Why can't the tower crane hook lift up when it can lower down?
3 Answers
Tower crane can lower the hook but cannot lift it up because the load is too heavy, or the lifting/lowering hook limiter is damaged. Introduction to tower cranes: Tower crane is the most commonly used lifting equipment on construction sites, also known as "tower-type crane". It is extended section by section (height) (referred to as "standard section") and is used to lift construction materials such as steel bars, wood formwork, concrete, steel pipes, etc. Tower crane is an indispensable equipment on construction sites. Certificates required to operate a tower crane: Operating a tower crane requires a special operation qualification certificate for tower cranes. Tower crane operators are divided into three levels: Junior (National Vocational Qualification Level 5), Intermediate (National Vocational Qualification Level 4), and Advanced (National Vocational Qualification Level 3).
I've operated tower cranes for over a decade and seen this situation many times. When the hook won't lift but can lower, it's most likely an issue with the hoisting motor—either the brake is locked up or the motor has lost a phase and burned out the coils. First, listen for a humming sound from the hoisting motor when you operate the lever. If there's sound but no movement, the brake is definitely stuck; if there's no sound, check the contactor points in the control cabinet. Another common cause is a jammed hoist limit switch or the wire rope getting tangled on the drum and pressing against the sensor. Last time this happened at our site, we found cement slurry had gotten into the limit switch. Never take shortcuts by manually releasing the brake—if the wire rope snaps, it could lead to a serious accident!
Operating a tower crane is most frustrating when encountering such situations. The ability to lower the hook indicates that the hydraulic and cable systems are basically functioning normally, but if the hoisting function fails, the control circuit needs to be thoroughly inspected. It could be due to poor contact in the control lever's hoisting contacts or a broken coil in the hoisting contactor. Additionally, check for any breaks in the wiring from the main power supply to the motor, especially at cable joints that are frequently bent, as these are the most prone to damage. Once during an early morning rush job, I encountered this issue and later discovered that mice had chewed through the copper wires in the cable. Now, during every shift change, I always test the jog lifting function first to address any problems immediately. By the way, a false start of the overload protector in the operator's cab can also lock the hoisting function.
