Gardner Denver TWISTAIR EWDQ D Operating And Service Manual Download

Page: 41 / 68

13–11–602 Page 31

Never paint, lubricate or alter a relief
valve. Do not plug vent or restrict dis-
charge.

Operation of unit with improper relief
valve setting can result in severe per-
sonal injury or machine damage.

Insure properly set valves are in-
stalled and maintained.

Blowdown Valve (FIGURE 4–3) – This valve normal-
ly is used for control functions, but also serves to relieve
reservoir pressure following a shutdown. See addition-
al blowdown valve description on page 32.

Oil Level Gauge (FIGURE 1–6, Section 1, page 4) –
This gauge is located on the oil reservoir and indicates
the oil level.

Minimum Discharge Pressure Valve –
(FIGURE 1–3, page 2) – An internal spring–loaded
minimum pressure valve is used in the final discharge
line to provide a positive pressure on the coolant sys-
tem of the compressor even if the air service valve is
fully open to atmospheric pressure. This valve also
functions as a check valve to prevent back flow of air
from the shop air line when the unit stops, unloads, or
is shut down.

The valve incorporates an orifice which, when air is
flowing through it, maintains pressure in the water res-
ervoir. A spring–loaded piston valve senses air pres-
sure on the upstream (reservoir) side of the valve.
When the system pressure rises, the spring is overrid-
den and the valve opens to full porting.

Removal of the bolts from the body of
the minimum pressure discharge
valve will release a compressed
spring which can result in personal
injury or machine damage.

FIGURE 4–3 – BLOWDOWN VALVE

The valve does not require maintenance or adjustment.
If the valve fails to function, check the valve stem O–
ring for sealing, valve orifices for restriction, or valve
and valve seat for burrs and dirt.

Inlet Valve (FIGURE 1–4, page 3, and FIGURE 4–4,
page 32, this section) – The Inlet valve restricts the in-
let to control delivery and closes to unload the com-
pressor. At shutdown, the inlet valve closes to prevent
the back flow of air.

The inlet valve position is controlled by air pressure in
its piston cylinder, which is controlled by the “Auto
Sentry–ES” through solenoid valves IVC and IVO. As
pressure to the piston is increased, the valve closes to
restrict air flow and compressor delivery.

Solenoid Valves IVC and IVO – These valves control
position of the inlet valve in response to signals from
the “Auto Sentry

–ES”. With both valves de–ener-

gized, the normally open IVC valve allows control pres-
sure to the inlet piston to close the valve. If IVC only
is energized, the inlet valve is held in its current posi-
tion. If both valves are energized, control pressure is
relieved from the inlet piston to allow the valve to open.

Pressure Regulator – The pressure regulator is used
to supply a constant and low control pressure to pre-
vent damage to the inlet valve from “slamming.” The
regulator should be set for 25–30 psig (1.7–2.1 bar).

Shuttle Valve (FIGURE 4–5, page 32) – Also known
as a double check valve, the shuttle valve is a device
which will take two (2) supply signals and allow the one
with the highest pressure to pass through. The shuttle