Marine Accident Investigation Branch Safety Digest 1/2005  Case 12

Fingers and Rotating Vee Belts Don't Mix

Narrative
An engineer on board a vessel was required to order spares for the accommodation fan units. As both fans were running, he switched off the power to number 1 fan, closed the delivery flap and opened the air conditioning unit access panel. He then waited for the fan to stop before checking the identification markings, condition and tension on the three vee belts.

Unknown to the engineer, number 1 fan delivery flap had not closed and sealed its duct, because the locking screws on the vent flap handle were slack (Figure 1). Both fans supplied a common air delivery duct, and the airflow from the running fan caused the fan on number 1 to rotate in the reverse direction soon after it stopped.

Unable to react quickly enough, the fingers of the engineer’s right hand were drawn into, and became trapped between the vee belts and the electric motor pulley (Figure 2).

The very graphic photographs illustrate the consequences.

Figure 1: Accommodation fan unit - delivery flap handle

Figure 2: Motor fan unit and vee belts

The Lessons
1. If you are required to work on rotating or other moving equipment, ensure that all precautions are taken to isolate and prove that it cannot restart unexpectedly. By issuing warning notices, locking off starter controls, removing fuses, and fitting locking devices on the plant, you will be reducing the opportunity for an unexpected, and probably very painful, accident to take place.

2. If the equipment is linked to other operating plant, ensure that the operating plant cannot affect the equipment you are working on. If it can, and only if safe to do so, isolate the linked plant as well, and advise a responsible officer of your actions.

3. If equipment operates unexpectedly, it will almost certainly happen when your fingers are in very close proximity to it. Where possible, make use of tools – specialist or otherwise – to carry out maintenance, and keep your fingers safe.

4. An effective risk assessment should have shown that the sealing of the common air delivery duct by the number 1 fan delivery flap was critical to prevent reverse running of the fan. This should have then identified the unsuitable precautions taken to prevent inadvertent rotation.