Manitowoc 2250 Service And Maintenance Manual

Reference Only
Manitowoc Published 11-06-15, Control # 040-13 1-27
2250 SERVICE/MAINTENANCE MANUAL INTRODUCTION
1
Main Pressure Monitoring
Each system digital display screens display the monitored
system pressure. The system pressure displayed on system
screen is charge pressure or greater. System pressure can
also be checked at each pressure sender diagnostic coupler
with a 10,000 psi (689 bar) high pressure gauge, when pump
is stroked.
Basic Operation
See Figure 1-11 or Figure 1-12 for the following procedure.
When a control handle is moved from neutral, an input
voltage in the handle command direction is sent to the PC.
The PC sends a variable plus or minus 0 to 2.8 volt output
that is applied to pump external EDC (Electrical
Displacement Control). The output current magnetizes an
armature and starts to block one of the orifice ports,
depending on command direction. Blockage of flow at
exhaust side of right orifice port causes a pressure difference
across spool. This pressure difference overcomes the
resistance of spool spring and moves the spool
proportionally to pressurize top servo pistons. The fluid from
bottom servo pistons is routed to tank. This tilts the
swashplate, stroking the pump in selected command
direction. As swashplate tilts, chamber spring is pulled in the
opposite direction of spool with linkage. This centers and
maintains spool in a neutral position until the 16 psi (1 bar)
chamber spring pressure is reached.
In travel pumps, the pressure relief and pressure-limiting
sections of multifunction valves respond when relief
pressure is reached. If travel pump pressure exceeds preset
pressure limit, the pumps de-stroke to prevent overheating of
system fluid. The hydraulic fluid pressure overcomes spring
resistance in pressure limiting relief valve (1, Figure 1-12
),
shifting spool to open a line for fluid pressure. Servo check
valve (2) is spring loaded with an opening pressure of 750
psi (52 bar). Hydraulic fluid from pressure limiting relief valve
flows through exhaust port of displacement control valve (3).
The exhaust port has a restricted orifice that develops
pressure for servo control cylinder (4) to pressurize and de-
strokes pump to limit system pressure. When rapid loading
produces pressure spikes, system relief valve (5) shifts. This
allows high-pressure fluid to return to tank through charge
pump relief valve (6). Alternatively, fluid transfers to low-
pressure side of closed-loop system through charge flow
make-up check valve (7).
In other system pumps, pressure limiting is controlled
through relief valve section of multifunction valves only. Flow
control orifice (8) is removed from pump EDC. Servo check
valves are removed from pump and lines to servo control
cylinders are plugged. These changes permit the pump to
react quicker to control handle commands.
SWASHPLATE
SERVO PISTONS
PILOT PRESSURE
ORIFICE
RF-02
PORT
MODULATION
ORIFICE
PORT
SPRING
CONTROL VOLTAGE
ARMATURE
SPOOL
PILOT PRESSURE
PILOT PRESSURE
SPOOL
SPRING
FROM CONTROLLER
FIGURE 1-11

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English