| Square inches | 23·11 | 35·63 | 43·98 | 72·38 ---+-----------------------+---------+--------+-------+-------- _d._ If we consider using any one of the three sizes of valves below, whose port areas may be assumed approximately as =========+================+===========+================ Diam. | Diam. of Valve | Circ. of | Valve Port Valve. | Port. Circ. | V. C. | Area (Net). | | Circle. | Square inches. ---------+----------------+-----------+---------------- 3″ | 2-1/2″ | 7·85″ | 3·5 3-1/2″ | 3″ | 9·42″ | 4·7 4″ | 3-1/2″ | 10·99″ | 6·3 ---------+----------------+-----------+---------------- given, then the necessary number of valves per section will be as in the table following: =================+============+============+============+============= =Size of Pump.= | =500= | =750= | =1000= | =1500= | =gal.= | =gal.= | =gal.= | =gal.= -----------------+--+------+--+--+------+--+--+------+--+--+------+--- =Size of Valves.=|3″|3-1/2″|4″|3″|3-1/2″|4″|3″|3-1/2″|4″|3″|3-1/2″|4″ -----------------+--+------+--+--+------+--+--+------+--+--+------+--- Necessary number | | | | | | | | | | | | of valves | | | | | | | | | | | | to satisfy | | | | | | | | | | | | (4) under _c_ | 6| 5 | 5| 9| 8 | 7|11| 10 | 8|19| 16 |14 -----------------+--+------+--+--+------+--+--+------+--+--+------+--- Necessary number | | | | | | | | | | | | of valves | | | | | | | | | | | | to satisfy | | | | | | | | | | | | (3) under _c_ | 7| 5 | 4|10| 8 | 6|13| 10 | 7|21| 16 |12 -----------------+--+------+--+--+------+--+--+------+--+--+------+--- The exact number and size of valves will, however, not be insisted upon provided the aggregate valve area and the aggregate valve outlet area for each section is not less than that given in the table under _c_ for the limiting lift of 1/2 inch. Manufacturers will note that with the established lift of 1/2 inch, the 3-1/2-inch valve will permit a valve outlet area more nearly equal to its port area than will either the 3-inch or 4-inch valves, and a _relatively_ less number of valves will satisfy the specifications. 34. DELIVERY VALVES. _a._ The total lift of delivery valves must not exceed one-half inch. This is to avoid valve slam, as explained in Art. 33. _b._ The aggregate valve-port area should be restricted to about two-thirds the suction-valve area.