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Pumps and Hydraulics, Part 2 (of 2)

Chapter 22: MARINE PUMPS.
By N. Hawkins
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About This Book

The volume provides a practical, systematically organized reference on pumps and hydraulic machinery, covering principles of hydro-mechanics, hydrostatics and pneumatics, and laws governing fluids; detailed treatments of air and vacuum pumps, compressors, air-lift devices, steam fire engines, mining and marine pumps, centrifugal, rotary and turbine pumps, injectors and ejectors, the pulsometer, and speed governors; utilities, attachments, valves, piping, tools, management guidance, worked calculations, tables, historical notes, a glossary, and numerous illustrations for engineers, millwrights, and operators.

MARINE PUMPS.

These are made both horizontal and vertical; the prime consideration being in all cases the amount of floor space the pump will require. This is especially true in reference to small steam vessels, pleasure craft, etc.

Owing to the unusual corrosion, caused by galvanic action, salt and various impurities, marine pumps are built of iron with brass linings, but frequently with the entire water ends of bronze.

The arrangement of the water valves in the most approved forms of vertical pumps is such that the pistons are always submerged, and the water valves sealed, thereby securing immediate lift of water through the suction pipe, and steady, quiet operation of the pump; many horizontal pumps of the ordinary duplex design are also used on shipboard.

The ship’s pump is common to all vessels and used to keep the “hold” free from water. It is usually worked by hand but it is the law in certain countries that the “ship’s pump,” aside from steam vessels—shall be driven by windmill power; it is said to be an odd sight to see the practical working of these at sea.

Fig. 447.

The illustration on page 156 shows a marine vertical pump of the Davidson pattern, designed to work against a pressure of 250 pounds per square inch. The table given herewith will show the sizes and principal details of these pumps.

Table.

Steam
Cylinder		 Water
Cylinder		 Stroke,
Inches.		 Gallons
per
Single
Stroke of
Each
Piston.		 Horse-power of
Boiler, based on
30 lbs. of water
per H. P.
per hour,
which the pump
will supply
with ease.		 Steam
Pipe		 Exhaust
Pipe		 Suction
Pipe		 Discharge
Pipe
  4 21⁄2   4   .084    165 H. P.   1⁄2   3⁄4 2 11⁄2
  41⁄2 23⁄4   6   .154    300    „   1⁄2   3⁄4 21⁄2 2
  51⁄2 31⁄2   6   .15    500    „ 1 11⁄4 3 21⁄2
                 
  6 4   8   .435    870    „ 1 11⁄4 31⁄2 3
  7 4   8   .435    870    „ 11⁄4 11⁄2 31⁄2 3
  7 41⁄2   8   .55 1,100    „ 11⁄4 11⁄2 4 3
                 
  8 5 10   .85 1,700    „ 11⁄2 2 41⁄2 31⁄2
  8 5 12 1.02 2,000    „ 11⁄2 2 41⁄2 31⁄2
  9 51⁄2 10 1.03 2,000    „ 11⁄2 2 41⁄2 4
                 
10 6 10 1.225 2,450    „ 2 21⁄2 5 41⁄2
10 6 12 1.469 2,900    „ 2 21⁄2 5 41⁄2
12 7 12 2.00 4,000    „ 2 21⁄2 6 5

The capacity for boiler feeding in the table is based upon sixty single strokes for each pump per minute.

The suction and discharge openings, as will be seen in the figure, are on both sides. The water piston is packed for hot and cold water and special valves are furnished as may be necessary.