IPAF Safe Working Load & Stability 2 — Questions and Answers
Question 1: What is 'outrigger pad pressure' and why must it be within safe limits?
- The force per unit area exerted by the outrigger on the ground — it must not exceed the ground's bearing capacity (Correct answer)
- The hydraulic pressure in the outrigger cylinders
- The pressure required to deploy the outriggers
- Outrigger pad pressure is only a concern for tower cranes
Correct answer: The force per unit area exerted by the outrigger on the ground — it must not exceed the ground's bearing capacity
Outrigger pad pressure is the load from the MEWP divided by the pad contact area. It must not exceed the ground's bearing capacity; otherwise the outrigger punches through the ground, causing the machine to tilt or overturn.
Question 2: What precaution should be taken when a MEWP is operating near an excavation?
- Maintain a safe standoff distance determined by the depth, soil type, and machine weight to prevent edge collapse (Correct answer)
- Only avoid operating within 0.5 metres of the edge
- Excavation proximity is only a concern for large boom lifts
- The operator should judge the safe distance visually
Correct answer: Maintain a safe standoff distance determined by the depth, soil type, and machine weight to prevent edge collapse
Operating near an excavation risks edge collapse from the MEWP's surcharge load. A safe standoff distance must be calculated by a competent person based on excavation depth, soil conditions, and machine weight.
Question 3: What does 'dynamic stability' mean in the context of MEWP operation?
- The stability of the MEWP when in motion — travel with a raised platform reduces stability compared to a stationary machine (Correct answer)
- The stability only when the platform is fully raised and stationary
- A stability test carried out during manufacture
- Stability during emergency lowering operations only
Correct answer: The stability of the MEWP when in motion — travel with a raised platform reduces stability compared to a stationary machine
Dynamic stability refers to the machine's stability when in motion. Travelling with an elevated platform significantly reduces stability compared to a stationary machine — most manufacturers prohibit or strictly limit this.
Question 4: What effect does uneven ground have on MEWP stability?
- It tilts the machine, raising its centre of gravity relative to its base and increasing overturning risk — must not exceed tilt alarm limit (Correct answer)
- Ground unevenness only affects comfort, not stability
- Only applies to wheeled MEWPs, not tracked ones
- MEWPs are designed to be unaffected by ground unevenness
Correct answer: It tilts the machine, raising its centre of gravity relative to its base and increasing overturning risk — must not exceed tilt alarm limit
Uneven ground tilts the MEWP, shifting its centre of gravity and reducing its overturning margin. The tilt alarm indicates when the safe gradient limit has been reached and operation must stop.
Question 5: A MEWP operator wants to lean out of the platform to reach a work area. What should they do instead?
- Reposition the MEWP so the work area is within reach without leaning — never lean out beyond the platform rails (Correct answer)
- Lean out if the task is quick
- Lean out if a colleague holds their harness
- Leaning out is acceptable if the platform is at maximum height
Correct answer: Reposition the MEWP so the work area is within reach without leaning — never lean out beyond the platform rails
Leaning out beyond the platform guard rails shifts the operator's weight outside the machine's designed stability envelope. The correct action is to reposition the MEWP so the task can be completed without leaning.
Question 6: What is the effect of carrying a long or wide load on a MEWP platform?
- It increases wind resistance and can shift the centre of gravity, both reducing stability — must be planned and approved (Correct answer)
- Long loads have no effect if they are within the SWL
- Wide loads are only a concern outdoors
- Load dimensions are irrelevant if SWL is not exceeded
Correct answer: It increases wind resistance and can shift the centre of gravity, both reducing stability — must be planned and approved
A long or wide load increases the surface area catching wind, multiplying lateral forces. It can also shift the platform's centre of gravity. Even if within SWL, this must be planned and the impact on stability assessed.
IPAF Safe Working Load & Stability 2
What is 'outrigger pad pressure' and why must it be within safe limits?