CPCS Crane Operations and Signals 2 — Questions and Answers
Question 1: When a crane is lifting a load and the wind speed increases, what effect does this have on the operation?
- No effect as cranes are designed for all weather
- It increases the dynamic loading on the crane and can cause the load to swing dangerously (Correct answer)
- It only affects the operator's comfort in the cab
- It improves the crane's lifting capacity
Correct answer: It increases the dynamic loading on the crane and can cause the load to swing dangerously
Wind increases the dynamic forces on both the crane structure and the suspended load. Wind can cause loads to swing uncontrollably, increasing the effective radius and potentially exceeding the crane's capacity. Most cranes have maximum wind speed limits specified by the manufacturer.
Question 2: What does the term 'duty chart' or 'load chart' refer to on a crane?
- A maintenance schedule for the crane
- A table showing the maximum safe load the crane can lift at various radii and boom lengths (Correct answer)
- A log of all lifts carried out by the crane
- The crane's insurance documentation
Correct answer: A table showing the maximum safe load the crane can lift at various radii and boom lengths
The duty chart (load chart) is a critical document showing the crane's safe working loads at different radii and boom configurations. The operator must consult this before every lift to ensure the load does not exceed the crane's capacity at the planned working radius.
Question 3: Who is the 'Appointed Person' in a crane lifting operation under BS 7121?
- The crane driver only
- The person responsible for planning and directing the lifting operation (Correct answer)
- The site security guard
- The person who hired the crane
Correct answer: The person responsible for planning and directing the lifting operation
The Appointed Person is the individual with overall responsibility for planning, supervising, and directing the lifting operation. They must be competent, have practical and theoretical knowledge of lifting, and ensure the lift plan is followed throughout the operation.
Question 4: What must a slinger/signaller verify about the load before attaching slings?
- The colour of the load
- The weight of the load, its centre of gravity, and the condition of lifting accessories (Correct answer)
- The manufacturer's logo on the load
- Whether the load has been on site for more than a week
Correct answer: The weight of the load, its centre of gravity, and the condition of lifting accessories
Before slinging, the slinger must verify the load's weight (checking delivery notes or markings), identify the centre of gravity, inspect the slings and lifting accessories for damage, and ensure the correct type and capacity of slings are used for the load.
Question 5: What is the minimum safe clearance distance that should be maintained between a crane and 400kV overhead power lines?
- 3 metres
- 6 metres
- 9 metres
- 15 metres (Correct answer)
Correct answer: 15 metres
For 400kV overhead power lines, the minimum safe clearance distance is 15 metres from the nearest line. This distance accounts for the risk of electrical arcing and the potential movement of the crane's boom, jib, and load. Lower voltages require smaller but still significant clearances.
Question 6: What does it mean when a crane's hook block is 'two-blocked'?
- The hook is carrying two loads simultaneously
- The hook block has contacted the boom tip sheaves, creating a dangerous condition (Correct answer)
- The hook is fitted with two safety catches
- The crane has been parked with two wheel chocks
Correct answer: The hook block has contacted the boom tip sheaves, creating a dangerous condition
Two-blocking occurs when the hook block is hoisted to the point where it contacts the boom tip sheaves (pulleys). This is extremely dangerous as it can cause the hoist rope to break, the boom to collapse, or structural damage. Anti-two-block devices are fitted to prevent this.
CPCS Crane Operations and Signals 2
When a crane is lifting a load and the wind speed increases, what effect does this have on the operation?