Westinghouse 5026 Instruction Pamphlet page 12

~2
CI{OSS COMI'OUl'<() .~m COMPRESSORS
steam cylinder, through passage /, chamber F and pas­
sage e, to the atmosphere. The downward movement of
the low pressure steam piston causes the high pressure
air piston to compress the air in the lower end of the
high pressure air cylinder, to its final pressure, for'cing
same through passage v' past discharge valve 42, and
through passage
w'
into the main reservoir.
When the pistons have moved as explained, the. low
pressure steam piston 8 has completed its downward
stroke; the upper ~nd of the high pressure air cylinder
is filled with air compressed from the upper end of the
low pressure air cylinder; and the upper end of the low
pressure steam cylinder is filled with steam exhausted
from the upper end of the high pressure steam cylinder.
However, just before the low pressure steam piston has
completed its downward stroke, steam is by-passed
through the three by-pass grooves
x'
from the upper to
the lower side of the low pressure steam piston, thereby
preventing an. accumulation of back pressure in the upper
end of the- high pressure steam cylinder. At this stage of
the cycle also, the high pressure steam piston 7 has
completed its upward stroke; the lower end of the low
pressure air cylinder is filled with air at atmospheric
pressure; and the lower end of the high pressure steam
cylinder is filled with live steam. Here again the com­
pressor is reversed, by means of the reversing valve plate
attached to the high pressure steam piston coming in
contact with the shoulder of the reversing valve rod,
which in turn, actuates the reversing valve, and the cycle
of operation already described is repeated.
The function of the relief valves as shown above inlet
valve 37 and under intermediate discharge valve 40,
23 OPERATION
Plates 1 and 2, is'to relieve the pressure acting on the low
pressure air piston, should it exceed the normal amount
due to back leakage past the intermediate discharge
valves. In the event of the development of excessive
pressure, valve 158 is unseated against the force of spring
161, which opens a passage between the air cylinder and
the exhaust port in the relief valve body. Spring 161 i,.s
adjusted to a slightly higher pressure than that normally
developed in the low pressure air cylinder, and the relief
valve will thus prevent the accumulation of pressure
which might interfere with normal operation of the com­
pressor.
-,
Lower Intermediate
Valve Cage with Upper Inlet Valve Chamber Cap
Relief Valve with Relief Valve
Fig. 7. Sectional Views of the Relief Valves