coal trade bulletin - Clpdigital.org

50
pressor frame. A special crank shaft is supplied,
of sufficient length to properly accommodate the
electric motor, and is provided with a proper fit
for securing the rotor or armature to it. A water
wheel may be connected to the compressor in the
same manner, if this form of drive is preferred.
Both low and high pressure cylinders are made
with separate liners forced into the main castings,
the spaces between the liners and sylinder castings
forming the water jackets. The air passages in
the cylinder castings cover the entire area outside
of the jackets, the inlet and discharge sides
being separated by longitudinal partitions on the
sides of tr- cylinders. The surface on the outer
side of Lie jacket walls provides considerable
cooling area in addition to that of the intercooler.
The air cylinder heads are accurately bored,
transversely, for cylindrical rolling inlet valves,
and provided with ample ports for the admission
of air. Proper openings are bored in the edges
of the heads to receive the poppet discharge valve
cages and plugs.
The air inlet valves are of the Corliss type, of
cast iron, turned and fitted to accurately bored
seats in the cylindrical heads, the inlet ports being
of ample area to fill the cylinder at atmospheric
pressure when the compressor runs at maximum
speed; they are slotted in one end to receive "I"
headed valve stems, and tapped in the other end
to receive screw handles, to remove them from
the cylinder head. To remove these valves it is
only necessary to remove the back bonnets and
withdraw- the valves by means of the screw
handles, without disturbing the cylinder heads or
valve gear.
The air inlet valves are driven by steel valve
stems having "I" heads on their inner ends.
The stems are equipped with collars, with ground
joints between these collars and the bonnets, to
prevent leakage of air around the stems. The
stems are supported in rigid cast iron bonnets
securely bolted to the cylinder heads. The stems
derive their motion, through cast iron rocker arms
keyed to them, from a single crank pin, attached
to a small disc which is keyed to the end of the
main crank shaft opposite the flywheel. The connection
rods for operating the inlet valves are
placed side by side on this pin, one rod reaching
horizontally to the low pressure valves, and one
vertically to the high pressure valves. All valve
gear connection rods have adjustable bronze heads
for taking up wear.
The air discharge valves are of the poppet type,
internally guided on cast iron plugs, and held to
their seats by light steel springs; they seat in
bronze cages, readily removable by unscrewing
the valve plugs, and are sufficient in number to
provide ample area for the escape of the compressed
air from the cylinders. They are set,
THE COAL TRADE BULLETIN.
with their cages, in ports or pockets, arranged
radially in the air cylinder heads, and readily accessible
for inspection or removal. As these
valves act in a direction radial to the axis of the
cylinder, they avoid losses in efficiency due to
clearance space to the greatest possible degree.
There are no long ports or pockets leading to
them, in which air is trapped alter compression
instead of being expelled from the cylinder. These
valves are pressed from special cold rolled sheet
steel, of a texture adapted to withstand successfully
the blows and shocks to which discharge
valves are subjected, and are light in weight to
reduce hammering on the seats.
The intercooler, for removing the heat of compression
in the air from the low pressure cylinder,
is a substantial, cylindrical cast iron shell containing
an amount of cooling surface sufficient to
pioduce thorough cooling of the compressed air.
It is located immediately over the low pressure
cylinder and frame, and has flanged inlet and outlet
openings, and cast iron flanged connections between
it and the high and low pressure air cylinders.
It is supported on its inner end by a hollow,
cast iron, flanged leg, into which any accumulation
of water or oil will drain. This water
or oil may be blown off through a drain cock, provided
at the bottom. A pop safety valve, attached
to an opening on top of the intercooler, prevents
unsafe pressures in the intercooler or low pressure
cylinder.
The intercooling surface consists of a nest of
aluminum tubes through which the cooling water
circulates, entering at one end, traversing onehalf
the tubes, and returning through the remainder.
The ends of these tubes are expanded into
tw-o headers, the outer header being bolted against
a packed joint on the outer end of the intercooler
body, while the other header, inside the intercooler
body, is free to move with the expansion or
contraction of the tubes. Suitable baffle plates,
in the interior of the body, are so arranged that
the air, in flowing through it, will be compelled to
pass three times across the tubes, thus insuring
a thorough cooling effect. By removing the bolts
securing the outer header, the whole nest of tubes,
with the headers, may be withdrawn from the base
or shell for inspection or repair. Both headers
have removable covers which give access to the
ends of the tubes for the removal of sediment or
for the insertion of new tubes.
Both high and low pressure pistons are of cast
iron, each made in one piece. The low pressure
piston is cored out to reduce weight, but is thoroughly
ribbed inside to provide stiffness, while
the high pressure piston is practically solid, making
it equal in weight to the low pressure piston,
to preserve the equality in weight of the reciprocating
parts necessary for perfect balancing. Both