Grading and Excavation Contractor | ONSITE EQUIPMENT SUPPORT AND REFUELING

Comment On This

Create A Link
To This Article
On Your Website

Anything that moves wears out over time. There is no getting around friction no matter how well a moving part is lubricated. What we can do is maintain our equipment to minimize the need for repair or repair the equipment so it doesn’t have to be replaced.

By Daniel P. Duffy

Movement of engine parts, movement of equipment and tools, and the operation of these attachments powered by these engines cause stress and friction, which results in strain and erosion of those parts of the equipment performing the work. Such movement also generates heat from contact friction and the combustion of fuel used to power the engine. Temperature extremes also cause strain to equipment parts whether they operate on hot embers or frozen turf. Overly dry conditions can result in the generation of large dust clouds that clog intakes and deposit grit into contact points. Overly wet conditions can cause moving parts to become caked with sticky mud.

The difference between repair and maintenance should not be forgotten. Maintenance is the regularly scheduled tasks performed to minimize the need for actual repairs. Maintenance reduces the potential for a part or piece of equipment breaking; repair is the after-the-fact (and potentially costly and time-consuming) fixing of equipment that has already broken. Onsite support function should emphasize maintenance, which can usually be done in the field without undue difficulty. A minimal tool kit is required for maintenance, while an entire shop of heavy equipment is usually necessary for repairs. Maintenance can be done outdoors even in bad weather, while repairs usually require a covered work area. There are two types of maintenance, preventative maintenance and predictive maintenance. The difference between preventative and predictive maintenance is that the former seeks to minimize the need for repair and replacement, while the latter is used in situations where equipment wear is inevitable and tries to determine a regular schedule of maintenance to prevent operational downtime.

When done right, maintenance saves money, while repairs cost money. A well-managed maintenance program can produce cost savings in excess of 25%. However, studies have shown that excessive maintenance quickly approaches the point of diminishing returns with almost $1 out of every $3 spent on maintenance being wasted on unnecessary work. The trick is to target the appropriate kinds and levels of onsite equipment maintenance.

So what kind of onsite maintenance and service can be done for construction equipment?

The Basics—Daily Inspections
Preventative and predictive maintenance begins with daily inspections of all your operating equipment, starting with visual observations. A great deal can be learned from simply walking around and looking at the equipment. Most obviously, leaks of fuel, oil, lubricants, and hydraulic fluid can be detected. The locations of the pools of the leaked liquids will also give a good indication of where the leak is occurring (Is fuel coming from the tank or the fuel line? Is the leaking hydraulic fluid associated with the transmission system or the loading bucket? Etc.).

Visual inspections can also be done to determine the general state of the equipment and the effects of wear and tear. Are the tires worn (either evenly or unevenly)? Uneven tire wear is a sign that the tires need alignment and possibly rotation. Significant even wear on the tread is a sign of old age and the need for the existing tires to be replaced with a new set of tires. Besides abrasion, damage to the tires can result from rock cuts, blunt impacts, and punctures that cannot be patched. Tire tread wear that occurs too quickly (according to the manufacturer’s specifications or the tire’s mileage ratings) is often a sign of overloading or operating on road grades that are too steep.

Another candidate for excessive wear and tear due to abrasion is the undercarriage. Undercarriages are complex mechanisms consisting of interlocking track shoes joined by link assemblies and locking pins that are kept in place by tension track assemblies, and which ride on roller groups and carrier rollers driven by sprockets and regulated by idlers. Tractor tread vehicles are designed to go where big tire vehicles cannot and are always subject to more intense and difficult operating conditions. Most of the undercarriage assembly is exposed for easy visual inspection that will show to the trained eye loose linkages, misaligned pins, or worn sprockets.

Equipment that plays in the dirt is bound to get a little dirty—or a lot dirty depending on its working environment. Many operators may proudly point to their equipment’s caked-on mud as proof of how hard they and their machine are working. However, every clump of dirt or embedded rock represents another source of wear and tear, if not to the machine’s moving parts, then to its painted surface. While these machines have bodies of thick steel, damage to the surface can lead to significant rust and corrosion problems. So morning inspections should determine whether the equipment was properly cleaned at the end of the working shift the night before. The same body inspections can determine if the equipment was subject to vandalism or parts theft since its last operating shift.

Daily inspections should also include an examination of the engine, the transmission system, the coolant system, the hydraulic systems, the communication system, and any other system required for safe and effective operation. Measurements should be taken of the fluid levels for coolant, transmission fluid, hydraulic fluid and brake fluid, as well as fuel. Going that extra mile requires frequent (though not necessarily daily) sampling and analysis of these fluids. These fluids have operating parameters that require certain values of viscosity and levels of impurities. Analysis of fluid samples can determine whether the machines are being properly operated and maintained, whether the fluids are old and need flushing and replacing, or if the right fluid for the operating conditions was chosen in the first place.

