HYDRAULIC SYSTEM 5540F/YB5515 SERVICE MANUAL
4-22 Published 10-21-2010, Control# 198-04
Hydraulic Swivel
General
The hydraulic swivel is at the center of rotation of the mast.
The purpose of the hydraulic swivel is to permit the flow of oil
between the hydraulic components on mast and boom and
the components on the lower structure during any rotation of
the mast.
The hydraulic swivel has seven passages Figure 4-24.
Grooves and ports in the shaft align with ports in the housing.
Seals between the grooves of the shaft inhibit leakage
between the passages. The seals fit tightly against the
housing. The housing rotates with the mast and the shaft is
stationary.
Functions
The numbers of each port is stamped on the housing and on
the lower end of the shaft.
Port No. 1
Hydraulic oil under pressure flows through this port when the
hoist block (main winch) is being raised. When lowering the
hoist block the hydraulic oil under low pressure flows through
this port.
Port No. 2
Hydraulic oil under pressure flows through this port when the
hoist block (main winch) is being lowered. When raising the
hoist block the hydraulic oil under low pressure flows through
this port.
Port No. 3
Hydraulic oil under pressure flows through this port when the
boom is being raised. When lowering the boom the hydraulic
oil under low pressure flows through this port.
Port No. 4
Hydraulic oil under pressure flows through this port when the
boom is being lowered. When raising the boom the hydraulic
oil under low pressure flows through this port.
Port No. 5
Hydraulic oil under pressure flows through this port when the
boom is being extended. When retracting the boom the
hydraulic oil under low pressure flows through this port.
Port No. 6
Hydraulic oil under pressure flows through this port when the
boom is being retracted. When extending the boom the
hydraulic oil under low pressure flows through this port.
Port No. 7
Hydraulic oil under low pressure flows through this port from
the winch motor drain.
Troubleshooting
Leakage between the passages of the hydraulic swivel will
cause loss of power or possible wrong operation of one of
the circuits. It is important to know the arrangement of the
passages in the hydraulic swivel. Remember that the oil will
always follow the path of least resistance.
FIGURE 4-24
a0466
Hydraulic Swivel Port Arrangement, Typical
Reference Only
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