SECTION 7 – HYDRAULICS
3120933 Rev. 0
USTC
7-5
Burst-Of-Speed and Telescope Out Relief Valve
On older models two inline relief valves are used to
protect the burst-of-speed and telescope out func-
tions. Newer models use a manifold block valve with
cartridges to protect these two circuits.
Test methods are similar for each circuit.
1. Attach a 0-4000 psi (0-276 bar) pressure gauge
to the gauge port on inline valves or manifold.
Note: Block valves have gauge ports labelled G-1
for the burst-of-speed circuit and G-2 for the
telescope out circuit.
2. For burst-of-speed tests, remove one end of the
hydraulic line between the main control valve
and the hoist control valve and plug.
3. Using all applicable safety practices, start the
truck engine, engage the PTO and set the outrig-
gers. Operate the crane at low engine speed.
4. Operate the appropriate control lever and note
the pressure reading on the gauge.
IMPORTANT: For telescope out relief valve testing,
be sure the outriggers and stabilizers are set. The
boom must be fully extended and “bottomed out”
to cause the relief valve to operate.
ting. If pressure is too high, turn the adjustment
screw counterclockwise to decrease the pres-
sure setting.
6. Tighten jam nut while holding the adjusting
screw or install the acorn nut.
7. Repeat step 4 to ensure that the pressure set-
ting is correct.
Figure 7-3. In-Line Relief Valve
Figure 7-4.Manifold Block Valve
