HSE Learning from Fatal Coating Plant Accident

Transcription

1 HSE Learning from Fatal Coating Plant Accident Incident description On Wednesday 4 th October 2006, at about 1700 hours, a five-man cleaning crew was cleaning a concrete mixer unit at the premises of a coating contractor. Pix 1 On this day the panel door for the switch that ensures the mixer motors cannot start was not locked. The machine was switched on in error by one of the cleaners, resulting in the death of two persons and injury to two others. The four victims had been cleaning the internals of the mixer. Pix 2 Pix 1 The cleaning takes place at the close of work. Prior to the actual cleaning work, the power supply to the concrete mixer motors should be isolated at three points. A Lock Out Tag Out (LOTO) procedure exists for the cleaning operation. There were three switches required to be activated to start the mixer motors. Anyone going into the mixer must carry the key of the third switch along, after switching off the motors and locking the panel. (No 3 in fig 1) Main Isolation switch for conveyor belt Main Isolation switch for mixer Mixer power supply Conveyor belt power supply Operator control panel Switch Figure 0 Cement mixer Safety Breaker Isolation box With lock Conveyor belt Pix 2 The cleaning process requires the cleaners to physically get into the confined space and chip away dried concrete off the mixer blades and walls. One of the two injured persons later died as a result of the injuries sustained in the accident. Immediate causes The cleaning procedure was not identified as a high risk activity. The switch (no 3) was not switched off, and the panel door remained unlocked while the cleaners were in the mixer in violation of the procedure. The supervisor was busy elsewhere thus the cleaning crew was left alone unsupervised. Lessons learned Pre-mobilization inspection team to update checklist to include additional rotating equipment control systems. Strict adherence to procedures by all cadres of staff. Maintaining / cleaning rotating equipment has a high risk which should be properly managed.

2 HSE BULLETIN No 4 02_Nov_06 CORPORATE QHSE DIVISION

3 PREVENTIVE MEASURES FOR CONCRETE MIXERS As a result of the multiple fatalities (3) in NIGERIA all Socotherm Groups are hereby immediately requested to review the below method of preventive actions for the reoccurrence of PTW/LOTO failure. The next series of slides and pictures will show you that there are several layers of fail safe methods to ensure their never is another incident like this again 1. Within the operators cabin a very strong illuminating light has been fixed, when the mixer is shutdown this will continually rotate with a blinding amber light

4 Lock out tag out key color codes Site emergency No s Amber rotating warning light which activates when de-energized from all the fail safe methods incorporated on the mixer

5 PREVENTIVE MEASURES FOR CONCRETE MIXERS 2. From the operators control panel on the next slide you can see the electrical panel has been adequately multi locked off and see the different numbers of individual locks and their color coding

6 View from Operators cabin showing Isolating Circuit Breakers with multi locks in place, note the color coding there are 2 Green, 1 yellow, 1 red and 1 blue which means there are 2 general workers (cleaners) in side the zone, 1 electrical, 1 mechanical and 1 production supervisor either inside or locked off as per the procedure SME_SSWP_025 Yellow = Plant Supervision Red = Electrical Blue = Mechanical Green = General Twin breakers because mixer has a two screw shaft function

7 PREVENTIVE MEASURES FOR CONCRETE MIXERS 3. Upon attempting to enter the concrete mixer there is a barrier gate that has an electrical sensor fail safe unit (see next slide) attached, once the gate is opened the concrete mixer automatically shuts down and sets the amber warning light to activate. Further note the safety signs warning all personnel who are not authorized not to enter

8 Electrical fail safe sensor, once gate is opened the concrete mixer is de-energized and the amber warning light in the control panel is activated, note the unauthorized safety signs Safety sign Electrical fail safe sensor

9 PREVENTIVE MEASURES FOR CONCRETE MIXERS 4. Entry into the mixer is dual controlled the mixer covers comprise of a sequence of 3 hatches, these hatches must be opened sequentially as hatches 1 & 2 have a flat iron plate welded on the outer cover preventing you opening them any other way. On hatch one is welded a mechanical fail safe device that has to be physically pulled up to open and gain entry into the hatch No 1, once opened the mixer will be de-energized, a turn buckle approach has been used instead of a rigid one this enables the turnbuckle to be retorque if found loose at maintenance operations

10 Mechanical fail safe device, once opened by unscrewing the nut and physically lifting the device from the welded nut, the mixer will automatic all de-energize and set of the amber warning light, note the turn buckle which will eliminate possible damage due to not being rigid and can be re-torque when found loose Nut that needs to be unscrewed Turn buckle assembly

11 PREVENTIVE MEASURES FOR CONCRETE MIXERS 5. Next slide shows how the hatches have been interlocked by welding a single piece of flat plate onto the hatch covers, note you must release the mechanical fail safe device before opening the hatches, and then you can only open hatch 1, other hatches cannot be opened first due to the welded flat plate

12 Welded flat plates on hatches 1 & 2 prevent you opening any other hatch first apart from hatch 1 which has the mechanical fail safe device attached Welded flat plate on hatch # 1 Welded flat plate on hatch # 2

13 LOTO KEY CONTROL Below are some simple requirements for adequate padlock & key control distribution and management Each padlock is colored and numbered Set of colored & numbered LOTO padlocks & keys Yellow = Plant Supervision Red = Electrical Blue = Mechanical Green = General

14 PREVENTIVE MEASURES FOR CONCRETE MIXERS This HSE Bulletin clearly shows that we simply do not rely on the PTW/LOTO but have also introduce a multi layer of fail safe devices. As Chairman & CEO, I call on all of you to look at your plant set up and incorporate similar devices, please do not rest with only the concrete mixer look at all other potentially high risk areas and review the risk and find ways of applying the multi layer fail safe systems Prepared by : Paul Gathercole Corporate QHSE Manager Approved by : Zeno Soave Chairman & CEO Socotherm