Page 195 - Chemical Process Equipment - Selection and Design

REFERENCES 167

rake horsepower is the driver power output needed to form of supporting sidewall and are suited to handling slurries
operate the pump. BHP = NHP/(pump efficiency). without clogging [Fig. 7,2(a)].
,
Driver ~ ( ~ ~ e NB o ~ ~ ~ efficiency) = b. Semienclosed impellers have a complete shroud on one side
~= BHPJ(driver
HHP/(pump efficiency)(driver efficiency). [Fig. 7.3(c)]; they are essentially nonclogging, used primarily in
small size pumps; clearance of the open face to the wall is
S CONCERNING CENTRIFUGAL AND RELATED PUMPS typically 0.02 in. for 10 in. diameters.
e. Closed impellers have shrouds on both sides of the vanes from
Axial AQW is flow developed by axial thrust of a propeller blade, the eye to the periphery, used for clear liquids [Fig. 7.3(b)].
practically limited to heads under 50 ft or so.
Centrifugal pump consists of a rotor (impeller) in a casing in Mechanical seals prevent leakage at the rotating shaft by sliding
which a Liquid is given a high velocity head that is largely converted metal on metal lubricated by a slight flow of pump liquid or an
to pressure head by the time the liquid reaches the outlet. independent liquid [Figs. 7.4(c) and (d)].
cuwes
~~ar~cte~s~c are plots or equations relating the Mixed flow: develops head by combined centrifugal action and
volumetric Aow rate through a pump to the developed head or propeller action in the axial direction, suited to high blow rates at
efficiency or power or NPSH. moderate heads [Fig. 7.3(e)].
Diffuser type: the impeller is surrounded by gradually Multistage: several pumps in series in a single casing with the
expanding passages formed by stationary guide vanes [Figs. 7.2(b) objective of developing high heads. Figure 7.6(c) Is of characteristic
and 7.3(d)]. curves.
Double su~hion: two incoming streams enter at the eye of the Performance curves (see characteristic curves).
impeller on opposite sides, minimizing axial thrust and worthwhile Single suction: the liquid enters on one side at the eye of the
for large, high head pumps [Fig. 7.2(b)]. impeller; most pumps are of this lower cost style [Fig. 7.2(c)].
Double volute: the liquid leaving the impeller is collected in Split case: constructed so that the internals can be accessed
two similar volutes displaced 180" with a common outlet; radial without disconnecting the piping [Fig. 7.2(a)].
thrust is counterbalanced and shaft deflection is minimized, Stuffing box: prevent leakage at the rotating shaft with
resulting in lower maintenance and repair, used in high speed compressed soft packing that may be wetted with the pump liquid
pumps producing above 500 ft per stage. or from an independent source [Figs. 7.4(a) and (b)].
Impeller: the rotor that accelerates the liquid. Volute type: the impeller discharges the liquid into a
a. Open impellers consist of vanes attached to a shaft without any progressively expanding spiral [Fig. 7.2(a)].

2. S. Chalfin, Control valves, Encyclopedia of Chemical Processing and
Design, Dekker, New York, 1980, Vol. 11, pp. 187-213.
3. F.L. Evans, Equipment Design Handbook for Refineries and Chemical
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Dekker, New 'York, 1979, Vol. 10, pp. 157-409. 315-332.
2. F.L. Evans, CNompressors and fans, in Equipment Design Handbook for 4. J.W. Hutchinson, ISA Handbook of Control Vdues, Inst. SOC. America,
Refineries and Chemical Plants, Gulf, Houston, 1979, Vol. 1, pp. 54-104. Research Triangle Park, NC, 1976.
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York, 1970, pp. 6.61-6.93. 6. J.L. Lyons, Encyclopedia of Valves, Van Nostrand Reinhold, New York,
4. W. James, C(ompressor calculation procedures, in Encyclopedia of 1975.
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Petrochemical Plants, 'Gulf, Houston, 1983, Vol. 3, pp, 251-396. 9. R. Weaver, Process Piping Design, Gulf, Houston, 1973, 2 Vols.
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Ejectors Pumps
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43-51 (1959). Ann Arbor Science, Ann Arbor, MI, 1983.
2. B.F. Dodge, Chemical Engineering Thermodynamics, McGraw-Rill, New 2. N.P. Cheremisinoff, Fluid Flow: Pumps, Pipes and Channels, Ann Arbor
York, 1944, pp. 289-293. Science, Ann Arbor, MI, 1981.
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Plants, Gulf, Houston, 1979, Vol. 1, pp. 105--117. 4. H. Gartmann, DeLaval Engineering Handbook, McGraw-Hill, New
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5. RE. Richenberg and J.J. Bawden, Ejectors, steam jet, in Encyclopedia 5. I.J. Karassik and R. Carter, Centrifugal Pump Selection Operation and
of Chemical Processing and Design, Dekker, New York, Vol. 17, pp. Maintenance, F.W. Dodge Cop., New York, 1960.
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I. F.A. Kristal and F.A. Annett, Pumps, McGraw-Hili, New York, 1940.
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Piping
9. S. Yedidiah, Centrifugal Pump Problems, Petroleum Publishing, Tulsa,
1. ANSI Piping Code, ASME, New York, 1980. OK, 1980.