Productivity improvement at mining sites through nozzle audits and spraying analysis

When researchers from Ernst and Young interviewed more than 60 senior mining executives from around the world last year, one word dominated the conversation — productivity.

The survey, conducted in association with the University of Queensland and the Imperial College London, confirmed what has long dominated speculation — that “productivity is the number one challenge in the mining sector and is firmly on the CEO’s agenda”.

Solutions to improving productivity, however, are more difficult to pin point so resolutely. Ernst & Young proposes that cost cutting only leads to modest, short-term results, and instead companies need to look “beyond point solutions, and adopt an end-to-end solution to transform the business.” [1] Transforming the business, however, is an easy concept for consultants to float, but not very helpful for managers who are on the ground, responsible for overseeing major operations.

A starting point to improving productivity, however, could be as easy as organising a spray systems analysis and nozzle audit. Effective dust control not only protects the health and safety of mine workers, but can improve productivity by decreasing equipment downtime, saving water and electricity costs, and ensuring that the end product meets industry requirements for moisture levels.

The following white paper will address productivity issues in the mining sector, and argue why effective dust control and well maintained spray equipment is the best first step for maintenance supervisors and production managers to take to improve productivity in their operation.


Productivity is a buzzword in mining, mainly because the global industry is failing so remarkably at improving it. A study by international consulting firm McKinsey found that worldwide mining operations are as much as 28 per cent less productive today than they were a decade ago. The study points to the fact that the industry, up until 2015, has had to ride a “demand supercycle” and expand production of certain major commodities by 50 pe cent in the same period. The result has been a drop in profitability. [2]

PwC found that the Australian industry is especially struggling to improve its productivity. It reported that mining equipment in Australia runs at lower annual outputs than most of its global peers, noting: “Australia is not best in class for output from any category of equipment and is below the annual output of North America across all classes of equipment.” PwC concludes that Australia’s lack of productivity is not a cause of poor conditions, but rather because of “the way people act”. It noted that while a better rated piece of equipment might deliver 5–10 per cent output improvements, changes in workplace practices can deliver 20 per cent plus in gains, at little or no cost. [3]

Water wise

An American handbook on dust control, issued by the National Institute for Occupational Safety and Health (NIOSH), confirms that dust control is a challenge worldwide. It notes that: “Most underground dust control methods yield only 25–50 per cent reductions in respirable-sized dust.” It goes on to say that because these levels of reductions aren’t enough to achieve compliance with dust standards, mine operators must use several methods simultaneously, “without knowing for sure how well any individual method is working”.[4]

It’s this blanket method that can cause serious problems for mine operators. A bulletin issued by leading supplier to the mining industry Spraying Systems Co. noted that from an operational perspective, having material that is too wet can cause it to stick to screen cloth and conveyors, can cause sludge to accumulate in chutes and areas around transfer points, and can lead to belt slippage.

Using too much water has two immediate cost effects. The obvious one is unnecessary water costs. In a sample cost analysis conducted by Spraying Systems in 2017, the company found that the original nozzles being used at a site for ore condition were too large. Changing the nozzles led to a saving of 1.6 million litres of water per hour (see Table 1), as well as more effective dust control. In another analysis, the company found that the use of worn nozzles on site was causing increased water output, wasting more than 1 million litres of water a day (see Table 2).

The perhaps less obvious cost effect of over wetting is a loss in productivity. At one plant, Spraying Systems found that upgrading the nozzles in a chute not only reduced the amount of water used, but saved on cleaning time and improved the flow, leading to a potential increased profit of $110,500 per hour (see Table 3). The company found more savings potential at a fixed plant, where poor dust control was leading to more hours needed to wash down the plant. A calculation estimated that the plant could save 202,560 litres of water per shift, as well as the labour costs of 8 hours of cleaning per shift (see Table 4).

Overuse of water though inefficient means is also likely to continue raising questions about the industry’s sustainability. A book published by the Commonwealth Scientific and Industrial Organisation (CSIRO) raised concerns over the future needs for water in the mining industry, which is likely to jump with the decrease in the quality of iron ore, and the increase in demand. In 2008 the ABS reported that the mining industry used around 508 GL of water, however CSIRO predicts that by 2020 Western Australia alone will need 810–940 GL of water.[5]


Health risks

Looking past productivity and cost issues, the need for efficient spraying systems to protect worker health should be of paramount concern to site workers. The American Journal of Respiratory and Critical Care Medicine published a study confirming that miners are not only at risk of traditionally linked diseases such as coal worker’s and mixed dust pneumoconiosis (more commonly known as black lung), and silicosis (also known as grinder’s disease); but they are also at risk of dust related diffuse fibrosis and chronic airway disease, including emphysema and chronic bronchitis.[6] Another study published by the American Cancer Society confirmed that there is a statistically elevated risk of gastric cancer among miners who smoke.[7]

In Australia, over the past three years 23 miners or former miners around Queensland have been diagnosed with coal miner’s pneumoconiosis, in what is being called “a resurgence” in black lung.[8]

The health risks associated with ineffective dust control should be of special interest to mining operators, with new regulations increasing the liability of workers health and safety on employers. In October 2017, the Queensland Government passed a landmark bill that introduced the offence of industrial manslaughter. The bill means that individuals could face up to 20 years imprisonment, and corporate offenders could be liable for fines of up to $10 million, if employers were found to have caused the death of their employees due to neglect.[9] Although the resources sector was given a last minute exemption from the law,[10] the legislation is evidence of a general appetite for increasing employer accountability for health and safety practices.

