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Stay clear of hammer when checking line pressures.
CHECKING THE HYDRAULIC PRESSURES
Install pressure gauges in the hammer pressure and return lines. The NPK
INSTALLATION KIT provides pressure test ports in the hammer shut-off valves
mounted on the dipper stick. Generally, the pressure line is on the left and the
return line is on the right. A glycerin filled gauge should be installed on a hose that
is long enough to be clear of the hammer and flying debris.
k1. Stick
k3. Check Valve
k4. Shut-off Valve
k5. On
k6. Off
k8. Test Ports
m3. Pressure Line to Hammer
m4. Return Line from Hammer
1. Determine Return Line Pressure
Turn both shut-off valves (k4) to the “on”
position and operate the hammer. The
return line pressure should not exceed
300 psi (21 bar).
2. Determine System Relief Valve
Pressure
Turn the pressure line shut-off valve
(k4) to the “off” position. Energize the
hammer control circuit and note the
relief valve setting.
The relief valve is only used for ultimate safety, when the hammer is removed or the
shut-off valve is closed, not to set the hammer operating pressure. Therefore, to
prevent overheating, loss of flow and reduced hammer frequency, the relief pressure
should be set a minimum of 500 psi (35 bar) above the hammer operating pressure.
3. Determine Hammer Operating Pressure
Open both shut-off valves. Operate the hammer and note the operating pressure.
The operating pressure of the NPK HYDRAULIC HAMMER is self-regulating,
determined by the gas pressure. If the operating pressure is low, check the gas
pressure, see pages 29 through 30.
MODEL
HYDRAULIC OPERATING
PRESSURE psi (bar)
CIRCUIT RELIEF
MINIMUM psi (bar)
GH06 1650 (115) 2150 (150)
GH07 1500 (105) 2000 (140)
GH1 1750 (120) 2250 (155)
GH2/GHS2 2250 (160) 2750 (190)
GH3 1900 (130) 2400 (165)
GH4 2200 (150) 2700 (185)
GH6 2400 (165) 2900 (200)
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