Pumps and Hydraulics, Part 1 (of 2)

by N. Hawkins

NATIONAL STANDARD PUMP SIZES.

Pump Sizes.			Ratio of Piston Areas.	Capacity At 100 lbs. at Pump.
Steam.	Water.	Stroke.	About	Number of 11⁄8 in. Streams.	Nominal Gals. per Minute.	Actual Gals. per Min. as per Art. 4.
14 × 7 × 12			4 to 1	Two	500	4830
14 × 71⁄4 × 12						520
16 × 9 × 12			3 to 1	Three	750	8060
18 × 20 × 12			3 to 1	Four	1000	9990
181⁄2 × 101⁄4 × 12						1050
20 × 12 × 16			23⁄4 to 1	Six	1500	1655

NATIONAL STANDARD PUMP SIZES.(continuation)

Pump Sizes.			[B] Boiler Power Required		Full Speed.
Steam.	Water.	Stroke.	Horse Power.	Steam Pres. at Pump, lbs.	Rev. Per Minute.	Piston Travel Feet Per Minute.
14 × 7 × 12			100	40	70	140
14 × 71⁄4 × 12
16 × 9 × 12			115	45	70	140
18 × 20 × 12			150	45	70	140
181⁄2 × 101⁄4 × 12
20 × 12 × 16			200	50	60	160

FOOTNOTE:

[B] This boiler power is required for continuous running at full speed and pressure. It is, however, often best to put in a larger pump than the existing boilers could drive at full capacity, as a small boiler will drive a 750-gallon pump at the 500-gallon speed with very nearly as good economy as it can drive a 500-gallon pump at full speed. The pump then does not have to be changed when the plant is enlarged and the boiler power increased.

A steam piston relatively larger than necessary is a source of weakness. It takes more volume of steam, and gives more power with which to burst the pipes if the throttle is opened wide suddenly during excitement.

It has been common to make all fire-pumps with water plunger of only one-fourth the area of steam piston, with the idea that pump could thereby be more readily run at night, when steam was low. The capacity in gallons is thus reduced 25 per cent. as compared with a 3 to 1 plunger on the same steam cylinders.

b. The above sizes of steam and water cylinders and length of stroke have given general satisfaction and will now be considered as standard.