Breaking Down Compactor Selection

Mickey Cereoli

In the life of a landfill, space - not time - is money. Keeping that in mind, a landfill compactor is essential to getting the most for your dollars. But what features can make one compactor more productive and efficient than another?

Regardless of the various compactor manufacturers' design philosophies, the following are key factors to consider to ensure that the machine you select delivers the performance your landfill requires.

Is Bigger Better? Landfill compactors come in several sizes and weights - from 50,000-pound class units to 100,000-pound machines. Heavier machines may not efficiently meet the needs of every application. A landfill should relate machine size to daily tonnage or tons per day (tpd), as well as to the delivery rate during the site's peak hours.

Many smaller sites that handle 300 tpd or less frequently only consider machines in the 50,000- to 60,000-pound weight class. But in most cases, trash does not flow into a landfill at a steady rate throughout the day.

Landfills typically experience two peak hours of delivery each day - one in the morning and one in the afternoon. For a 300-tpd site, approximately half of the landfill's daily tonnage (about 150 tons) will be delivered during these two peak hours, and a machine in the 50,000- to 60,000-pound weight class is too small to correctly spread, place and compact trash delivered at this rate. Instead, small landfills should consider machines in the 70,000- to 80,000-pound class to help extend their landfill's life.

Compactors in the 70,000- to 80,000-pound class also are often the optimum size for most mid- to large-sized landfills. Used in multiples, machines of this size can handle even the largest volume sites.

On the other hand, larger, better-funded, high-volume sites, frequently use compactors in the 100,000-pound class. But landfill managers should weigh the advantages and disadvantages to such heavy machines. Because compactors in the 100,00-pound class cost more, it limits the number of machines a landfill can afford to have operating on a single site and could leave a site vulnerable should downtime occur. Also, 100,000-pound class machines may not be able to match a site's gradability and tractive requirements, depending on the material type.

How the Wheel Works Buyers should look for compactor wheels that offer more than good wear life and minimal maintenance. The key concept to understand when approaching landfill compactor wheel design is the difference between compression and compaction.

Compression is accomplished by loading a predetermined amount of material into a space designed to withstand high pressure. The material then is squeezed together by a force that collapses the volume into a smaller space. By removing air voids from the original mass, compression allows the material's original volume to be reduced.

The compressed mass requires additional forces, such as hydraulic pistons, ropes or bands, to maintain its reduced volume. If released, the mass, depending on the material type, can expand to 30 percent to 50 percent of its original volume. Cans and bottles, for example, will retain their compressed size.

Compactor trucks, compactor containers and balers all achieve compression and, to a certain degree, compaction. These machines only will compact as long as the trash is confined or contained.

But you can expect an entirely different function from landfill compactors. Landfill compactors are expected to make multiple passes over the positioned material to achieve the desired compaction without containment.

Compaction requires material to be broken down and manipulated into a configuration where it becomes compactible. Compaction cannot be achieved just by repeatedly running over material. An aggressive action must take place to break the material down, make it fit together and, finally, be placed with a minimal of air voids.

For example, when you buy a bag of potato chips, it's full of air voids. However, when you crush the contents, you actually have less product - probably about 10 percent of the original volume. This is because after you make the particles smaller, they take up less space and the air voids have been removed.

A landfill compactor's wheel design is key to true compaction. Consequently, you'll want to consider how deep the compactor's teeth penetrate, whether the wheel creates an aggressive action and whether the wheel will remain clean during operation.

Penetration depth allows a larger lift to be manipulated and compacted. Machines with smooth drums simply compress material. Compactor wheels featuring deep penetrating teeth, however, provide compaction at a point well below the surface or below the drum contact point.

Compactor wheels also should have an aggressive tooth design to create the shredding effect necessary to break the material into compactible particles. Aggressive action allows more trash to be compacted into each cubic yard of placed trash.

Compactor wheels manipulate waste and help the particles fit together, so look for machine designs that work the material under the wheel and teeth to find the best possible "fit" for the broken-down particles. The wheel design should not simply push the particles straight down.

To maintain compaction, the wheels also must be kept clean. When a wheel is packed with material, it limits the machine's ability to compact, as well as impedes the machine's tractive effort. Buyers should look for a compactor that features scraper bars designed to keep wheels free from debris.

Buyers also should match their blade design to their needs. There are basically three types of blades available today: straight, semi-U and shovel.

The most commonly used design is the straight, open-ended blade. It is used to push trash short distances and spread it for easier compaction.

Semi-U and double semi-U blades are useful when trash must be moved further from the tip area.

A shovel blade typically is used to spread trash, as well as carry other material such as daily cover.

Comfort is Key Operator comfort, while not a direct contributor to compaction, is a key factor to consider when selecting the right machine for your operation because it can improve productivity.

Buyers should look for a comfortable, operator-friendly cab with all-around visibility and easy-to-understand, ergonomically designed controls.

Cabin noise levels should not exceed 75 decibels (dba). Some cabins feature ventilation systems that draw air through fine filters and slightly pressurize the cab. These systems provide a comfortable work atmosphere for operators and prevent the entry of polluted air into the cabin.

Amenities such as cab heating and air conditioning, heated and air-suspended seats and AM/FM stereo cassette are available on some machines and can increase operator comfort.

Once you've chosen a machine, you want it to work. Of course, downtime for a landfill compactor - or any equipment for that matter - is essentially unavoidable. However, downtime can be minimized with the proper design. Components and service points should be easy to access. Buyers also need to look for a design that protects vital components and keeps them clean and free of debris.

Additionally, features such as extended-service intervals, an electrical system disconnect switch and central-lubricating systems can reduce downtime and make servicing easier.

With today's skyrocketing fuel costs, fuel economy is an important factor in any equipment purchase decision. Consequently, you should compare fuel consumption rates and be attentive to even the slightest differences. A savings of two or three gallons per hour can save a landfill considerable money.

For example, three gallons per hour over a machine's possible life cycle of 10,000 hours can result in savings of $45,000 or more (based on today's fuel prices).

A buyer also should consider a compactor's overall design. First, is the machine designed specifically for the landfill environment? Machines that are adapted from loader or general construction designs are less capable of withstanding the elements found in landfill applications and may not offer the features necessary to successfully operate in the landfill.

A good landfill compactor design should offer ample protection for machine components, as well as service accessibility. For example, machines designed specifically for landfill use protect against wire wrap-around and subsequent damage to seals or other wheel components. They also have engine compartments that are sealed against the entry of trash or debris that can cause overheating or fire.

Finally, consider whether the machine is capable of delivering the performance necessary for your individual application. All operations are unique. Selecting the right machine for your needs takes time and often is frustrating, but when you make the right decision, it's time well-spent.

Your landfill compactor is one of the most important piece of equipment on your site. So look for an experienced manufacturer who truly understands your needs and has found the delicate balance between all of the features discussed. Then, ask for a demonstration, put the machine through your tests and see what will work best for your company.