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Corrosion Prevention Incident Prevention/Mitigation MINING HAZARDS Plant Maintenance

The real dangers of corrosion | Case study in corrosion prevention

Corrosion prevention | Corroded walkway

At about 3.00 pm on 6 November 2007 Ian Battams, an underground maintenance worker at the Perilya Broken Hill Southern Operations, fell through the handrail of a raised walkway while cleaning the screens of the mine’s dewatering filtration system. The incident has become a case study in corrosion prevention for mining.

CASE STUDY CORROSION PREVENTION

SERIOUS INJURY INVOLVING A FALL FROM HEIGHT AT THE PERILYA BROKEN HILL SOUTHERN OPERATION ON 6 NOVEMBER 2007

The following case study is an extract of the Investigation Report prepared for the Director-General of the Department of Industry and Investment by the Investigation
Unit, Thornton.

STARTING WORK

On the day of the incident, Mr Battams began work at the Perilya Broken Hill Southern Operations at about 7.00 am. He attended a start up meeting in the Fixed Plant Coordinator’s office and then went to a safety meeting.


At about 7.40 am Mr Battams, with the other four members of the fixed plant team, returned to the Coordinator’s office to receive their work instructions for the day. The team then caught the shaft man-cage from the surface marble arch down to the 24 Level. At the 24 Level they stopped at the crib room and office to put their lunches away and have coffee. They then went to their respective jobs.

SERVICING 24 LEVEL PUMPS
Mr Battams maintained the 24 Level pump station regularly each shift. He inspected the pumps, checked the oil and water levels, and took pressure and hour readings, which he noted in a book. While at the pumps Mr Battams cleaned the sieves, a task requiring the pumps to be turned off and isolated. He notified the Mine Control Centre (MCC) when he did this.

The maintenance at the 24 pump station was a job that took some time. Mr Battams did not finish until about 12:50 pm. He performed this work alone, which was usually the case.

After having lunch in the crib room, Mr Battams returned to the 24 pump station to do a final check that the pumps were running satisfactorily. Then he went to where the Integrated Tool carrier (IT) was parked and completed a pre-start check.

Mr Battams drove the IT up the incline to the 23 Level maintenance bay. He parked the IT and then walked back past the 23 plat into the pre-screen area. On arrival he did a quick visual check of his surrounds.


“As he fell it appears he grabbed at the ladder near to him to stop himself, but a piece of ladder came away in his hand…”


CLEANING PRE-SCREEN FROM FLOOR
Satisfied the area was safe from rock fall, Mr Battams got the nearby water hose and hosed down the two troughs at floor level on each side of the pre-screens.

P1000790When he finished the floor level clean up he dragged the water hose up onto the raised walkway so he could hose the screens (see photo next page).

Mr Battams used the ladder near the steam high pressure cleaner to access the walkway (see photo next page). On the walkway he picked up the hose and cleaned the steps that were raised above the walkway. That done he hosed down the screens standing on the raised step, with the waste material falling into the trucks below. Each section of screen has a strainer at each end. Mr Battams hosed one strainer and then turned to step back onto the walkway to go to the other strainer.

STUMBLES & FALLS
According to Mr Battams, while stepping back onto the walkway, he stumbled hitting the handrails of the elevated platform. He could not explain why he lost his footing. As he fell it appears he grabbed at the ladder near to him to stop himself, but a piece of ladder came away in his hand (see photo next page).

The handrail gave way under the impact of Mr Battam’s falling body and he fell about 2.5 metres to the concrete floor below.

Lying on the floor, Mr Battams saw he had dislocated a finger on his left hand. Although he couldn’t see his right leg he could wriggle his toes. But when he tried to get up he found the leg would not support him and he was in pain. He lay back down to ease the pain, using his helmet to support his head.

Mr Battams got his cap lamp and shone it up the drive in the hope someone would see it and come to his aid. He checked his watch and found it was about 3.00 pm.

He made himself as comfortable as possible and continued to call out for help. At one point he appears to have lost consciousness for some time.

FITTER FINDS INJURED CO-WORKER

By about 6.20 pm the other team members became worried. Mr Battams usually returned to the 24 Level with his IT at about 6.15 pm.

A maintenance fitter went in search of him. He drove his Toyota ute up the drift from the 24 Level to the 23 Level pre-screens to check on Mr Battams.

