With a 20-in (508-mm) Hg inlet vacuum, 5 percent entrained gas, and 10 percent dis-
solved gas, Table 3 shows that the liquid displacement is 74 percent of the rated displace-
ment. Thus, the output of the pump when handling this viscous, gas-containing liquid will
be (600 gal/min)(0.74) = 444 gal/min (28.0 L/s) without slip.
- Compute the effect of slip on the pump output
Slip reduces rotary-pump output in direct proportion to the slip. Thus, with 10 percent
slip, the output of this pump = (444 gal/min)(1.0 - 0.10) = 369.6 gal/min (23.3 L/s).
Related Calculations. Use this procedure for any type of rotary pump—gear, lobe,
screw, swinging-vane, sliding-vane, or shuttle-block, handling any clear, viscous liquid.
Where the liquid is gas-free, apply only the viscosity correction. Where the liquid viscos-
ity is less than 600 SSU but the liquid contains gas or air, apply the entrained or dissolved
gas correction, or both corrections.
SELECTION OF MATERIALS
FOR PUMP PARTS
Select suitable materials for the principal parts of a pump handling cold ethylene chloride.
Use the Hydraulic Institute recommendation for materials of construction.
Calculation Procedure:- Determine which materials are suitable for this pump
Refer to the data section of the Hydraulic Institute Standards. This section contains a tab-
ulation of hundreds of liquids and the pump construction materials that have been suc-
cessfully used to handle each liquid.
The table shows that for cold ethylene chloride having a specific gravity of 1.28, an
all-bronze pump is satisfactory. In lieu of an all-bronze pump, the principal parts of the
pump—casing, impeller, cylinder, and shaft—can be made of one of the following mate-
rials: austenitic steels (low-carbon 18-8; 18-8/Mo; highly alloyed stainless); nickel-base
alloys containing chromium, molybdenum, and other elements, and usually less than 20
percent iron; or nickel-copper alloy (Monel metal). The order of listing in the Standards
does not necessarily indicate relative superiority, since certain factors predominating in
one instance may be sufficiently over-shadowed in others to reverse the arrangement. - Choose the most economical pump
Use the methods of earlier calculation procedures to select the most economical pump for
the installation. Where the corrosion resistance of two or more pumps is equal, the stan-
dard pump, in this instance an all-bronze unit, will be the most economical.
Related Calculations. Use this procedure to select the materials of construction for
any class of pump—centrifugal, rotary, or reciprocating—in any type of service—power,
process, marine, or commercial. Be certain to use the latest edition of the Hydraulic Insti-
tute Standards, because the recommended materials may change from one edition to the
next.
SIZING A HYDROPNEUMATIC
STORAGE TANK
A 200-gal/min (12.6-L/s) water pump serves a pumping system. Determine the capacity
required for a hydropneumatic tank to serve this system if the allowable high pressure in