Off Rd Hauling

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Off-Road Hauling

ByP&Q Staff| August 22, 2013

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The heavy lifting, so to speak, in a quarry operation is performed by haul trucks. The main job of a haul truck

in a quarry environment is transporting material from the quarry face to the primary crusher.

There are two main kinds of haul trucks: rigid frame and articulated. Rigid frame haulers are typically used

when there is a haul road in place, or a smooth path between the muckpile and the crusher. Artics are used

when the terrain is uneven, the ground is soft or conditions are usually muddy.

Todays haul trucks are much different than those of years gone by. With increased payloads, horsepower,

torque and fuel efficiency, these trucks not only increase productivity but also can lower an operations cost-

per-ton.

Savvy production managers know that haul trucks must be matched to job specifications. It is worth reviewing

your operation and equipment fundamentals just to make sure your assumptions are correct.

It is also good practice to match haul trucks to the machine that loads them. That means:

The right number of trucks and the right capacity to serve the crusher and/or stockpiles without making the

loader wait or causing a line of trucks waiting on the loader. Both situations hurt productivity and drive upcost.
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Truck-bed size and a configuration that makes a good loading target, allowing quick spotting of the bucket

and even load distribution. Optimum load time is about two minutes, or three to four passes with no partial

bucketloads.

When thinking about a haul-truck purchase, it is wise to make todays purchase with tomorrow in mind. How

many trucks of what size will you need two years from now? Five years? Will you replace or add crushers?This could change the needs of your hauling operation.

Many aggregates plants are considering the elimination of as many haul trucks as possible, due to increases

in fuel costs. Those that are planning to stick with haul trucks, are moving to larger loading and hauling units,

able to handle the same tonnage with fewer machines. The objective is increased productivity, not

necessarily higher total production. In other words, a producer that was using four 35-ton units might switch to

three 50-ton units.

Production remains about the same in this scenario, but with a substantial improvement in tons-per-manhour

and lower maintenance costs. Over the years, there have been a number of progressive improvements to

trucks, including:

New cabs: Cabs are no longer just a place to sit, but have become the truck operators office. Typical

features include not only heating and air conditioning, but radio mount, and well-placed controls. Greater

window capacity offers better visibility. These cabs are built for sound reduction and come equipped with

suspension seats.

Horsepower ratings:Gross horsepower ratings may be misleading. Net horsepower is also an important

rating for comparison, since this more closely measures the power that can be applied to moving the truck.

Retarding systems: Two types of retarding systems became available: One acts on the driveline, the other

works through the brakes. The brake-retarding system spares drivetrain components from tremendous

reverse-torque loads and helps prolong machine life. In addition, the brake-retarding system takes advantage

of advanced brake systems. The most effective brakes today are oil-cooled, multi-disc type, which provide up

to five times the life of shoe brakes and never need adjusting. Multi-disc brakes are not to be confused with

caliper-disc brakes, which are similar to automotive-type disc brakes and rely on a pliers-like squeeze to slow

the wheel. The multi-disc design multiplies the braking surface, but eliminates metal-to-metal contact. A

pressurized flow of oil separates discs and carries away friction-generated heat. One system combines

retarding, emergency, service and parking functions in a dual-piston design.

Frame design:Basically, the life expectancy of a truck comes down to chassis strength. Frames should be

box-section construction with high weld penetration in the manufacturing process and castings at high stress

points. Frames should also be weldable to allow field repairs without high-technology weld procedures.

Electronic controls:Modern electronics allow substantial improvement in the control of various machine

functions and components. Electronic transmission control, for example, assures smoother shifts to minimizetorque spikes. The result: greater transmission and engine life and greater fuel efficiency. Electronic

monitoring systems for vital machine functions are not only more reliable than mechanical gauges, they give

the operator both visual and audible alarms. Future applications will contribute to further improvements in

machine reliability, performance, and fuel economy.

Traction control:If your haul road is subject to periodic slippery conditions, a traction-assist feature on the

rear axle may be worthwhile, not only for improved control and handling but also for reduced tire wear. Two

types are available: (1) Mechanical systems similar to automotive-type, limited slip differentials; and (2)

Electronic controls that monitor wheel rotation on each side independently and, when one exceeds the other

by a set limit, applies the brakes, transferring torque to the tire with better traction. Electronic traction assist

does not interfere with normal differential action and places no increased stress on the driveline.