Even after this multipoint inspection, the equipment is still not ready to work the site. Before it can be let loose, each of its systems needs to be physically tested in a safe, neutral location. These tests should include (but are not limited to) the brakes, the clutch and transmission system, the hydraulic lift systems operating a key equipment part (dozer blade, loader bucket, excavation bucket, equipment add-ons like jack hammers, etc.), and any operating part requiring in-place safety devices. Electronic components of the machine should also be tested prior to operation. These include its global positioning system or laser level sensors, lights, and signals, as well as the operator’s in-cab communication system.

The result of these and all other daily inspections and observations should be recorded on a standard report format for submittal to the construction manager and copied to the site’s project records. Given our litigious society, these records can be an owner’s first line of legal defense against a lawsuit resulting from an onsite equipment-related accident. These records should also record what was done when a system or part failed its daily inspection. The first step is to remove the equipment from the vehicle pool until its problem can be repaired or otherwise corrected. The inspector should tag the questionable part, both in his inspection report narrative and physically with a red tag or other marker that makes it clear which item needs to be addressed. Repaired machines can be returned to the job where they once again are subject to a complete daily inspection prior to being operated.

Taking services to the field

Liquid Levels
One liquid reservoir found in every piece of equipment and vehicle and requiring constant replenishment is the fuel tank. As with other fluids, environmental spills are a concern. But with diesel fuel, the primary concern is fire and explosion safety. Fuel should be stored in approved containers that have been properly grounded (including connecting bonding wires, storage tank, and the equipment). The fuel is hauled to the site on tanker trucks designed for this operation. Not only is the location of the fuel tank important, so as to stay well outside the areas of heavy traffic, but so is its orientation and layout compared to the approach paths of equipment with their hot engines and tailpipes. Refueling should be done from protected “islands” or stations protected whenever possible by bollards, curbing, earthen berms, or sandbags.

Fuel storage tanks used on construction sites for the duration of the project are by definition temporary. This is usually defined as a tank that is onsite for less than a year. Temporary tanks require multiple layers of protection against damage to them and harm to the environment. First off, each tank shall be designed and constructed in accordance with nationally recognized standards (UL 142/2244 or equivalent. UL 2085 is the listing for protected tanks). A poorly designed and installed tank is a danger no mater how well it is protected. Tanks of a certain size (typically 600 gallons or larger) require fire-resistant protection and sufficient isolation distance to property lines, combustibles, buildings, and other tanks (10 to 20 feet being a common requirement). Guard posts need to be installed around the tank as protection against vehicle impacts. The tank should be installed in a secondary containment structure that has a storage capacity of 110% of the tank’s volume. Overfill and spill protection should be provided for filling and withdrawal connections. Usually spill protection is equivalent to 5 gallons of fuel while overfill protection is provided by a floater switch automatic shut-off. In general, the tanks should be properly vented and provided with the necessary shut-off valves.

In addition to fuel, equipment and vehicles must maintain required levels of oil and lubricants, hydraulic fluids, and coolants. The keys to maintaining any vehicle operating fluid are: Keep them clean and replace them regularly. Cleanliness may be next to godliness, but it can be next to impossible on a rugged job site. Life becomes easier for all those involved in equipment maintenance if the parts and systems are designed to keep the equipment fluids clean and free from debris. These include keeping hoses plugged and capped until properly routed, removing manufacturer’s dirt from these parts prior to their installation, and replacing or repacking any part at the first sign of seepage (cylinders especially so, but also rings, gaskets, seals, hose connections, radiators, pump housings, etc.). Even after all of these precautions, fluids can still become contaminated, so it pays to have a fluid analysis performed at least every 500 operating hours, or at least once a year. Drain and flush all fluid lies and reservoirs prior to adding replacement fluids. Fluids should be drained when warm (usually just after equipment operations). The extracted fluids should be removed with a filtered transfer cart. Concurrent with the fluid draining, all associated filters should be removed and replaced with new clean filters. An examination of a filter that has been cut open to show its insides can give an indication of the equipments level of usage and harshness of its work environment.

As far as mechanical maintenance goes, maintaining a fluid system is relatively simple. However, offsite maintenance facilities have advantages, especially in regards to environmental protections. When changing or servicing fluid systems in the field, care must be taken to ensure that the job does not result in oil or chemical spills (and all the regulatory and legal headaches associated with them). Fluid maintenance should be confined to a small, designated area well away from surface waters. If these can be surrounded with earthen berms or sandbags, so much the better. Utilize drip pans and easy-to-apply absorbent materials in a standard spill response kit. Make sure the old fluids are properly stored for recycling or safe disposal.

Tires
The operational lifetimes of tires are a function of their operating environment, which can be rated from easy to moderate to difficult. In an easy environment, wheeled vehicle operations are usually confined to paved roads (gravel, concrete, or asphalt). Here, tires can wear slowly and evenly without serious fear of premature damage. In a moderate work environment, the wheeled vehicles either work some part of their shift in off-road conditions or on rough and poorly maintained roads. As a result some of the tires can succumb to premature damage as a result of cuts, punctures, or shock impacts from running over large objects or into large ruts and potholes. The last category, difficult operating conditions, subjects tires to premature damage instead of normal tread wear, resulting in more frequent tire replacements.

