ACCIDENT INVESTIGATION

ACCIDENT NO : 1

Crew injures from oil heater explosion-Official report  (INVESTIGATION & LESSON LEARNT)

                    Over a period of two days at anchor, one of the two vertical thermal oil heaters of a product tanker was observed to be not firing reliably. The crew opened and cleaned the burner unit and also adjusted the igniter electrodes twice, but after the second attempt, the heater refused to fire. On the third day, the C/E discussed the remedial action plan with the crew. They opened up the burner unit and cleaned the burner lance and igniter electrodes again. This time, the heater operated for about 90 minutes (eight firing cycles), after which it again failed to ignite. 

                Resuming work after lunch, the electrician re-inspected electrical systems while the 3/E and cadet dismantled and cleaned the burner lance and nozzle unit, reassembled it under the C/E’s supervision and refitted it to the heater one more time. When the test firing commenced, the 3/E, cadet and electrician positioned themselves on the top of the heater to monitor the automatic starting and firing sequence. The forced-draught fan went through a four-minute purge programme, but when the igniter sparked, there was a violent explosion.

               The explosion lifted the thermal oil heater casing top, snapping most of the securing bolts. The burner arrangement was pushed out of alignment and the inspection cover was torn from its securing bolts. The ducting from the externally mounted forced-draught fan was torn apart at the flexible insert. Fuel lines running across the top of the thermal heater were deformed, and at least one began to leak from a weakened joint. The explosion triggered the engine room fire detection system, initiating a fire alarm on the panel at the fire control station, and also activated the local automatic water mist system. The three persons on top of the heater suffered burns over large portions of their bodies as the flame front engulfed them momentarily, but they were able to walk from the area to the accommodation.

               They were assisted by the mustered crew, who removed the remnants of the burnt coveralls and ill-advisedly pierced and drained (lanced) the blisters before placing dressings on the burns. The injured persons were also given painkillers and water to drink but remained seated in a cabin despite being in severe pain and trauma. About half an hour after the explosion, the Master reported the incident to the port control and his local agents and requested medical assistance. Unfortunately, his request for helicopter evacuation (medevac) was initially denied due to the mistaken assumption ashore that helicopter operations over a tanker that had just suffered an explosion would be hazardous. Subsequent miscommunication between the response teams on shore added to this delay. Paramedics boarded by launch about an hour after the accident and after rendering further medical treatment, they insisted on immediate evacuation of the casualties by helicopter. Eventually, after another hour, the men were winched off and conveyed to a shore hospital.

Result of investigation

1 The burner nozzle had been incorrectly assembled, probably during the several investigation and repair attempts. As a result, the needle valve stem became bent and due to an improper seal, the circulating fuel continued to spray into the furnace during the pre-ignition start sequence;

2 The crew, except the C/E, had very limited experience in servicing this equipment;

3 The manufacturer’s manual was poorly written, and lacked a clear drawing of the burner, details of spare parts, instructions for troubleshooting, servicing, inspection or testing;

4 In order to reduce maintenance costs, at some time prior to the incident, the company had approved a change of fuel from heavy fuel oil (HFO) to marine gas oil (MGO) for the heater, but the crew failed to make the necessary changes to the fuel pre-heating circuit and the auto-start programme;

5 Excessive diesel fuel entered the furnace which was probably at about the operating temperature (about 160 °C), and instantly vaporised (flash point ˜ 68 °C) and formed an explosive mixture with the charge air;

6 The crew failed to refer to the proper sources for advice on the treatment of burn injuries, resulting in the casualties being given inappropriate first aid (especially the deliberate uncturing of blisters);

7 The port’s contingency plan for responding to a vessel casualty and medical emergency in the anchorage lacked detailed documentation that would have ensured reliable information exchange among the concerned parties.

 
Corrective/preventative actions

1 The ship’s operator renewed the burner units for both oil-fired heaters and altered the control system to better suit the fuel being used and the load demands placed on the heaters;

2 The heater’s makers reviewed and amended relevant sections of the equipment’s service manual and relayed the incident details to ancillary equipment suppliers, including the burner equipment manufacturer;

3 The port reviewed the emergency contingency plan and implemented revised procedures, including training, drills and exercises for its staff.

Lessons learnt

1 Ship’s crew must remain vigilant to safety even when conducting repeated or seemingly simple tasks; 

2 Manufacturers must provide comprehensive and accurate documentation for onboard service and maintenance and the crew must follow these along with the more generic procedures given in a ship’s SMS;

3 Manufacturers should conduct research and implement engineering solutions to resolve potential design weaknesses that may lead to failure or hazardous conditions in service;

4 It is desirable that critical items of equipment are serviced by specialist shore-based technicians, but if this is impracticable, ships’ crews must be given appropriate training arranged by the makers or suppliers of such equipment;

5 In case of illness or injury on board, ships’ crews must first refer to the approved publications carried onboard, if required, supplemented 

                An international cooperative scheme for improving safety by correct radio medical advice obtained from shore. They must be capable of providing immediate and appropriate first aid. Burn injuries should always be immediately cooled, under clean, cold running water, for at least 10 minutes. 

