3-25
VALVE SETTINGS:
Approximate factory settings are 300 psi (21 bar) on extension (upper valve) and 800 psi
(55 bar) on retraction (lower valve). Valves are fine tuned, however, to control boom stage
sequencing at all boom angles and normal hydraulic oil temperatures. Setting the valves
higher than required will generate additional heat in the hydraulic system and also waste
fuel. Turning the adjustment screw in on the sequence valve adjustment will increase the
valve setting.
TROUBLESHOOTING:
If boom stages fail to sequence properly, it is probably due to a sequence valve being set
too low to overcome a tight boom stage, or there is contamination or malfunction of the
sequence valve. Dirt in either cartridge (relief or check) could cause a sequencing failure.
All cartridges may be removed for cleaning or replacement. Disconnection of hydraulic
hoses is not required to remove the valve cartridges.
BOOM CYLINDER HOLDING VALVE
A holding valve is directly connected to the base of each boom lift cylinder barrel and to the
base of the primary crowd cylinder rod. These valves are designed to hold the boom in
position should loss of power or pressure line failure occur.
To check the boom lift cylinder holding valve, set the outriggers, place the boom in the
horizontal position over the front of the crane and raise a rated load about three feet above
the ground using the boom lift cylinders (not the hoist). An example of rated load is 7500
pounds (3390 kg) at a 36-foot (11 m) load radius, with outriggers extended and the boom
over the front. The 7500 pounds (3390 kg) includes a 7060 pound (3190 kg) load and the
440 pound (200 kg) sheave block. Turn the engine off and move the BOOM lever to the
LOWER position. If the boom moves down, a holding valve may be malfunctioning or a
boom lift cylinder may have leakage past the piston seal.
W A R N I N G
Before working on the holding valves or plumbing to the boom lift cylinders, always
relieve trapped pressure by lowering the boom fully, turning off the engine, and
cycling the BOOM lever.
To determine whether the problem is in the left or right-hand cylinder, put a pressure gauge
with a range of at least 5000 psi (350 bar) on the 1/4" size port on the side of one of the
holding valves.
W A R N I N G
Disconnecting the RCL hose from a single holding valve may cause the boom to
lower if the other holding valve is faulty. Ensure that the boom is fully lowered or
blocked before disconnecting the hose.
N O T I C E
The RCL will not function properly with one hose disconnected from a cylinder.
BMC uses multiple RCL models. If your crane has hoses connecting the cylinder to the
RCL computer, the cylinders are hydraulically connected. They must be isolated for the
following procedure. Fully lower the boom. Isolate the cylinders from each other by
disconnecting the piston and rod side RCL hoses from one cylinder. Cap the hoses and
plug the hole in the holding valve. Note that the caps and plugs will experience full system
pressure, and adequate care must be taken to ensure the caps and plugs are properly
installed. Note the RCL will not function properly with one cylinder disconnected.
Summary of Contents for RT-300-2G
Page 6: ...1 2 DIMENSIONAL DATA Courtesy of Crane Market...
Page 7: ...1 3 RT 300 2G TURNING DIMENSIONS Courtesy of Crane Market...
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Page 33: ...2 17 CAPACITY CHART FOR RT 300 2G Courtesy of Crane Market...
Page 34: ...2 18 CAPACITY CHART FOR RT 300 2G METRIC Courtesy of Crane Market...
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