Thursday 17th Oct, 2019

BULKtalk: The hidden dangers in bulk materials handling

Rio Tinto’s Steve Davis explores some of the dangers hiding within the bulk materials handling industry and how they can be avoided at the design stage.

Australia is one of the safest industrial regions on Earth. I believe that most of us in the bulk materials handling (BMH) industry genuinely believe in the safety message. We have an innovative BMH industry in Australia, but we still supply systems that are unsafe to operate and maintain. We can do better.

This article considers some of my observations from experience in Australia and elsewhere, across several industries and operators. We are getting better as an industry, but we are not there yet.

People

Australia is a diverse country and we promote equal opportunity. The Australian Bureau of Statistics’ 2016 Census of Primary Australian Languages shows that 20 per cent of our population do not speak English as their primary language. Our resource industry now employs a diverse workforce, with male and female workers who may not have “standard” English as a first language. This is a good thing for our industry.

Has our industry kept up with these changes? Signage and documentation are the communication media used for safe operations and maintenance, yet for many the message may not be clear.

Do we need simpler graphic signage or even a multi-lingual approach? Misunderstanding leads to mistakes. I often see trilingual signage on my overseas travels, typically English, French and Spanish, but this is not common and is not certainly not universal for our community. Graphic symbols may not be immediately obvious to all: should the industry find an appropriate system to improve safety for everyone?

Similarly, workers aren’t all shaped the same, which presents a challenge when designing the optimal location for instruments, controls, handles and viewpoints. I am 1.86 metres tall and I sometimes miss low things, but there many who are shorter or taller. What height is an unsafe stretch to controls? Similarly, minimum width walkways are a squeeze for me, especially when columns, hose reels, light fittings, pull wires and other intrusions reduce this significantly. Short door latches may make operation impossible. The list of potential design considerations is endless, and we may need to reconsider our approach.

The phrase “familiarity breeds contempt” often comes to mind. If you were to walk past a hazard four times a day for years, would you still recognise the hazard? Especially if it has not previously caused an issue, or if there was
a distraction.

Barriers and guards protect from hazards in this situation but pull cords and personal protective equipment may not be sufficient, and procedures are easily forgotten.

Design for Safety

In Australia, we have good safety legislation and design standards, but this does not cover every eventuality. Do we just quote the Standard, follow the guidance to the letter, or interpret the situation accordingly?

We hold HAZOPs, HAZIDs, CHAIR reviews and similar to risk assess projects. From participation, I do not believe these always achieve the aim. Man hour cost results in rushed outcomes. The team often does not comprise people with actual construction, operations and maintenance experience, so we may ignore key issues. The risks raised are not always followed through.

Reducing the likelihood of an incident does not reduce consequence of the incident, as many seem to believe and use in matrix assessment.

Design for safety should consider and include workers using the facility, especially construction, operation and maintenance. Many of our designs are for the convenience of one-off construction, with token consideration of how to operate and maintain the facility 24/7 for 20 plus years. We can do better by engaging a wider review team and changing focus.

Operation and Maintenance

We might have the latest devices to identify failure early through on-line monitoring, we have better quality components, but when something does fail, we need to have a safe and sensible process for the people repairing it.

Cost of producing maintenance manuals for engineering, procurement and construction management projects is one reason we do not get them. However, this does not preclude designing materials handling equipment to be easily and safely maintainable. Should we develop an Australian Standard for minimum needs?

Almost every component can fail or wear out, so it is important to be able to safely access and repair them. Maintenance considerations include methodology, clearances, isolation of energy sources, lifting, alignment and tools. It is ridiculous to expect dismantling of major structure with a large crane to remove a pulley or drive. It is unnecessary to have to remove cable trays and pipework to remove a motor. Reconsider manual lifting of anything heavier than 10 kilograms, or which has poor ergonomic approach.

Guard systems have improved, and many now meet legislation, but guard removal and storage for maintenance access is often not considered. This can lead to on-site modification and sometimes removal. It’s important to note that only one tool removable fixing per guard is sufficient, four bolts per panel takes much more time.

Spillage and Dust

Managing spillage and dust begins in the design office.

If cleaners and skirts are not selected and installed with safe access, they will not be maintained and result in carry back and spillage. If maintained, there is still a risk of injury through unsafe access.

Spillage costs our industry billions in clean up every year; it diverts qualified people from more valuable work, causes belt problems and damage, and is often a safety trip hazard. Structures have collapsed from overload because the design does not shed spillage. Poor design allows accumulation in pockets where corrosion starts.

Alumina build up on all flat surfaces; corrosion from wet bauxite.

Dust management in most plants is a token gesture, often with minimal design input. Spray bars that cannot be maintained on line, with nozzles generating the wrong size droplets in the wrong location. Arbitrarily sized dust collectors with inaccessible extract ducting, designed like a water pipe. Dust is dumped straight back on the conveyor for release downstream. We know how to manage dust, so why is this a forgotten aspect in so many facilities?

Idlers and Pulleys

Idler replacement is rarely well considered in design. We anticipate replacement at random intervals of 10 per cent of the idler rolls over a five-to-ten-year period. Each replacement requires full isolation, belt lift and manual removal and replacement. In many conveyors, personnel access to replace idlers is unsafe. Moving replacement rolls to the conveyor and removing the old ones should be a design consideration.

There are many developing technologies that can remotely identify a failed roll, but there is no consistent design that gives safe maintenance access for change out. The location of cable trays, pipes and guard stanchions often place barriers to maintenance. Automated roll change devices have been available for many years but are expensive and so far unproven, prompting the need for a rethink on conveyor design.

How difficult is it to change these rolls?
How difficult is it to change these rolls?

Pulleys also fail, whether bearings, lagging or shells and it’s preferable to remove them without cutting the belt or dismantling the entire support structure. Pulley weight has increased with the size of the conveyors. Conveyor design should not only provide the minimum number of pulleys but also consider the location and access to remove and replace them. A “C” hook is often required to facilitate removal and should be part of the design. If a pulley change out takes longer than a day, the design of the system has failed.

Liners and Bars

Chutes are a part of every conveyor system and will have a wear material lining, which often need regular replacement. There is a trend towards rotable chutes or parts of chutes to allow for off-site liner replacement, which can be a faster and safer process without the need for confined space work. It’s important not to ignore the lifting process and lugs required to remove and replace chutes.

As an industry, there needs to be more alternate connection methods for chute flanges beyond “M20 bolts at 120 millimetre centres”. Having to remove and replace many nuts and bolts is time consuming and therefore often rushed and unsafe. Some designers have begun using locating pins and fewer bolts to make maintenance safer and easier.

There are excellent Australian developments in wear liner materials that give longer life and easier repair. However, there are still chutes made that use fewer effective materials and fixings, have heavy liner pieces and that need on-site repair and confined space entry.

Can these liners be safely replaced?
Can these liners be safely replaced?

Spile bars for isolating above feeders and other equipment are still features in some facility designs. These function well if they can be inserted and removed. Much effort is required to lift multiple bars, often well over 20 kilograms each, and push them into an empty hopper above shoulder height. The ergonomics are poor and manual handling injury follows. Expecting this when the hopper is full, and removing the bars from a full hopper, is asking too much unless mechanically assisted.

Summary

I have considered a few of the many aspects of our BMH systems but there are many others. We need safe expeditious and cost-effective maintenance strategies, because people complete all maintenance on our sites. Good initial design of the BMH systems, good components installed well and with safe access and methodology for maintenance will reduce costs and improve health and safety. Complacency is perhaps the largest of the hidden dangers.