Lit. No. 30118, Rev. 00
June 15, 2020
17
HYDRAULIC SYSTEM
CHECK VALVES
The check valves supply make-up
fl
uid to the
low-pressure side of a ram that is extending or
retracting through a relief valve due to impact on
one or both wings.
A pilot-operated check valve (PC) allows
fl
uid to
fl
ow
in only one direction unless it receives pilot pressure
through another circuit to shift it to an open position.
Tighten check valves to
19–21 ft-lb
.
Relief Valve Settings
RV1
Pump
2250 ± 100 psi
RV3
DS Ram Rod End
2200 ± 100 psi
RV4
PS Ram Rod End
RV5
DS Ram Base End
3400 ± 100 psi
RV6
PS Ram Base End
RELIEF VALVES
When all cartridge valves are closed, hydraulic
fl
uid is trapped in the ram by the solenoid cartridge
valves, check valves, base-end relief valves, and
rod-end relief valves.
When the snowplow contacts an object while
plowing, force of the impact increases hydraulic
pressure in the base end of the ram. When
pressure exceeds 3400 psi, the ram's base-end
relief valves open, allowing hydraulic
fl
uid back to
the reservoir. Due to the small volume on the rod
side of the piston,
fl
uid is not replaced. This causes
a slight temporary vacuum in that circuit.
When the snowplow contacts an object while back
dragging, force of the impact increases hydraulic
pressure in the rod end of the ram. When pressure
exceeds 2200 psi, the ram's rod-end relief valve
opens, allowing hydraulic
fl
uid into the reservoir
passage. The base-end check valve allows
fl
uid to
fi
ll the base end of the ram. Because of di
ff
erential
area on either side of the ram's piston,
fl
uid
fl
ows
from the reservoir to the base end.
NOTE: See "Striking an Object While Plowing
Forward" and "Striking an Object While Back
Dragging" schematics for details.
Check Valves
CV1
CV08-2004
CV2
CV3
CV4
CV5
CV08-2059
Primary
Manifold
CV5
Secondary
Manifold
CV3
CV4
CV6
CV2
CV1
Primary
Manifold
Secondary
Manifold
RV3
RV1
Pressure
Test Port
RV4
RV5
RV6
