Proportional Relief Valve (Prv) - Toro Reelmaster 3550-D Service Manual

Cutting Unit Circuit Testing − Proportional Relief
Valve (PRV) Pressure Test:
Test the performance of the mow control manifold pro-
portional relief valve (PRV) to make sure that the maxim-
um amount of fluid is available to the cutting unit motors
up to the set relief pressure. This test also ensures that
pump (P1) is capable of generating enough pressure to
open a properly functioning proportional relief valve.
Special Equipment Required:
S Flow Meter with Pressure Gauge that has at least
a 12 GPM (45 LPM) capacity.
S Phototach (non−contact tachometer).
1. Park machine on a level surface with the cutting units
lowered, reel engage/disengage switch in the disen-
gage position, and the mow/transport switch in the
MOW position. Engine should be off and the parking
brake disengaged.
2. Read Precautions for Hydraulic Testing in this
chapter.
3. Disconnect the inlet hose from the front hydraulic fit-
ting of the front left (#4) reel motor (Fig. 32).
4. Install tester between the hose and hydraulic fitting.
Make sure the flow control valve on tester is fully open.
5. Make sure backlap knob on the hydraulic manifold is
in the MOW position, and the reel speed knob is set to
maximum.
6. Start the engine, and move throttle to full speed
(3220 + 50 RPM).
7. Make sure hydraulic fluid is at normal operating tem-
perature by operating the machine for approximately 10
minutes.
8. Verify with a phototach that the pump speed is ap-
proximately 3090 RPM.
CAUTION
Keep away from reels during test to prevent per-
sonal injury from the rotating reel blades.
9. Engage cutting units.
10.Watch pressure gauge carefully while slowly closing
the flow control valve.
11. System pressure should reach 3000 PSI (207 Bar)
before the relief valve opens.
12.Set throttle to low speed and shut off engine.
Reelmaster 3550−D/3555−D/3575−D
1
1. Mow control manifold
1
2
#4
FRONT
#2
1. Reel motor #4
13.If specification is met, test pump (P1) flow (see Cut-
ting Unit Circuit Testing − Gear Pump (P1) Flow Test in
this chapter) If specification is not met, test relief valve
(PRV) solenoid, clean or replace valve (see Hydraulic
Manifold Service in this chapter) and retest.
14.Disconnect tester and reconnect hydraulic hose.
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2
Figure 31
2. Proportional relief valve
(PRV)
#1 #5
#3
Figure 32
2. Inlet hose
Hydraulic System