These suction pipe sizes, although larger than common for trade pumps of the same size, are believed to be amply justified by experience, and exert a powerful influence toward enabling the pump to run smoothly at high speed with water cylinders filling perfectly at each stroke. No defect is more common than restricted suction pipes.] _b._ A single suction entrance at the end of the pump is to be provided unless otherwise specified by the purchaser. Some situations render desirable side suction entrances, for permitting drafting water from two different sources of supply. These additional openings are to be considered as extras. Ordinarily, the purchaser can provide for such situations by proper piping at the single end suction entrance. If there is to be but one suction opening on casting, this had best be at center, for the reason that, if suction pipe ever gets to leaking air, this air stands a better chance of being distributed equally to the two plungers, and has less tendency to make the pump run unevenly. _c._ Standard flanges and standard bolt layouts as adopted by the Master Steam Fitters, July 18, 1894, must be used on all the above pipe connections, as per table given below. SCHEDULE OF STANDARD FLANGES. ==============+==============+========+==============+========= Size of Pipe ×| Diameter | Number | Size | Flange Diam. | of | of | of |Thickness of Flange. | Bolt Circle. | Bolts. | Bolts. | at Edge. | | | | Inches. | Inches. | | Inches. | Inches. --------------+--------------+--------+--------------+--------- 3 × 7-1/2 | 6 | 4 | 5/8 × 2-1/2 | 13/16 3-1/2 × 8-1/2| 7 | 4 | 5/8 × 2-1/2 | 7/8 4 × 9 | 7-1/2 | 4 | 3/4 × 2-3/4 | 15/16 4-1/2 × 9-1/4| 7-3/4 | 8 | 3/4 × 3 | 15/16 5 × 10 | 8-1/2 | 8 | 3/4 × 3 | 15/16 6 × 11 | 9-1/2 | 8 | 3/4 × 3 | 1 7 × 12-1/2 | 10-3/4 | 8 | 3/4 × 3-1/4 | 1-1/16 8 × 13-1/2 | 11-3/4 | 8 | 3/4 × 3-1/2 | 1-1/8 9 × 15 | 13-1/4 | 12 | 3/4 × 3-1/2 | 1-1/8 10 × 16 | 14-1/4 | 12 | 7/8 × 3-5/8 | 1-3/16 12 × 19 | 17 | 12 | 7/8 × 3-3/4 | 1-1/4 14 × 21 | 18-3/4 | 12 | 1 × 4-1/4 | 1-3/8 --------------+--------------+--------+--------------+--------- Do not drill bolt holes on center line, but symmetrically each side of it. On steam and exhaust openings loose flanges threaded for wrought-iron pipe must be provided. Where the situation will not permit of a standard flange on exhaust opening for lack of room, a special flange threaded to fit the proper size wrought-iron pipe may be used. 40. AIR AND VACUUM CHAMBERS.