the top of the magnet valve and releasing
it quickly several times. If the blowing
persists shut off the air from the apparatus
and unscrew the plug at the bottom of the
magnet valve. Carefully lower the plug
straight down and the spring and lower
valve will drop down with it. Wipe the
valve perfectly clean and with a small
stick and piece of cloth also clean the
valve seat.
(2) When replacing the lower valve, spring,
plug or valve nut, first remove the cap
over the armature so that in case the
valve stem does not properly enter the
hole in the stem (k), it is free to be lifted
by the advancing stem instead of being
damaged. If the inlet or exhaust valve is
not tight, the difficulty can sometimes be
overcome by inserting a small screwdriver
in the top slot and spinning it a few times
on the seat.
c. Exhaust Valve Leakage.
(1) In case a standard valve "blows" through
the exhaust port when the coil is
Figure 22. Cross section of open-coil type standard
energized it is a sign that the exhaust
magnet valve.
valve (d) is not seating properly on the
seat (e). This may be due to any one of
the following causes which are mentioned
The spring (a) not only closes the valve
in
(b) but at the same time lifts the valve (d)
off its seat (e) and leaves a clear opening
for the escape of air from the operating
cylinder through the passage (j and f) to
atmosphere. When the magnet coil is
energized the armature (h) pushes down
on the stem (k), opens the valve (b) and
admits air from the supply to the operating
cylinder through the passage (p), and at
the same time closes the exhaust valve
(d).
(6) The maintenance procedure for all valves
is practically the same.
b. Inlet valve leakage.
(1) Occasionally a valve will "blow" (i. e.,
give out a hissing sound) due to leakage
of air, if this occurs when the magnet coil
is de-energized and the air blows out of
the magnet exhaust port (f), it is an
indication that the lower (inlet) valve is not
seating properly. This trouble is caused
generally by the presence of a little dirt on
the valve seat and in most cases can be
"cured" by pressing down the pinion and
Figure 23. Cross section of open-coil type standard
co-ordinated magnet valve.
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