When the fitter entered the pre-screens he found Mr Battams on the floor lying on his left side facing the screens. Mr Battams told him he couldn’t move as he had injured his right leg and needed medical help. The fitter noticed that Mr Battams appeared to be in discomfort and was wet and shaking.

Hose-and-Failed-LadderwayMr Battams asked the fitter to call for help from the 23 Level plat phone as the phone at the pre-screens was not working. This the fitter did. The Mine Control Centre asked him to stay at the 23 Level plat phone. After finishing this call the fitter called the 24 Level office and alerted the rest of the service crew to the situation.

In response service crew members and the platman went to the pre-screens area to help and comfort Mr Battams.

One of the crew returned to the 23 plat and the fitter told him to take the cage up to the marble arch to get the rescue team.

RESCUE TEAM ARRIVES

The mines emergency procedure was put into action. When the mine rescue team arrived they gave Mr Battams pain relief and placed his leg in a position for transport. It took about an hour to get him to the surface. One of his service crew mates said that Mr Battams was in considerable pain for the whole of the trip.

The rescue team and Mr Battams arrived at the surface at about 7.45 pm where an Ambulance crew was waiting. They placed Mr Battams in the ambulance and gave him morphine to ease the pain.

He was taken to the Emergency Department at Broken Hill Base Hospital. His family met him on arrival.

Mr Battams had X-rays taken of his right leg and foot. His injuries were assessed as a fractured foot and broken femur of the right leg, and broken bone and dislocated finger of the left hand.

Next day medical staff decided Mr Battams should be flown to Adelaide, South Australia, for surgery and further treatment.

The surgery performed in Adelaide involved inserting a plate into his right foot, and a rod and a number of pins repaired his broken femur.

Mr Battams was later transferred to Mildura Base Hospital in Victoria, which was near his home, for further care and rehabilitation. He was released from hospital on 23 November 2007 to continue convalescence at home.

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ACTION TAKEN BY THE MINE 

The incident site was cordoned off and the scene preserved for investigation.

The redundant ladderway to the crows nest above the pre-screens was removed, along with the walkway structure and its access ladderways.

A risk assessment was conducted to identify interim measures for cleaning the screens. The risk assessment determined that a scissor lift would be used to hose the screens.

In June 2008 Perilya had an expert engineering company conduct a structural review of all underground steelwork. This was required by recommendations identified during the course of this investigation. Perilya reviewed designs for a replacement walkway for the 23 Level pre-screens in June 2008.

Following the incident the mine reassessed the pre-screens and began an evaluation and upgrade project. Pipe work and other structures were replaced, with a permanent raised walkway and access being completed in June 2010.

The 23 level pre-screens area upgrade also included installing improved lighting, ventilation and communications.

FACTS DETERMINED BY THE INVESTIGATION

Following the incident, the mine reassessed the pre-screens and began an evaluation and upgrade project. Pipe work and other structures were replaced, with a permanent raised walkway and access being completed in June 2010.

The 23 level pre-screens area upgrade also included installing improved lighting, ventilation and communications.

The following facts were determined by the investigation:

  • The underground environment at the 23 Level is a corrosive one, with ample water and oxygen present to react with the iron and steel.
  • The pre-screens had been in such an environment since they were constructed by previous mine owner, Pasminco, in about 1991-2.
  • Perilya Broken Hill Limited had a system of inspections for plant that should have identified the corrosion to the pre-screen particular the galvanized steel pipe of the guardrails.
  • Rusting on ladders at the pre-screens was identified, reported and included as a corrective action in the maintenance system. However, no work was undertaken to replace the handrail and ladders as required by the maintenance work order.

The primary cause of the incident was a slip by Mr Battams that caused him to fall against the handrail which failed under load and did not prevent him from falling off the walkway to the floor below.

The investigation identified the following organisational failings and other factors that contributed to the incident.

UNSAFE PLANT

The handrails provided at the pre-screens raised walkway to prevent persons from falling off were found to be corroded:

  • steel of the pipe of the handrail was found to be very thin, offering little strength when a force or load was applied, and
  • inspections of the pre-screens plant after the incident by the Inspector and Investigator readily identified surface rust and possibly deep corrosion on other steel components of the plant.

Further examples of unsafe plant and equipment were identified, in particular the ladder that went from the platform up to a crows nest near the roof of the cavern. This ladder appears to have been redundant for some time and had a sign attached prohibiting unauthorised access.

