Bridge & Trolley Travel Operations
Bridge and trolley motion control, brakes, limit switches, end stops, buffers, bumpers, skewing, and rail alignment.
- Explain bridge brake and motor brake function and travel limit switches
- Describe end stops, buffers, bumpers, and runway stops and their purpose
- Define skewing and explain its causes and effects on crane components
- Identify rail alignment issues, rail sweeps, and wheel wear causes
Lesson 1
Bridge Brakes, Motor Brakes & Travel Limit Switches
Bridge Brakes
The function of bridge brakes is to stop and hold bridge motion. When the operator releases the bridge travel control, the bridge brakes engage to bring the crane to a controlled stop and prevent it from drifting along the runway.
Bridge Brakes
Stop/hold bridge motion
Engage when control is released
Prevent drift along runway
Bridge Motor Brake
Device to stop/hold bridge travel
Mounted on bridge drive motor
Spring-applied, electrically released
Bridge Motor Brake
A bridge motor brake is a device to stop and hold bridge travel. Most bridge motor brakes are spring-applied and electrically released - when power is applied, the brake releases and the bridge can move. When power is removed (control released or power failure), the spring engages the brake to stop the bridge.
Bridge Limit Switches
A bridge limit switch is a device that stops travel at the end of the runway. Bridge limit switches are positioned near the ends of the runway to slow or stop the crane before it reaches the end stops. This prevents the crane from colliding with runway stops at full speed.
Travel Limit Switches
The reason to check travel limit switches is to prevent the crane from striking end stops. A malfunctioning limit switch allows the crane to travel into the end stops at speed, causing shock loads and structural damage.
Bridge brakes stop and hold bridge motion. A bridge motor brake is a device to stop/hold bridge travel. Bridge limit switches stop travel at the end of the runway to prevent striking end stops.