The following is an excerpt from the plenary session paper presented at the recent maintenance engineering conference held in Sudbury, Ont. The conference was sponsored by the Canadian Institute of Mining and Metallurgy.
The maintenance component of the mining industry is in sorry shape. We accept poor equipment and poor availability of machinery as part of the price of working underground. We order underground fleets to support poor availability. We tolerate roadbeds underground that, were they on surface, would torture test the most rugged all-terrain vehicles. Underground equipment maintenance is breakdown maintenance. Broken drive lines, broken hoses, broken hydraulic cylinders, equipment breaking in half, wheels and/or spindles breaking off — the list goes on. On raise drills, such components as gearboxes, pumps and motors often are changed only when they fail. Why? Poor operators, poor roads, poor equipment, poor maintenance — all contribute to breakdown maintenance. This is not necessary. The mining industry could save itself a lot of money by following simple principles and procedures. But first it must be recognized that the problem exists.
Twenty-five years ago a mechanic had to repair track loaders, battery locomotives and mine cars. This equipment was extremely simple, rugged, and required little maintenance. The move to trackless equipment (with diesel engines, hydraulic, pneumatic and electric systems) was a major change. We provided some training and went after more qualified maintenance personnel. But we have not devoted the resources to gain improvements in maintenance to compare with advances in direct mining.
In spite of having one of the most highly educated and skilled work forces of any industry in the world, most mining companies and mining contractors still get little out of them other than effort. Programs to involve employees directly in cost reduction and maintenance improvements are still in their infancy. Especially when compared with the North American aircraft and chemical industries or the Japanese manufacturing industry, where employees participate in cost reduction and process-improving ideas on a regular basis.
A survey of 12 major Canadian mining companies found that direct maintenance labor for underground equipment averages 30% of direct mining labor. Generally, direct labor represents half of total labor, which, in turn, is half of total product cost. Thus, maintenance labor is 8% of total product cost. When maintenance parts and materials are added to the labor cost, it doubles to 16% of total product cost. A 25% improvement in maintenance cost is considered a reasonable goal. This would result in close to a 4% reduction in product cost. This potential saving is far more significant than was anticipated when this paper was first contemplated. How can we achieve this cost improvement? We must recognize that there is a problem in mine equipment maintenance and then address the problem.
I believe we will make great strides in our maintenance programs over the next decade. Breakdown maintenance will only account for a fraction of what it is today. Equipment availability will improve dramatically and may ultimately result in smaller equipment fleets. Equipment life will be extended. How can we achieve these lofty goals? We will achieve these targets using a number of techniques, some of which are as follows:
* reliability-centred maintenance implementation;
* on-board equipment monitoring;
* scheduled component exchange;
* automatic lubrication systems;
* closed service systems for fuel, lube, hydraulic, transmission and other equipment fluid;
* high-speed, smooth roadbed standards;
* improved equipment components, especially in high failure areas;
* automated loading cycles; and
* automated drilling cycles.
Reliability-centred maintenance (RCM) is a comprehensive, engineered approach to determining the maintenance requirements of critical and capital-intensive equipment. Because it involves analysis of all elements of an organization that use equipment, RCM serves to heighten awareness of proper operational and maintenance requirements within the organization. This means involving operators and maintenance personnel. The introduction of powerful computerized data-collection systems into the mining industry will render the technique workable in all organizations. The imperative is the requirement to dedicate the necessary resources toward improving the level of maintenance and equipment operation to a point where unscheduled equipment failure is not tolerated.
Reliability-centred maintenance is therefore a system designed to:
* reduce failures from unexpected breakdowns;
* significantly reduce losses associated with the setups and commissioning of equipment;
* increase the life span of equipment, thus reducing the capital equipment commitment required to remain competitive; and
* reduce the costs associated with the provision of maintenance, including costs for both labor and spare parts.
RCM, which originated in the aviation industry, was developed to identify and determine the mode and consequences of failure and to select, based on maintenance data, the appropriate tasks required to anticipate failures before they occur. It presupposes that failures can be anticipated in the vast majority of cases, provided that the failure mechanism is understood and that operational system performance observations are recognized and used.