As Mr Battams fell he grabbed at the ladder hoping to stop his fall, only to find that a section of the extremely corroded ladder stile came away in his hand.

FAILURE OF SAFETY SYSTEMS AND RISK MANAGEMENT

Perilya Broken Hill Limited failed to adequately inspect the 23 Level pre-screens to ensure safe plant.

The mine’s overarching HSE safety management system, along with the Mining Department’s Safety and Health Management Plan, had risk management processes for plant safety. These included:

  • daily workplace inspection upon first entry of an underground work area
  • safe work procedure on how to conduct a workplace inspection before starting work
  • a safe work procedure for cleaning of the pre-screens
  • planned task observations
  • formal inspections of the 23 Level prescreens to identify hazards.

Non-conformances or failings of the management system were:

  • no specific standard for workplace inspection of fixed plant
  • no safe work procedure or written instruction on how to perform an inspection of handrails and ladders at the 23 Level pre-screens.
  • No records found of formal inspections of the 23 Level pre-screen

“The handrails provided at the pre-screens raised walkway to prevent persons from falling off were found to be corroded.”

Corrosion Prevention – LADDER CORROSION REPORTED BUT NOT FIXED

A member of the fixed plant maintenance team noted that the access ladders to the walkway at the 23 Level pre-screens were rusty and reported this as a safety issue to his coordinator. The report was entered into Maximo, the mine’s maintenance planning software, on 10 April 2007.

MAXIMO is a maintenance database and work order system. It supported repair and preventative maintenance activities, along with reporting of inspections and follow up actions.

This system generated work orders and the daily floor plans which list planned preventative and corrective maintenance tasks for plant and equipment.

The 23 Level pre-screens work order was generated by the Mine Services Planning Co-ordinator each Friday. It specified inspections and cleaning.

The pre-screens work order listed work plan details for the week including the inspection of handrails and ladder ways. There were no instructions, written or verbal, on how to conduct this inspection.

It appears the inspections of the handrails and ladders performed by mine services employees were restricted to visual inspections. No attempt was made to perform non-destructive or physical testing of the structures.

The floor plan that listed tasks for each maintenance team was printed from the Maximo system for each shift each day. This floor plan was given to the relevant service team. The fixed plant services team received a plan for Fixed Plant Mechanical Maintenance.

Floor plans supplied by Perilya for the period 11 April 2007 to the 6 November 2007 note a corrective action for the prescreens as: “Replace handrails and ladders that are rusted.”

If work was undertaken against this action it should have been recorded. If the action was completed the task would be removed from the floor plan. The floor plans noted above had no record of work being undertaken for this corrective action.

The fitter who reported the corroded ladders said during his giving of evidence that nothing was done with regard to the Maximo entry requiring replacement of the handrails and ladders.

Corrosion Prevention – FIXED PLANT STANDARD NOT MAINTAINED

To comply with the requirements of the Mining Department Safety and Health Management Plan the Mine Services Superintendent inspected the 23 Level pre-screens and other locations where maintenance work under his control was undertaken.

As part of these inspections, the Mine Services Superintendent recalls inspecting the prescreen area about mid-August 2007. He made a visual inspection of the handrails and found them satisfactory. He looked at the handrails at the end of October 2007 and again found them satisfactory.

The Mine Services Superintendent did not conduct any physical testing of the structure as he did not consider the pre-screen environment to be corrosive. There were no corrosion prevention strategies used by the site.

This incident investigation found that kickplates were missing from the raised platform in the prescreens area. Kickplates are required by Australian Standard, AS1657- 1992: Fixed platforms, walkways, stairways and ladders – Design, construction and installation.

Redundant hinges indicated that kickplates may have once been fitted.

No one who worked in the area or performed inspections on the walkway noticed the kickplates were missing.

This further indicates that the inspection system applied in the prescreens area was unable to identifying non-conformances and potential risks.

This incident investigation found that kickplates were missing from the raised platform in the prescreens area. Kickplates are required by Australian Standard, AS1657- 1992: Fixed platforms, walkways, stairways and ladders – Design, construction and installation. Redundant hinges indicated that kickplates may have once been fitted.

