The hydraulic excavator is a marvel of modern machinery. They can perform spectacular operations of excavation, extraction, unloading, to name just a few. They reign in the mining sector and on construction sites. Yet they all operate on the same very simple principle. They use an engine, usually diesel-powered (battery-powered engines are starting to emerge), to drive hydraulic pumps that pressurize oil that help to move large steel components.
You can divide the excavator into three parts – the undercarriage (the tracks, rollers, and final drives), the house (the cab, engine, slew motor, valve bank, and counterweight), and then the excavating arm (the boom, dipper arm, and cylinders).
Each component in the excavator makeup is as vital as the other which creates a machine where the whole is greater than the sum of the parts. Unless each part is operating, the excavator would not be able to operate.
1. UNDERCARRIAGE
This is where the machine connects to the ground. It helps to stabilize the excavator and move it in the desired direction. The final drives are located at the back and move the tracks via a large sprocket which allows the machine to move forward, backward, and sideways. In the front of the tracks, you will find the idler wheel and the track adjuster through which the tension of the tracks can be tweaked. The tracks are made up of links, chains, and shoes (also known as grousers) that are supported along with a series of lower and upper rollers. Tracks can be made of hard steel composition, designed for use in rough areas.
Slew ring, swing gear, and swing bearing. The slew ring, swing gear, and swing bearing connect the excavator’s house to its undercarriage. Technically, this component area could be part of the house group, but it’s also built into the undercarriage. It is the turntable region of the excavator and lets the house revolve on the track assembly.
2. UPPER CARRIAGE
One of the many great virtues of an excavator is the ability of its upper carriage to move a complete circle (360 degrees). Backhoes can dig like excavators, but they’re limited to a 200-degree side-to-side movement. What connects the undercarriage to the upper carriage is a turntable. This turntable is made up of a ring gear that is driven by the slew motor. The upper carriage is then connected to the excavating arm, making it the central command and control center.
Here are the main components you’ll find in an excavator’s upper carriage:
Excavator cab and controls. The cab serves as the operator’s seat and control point. Most modern excavators work on a joy-stick and foot pedal principle that keeps an operator’s hands and feet busy.
Engine and pumps. The vast majority of hydraulic excavators use diesel engines to drive their hydraulic systems. Its fuel and oil tanks are also secured in the upper carriage.
Main control valves. While the diesel engine is the primary power source, it’s the hydraulic system that produces the excavating force. An excavator’s main hydraulic pump has a central control valve that regulates the volume of hydraulic fluid circulating in the system. The pump and controls also dictate the pressure held in the main and auxiliary hydraulic lines.
3. ARM
Without the excavating arm, the machine would be an undercarriage-mounted house with only the ability to move its self about. But add an arm and the machine goes to work. This is where the magic happens. The arm components let the machine dig, bail, load, throw and place material. Here are the main parts you’ll find on an excavator's arm:
Boom. An excavator’s boom is the largest part of the arm. Booms are the upper arm portion and are mounted to the upper carriage. The boom is controlled and powered by a hydraulic boom cylinder (or two in larger machines), which is part of the machine’s primary pressurized system.
Stick. An excavator’s stick is also called a dipper or an arm. Regardless of terminology, the stick intermediates power from the boom to the bucket.
Bucket/Attachment. The bucket is where work really gets done. The bucket is the third arm component, and it can take many shapes as well as numerous attachments. Here is a list of other attachment options
Augers. Turn your excavator into a hole-digger with an auger attachment.
Compactors. For hard-pounding base fill - often used in landfills
Grapples. Lifting logs, bales, or lumber is safe and secure with a grapple attachment.
Hammers. Breaking rock is a hard job, but not with a hammer work tool attached - often used in demolition jobs.
Rakes. Cleaning a brush site is simple with a rake attached.
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