6 Frequently Asked Questions About Mine Maintenance Facilities (Truck Shops)
12 October, 2015 | Blog
When designing a mine maintenance facility, several decisions must be made while considering multiple options available on the market; these options have their own benefits and drawbacks. Making the right choice can seem like a large undertaking. To help you make informed decisions, this article includes answers to questions we most frequently receive about mine maintenance facilities.
Should I go with a dome or conventional type of building structure?
Like most design decisions, the answer depends on several factors. For the type of building structure that best suits mine maintenance requirements, the main items to consider are: budget, life of mine, shop productivity, truck shop relocation requirements, and the desired comfort for the maintenance crew. These considerations can be factored in based on the following list of pros and cons for each type of building structure.
Dome-type – Pros
- Lower cost (typically $250 to $350 per sq. ft.)
- Ability to be easily relocated as the mine expands or changes location. Note that this can affect the building warranty and it is best to use the supplier to ensure proper disassembly and reassembly of the building
- Can be installed without the use of a concrete pad, which significantly reduces construction time and costs
- Most components are pre-assembled and fabricated off-site with a quick on-site installation and setup
- Short on-site construction period (can be as little as a few weeks)
Dome-type – Cons
- The building structure has a typical life span of 5 to 7 years before the dome fabric and structure require maintenance.
- Greater heat loss than with conventional buildings, if installed in northern climates. Hence, this could lead to higher heating requirements and larger operating costs. On the other hand, certain design options can include adding extra insulation between the trusses.
- Less available space for offices, locker-rooms, lunch rooms and warehousing than with a conventional building. However, containerized buildings or trailers can be used for additional space and connected via a utilidor.
- Less comfortable for the maintenance crew, which affects productivity.
- Cannot accommodate a large amount of warehousing space in the same building as the maintenance bays and would require a remote warehouse building. However, it would be possible to interconnect them using a utilidor capable of accommodating a forklift.
- Typical structural designs are not sized for suspended piping networks and radiant heating units.
- Overhead crane installation is feasible in some types of dome designs, but will typically be of lesser capacity. Gantry cranes are typically used in these types of buildings.
- There is a limitation to locating access doors. Larger access doors are limited to the extremities of the dome, and smaller garage doors can be installed to the sides of the dome.
Conventional-type – Pros
- Can accommodate large spaces for administrative offices, locker rooms, mechanical and electrical rooms, workshops, warehousing, etc.
- Expandable design opportunities
- Can be custom designed to accommodate unique design and configuration requirements.
- Long construction life with minimal infrastructure maintenance requirements (20+ years)
- Can be designed to accommodate heavy suspended loads off walls such as piping networks and radiant heating units.
- Simpler designs can benefit from pre-engineered structures.
- Overhead doors can be easily integrated into the structure of the building.
Conventional-type – Cons
- Higher construction costs with few modular opportunities ($350 to $500 per sq. ft).
- Long construction period (several months) that can push construction into unfavorable winter conditions, if installed in the north.
- Requires a large number of concrete pours and remote sites will likely need a local batch plant for its construction.
- Expensive decommissioning and dismantling.
What is a pre-engineered building structure?
The term pre-engineered is popular when speaking about low-cost industrial infrastructures. The term pre-engineered structure gives the impression of a pre-designed and already sized structure available for off-the-shelf purchase and construction with large cost savings tied to it.
In structural engineering, a pre-engineered building is designed to be fabricated using the best suited inventory of raw materials available from all sources and manufacturing methods that can efficiently satisfy a wide range of structural and aesthetic design requirements.
There is truth to the idea that pre-engineered structures come with accelerated steel delivery and cost savings, but in the case of truck shops, customization is commonly needed in order to account for crane selection, overhead doors, HVAC systems, piping systems, administration offices, etc.
Where the pre-engineered structure will ultimately have added-value and high-cost savings is in the supply of simple geometry buildings, warehouses or in typical workspaces that require a simple shell to protect against the environment.
Which capacity size should I choose for my overhead crane and how many would I need?
Choosing an overhead crane would depend on what the largest piece of equipment is to be removed (such as an engine block or dump body).
Depending on the climate, some mines decide to lower the capital cost of the truck shop and opt for removing the mine truck dump body to the outside of the building using mobile cranes, which reduces the overhead crane size significantly. As for maintenance on a Caterpillar 795F mine truck, an overhead crane capacity can change from 70 tonnes to 25 tonnes. For a 20-metre-wide maintenance bay span, the difference in cost for the crane can be in the range of $120,000.
The quantity of cranes depends on three factors:
- The service agreement with the mine fleet supplier (if any). There may be servicing agreements with the fleet supplier if they are contracted to perform maintenance activities for the client. One such requirement could be a dedicated crane for each maintenance bay.
- The acceptable maintenance downtime. If a crane is being shared with two or more bays, some maintenance activities would have to be delayed if the crane is needed for two or more bays at the same time, so this would need to be considered. Regular maintenance activities can, however, be scheduled to control this risk.
- The maintenance bay layout. An efficient layout would be to design the building with a nose to nose configuration, which would allow for the installation of one overhead crane for two bays.
How many bays are needed for my truck shop?
There are maintenance calculation spreadsheets that can calculate precise maintenance bay quantity requirements based on the scheduled preventive maintenance activities with forecasted fleet sizes. However, the general rule of thumb is one maintenance bay per five mine trucks. Additional bays for welding, washing and tire changing also would need to be considered.
What is the best way to deal with interior welding fumes in a truck shop?
Welding fumes are one of the greatest challenges when designing a truck shop layout and ventilation system. Some typical approaches used in the industry, from cheapest to most expensive, are as follows:
- Use of welding curtains to protect against arc flash and moderately contain the fumes, in combination with an extraction hood or nozzle to capture the fumes locally
- Use of a retractable enclosure on a caster or rail system with a dedicated ventilation system. This installation is practical when the parts are relatively small. The approach would be to place the piece on the maintenance bay floor using the overhead crane and cover it by pulling the enclosure over it to seal the welding zone
- Designing a dedicated enclosed welding bay with its own ventilation system. Though it comes with a cost, this is the ideal situation given that it provides the possibility of welding any equipment large enough to enter the bay
How do I deal with waste oil?
Given the large amounts of annual waste oil accumulation from mine truck maintenance, mine sites would typically look to contracting an oil collection company to take away the oil. Northern climates could use the oil for heating purposes.
When collecting waste oil for heating purposes, the mine would take responsibility for sampling the waste oil to determine whether it meets the oil quality code requirements for burning.
A typical installation for this approach would involve designing a waste oil collection system with two segregated waste oil tanks that could each be isolated, once filled, to be sampled and quarantined. This ensures that the oil will be untouched after sampling and can be used for burning purposes. If the oil does not meet quality standards, it would then have to be shipped off site (at a cost) for disposal by an oil collection company.
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