Machinery Insights: 16 Excavator Parts You Need to Know

Knowing your excavator's parts is essential, not just for operation but for long-term maintenance and troubleshooting. As an operator, you might not need the detailed knowledge of a mechanic, but a basic understanding of the machine's components is beneficial. Excavators, though varied in makes and model, share many common parts. These can be broadly categorized into two main sections: the upper structure and the lower structure. In this article, we'll break down these essential components, providing you with the insights needed to navigate and maintain your excavator effectively.

Lower Structure of a Track Excavator (Undercarriage)

The lower structure, or the undercarriage, is the foundational section of an excavator. It's the part that makes contact with the ground and enables movement. We'll focus on track excavators, also known as crawler excavators, and explore the five key elements that make up the undercarriage: tracks and track pads, rollers, idlers, sprockets, and the swing drive/slewing ring.

1. Tracks and Track Pads

• Tracks: Made of reinforced steel, crucial for mobility.
• Track Pads/Shoes: varied in size, equipped with grousers for ground grip.
• Track Bolts: Link the track plates together, forming the crawler system.
• Track Frame: Anchors the crawler system to the excavator.
• Track Chain: Connects tracks to the sprocket and idler, ensuring consistent movement.

2. Rollers

• Types: bottom and top rollers.
• Function: Guide chains between the sprocket and idler.
• Features: Some have rock guards for protection against debris.

3. Idlers

• Role: Major guiding wheels within the undercarriage.
• Collaboration: Work with rollers and sprockets for smooth track operation.
• Size and placement are keys to efficient movement.

4. Sprockets

• Function: Engage with the track chain links.
• Primary Role: Move the chain, propelling the machine forward or backward.

5. Swing Drive/Slewing Ring

• Importance: Crucial for the excavator's rotational movement.
• Operation: hydraulically operated, requiring regular greasing.
• Function: Enable the upper structure to pivot relative to the lower structure.

Upper Structure of a Track Excavator (House)

The upper structure, or the "house" of the excavator, combines the carbody with the boom-and-arm mechanism, forming the core of the excavator's functionality. We will explore 11 key components that make up this upper structure, moving from rear to front.

1. Counterweight

• Purpose: Maintains balance during operation.
• Example: A CAT 395 excavator has a 15.5-ton counterweight for a 94-ton operating weight.

2. Engine Compartment

• Fuel Tank: Stores diesel fuel.
• Engine: Powerhouse of the excavator, near the cab for easy maintenance access.
• Hydraulic Fluid/Oil Tank: Essential for hydraulic mechanisms.
• Main Control Valve: Connects engine to hydraulic devices, controlling oil pressure.

3. Cabin

• Control Center: Equipped with essential controls and safety features.
• Features: 360-Degree Rotation for maximum visibility, ROPS for safety in rollovers, and FOPS for protection against falling debris.

4. Boom Cylinder & Boom

• Boom Cylinder: Controls vertical movement of the boom.
• Boom: Supports the arm, pivotal in digging mechanism.

5. Arm Cylinder & Arm:

• Arm Cylinder: Facilitates extension and retraction of the arm.
• Arm (Dipper/Stick): Connects to the boom, carrying the bucket.

6. Boom/Arm Linkage

• Components: Pins and bushings connecting the boom and arm.
• Maintenance: Regular greasing for smooth operation.

7. Bucket Cylinder, Arm/Bucket Linkage & Bucket:

• Bucket Cylinder: Allows digging and dumping actions.
• Arm/Bucket Linkage: Joint mechanism connecting the arm and bucket.
• Bucket: Primary earthmoving component, interchangeable with other attachments.

To further enhance your understanding of an excavator's anatomy, we've created a detailed infographic with FAQs. This visual guide neatly outlines all the components we've discussed, both in the lower and upper structures of a medium KOBELCO SK350 track excavator. Check it out at almarwan.com.