Configuring an excavator for a specific application requires some planning. Many factors come into play, such as the working range of the boom and bucket bar, material density, required output, use of attachments and quick connectors, and lifting capacity requirements, to name a few.
Manufacturers offer a variety of bucket bar and boom options for midsize excavators. For example, Caterpillar typically offers heavy-duty (HD), extreme service, and long boom, depending on the model. Heavy-duty boom and bucket bar configurations are typically used for earthmoving applications. Extreme service rod and boom combinations are for demanding applications, such as demolition with a large number of attachments.
Long Reach Arm and Boom
The front end adds some weight compared to using a standard heavy-duty boom, so you will have less cycle time. But it is application-specific. When you're running hammers or scissors and multiprocessors continuously, you want the machine to last longer, so you turn to a boom and bucket configuration that can handle that kind of abuse.
You have every bucket bar option and every moving arm option, including extra-long reach configurations. You can see the maximum digging depth and maximum flat bottom depth for each machine.
Contractors should understand the application they are using the machine for before selecting a combination of work equipment. General items to consider include job scope, haul size, productivity and bucket options needed, and whether one or more attachments have potential use.
Your primary bid for the job will determine the appropriate configuration. Underground contractors and basement excavators typically purchase long booms for optimum efficiency. Off-road pipelining or land clearing contractors will purchase medium arms for stability and optimum productivity. Large excavator contractors will purchase short arms for boom strength and optimum productivity.
Contractors digging trenches and putting in sewer/water lines often want to reach out, so they may order a long arm with a coupler and two buckets. If the contractor is adding an attachment such as a thumb, the person would order a mid-arm for added stability. If the contractor is digging into tough material, he'll buy a short arm for an extra breakout.
Digging Bucket &nbs
In applications where a long boom/boom combination is used, the main benefit is an expanded working range that can add versatility to certain applications.
Longer moving arms and bucket bar options typically reduce arm crowding forces. Longer work equipment typically reduces lateral lift forces due to its greater impact on machine stability, while forward lift forces are more dependent on hydraulics. Shorter moving arm/boom options can have the opposite effect when the working range is limited.
Arm length is also directly related to the bucket size that can be used. The shorter the boom, the higher the boom force and the larger the bucket.
In all respects, it appears that a shorter arm will provide higher productivity. But in reality, it depends on the application and type of material the contractor is excavating. A shorter arm will fill buckets of hard materials faster; but with softer materials, an excavator with a shorter arm will have more movement and more pipe joints.
There are other trade-offs to consider. One disadvantage of shorter work equipment is a reduced working range that limits the ability to reach the desired depth or dumping height. The benefit of a shorter boom/arm combination is that the workforce is closer to the machine, so the operator typically experiences greater stability and can use a larger range of attachments and bucket sizes if the application requires it.