Hydraulic brakes:The result is superior reliability, response, control, serviceability and modulation. Theparking brake is integrated into the gear selector for easy operation.


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Increased engine-service intervals:For some trucks, 500 hours is common twice that of previous truck

models. On-board engine oil evacuation and pre-lube can reduce oil-change labor time by as much as 50

percent.

Comparing costs

Having determined production requirements, and narrowed the field of candidate trucks and now it is just a

matter of comparing costs. Comparing cost, unfortunately, is not as straightforward as it could be. There are

two reasons for this:

1. Specs vary, so you will need to be careful in comparing features, performance, and ratings. This is

especially true for body capacities, horsepower figures, torque curves, and related information.

2. Owning cost goes far beyond the initial purchase price. Over the life of the machine you have to add

maintenance expenses-fuel, lubricants, antifreeze, belts, filters, etc.-plus parts and repairs. Seemingly minor

variations in fuel consumption, payload and performance can make a substantial difference in total cost over

the life of the truck.

This projected cost should be part of your truck selection criteria-along with requirements for routine

maintenance. Routine truck service is facilitated by clustering of lube points, ground-level access to filters and

fill points and modular components. In some machines, the time required for service can be significantly

reduced when work can be done without removing major components.

The greater the maintenance requirement and the more difficult access to maintenance points and time

needed for the work the greater the long-term cost and risk maintenance will be overlooked. Increased

equipment sophistication and high cost of service operations have prompted another trend: increased

reliance on equipment dealers and maintenance contracts. Todays equipment dealers offer a much broader

variety of product-support choices than in the past. Among these are:

Component rebuilding and replacement programs.

Plans to monitor machines on the job and schedule repair before failure.

Guaranteed maintenance contracts that assure product availability and put a lid on cost.

The aim, of course, is to keep machine availability and productivity up and eliminate unscheduled downtime.

In addition, long ownership periods typical of the aggregates industry are likely to drop as managers trade

machines at the end of peak economic life usually a much shorter life term than mechanical life. The net

result is, again, improved cost control and reduced cost per ton.

Finally, you may find that tax considerations make equipment usage through leasing more attractive than

outright purchase.

Computerized management

Small companies have already helped aggregates-plant operators become better business people, improving

their ability to manage the business and track material and labor cost.

Software is available to help design plants and control functions in addition to traditional accounting

programs. Other software, from various manufacturers, is available to give valuable help in equipment

selection, maintenance management and fleet management.


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One program, for example, allows equipment users to compare several equipment investment choices with

relative operating cost and productivity before purchase. Another program schedules maintenance and tracks

productivity of individual machines.

A more advanced program allows users to model various job conditions to optimize haul road layout and

equipment selection. Another analyzes whether equipment repair, rebuilding, or replacement is the mosteconomical choice. These tools can help take pain-and cost-out of new haul truck buying decisions. Here are

two additional job areas where a little extra effort can pay big dividends in higher productivity, improved

equipment life and reduced cost:

Haul roads: If you do not have a haul-road maintenance program, it is smart to implement one. Roads should

be adequately watered and well graded, with a minimum of obstacles. Turns should be as wide as possible

and super-elevated; edges must be bermed. A good haul-road maintenance program is one defense against

premature and costly tire replacement.

Tire maintenance: Like maintaining haul roads, a tire-maintenance program can cost little and help a lot. Tire

manufacturers and industry consultants agree on the basics: paint correct pressures on the rim and check

regularly; inspect tires regularly for damage; make sure all tires on the machine match and maintain haul

roads. More detailed programs and personnel training are available from equipment dealers and industry

consultants.

Driver education and training

Frequently overlooked as a way of managing equipment costs, operator training can play an important role in

cost-effective fleet management. Even the best operators can use a refresher course, an orientation to new

equipment or an opportunity to un-learn bad habits. Poor operating habits, such as pulling away from dumps

with the bed up or careless loading can quickly cancel out the steps youve taken to reduce cost per ton.

Again, training is available from most dealers.

Truck-loader matching

The most important consideration when matching loaders and haulers is finding units with compatible

capacities to get maximum loading efficiency. Generally, filling the hauler in three passes is considered ideal.