No one who worked in the area or performed inspections on the walkway noticed the kickplates were missing. There were also no corrosion prevention strategies used

This further indicates that the inspection system applied in the prescreens area was unable to identifying non-conformances and potential risks.

PERSONS WORKING ALONE WITHOUT SUPERVISION

Risks to employees working at the 23 Level were increased by the fact they were allowed to work alone and unobserved.

In addition, the phone, the only means of communication from the area, was found to be defective. It had not been working off and on for some time.

Mr Battams had cleaned the 23 Level prescreens and maintained the 24 level pump for at least the previous five years. Generally he did both these jobs on his own during that time.

Most of the fixed plant team work alone, often in areas where potential risks were present. Other service personnel described working alone in places where slips or trips could occur.

This risk became a reality when Mr Battams lay injured, unable to raise the alarm, for nearly three and a half hours before someone noticed he was missing.

When questioned the general manager noted that Perilya did not have a procedure in the HSE management system for working alone. It was indicated that there was an informal practice for people working alone to contact the MCC at regular intervals. From the evidence of this incident, it appears not all employees were aware of this practice.

Regular visits by a supervisor to an area where people are working alone is a way to monitor their safety. Mr Battams’ supervisor, the Fixed Plant Coordinator, did not visit the 23 Level pre-screens, and he infrequently went underground.

It appears the limited frequency of the Coordinators visits underground was not known to company managers until after the incident.

STRATEGIES TO PREVENT RECURRENCE

FAILURE OF STRUCTURES A KNOWN RISK
Failure of structures is identified on the Department’s internet site as a mechanical engineering key risk (Mechanical engineering key risks: www.dpi.nsw.gov.au/minerals/safety/resources/mechanical/key-risks).

The majority of metalliferous mines in New South Wales have been operating continuously for long periods of time, some for a hundred years or more. This is particularly so for mines in the Broken Hill and Cobar mining districts.

New owners of mines such as the Perilya Broken Hill operation inherit plant and equipment that may have been in place for years. This was so with the pre- screens fixed plant which was about 10 years old when Perilya began mining.

IDENTIFYING WORK ENVIRONMENT RISKS
Environmental conditions must be considered when identifying and assessing the risk of plant and structural failures. Exposure to conditions that promote corrosion and fatigue of structures must be recognised as a hazard, not only at surface mines and processing plants, but also underground.

NEED TO REVIEW AND AUDIT MAINTENANCE SYSTEMS
Mine maintenance and other related systems must be audited to make sure their associated risks are effectively controlled. This is to ensure that:

  • Risk assessments identify all potential hazards. There must be recognition of the increased risk of failure of plant that is increasing in age and is located in an environment that may contribute to corrosion and structural failure. This must not be restricted to operational plant and must be equally applied to little used and redundant plant.
  • Corrosion Prevention – Structural components that are required as part of safe plant and access, such as handrails, guardrails and ladderways, must have an inspection and maintenance schedule that is equal to, or of higher priority, as that of the operational components of that plant.
  • Fixed access ladders and guardrail installations must be periodically inspected by visual and physical checking for rust, corrosion and structural integrity. They must be maintained in good condition so that no worker is endangered.
  • Competent and qualified people must conduct the required testing and inspections to ensure structures do not fail.
  • Records of inspections and maintenance of fixed structures, including walkways, handrails and ladderways, must be kept and maintained.
  • The effectiveness of documented systems must be periodically checked by monitoring, review and auditing by line and senior management.

NO SAFE WORK PROCEDURE FOR WORKING ALONE
This incident investigation identified that no formal safe system of work for persons working alone was in place at the Perilya Broken Hill Southern Operations. In addition, the underground phone system was unreliable and beyond the reach of the injured worker.

Most of the fixed plant maintenance team worked alone, often in areas that had high potential for risk. In particular, they were exposed to risks from slips, trips and falls while accessing fixed plant

SAFE WORK PROCEDURE REQUIREMENTS
Safe work procedures for persons working alone must include:

  • appropriate working communication systems (such as the PED and RFID systems that are used throughout the coal and metal mining industries)
  • regular contact with other persons, such as the control room operator, with regular reporting-in and checking
  • adequate and competent supervision

This extract of the Investigation Report, ‘Serious injury involving a fall from height at the Perilya Broken Hill Southern Operation on 6 November 2007’, has been reproduced with kind permission of Resources & Energy, NSW Trade & Investment.

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