V Belts are very commonly used in air conditioning. They are used to step-down the speed of the motors driving the air conditioning blowers. They are intrinsically safe with all the in-built safety features. However, there are innumerable accidents which have been reported, some of them ghastly to the operators and technicians while carrying out repairs and inspection. The following article explores some of these accidents.
It is to be noted that these accidents are applicable to not only refrigeration equipment, but also to other machinery, wherever rotating exposed components are involved.
Incident 1: Electrical officer hand injured due to sudden starting of AC Blower
An electrical officer was working on an accommodation AC blower of a ship. Normally, these have V Belts through which the RPM of motor is brought down to the blower RPM. The electrical officer had stopped the blower electrically and proceeded to work on the blower. Suddenly, the blower was started by someone and the electrical officer’s hand had got caught between the belts and the pulley and there was a substantial injury. This reinforces the need for electrical lock out tag and care when working on rotating machinery and particularly, with AC blowers.
Normally, these V belts are provided with protective guards. Somehow, often, these guards are removed and are never put back in place.
Fingers and Rotating V Belts Don’t Mix.
Incident 2: Engineer injured due to draught from other running AC Blower (Source: MAIB Safety Digest 1/2006)
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. 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 V belts and the electric motor pulley.
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.
Incident 3: Injury to Electrical Officer while checking belt tension
A 2009 built Hong Kong registered cellular container vessel with a summer deadweight of 85760 MT, departed from Kaohsiung, Taiwan on 24 July 2013, bound for San Pedro, USA where her expected arrival was 6 Aug 2013.
Figure 1: Accommodation fan unit – delivery flap handle
Figure 2: Motor fan unit and Vee belts Figure 3: Finger Injury
On 2 Aug 2013, while the vessel was at sea, routine maintenance on AC Blowers was planned as required by vessel’s PMS. AE/O and the fitter were assigned to carry out the job.
During the maintenance of No 2 blower, AE/O’s fingers got caught between the belt and the wheel causing injury to two fingers of left hand.
He was given first aid on board and in consultation with CIRM, vessel was diverted to Oakland to evacuate AEO for further treatment.
No abnormality with AC blowers was reported prior commencement of the job.
Prior starting the maintenance, necessary precautions were taken by the senior engine officers. The equipment was isolated and the power was switched off to the equipment. The maintenance involved greasing of the bearing of both the blowers. The maintenance procedure was well understood by the injured officer.
With the intention of checking the belt tension, the crew member pressed the belt with his left hand while moving the belt with the right hand. During this process, when the belt was in motion, the crew member’s hand was caught between the belt and the pulley on the fan side.
Incident 4: Injury to Electrical Officer due to air draught when AC Blower room was opened
There was another case of an electrical officer working on an Accommodation AC Blower. He had electrically locked the blower out, so there was no chance of accidental starting of the blower. Another engineer had entered the blower room. Due to the draught of the air, the blower started rotating, the bearings being very free. The Electrical Officer was caught offguard and his hand got carried between the pulley and the belts and there was substantial injury.
Incident 5: Injury to Second Engineer’s hand due to sudden cutting in of AC Compressor
On 14 August 2017, a container vessel was on her way from Savannah, USA to Cartagena, Colombia. During the evening at 2055 hrs LT the usual night rounds were carried out by the duty Second Engineer. During the rounds, one of the V belts of the accommodation AC compressor was found lose and slipping on the pulley. The Second Engineer in an attempt to carry out the replacement of the lose V belt, decided to stop the AC by closing discharge valve of the condenser. The compressor tripped with low suction pressure but was still on standby mode. Unfortunately, the electric motor for the compressor was not switched off from the breaker before beginning to cut the belt for replacement. The compressor restarted during this time and the Second Engineer’s right hand was caught in between the pulley and the belt resulting in severe injury and loss of four fingers of the right hand.
Vessel Master immediately proceeded full speed towards next port and 14 hours after the incident the injured individual was disembarked onto a Colombian coast guard speed boat and transported to the local hospital for surgery and recovery. From the above preliminary report from the vessel it would appear that the replacement of the lose ‘V’ belt was attempted without de-energising the compressor’s electric motor and while the compressor was stopped it remained in Stand By mode.
This incident and resultant severe injury serves to remind us, yet again, of the need to strictly adhere to safe working practices and company permit to work system. The SP-023 – Machinery Or Electrical Equipment Power Isolation Procedure and associated permit form FM-110- Machinery OR Electrical Equipment Power Isolation Permit clearly define the process to be followed and mitigating actions to be put in place in order to work on machinery and equipment which could be turned on, or started automatically or from remote control system.
Immediate Follow Up Actions
1. An extraordinary safety meeting to be held on board at earliest convenience and this safety alert discussed with all personnel on board.
2. Ship board practices pertaining to permit to work, and SP-023- machinery or electrical equipment power isolation procedure, in specific, to be reviewed by the Master and the safety officer, and any shortcomings addressed immediately.
3. Master and Safety Officer to hold a training session with all personnel explaining the importance of adherence to Permit to Work system and ‘Isolation permit’ in particular. Any feedback on how the organization can prevent similar incidents from recurring are welcome and to be sent to your Superintendent and Marine Superintendent for further follow up and action if required.
Incident 6: Hand injury to Electrical officer (Source : MARS 201762)
The vessel was underway on the open ocean in rough weather. The electrical officer and another crew were to check the tightness of the accommodation blower’s V-belts. Prior to the job the lock-out/tagout procedures were followed and the blower suction, outlet and recirculating flaps were closed.
The blower door was opened for inspection and team started checking the V-belts for tightness. As they were finishing their inspection the vessel took a roll due to the sea state. Both men lost their balance, and in an attempt to hold on to something the electrical officer’s left hand fell on the blower’s V-belt. As his weight came to bear on the belt, it caused the belt to move, trapping his hand between the V-belt and the blower pulley wheel. The victim was able to extricate his hand but not without negative consequences. Two fingers and his thumb were badly injured. After receiving first aid, he was evacuated from the ship by helicopter.
Crews should take vessel movements into consideration in their risk assessments before undertaking a task. Less essential tasks should be done when there is minimal vessel movement.
In this instance, there was no securing arrangement to prevent the door from moving when it was open. A securing hook arrangement was fabricated for the doors in order to secure them while open.
Incident 7: Crew member loses part of thumb for ignoring LOTO (Source : MARS 201737)
A lone crew member was about to do some maintenance on a ventilation duct fire closure for the hold. As he started to open the ventilation door, the cargo hold ventilators were switched on by someone else in another location. This caused the ventilation door to suddenly be sucked closed. The crew member’s thumb was trapped between the handle of the cleat and the door frame causing the thumb to be severed above the first joint.
Always lock out, tag out (LOTO) before attempting a job. LOTO, in this instance, may not be self-evident but any job that risks a potential release of energy should be LOTO.
General Rotating Equipment Safety Precautions
• Always replace protective guards after completion of the work.
• Never wear loose clothing or jewelry when working near moving mechanical parts. They can get caught in belts, pulleys and fans causing serious injury.
• Do not try to stop moving machinery with hand. This may cause injury to fingers.
• Wear protective hand gloves during work on rotating equipment.
• Ensure equipment is electrically locked out before commencement of the work.
• Be aware that air conditioning blowers could move even with external air draught.