Four or five passes is considered acceptable, especially in high-capacity, off-highway truck loading.

When an operator loads a hauler with shot rock, he takes the first bucket out of the bank as near to the truck

tail as possible then moves one bucket width farther down the bank to scoop the next bucket. With each

bucket load, the trip between the bank and the hauler gets longer, extending the cycle time and reducing

loader productivity. Three passes is considered ideal for loader/hauler productivity because it keeps aloaders Y-cycle time within acceptable limits.

When matching capacities:

Look at the weight the hauler can carry. Off-road trucks generally have a payload 10 to 20 percent over their

nominal-rated load capacity. A 50,000-lb.-capacity hauler may be capable of carrying as much as 59,400 lb.

Look at the density of materials the hauler will carry. Most shot rock weighs approximately 3,000 lb./cu. yd.

Divide the rated capacity of the hauler by the desired number of passes to fill it. The result will be the weight

of material that must be carried in each bucket load.


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This number, however, is not necessarily the same as the rated capacity of the bucket. Bucket capacity is

calculated on the basis of a 2:1 heap and a 100-percent fill

factor. Buckets are not always 100-percent full when loaded.

Bucket fill factor varies with changing conditions, the type of material loaded and the size of the blasted rock.

A loader excavating shot rock may have a fill factor of 75 to 90 percent, while another working in sticky clay

may have a much higher one.

Teeth, edge segments or other accessories on the bucket lip can increase bucket capacity significantly. To

approximate how much each bucket load will contain, multiply the rated bucket capacity by the fill factor. By

multiplying various bucket sizes by the probable fill factor for the material, the buyer identifies the correct size

bucket and, therefore, the correct size loader.

Ideally, the loader should fill the hauler close to its rated capacity in an even number of loads. It takes just as

long to load three buckets plus a partially full bucket as it does to load four buckets.

Other considerations

A number of additional factors should also be considered in loader/hauler matching:

Compare the loaders reach with the width of the hauler body. A loaders reach is measured from the front of

its front tires to the tip of the buckets cutting edge when the boom is fully raised and the bucket is dumped at

45-degrees. Comparing the loaders reach to the width of the hauler bed ensures the loader can place a load

to the far side of the hauler body.

Compare the width of the loader bucket in relation to the length of the hauler body. Some equipment

manufacturers recommend that bucket-width-to-body length should fall within a ratio of 1:1.4 or 1.5. The

bucket should be wide enough to provide a degree of protection for the front tires but not so wide that it will

be difficult for the operator to avoid bumping the back of the hauler cab or dumping material too close to theend of the hauler body. Rocks that land too close to the end of the body are likely to roll off the hauler the first

time it goes up a grade. Not only does this waste material, but rocks spilled on the haul road can damage

tires and require additional time and money for road maintenance. Even if the rock does not roll off the hauler,

it places an undesirable weight distribution on the rear axle, which can increase axle and tire wear.

Compare the loaders dump height in relation to the height of the haulers side. Compare both units the way

they will be equipped in actual use. The teeth on a rock bucket, for example, can reduce dump height by as

much as a foot. Also, adding sideboards or larger tires on a hauler can increase its height significantly.

Making this comparison ensures the operator will not have to roll the bucket back to clear the side of the

hauler, which increases cycle time.

Consider the loaders hydraulic-system cycle time. Hydraulic cycle time should complement its travel speed.

A loader that requires excessive time for its boom to raise fully before dumping will produce slower loading

cycles than a unit that can load, lift and dump without delay.
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Going to the artic

While rigid-frame haul trucks are found in most quarry operations, the articulated hauler was developed for

transport under difficult conditions. Its mobility is such that it can take the shortest distance between two

points, with little need for well-maintained haul roads. This leads to high efficiency and low cost per ton, which

forms the foundation of successful haulage.

The basis of the articulated hauler is the connection between the front and rear frame. This makes it possible

for tractor and trailer to move independently of each other, which drastically reduces stresses on the frame

when driving off-road. It makes it possible to transport heavy loads under difficult conditions. Steering is

simple and effective, and all wheels remain in contact with the ground in off-road operation.

