74. On completion of the plant the pump will be operated with all outlets closed and, under this condition, the power consumption must not be more than 50% of that required under test conditions.
75. Same as for Class 1.
76. To test the capacity of the plant, .... hose lines each 75 ft. long shall be attached to the inlets, each hose to be fitted with standard vacometer with ⁷⁄₈-in. opening. Under these conditions a vacuum of 1 in. mercury must be maintained in each vacometer.
77 and 78. Same as for Class 1.
CLASS 5
To Give Widest Competition.
1. Same as for Class 1.
2. Exhauster to be piston, rotary or centrifugal fan type.
3. The piston type of exhauster shall be double-acting and so designed that the cylinder clearance shall be reduced to a minimum, or suitable devices shall be employed to minimize the effect of large clearances.
4. The induction and eduction valves may be either poppet, rotary or semi-rotary, and shall operate smoothly and noiselessly.
5. The piston packing shall be of such character as to be practically air tight under working conditions and constructed so that it will be set out with its own elasticity without the use of springs of any sort. If metallic rings are used, they must fill the grooves in which they are fitted, both in width and depth, and must be concentric; that is, of the same thickness throughout. The joint in the ring or rings to be lapped in width but not in thickness, and if more than one ring is used they are to be placed and doweled in such position in their respective grooves so that the joints will be at least one-fourth of the circumference apart.