Organizations now look to various means for improving maintenance programs. In the broad sense, maintenance managers have begun a review of maintenance procedures including the introduction of an analytical approach to equipment design and layout, determining how maintenance is to be integrated into the production process and identifying the tasks associated with effectively maintaining equipment. This is a significant change for many organizations, as the current methods used for operating and maintaining production equipment are often reactionary in nature. While the RCM system is an existing system, it seems ideally suited to the mining industry and either this system or a similar maintenance system will become the norm in the next decade.
On-board equipment monitoring is an inherent component of RCM. Most new open pit equipment has on-board equipment-monitoring. Of course, open pit equipment is expensive, generally starting at $250,000 per unit and increasing in cost as size or capacity increases. Equipment this expensive justifies on-board equipment monitoring.
Why do we not insist on the same equipment monitoring for our trackless fleets? Only the smallest underground loaders, trucks and service vehicles cost less than $200,000. Do we lose perspective when we go underground? Is it because it is dark underground that we cannot see the necessity for the same conditions and maintenance as surface equipment? The equipment is equally expensive with $300,000 load-haul-dump units, $500,000 drill jumbos and million-dollar raise drills.
On-board monitoring and expert systems are available from several sources. Ultimately, these systems will not only monitor but also store data on the maintenance history of equipment and thereby protect the equipment from abuse or impending failure. Even automobiles are now equipped with on-board monitors.
Scheduled component exchange is rarely practiced in underground maintenance. Engines are usually changed on a scheduled basis because regulatory emission checks point out the impending failures. On the other hand, transmissions, torque convertors, differentials, hydraulic pumps, valves and cylinders are usually changed when they fail. A failed differential costs 10 times as much to repair at failure compared with the cost of being changed on a schedule that leads to bearing and seal replacement. A more startling example is a raise boring machine gearbox. It can cost up to $30,000 to repair after failure; new bearings, seals and pins cost only a few thousand dollars. A combination of RCM and on-board monitoring helps develop historical data, resulting in scheduled component exchange. RCM will reduce dependency on breakdown maintenance.
Automatic lubrication systems are commonly used on surface equipment and stationary mining and mineral processing equipment. Why do we not use it on our $100,000 or $500,000 pieces of equipment underground? This system will be in place within the next few years. Some companies are beginning to specify automatic lubrication systems on replacement equipment.
Closed high-volume fuel and lube service systems are rarely (if ever) used on underground equipment. A few companies have installed fuel systems (primarily for fire prevention) and have found a bonus in improved productivity through faster fueling without spillage. Cleanliness, which is a factor in closed service systems, is not even discussed. Open pit equipment is often equipped for high-volume closed fueling, as well as the addition or changing of lube oil, hydraulic oil, transmission oil and other vehicle fluids. These systems will eventually be found on all underground equipment to improve fluid addition efficiency. Equipment will become more reliable as a result of the inherent cleanliness of the systems.
Roadbed maintenance is generally a last consideration. It must become a part of the maintenance systems. Smooth travelways are essential to sustain high levels of equipment availability. Roadbed maintenance is a high priority in open pit operation and will receive the same attention in underground mines in the 1990s.
Equipment components will improve in the next decade as the RCM system provides increased data on repetitive component failure. A way will be found to prevent or reduce failures from abuse and/or heavy-duty work cycles.
Automated loading cycles are being developed. HDRK is working on automating the loading cycle. There is pressure to develop a fully automated underground loader. (This seems akin to orbiting the Earth before embarking on a mission to land on the Moon.) The most damage or equipment abuse occurs during the loading cycle. An operator can charge the muck pile or spin tires while loading or lift the rear end of the loader right into the back. Automation of the loading cycle, based on the most efficient loading procedure, seems to be warranted immediately. The operator would simply drive to the muck pile and switch the machine on auto-load, then back out and tram to the dump or truck with the machine switched back to manual mode.
RCM carries similar advantages when applied to drilling. Systems and equipment are now available and will be implemented in the next few years to utilize full automated drilling equipment at the face.
Do I seem optimistic about the potential for improvement in underground equipment maintenance in the mining industry? Perhaps. However, compared with the great strides made in mining productivity, it seems time for the maintenance sector to move to centre stage and begin to earn rewards.
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