Rigid haulers are fine on paved or graded roads, but when the going gets tough, articulated haulers are often

used. The idea behind articulated haulers began in the late 1960s. Only during the past decade, however,

have North American operators begun to realize how versatile and practical articulated haulers can be on

their job sites. Today, articulated haulers are seen in a variety of off-road applications.

On the move

An articulated trucks configuration allows it to turn 45 degrees left or right, giving the operator a great deal of

maneuverability in tight situations. An articulated hauler can also work in soft ground conditions and weather

that would bog down other off-road equipment.

The trucks articulation, automatic transmission and all-wheel drive combine to pull the truck through soft or

sticky ground conditions and up steep inclines. The phenomenal growth of the articulated hauler can be tied

to its versatility and practicality. Contractors are finding that you can use an articulated hauler anytime and

anywhere you have to move a large volume of material under a variety of conditions.

Articulated haulers are most cost effective where construction is seasonal. Since articulated haulers can work

in all kinds of weather, they extend the working season. In some cases, they can even work year round. They

are easy to load and have the highest payload-to-weight ratio of any earthmoving equipment.

Another reason articulated haulers are so productive is that they do not necessarily need haul roads to

maintain effective cycle times. When a haul road is available, a hauler can attain speeds comparable to or

greater than other off-road vehicles. Maximum travel speeds can reach 30-35 mph.

Articulated haulers are not recommended for high-impact loading, but can easily handle overburden, sand,

and gravel and they are generally only available in capacities of 25 to 40 tons, much smaller than many rigid-frame trucks.

IN AND OUT

The person who first said, time is money might well have been thinking of the subject of loader/hauler

matching, particularly as it applies to aggregate production. Stated in its simplest form, producers need to

dump the material in, and haul it out. The purpose of finding the optimum match is to minimize the length of

time it takes a loader to fill a hauler and send it on its way.

By minimizing the time for each load cycle, aggregate producers can increase daily output and, therefore, the

amount of money each piece of equipment produces. Incorrectly matched units can lead to truck bunching or

loader idling, both of which waste money.


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Loader/hauler matching for aggregate operations involves a number of different factors than for other

applications. For example, equipment used in aggregate production usually performs the same tasks all day,

every day. High-production capability, therefore, is the equipment buyers prime selection criterion.

A typical construction contractor, on the other hand, is usually more interested in equipment versatility.

Loading material into a hauler may be only a small proportion of the tasks the loader has to perform. The goalof choosing a loader or hauler for aggregate production is to match the capacities of the two pieces of

equipment. In most cases, the aggregate producer is not purchasing new loaders and new haulers

simultaneously.

The objective in this case is to find the most productive piece of equipment that is compatible with existing

equipment. A new loader or hauler that has exactly the same capacity as the old one may not be the best

choice as a replacement.

Making a plan

The first step in matching equipment is to determine where and how it will be used. Loaders intended for use

in primary production digging shot rock or bank material require properly sized rock buckets.

Secondary production-loading gravel or other processed materials from stockpiles into haulers for

transportation off the property-demands slightly different equipment options. Secondary product loaders need

material-handling buckets sized to fill company and customer trucks quickly. Haulers must be sized so that,

when fully loaded, trucks stay within local regulations on gross vehicle weight and have the speed and the

other performance characteristics required for on-highway use.

In smaller aggregate operations, the same loader or hauler often may be used in both primary and secondary

production, so the buyer must choose equipment that can handle both jobs without sacrificing productivity in

either case. The piece of equipment may also be asked to perform other miscellaneous tasks. For example, a

loader with a quick-change attachment-bracket system and a number of properly sized attachments allows

increased utilization for tasks such as maintaining a quarrys haul roads, grading parking lots and clearing

snow.

Getting the whole story

Finding loaders and haulers with compatible capacities is part of increasing productivity, but it is not the whole

story. Take into account the operation as a whole not just the areas where haulers are loaded with shot

rock or aggregate.

Consider the width and condition of the haul roads this may limit the size of haulers that can be used

effectively.

Consider capacities of other equipment involved in aggregate production, such as the crusher. If this area is a

bottleneck, adding higher-capacity loaders and haulers may not increase productivity as much as expected.

Take into account legal restrictions imposed on haulers that operate on highways.

Off Rd Hauling

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