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HSE Learning from Fatal Coating Plant Accident

Incident description

On Wednesday 4th 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

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 Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for mixermixermixermixer Operator Operator Operator Operator

control panelcontrol panelcontrol panelcontrol panel

Safety Breaker Safety Breaker Safety Breaker Safety Breaker Isolat ion box Isolat ion box Isolat ion box Isolat ion box With lock With lock With lock With lock

Mixer power Mixer power Mixer power Mixer power supplysupplysupplysupply

Conveyor belt Conveyor belt Conveyor belt Conveyor belt power supplypower supplypower supplypower supply

Cement mixer Cement mixer Cement mixer Cement mixer

SwitchSwitchSwitchSwitchMain Isolation switch for Main Isolation switch for Main Isolation switch for Main Isolation switch for conveyor beltconveyor beltconveyor beltconveyor belt

Conveyor belt Conveyor belt Conveyor belt Conveyor belt Main Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for mixermixermixermixer Operator Operator Operator Operator







Conveyor belt Conveyor belt Conveyor belt Conveyor belt Main Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for Main Isolat ion switch for mixermixermixermixer Operator Operator Operator Operator







Conveyor belt Conveyor belt Conveyor belt Conveyor belt

1 2 3

Figure 0

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 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.

SOCOTHERM is a Public Company listed on the Italian Stock Exchange STAR High Requirements Segment

HSE BULLETIN No 4 HSE BULLETIN No 4 02_Nov_0602_Nov_06

CORPORATE QHSE DIVISIONCORPORATE QHSE DIVISION


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


Amber rotating warning light which activates when de-energized from all the fail safe methods incorporated on the mixer

Lock out tag out key color codes

Site emergency No’s



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


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 Twin breakers because

mixer has a two screw shaft function

Yellow = Plant SupervisionRed = ElectricalBlue = MechanicalGreen = General


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



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

Electrical fail safe sensor

Safety sign


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 re-torque if found loose at maintenance operations



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


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



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


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 SupervisionRed = ElectricalBlue = MechanicalGreen = General



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 ManagerPaul Gathercole Corporate QHSE Manager

Approved by : Zeno Soave Chairman & CEO SocothermZeno Soave Chairman & CEO Socotherm

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