Spray systems analysis and nozzle audits

From productivity through to cost and health concerns, many of these issues can be addressed with a simple spray systems analysis and audit. A spray systems expert visits a mine site, to study the entire system as a whole process, and determine the best spray system moving forward. This includes both prevention and suppression systems to ensure effective dust control. The difference here is important, as outlined in the report by Spraying Systems. A prevention system adds immediate moisture to a product to prevent dust in the first place. The level must be exact, as too much moisture can compromise the integrity of the material and clog up equipment, while too little moisture will not be effective.

For dust suppression, that is dust that becomes airborne in the extraction and processing steps, the size of the spray particles is especially important. Dust capture is most effective when dust particles collide with water particles of the same size. If they are too large, they won’t collide with even the smaller dust particles, and if they are too small, they will evaporate too quickly and release the captured dust particle.

Unfortunately, inefficient maintenance of a spray system can easily lead to any of these problems. Water quality that contains debris can clog up in the nozzles, and wear them out. Other issues that can arise include plugging and clogging, corrosion, and caking.

Fortunately, Spraying Systems offers its clients regular spray systems analysis and audits. The analysis ensures that mines have an efficient system to control and supress dust. The analysis should not only be conducted on new mining operations, but also on established ones that have either increased or decreased their production. Spraying Systems also offers annual nozzle audits. For these audits, an expert checks every nozzle and recommends the best replacement.

For Maintenance Supervisors and Production Managers, picking up the phone and organising a spray analysis or nozzle audit is a simple first step in addressing the larger issues of mine productivity and worker safety.

Table 1

Spraying Systems determined the below based on an audit and spray analysis at a single site. These sprays were being used for Ore Conditioning (raising moisture content), which is beneficial for improving dust prevention. The original nozzle was designed too large and was over wetting ore, and causing chute blockages and conveyor carry back issues. There were 46 stations on site. Nozzles were changed to a much smaller nozzle that saved large amounts of water. This also reduced chute blockages and conveyor carry back and improved dust prevention. The cost savings calculations below are based on if all stations were operational, however there is still a significant cost savings even if only a portion were operating. If a production manager were to factor in 24-hour operation over one year, the saving on water would pay for the nozzles several times over and they would still be left with a profit.

Ore Conditioning Sprays
Original Nozzle l/min @ 7 Bar New Nozzle l/min @ 7 Bar No. of Nozzles across Site Original Nozzle Total l/min @ 7 Bar New Nozzle Total l/min @ 7 Bar Savings l/min Savings l/hour
                           241                              90                            184                  44,344              16,560        27,784    1,667,040

Table 2

The below table indicates the amount of water used on site when spray systems are operating at peak efficiency. As nozzles wear, water output increases, which cannot be not be noticed visually. As water increases, moisture content becomes incorrect and over wetting starts becoming an issue. Sprays become isolated and dust emissions begin to increase. Looking at the below table, averaging a five per cent increase due to wear, the consumption of water in one day is significant. This continues to increase as the nozzle continues to wear. The cost saving would pay for the nozzles several times over and still leave the operator with a profit.

Worn Nozzles on Site
Total Water used Moisture and Dust Management operating Efficiently – l/min Worn Nozzle 5 per cent increase – l/min Worn Nozzle 5 per cent increase per l/hour – wastage Worn Nozzle 5 per cent increase l/day – wastage
                     14,975                            749                      44,925            1,078,200

Table 3

Spraying Systems determined the below based on an audit and spray analysis at one site. When chutes become blocked, it causes the ore that is passing from one conveyor to another to deflect incorrectly, which causes ore to wear the chute itself. This causes expensive repairs and unnecessary spillage. This additionally causes tracking issues for the belt and uneven loading to the next conveyor causing further damage and more spillage. When the chute becomes blocked, production needs to be stopped and sprays turned on to remove the ore build-up off the wear deflection plates. This results in lost production time. By changing the nozzle to a more effective nozzle, water is saved and lost production is greatly reduced, which increases profits. The calculations below are based on one chute. At this given site there are 47 chutes that can stop anywhere from once to several times per 12 hour shift, depending on the condition of ore. This is only an issue when running ore fines.

Chute Spray Upgrade
No. of Chute Sprays Original Nozzle l/min @ 7 Bar New Nozzle l/min @ 7 Bar Original nozzle Clean Time – minutes Original Nozzle Total Litres New Nozzle Clean Time – minutes New Nozzle Total Litres Saved Litres per clean cycle Saved Clean Time – minutes – Saved Production Iron Ore Price per tonne Increased Production Profit based on 6500 Tonnes per Hour
           7                    54                    48                    20              7,560                    3            1,008            6,552                            17 $ 60.00 $ 110,500.00

Table 4

The below table indicates the amount of water that is used to wash down (standard wash down nozzle) a fixed plant to clean the dust that settles over the structure. Depending on the site, there can be several personnel whose position is to wash the plant down daily. If dust management is improved, less wash down would be necessary, saving on both water and labour.

Plant Wash down – Manual Labour
Cleaning Nozzle l/min @ 7 Bar Cleaning Output – Litres / Hour Hours of Shift Approx. Hours of Cleaning per shift Total Output litres per shift
                   422              25,320                      12                      8      202,560

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