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Compactor Design Guide

Compactor Types & Functions

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Construction Design & Materials

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Design Considerations: Construction Materials & Design

Industrial Compactor Construction

Structural Steel vs Formed Steel Support

Structural steel supports used in compactor construction come in a variety of shapes including channel, I-beam, and tube. Of these forms, the tube is the strongest and is often used on the sides of the compaction chamber for support in critical areas Additionally, the closed tube shape reduces debris deposits on the outside of the unit.

A combination of these supports are used to strengthen the steel plate used throughout the compactor. Larger numbers of supports as well as stronger shapes are critical in areas such as the compaction chamber floor and ram top which are susceptible to high impact forces when heavy material is dropped into the compactor.

Forming a steel plate into a support shape will increase the strength of the steel; however, the shape is not nearly as strong as a structural shape of the same dimensions. Structural shapes have added strength at the bend points, formed shapes do not (in fact, forming the steel may actually weaken it at the bend point).

When evaluating a compactor's integrity: the type, size, and number of supports in critical areas is crucial and more so for heavy duty applications.

Breaker Bar

The name says it all. The structure of the breaker bar must be strong enough to withstand the forces generated by the compactor. If the breaker bar bends past its yield point, the compactor will become deformed and useless. To evaluate the quality of the breaker bar, have the compactor manufacturer give you the section modulus of the breaker bar and what forces it can withstand. The breaker bar should be able to withstand at least 2-1/2 times the force generated by the cylinders.

Thrust Beam

Located at the back of the compactor, the thrust beam is used to attach the cylinder(s), and must be able to withstand 1-1/2 times the force of the cylinder(s). Bending this component beyond the yield point will destroy the compactor. 

Compaction Chamber Floor Plate

Compaction Chamber Floor PlateSteel used in construction of the compaction chamber floor should be high quality and relatively flat. SP Compactors use AISI grade steel A36 for commercial units, and a harder steel AISI 1045 for all industrial ad precrusher units. (AISI 1045 steel is considered work hardening, which means that the steel actually gets harder the longer it is used.)

It goes without saying that higher grades of steel are stronger, more consistent in strength throughout, and relatively flatter. A wavy floor will cause waste material to build up between the ram and floor. As such, lower grades of steel will wear and weaken more quickly, significantly shortening the life of the floor and the compactor.

Ram Guide System DiagramNote: the steel used on the bottom of the ram, which rides on top of the chamber floor, should conversely NOT be as hard as the chamber floor steel. Both plates will last longer if the two steel plates working

Ram Guide System

A ram guide system maintains the ram from fishtailing side-to-side, and bucking up-and-down during movement.

Compactor Ram System GuideIdeally, the ram should ride on the compaction chamber floor. This uses the entire surface of the floor to support the ram and resist waste material build-up between the ram and the compaction chamber floor. Engineering shows us that the ram riding on the floor will not cause any significant loss of forward force from the friction between the ram bottom and the compaction chamber floor. Once the ram is moving, the coefficient of friction is the same whether the supporting area is one square inch or one-thousand square inches keeping weights and materials consistent.

Top right: Structural tubing mounted to the thrust beam serve as a guides for the ram. Above and inset: The 3-point guide shoes wrap around the tubes to limit ramp movement and promote smooth ram operation. 

Forward force lost between a ram which rides on the floor and one that is suspended above the floor is negligible. The actual guide system consists of a number of adjustable wear blocks at the back of the ram and ram hold-down bars above the ram on each of the compaction chamber walls. Wear blocks are made of a special hardened plastic such as Nylatron which will slowly wear before the steel wall or support it is in contact with wears. The principle is to give the guides a good surface to work on so that the ram movement remains stable. Any movement side-to-side or up-and-down will cause the compactor ram and compaction chamber to wear more quickly; shortening the life of the compactor. 

Cylinders

A hydraulic cylinder is measured by its bore (the inside diameter of the casing), rod (the outside diameter of the movable rod), and stroke (the length the rod is able to move). The force that the cylinder can exert is determined first by the size of the bore; a larger bore cylinder is capable of exerting greater forces. The diameter of the rod determines whether or not the rod can withstand the force it is generating. A larger rod means a stronger cylinder.

Some compactors are equipped with one cylinder (single cylinder models); others with two (dual cylinder models). Generally, two cylinders of the same size will have twice the force of one, and they can be spaced to spread the force generated against the ram face more evenly than one cylinder pushing in the middle. Larger compactors with wider ram faces tend to have less side-to-side ram movement when they employ two cylinders.

Cylinders for Industrial Compactors  Industrial Compactor Cylinders

In addition, longer cylinders must be supported to assure against sagging or bending from the force they generate, and their own weight and the weight of the oil inside when they are fully extended.

Industrial Compactor with CylindersMany compactor models use two hydraulic cylinders which are crossed. The cylinders are mounted on each side of the compactor and opposite sides of the ram. This design helps to shorten the overall length of the compactor and is useful in certain applications.

However, one notable shortfall is that crossed cylinders do not generate as much force as straight push cylinders of the same size. A crossed cylinder pushes at an angle to the ram movement which reduces the forward force of the ram. Cylinders with greater final angles to the ram face will have less final forward thrust on the ram.

Pump

Industrial Compactor PumpThe hydraulic pump moves the oil into the cylinder(s). The rating for the pump is in GPM (gallons per minute). The larger the number, the faster the pump can move the oil and the faster the ram will move forward and back.

Two considerations should be made when the pump is specified. First, the internal operation of the pump is designated as vane or gear. In order to keep noise levels during operation at a minimum, the vane pump design operates at a lower noise or decibel level.

The pump will have an effect on how loud the machine will operate and at what speed the ram will move. A vane pump will operate at a lower decibel level than a gear pump and will help to keep the equipment operating within OSHA restrictions.

A constant displacement pump will maintain operating speed even under load conditions; as opposed to hi-low pump which slows the cycle time when under pressure. If cycle times are being assessed, consideration should be made concerning the speed of the compaction cycle when it is actually compacting the waste material.

Electrical Components

Industrial Compactor ElectricalAll components should be UL listed for compatibility and safety. Once the control panel is complete the entire panel can be UL certified if necessary. In this case a UL inspector will check the panel and mark it as certified.

The components should be NEMA rated, which are designed for heavy duty industrial use and readily available for repair or replacement if necessary.

electrical components of Industrial CompactorsAn electrical panel can be designed to be controlled with relay logic or PC logic. Relay logic uses individual switches, timers and relays to direct the control of the operation of the compactor. If a control fails, it can be readily replaced with a like control.

PC logic uses an electronic control board to control the operation of the compactor. If this board fails, a new control board must be purchased from the manufacturer for replacement.