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4. Operation
The pressure reducing valve reduces pressure by the throttling the valve. The valve is composed of the
main valve and main valve seat for throttling, and air pressure control space, diaphragm, pilot valve, and
piston for pressure sensing and activation.
(1) When the pressure reducing valve is mounted correctly, main valve [9] and pilot valve [17] should
be closed when air pressure is no-pressure because of spring force. Slowly open the gate valve and
allow the high pressure fluid to flow in. Inlet pressure is applied to the downside of the main valve.
High pressure fluid passes through strainer [26] via inlet pressure passage [41] to also apply inlet
pressure to the downside of the pilot valve.
(2) Introducing air pressure into air chamber [44] flexes pilot diaphragm [8] to open the pilot valve.
(3) Inlet pressure via inlet pressure passage and pilot valve enters the upside of the piston. The pressure
overrides the pressure on the downside of the main valve and the load of main valve spring, to open
the main valve. The fluid then begins to flow from the inlet side.
(4) Reduced pressure is led to diaphragm chamber [43] via reduced pressure sensing port [42]. The
diaphragm receives the reduced pressure to be balanced with the air loading pressure, and control
the pilot valve travel.
(5) The change of pilot valve travel changes the flow rate of fluid to the upside of the piston, and
controls the main valve travel to obtain appropriate reduced pressure.
5. Nominal Size Selection Method
5.1 Standard loading pressure-setting pressure chart line
0.8
0.6
0.4
0.2
0
0.2
Loading pressure MPa
Rc1/4 Air loading
pressure port
0.4
0.6
0.8
1.0
‑3‑
No.
Parts name
1
Body
8
Pilot diaphragm
9
Main valve
11
Main valve seat
12
Piston
13
Cylinder
17
Pilot valve
18
Pilot valve seat
26
Strainer
41
Inlet press. passage
42
Reduced press. Sensing port
43
Diaphragm chamber
44
Air chamber
The setting pressures corresponding
to the loading pressure are shown left.
(P
: 1.0 MPa) As slight deviations
1
from the loading pressure-setting
pressure chart line shown left may
occur depending on conditions, such
as the length of the air line, etc., a
setting pressure which is high enough
to cover such deviations should be
selected.
■EPDT-101■
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