Pumps and Hydraulics, Part 2 (of 2)

by N. Hawkins

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.