For more articles regarding accidents and investigation.....keep reading the blog......

ACCIDENT & INVESTIGATION (2) - Galley Fires on three different vessels...

 The following extracts are taken from the UK MAIB Safety Digest…..

Narrative 1

                     A 3,222gt general cargo vessel arrived in port and by 1830 was secured alongside. With cargo discharge not due to start until 0600 the following morning, the crew were stood down with just one seaman doing a "night aboard." Although some crew members went ashore, most, including two superintendents who were on board, retired to their cabins. Those who had gone ashore returned by midnight. The chief engineer and the watchkeeper stayed up watching TV until about 0130 when the chief engineer retired to his cabin, leaving just the watchkeeper awake and preparing some food in the galley.

                  At about 0310, the fire alarm sounded. Investigation indicated a fire in the upper engine room, steering gear, or separator room, although smoke was evident in the accommodation. The general alarm was sounded, shore authorities informed, and the ship's whistle sounded. Further investigation by the chief engineer established there was little or no smoke in the engine room. However, when he checked the accommodation fan room he found it full of smoke. Realising the fire was in the accommodation, he retired to the open deck where the master confirmed that four seamen were missing. The chief officer, wearing an SCBA set, rescued two seamen from their cabins, while other officers found one of the superintendents unconscious, behind his cabin door. With the watchman unaccounted for and thick smoke found in the mess room, the master and chief officer, both wearing SCBA sets, entered the area to carry out a search. They found the galley door shut but radiating intense heat. They eventually found the missing seaman, unconscious, on the port side.

               Two fire-fighters, who meanwhile had boarded the vessel, assisted in removing the seaman to the open deck, but he later died. Further investigation confirmed that the seat of the fire was the galley stove. The source was overheated cooking oil in a chip pan that had been placed on top of the galley stove. The result of this fire in human terms was one dead, three crew members requiring a lengthy period of convalescence, and three others suffering from smoke inhalation. In financial terms, the fire caused considerable smoke and heat damage to the galley and mess room, and minor smoke damage to the accommodation and service spaces.

Narrative 2 

               A 20,446gt ro-ro vehicle/passenger ferry was on passage from the UK to France. At about 1715, a new heating element was fitted to a deep fat fryer in one of the passenger galleys. It was then refilled with oil, the electrical supply reconnected, and the unit switched on. Some time later, the galley supervisor noticed that the temperature of the oil had risen above its normal operating range of 170°C, so took the following action:

1. telephoned for the assistance of an electrical officer
2. placed the fire cover over the fryer
3. turned the operating switch to the "off" position.

                 The temperature of the oil, however, continued to rise and, once it reached 260°C, smoke was seen. A further temperature rise to 320°C resulted in the vapours igniting. The flames were smothered using a fire blanket, and the bridge was informed of the situation. The electrical supply was isolated at the local distribution box, and the fire was extinguished using a combination of the fixed water Hi-fog system, portable foam and CO2 extinguishers. Further investigation found that the "on/off" switch energised a coil in the contactor unit to engage the power supply. In this case, one or more of the contacts inside the contactor unit had fused together, allowing current to flow to the heating element continually as long as the power supply was connected. This effectively bypassed the local "on/off" control switch. In addition to the repairs to the existing system, a local electrical isolation switch was fitted adjacent to the deep fat fryer.

 
Narrative 3

              A ro-ro vehicle/passenger ferry was on passage. In one of the passenger galleys, the staff were beginning preparations for cooking lunch. As part of the preparations, a tray of cooking oil was placed in one of the ovens to heat up. Everyone forgot it was there until about 1230, when a member of staff noticed smoke emitting from the oven. The oven door was opened very briefly and then closed again quickly, the power to the oven and galley were tripped off, the space vacated and all the shutters were closed. The bridge was informed and a fire party assembled to stand by while the oil cooled down.

The Lessons

             Heating cooking oil can be a very dangerous business indeed UNLESS a safe system of work is followed, with safety devices fitted and working. It has a flash point in the region of 310° to 360°C. The minimum flash point of the cooking medium should be 315°C (600°F).

              Deep fat fryers should be fitted with fire safety lids, with a second thermostat to provide a thermal cut-out, (see Merchant Shipping Notice M1022).

              Ordinary cooking pots filled with cooking oil are not, and cannot be used as, chip pans! Just a moment's inattention can result in overflow, a serious fire, and the generation of thick and potentially lethal smoke.

THINK SAFETY. Have fire blankets and fire smothering equipment readily to hand, fit electrical isolators close to the equipment (NOT above it!) and ensure that catering staff who operate the equipment always follow safe procedures. Above all, never use water to extinguish a fire, and never ever carry a pot/pan of hot oil out of the area in which you are working. Water will instantly turn to steam and explode, and shower hot and burning oil everywhere. Remember: attempting to carry a pot/pan of burning or hot oil will usually result in it spilling over the person carrying it.