99008 Flash Burns Checking Starter Motor

Flash Burns Checking Starter Motor
Report No. 990008

This report is relevant to medium/high voltage diesel electric propulsion systems being used in many vessels.

An Electro-Technical Officer (ETO) received flash burns to his hands from the 3,300 Volt No. 3 Bow thrust starter panel. Fortunately, there was a rubber mat suitable for high voltage in front of the panel, which probably saved his life. The incident could also have caused a fire or blackout. There were plasma burns inside and above the starter panel. The ETO was required to carry out planned maintenance on No.2 and No.3 thruster motors, consisting of resistance and megger checks, which should be carried out on isolated equipment.

After the incident, a burnt out multi-meter (reading to 600 volts and set to voltage) was found at the scene of the incident, along with an unused megger meter. The breakers to No. 2 and 3 bow thrusters were isolated (No 3 breaker must have jumped out at the time of the short circuit). The automatic voltage regulator to the generator in service was damaged. The voltmeter was not suitable for use on high voltage unless used with fused leads and 18" long 1000:1 ratio high voltage probes, even though it had a sign on the back "suitable for 4,800 volt amps".

It is not certain whether the ETO:

Ø was deliberately checking the voltage on live 3,300 volt equipment

Ø assumed he was working on isolated equipment but checking its voltage anyway

Ø believed he was working on 440V equipment (signs indicated "high voltage")

Ø had mistaken No.2 and No.3 bow thrust starter panels (on opposite sides of the compartment) or mistaken the breakers (on different high voltage switchboards). All are clearly marked.

To avoid similar incidents in the future the following steps are advised:

1. Highlight all planned maintenance items involving high voltage equipment as requiring special safety procedures, risk assessment and if necessary specific written maintenance procedures. No Planned Maintenance work should be undertaken on LIVE high voltage equipment.

2. Ensure that the Chief Engineer and engineering staff are aware of the work being done by the ETO

3. Complete a work permit(s) signed by he Chief or Second Engineer.

4. Isolate the high voltage equipment at the switchboard and use a "lockout" type "do not switch on" sign. If possible lock the breaker in the 'open' position.

5. Check the source light on the starter panel door. If source light is on, then the panel is 'live'.

6. Remember that built-in redundancy arrangements may result in power supply to electrical equipment from separate sources, all of which must be isolated.
7. Check the power supply is off by using the neon wand fitted inside the starter panel.

8. Have the work site and isolation checked independently before starting the planned maintenance.

9. Only use suitable meters.

The accident investigation also found that:-

1. The job description for the ETO indicated that he "reports" to the Chief Engineer. This was interpreted to mean that it was necessary to report on tasks completed. The job description should be made clearer to indicate that work must be pre-planned with the Chief Engineer, who must know what electrical work is being done on board ship.

2. The Master/Deck Officers were signing work permits for tasks under the responsibility of the Chief Engineer. A consequence of this was an "open loop", where there was no crosscheck of work that the ETO had completed against the work permits issued. No one was aware that work permits for electrical, engineering or cold work were not always initiated.

Some of the recommendations from this incident are reproduced below, where they are relevant to other ships.

1. Safety signs should be reviewed including supplementing high voltage signs to indicate the supply voltage and providing additional electrical resuscitation signs.

2. The provision of rubber mats in front of switchboards and electrical panels should be reviewed and additional mats ordered if necessary.

Note that it may be safer to use air powered or low voltage cordless tools in a marine environment rather than to use 230 or 110 volt electrical tools.