vertical pumps are used. One appHcation of this design is as an intake of cooling water from a river or a hoi ding basin via a pipeline. 

Sump Pumps These are small single-stage vertical pumps used to drain shahowpits or sumps. They are of the same general construction as vertical process pumps but are not designed for severe operating conditions. 

This specification covers horizontal, end suction, vertically split, single-stage centrifugal pumps with top centerline discharge and hack pullout feature. 

An example of a typical turboexpander is shown in Fig. 29-46. Radial-flow turbines are normally single-stage and have combination impulse-reaction blades, and the rotor resembles a centrifugal-pump impeller. The gas is jetted tangentially into the outer periphery of the rotor and flows radially inward to the eye, from which the gas is jetted backward by the angle of the rotor blades so that it leaves the rotor without spin and flows axially away. 

In this group the impeller or impellers are mounted onto the shaft with the bearings on both ends. The impellers are mounted between the bearings. These types of pumps are further divided into single stage (one impeller) or multi-stage pumps (multiple impellers). 

Power is generated by the pressurized gas expanding through an 11,000 rpm single-stage, radial-inflow turbine expander, which drives a synchronous generator. Exhaust gas from the expander is liquified by air-cooled condensers and is pumped back to the heat exchangers to repeat the cycle. 

In-house correlation of pumps should be made using gpm vs. cost with head as a parameter. These should result in step functions, since one size pump with different impellers can serve several flow rates and heads. Different correlations should be made for each type of pump. The price of a vertical multistage pump may be quite different from a horizontal splitcase multistage pump. A sump pump with a 15-ft drive shaft would cost more than a single-stage horizontal pump with the same gpm and head. 

The sliding-vane compressor is widely used as a vacuum pump as well as a compressor, with the largest volume approximately 6,000 cfm. The lower end of the volume range is 50 cfm. A single-stage compressor with atmospheric inlet pressure is limited to a 50 psi discharge pressure. In booster service, the smaller units can be used to approximately 400 psi. 

Consider the aqueous waste described in Example 11.1. (Qf = 26 m /hr, Cp = 0.035 kmol/m and jtf = 1.57 atm.). A 30 atm (PF) booster pump is used to pressurize the feed. Hollow fiber modules are to be configured in parallel (single stage) with the feed distributed equally among the units. The following properties are available for the HFRO modules ... 

In subsequent years, Savery made important improvements that benefited future steam inventions. In June 1699 he demonstrated to the Royal Society a pump with two receivers, each with a separate, hand-controlled steam supply. This ensured improved continuity of operation, allowing one receiver tn operate in its vacuum stage and the other under steam pressure. In 1701, he added two more critical steps a second boiler, avoiding the need to shut down the fire and pump, between stages and he replaced the two interconnected steam cocks with a single valve, run with a manually operated long lever. This may have been the inspiration for the modern slide valve and his inventiveness created, in effect, the world s first feed-water heater. 

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.)...

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

Figure 3-12. Single-stage, high speed (>5000 ft) centrifugal process pump. Pumps are high speed, gear driven, and especially suited for applications in light hydrocarbon liquid service. (Courtesy Sundstrand Fluid Handling, Inc.)...

Figure 3-50. Typical centrifugal pump characteristic curve vrith auxiliary specific speed curve. Double-suction, single-stage, 6-in. pump, operating at 1760 rpm constant speed. (By permission, Karassik, I. and Carter, B., Centrifugal Pumps, McGraw-Hill Book Co., inc., 1360, p. 197.)...

The values are averaged from tests of conventional single-stage pumps, 2-inch to 8-inch, with capacity at best efficiency point of less than 100 GPM on water performance. 

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