Different equipment tends to operate in different environments. Wagons, articulated trucks, and construction/mining trucks tend to operate in easy conditions and have the longest tire lifetimes. Wheel loaders, wheel scrapers, and motor graders work in more moderate environments. Skid-steer loaders and load haul dump units operating in more difficult terrain have the shortest tire life spans. However, given the wide variety of work environments and operating areas within each working environment, there is no scientific way to accurately predict tire wear and tear. Surveys and statistical data can only provide rough estimates and identify those factors that will have the greatest impact. Factors affecting tire lifetimes include whether or not the truck is overloaded and to what degree it is overloaded, if the truck is operating on sharp curves and/or steep grades, and if the operating surface consists of basted material and sharp rocks.

It seldom makes financial or operating sense to have an on-site stockpile of tires for trucks and other vehicles. The vehicles themselves come with spares that will serve temporarily until permanent replacement tires are available from local sources. All but the largest dump or mining truck tires can be obtained from local dealers. Recapping is an option and can reduce the overall unit costs associated with tire replacement by extending a tire’s lifetime. However, recapped tires may not perform as well as new tires and the time required for recapping may result in truck or vehicle downtime. Replacement and recapping fall under the category of repairs. Proper maintenance of tires means the proper operation of wheeled equipment within the manufacturer’s load, grade, and surface parameters.

Mechanical Systems
Onsite mechanical servicing of equipment and vehicles includes the maintenance and repair of power trains (transmissions, engines, etc.) and undercarriages.

Transmissions are the very heart of a machine designed to translate energy from an engine into useful work or movement. However, power trains are extremely vulnerable to damage from particles floating in the lubrication system. When the operator is meticulous in keeping foreign particles out of the lubricant, this debris usually consists of ferrous particles worn off of the equipment parts themselves.

The power train consists of surfaces vulnerable to wear in the engine and transmission. The key to power train maintenance is keeping lubricants clean. Ordinary oil filters don’t always remove the very small particles that can still do considerable damage. Higher levels of cleanliness can be achieved with magnetic filters.

Undercarriages are used by equipment that must operate in harsher operating environments than wheeled vehicles. These environments require tractor-tread vehicles due to their roughness and resultant impacts on vehicles as they move over the presence of large sharp objects and rocks or the presence of clogging dust and mud. Wear and tear on an undercarriage cannot be avoided, but a well-designed undercarriage wears at a predictable rate. But even the best designed undercarriage needs to be properly maintained. To begin with, use the narrowest shoe possible to minimize contact area. Those extra-wide tracks used by “swamp dozers” like the modified Cat D6 wide track are necessary for soft ground conditions but increase impact loads when operated on hard ground. Keep the operating speeds down to the minimum required to perform the work, especially when backing up. Don’t always turn in a single direction; alternate turning left and right for another operational pass. Always keep the track tension properly adjusted.

Since wearing down of tracks is almost unavoidable, it pays to measure the rate of wear so as to accurately predict when the tracks will need replacement. If a dozer track shows 20% wear at 1,000 operating hours, it can be projected that the tracks will provide another 4,000 hours of operation in similar work environments. These checks allow for a panned maintenance schedule where parts are replaced before they fail and take a machine out of the equipment pool.

Marshalling Yards and Lay-Down Areas
Marshalling yards and lay-down areas are provided for storage and staging of equipment and materials. Marshalling yards tend to be located offsite, while lay-down areas are set up at the construction site. It is at these locations that vehicle and equipment maintenance is performed; maintenance equipment, tools, materials, and supplies are stored; and the equipment is parked. Usually these areas are surrounded with fencing and other security measures to prevent theft and vandalism. Marshalling yards tend to be much larger, with bulk materials stockpiled in depots pending delivery to the job site. Onsite lay-down areas not only provide a secure, controlled environment for vehicle maintenance work but also minimize vehicle and equipment traffic in and out of the site.

The term lay-down comes from the use of the area as a place where tools, materials, and equipment are “laid down” while they are waiting to be used. While designed for temporary storage and staging of construction needs, lay-down areas must meet local building and fire codes (even if they are open air and contain no shelter or building). They must be kept clean and orderly by continuous policing of the area and housekeeping of its contents. Though separate from the main construction zone, all work safety rules equally apply to the lay-down areas.

The actual size of the lay-down area depends on the nature of the material being stored (e.g., compact concrete blocks or long pipeline segments); the footprint size, number, and type of equipment being parked; the need for quick and safe access into the area; equipment and vehicle movement within the area; the presence of buildings or shelters; set-back and buffer distances; and the area needed for onsite equipment maintenance. These maintenance areas should be located away from storm drains or other places where fluid spills can harm the environment.

Contributing writer Daniel P. Duffy, P.E., is an environmental engineer employed by URS Corp. in Akron, OH.

GEC - May 2007

Back To Table
Of Contents