Although suction chambers are not regularly subject to a pressure, it is sometimes desired to connect them to public water supplies, and where foot valves are used there is a chance of getting pressure on the suction, so that ample strength is necessary.
Foundry finish may be permitted on the joints at water cylinder heads and at hand-hole plates, provided surfaces are so true that a rubber packing not over 1⁄16 of an inch in thickness is sufficient to secure perfect tightness.
d. Conveniently placed hand-holes of liberal size must be provided for the ready examination and renewal of valve parts at the yoke end of water cylinders and in the delivery chamber.
This will necessitate holes not less than 6 × 8 inches, or its equivalent, for the two largest-size pumps, and holes proportionately as large for the 500 and 750-gallon pumps. The easy access to the valve parts is of vital importance, and must receive careful attention.
e. The thickness of metal for cylinder shell, valve decks, partitions, ribs, etc., will depend largely upon the form of construction, but, in a general way, to establish safe minimums for the average water cylinder, of nearly cylindrical form, whose flat surfaces are stiffly ribbed, we submit the table below:
| Size of Pump. | 500 gal. | 750 gal. | 1,000 gal. | 1,500 gal. |
|---|---|---|---|---|
Thickness of cylinder shell when of nearly cylindrical form | Inches. | Inches. | Inches. | Inches. |
| 7⁄8 | 1 | 11⁄8 | 11⁄4 | |
Thickness of valve decks when well ribbed | 11⁄4 | 11⁄4 | 11⁄4 | 11⁄4 |
Thickness of transverse partition, depending on ribbing | 11⁄4 to 11⁄2 | 11⁄4 to 11⁄2 | 11⁄2 to 2 | 11⁄2 to 2 |
Thickness of longitudinal partition, depending on ribbing | 11⁄4 to 11⁄2 | 11⁄4 to 11⁄2 | 11⁄4 to 2 | 11⁄2 to 2 |
Thickness of ribs | 3⁄4 | 7⁄8 | 1 | 1 |
Thickness of suction chamber | 5⁄8 | 3⁄4 | 3⁄4 | 7⁄8 |
Thickness of delivery chamber | 7⁄8 | 1 | 11⁄8 | 11⁄4 |
Lighter construction than herein specified will not be regarded as satisfactory, and any construction will be finally passed upon on examination of drawings.
f. The bolting of all parts of the water end is to be of such strength that the maximum stress at bottom of screw thread will not exceed 10,000 lbs. per square inch (disregarding for the moment the initial stress due setting up nuts) for a water pressure of 200 lbs. per square inch, computed on an area out to centre line of bolts.
No stud or bolt smaller than 3⁄4-inch should be used to assemble parts subject to the strain of water pressure, as smaller bolts are likely to be twisted off.
Although these pumps are not expected to be designed for a regular working water-pressure of 240 or 320 lbs., it is expected that bolts, shells, rods, etc., will be figured to stand this comparatively quiet, temporary, high pressure, exclusive of further allowance for initial strain due setting up of bolts, with a factor of safety of at least four.