====================+========+=======+=======+========
=Size of Pump.= | =500= | =750= |=1000= | =1500=
| =gal.= | =gal.=|=gal.= | =gal.=
--------------------+--------+-------+-------+--------
=Solid Bronze.= | | | |
| | | |
Thickness at |7/16-in.|1/2-in.|1/2-in.|9/16-in.
extreme end | | | |
| | | |
Tapered evenly from |9/16 „ |5/8 „ |11/16 „|3/4 „
end to a thickness | | | |
next to bearing | | | |
of not less than | | | |
| | | |
Thickness at center |3/4 „ |3/4 „ | 3/4 „|13/16 „
bearing at least | | | |
--------------------+--------+-------+-------+--------
_f._ In other respects, the specifications for plunger bushings,
already given in Art. 28, will apply to the above.
_g._ The water piston used in the shell described above must expose not
less than 2 inches in width of fibrous packing, and must be of bronze,
with disc and follower accurately turned to a sliding fit, so that the
leakage past it will be a minimum, even when no fibrous packing is in
place. There must be at least 2 inches in length of metallic bearing on
both disc and follower.
The follower must be accurately centered and fitted to hub of piston,
so that alignment will not be disturbed if taken apart.
_h._ The water piston must be of simple and strong construction, with
follower bolts tightly fitted, and with fibrous packing so cut as to
prevent by-passing.
_i._ All materials used in construction of piston, except packing, must
be brass, bronze, or other non-corrosive metal.
_j._ Bushing studs must be of Tobin Bronze, and of such size and
number, that the maximum stress at the bottom of the screw thread
shall not exceed 10,000 lbs. per square inch, in the event of plunger
becoming fast in the bushing with 80 lbs. of steam in the steam
cylinders.
_k._ For each bushing stud there must be provided a composition nut and
check nut.
_l._ All minor parts exposed to the action of water in water cylinder,
that are not herein specified, must be of brass, bronze, or other
non-corrosive material.