Excavator Unscrewing Itself: What's the Problem and How to Avoid

We have all interacted with an excavator. Well, a majority of us have never entered the excavator cab. We have, however, seen one in a road construction site, a building site, or a farm digging the earth or loading some super heavy load onto a dump truck. An excavator is such a powerful piece of machinery that has revolutionized construction sites' operations.

In this article, we dive into the world of excavators. We learn how the excavator works. Of special attention to us is to establish whether an excavator can unscrew itself. We look into the reasons why this problem happens and how one can avoid it. To best understand this issue, we explore the machine we call the excavator and understand how it works.

What is an excavator, and how it works?

An excavator is a heavy machinery whose size varies according to user needs. The excavator comes with a variety of attachments which make it an all-purpose powerful machine. An excavator can be wheeled or tracked, but we mostly see the latter. The compatibility with various attachments makes the excavator such a versatile machine.

For many years, excavators were a bit bulky and cumbersome to operate. In 1993 however, Yanmar, an expert in excavator engineering, launched 'zero tail swing' counterweight technology. This is the basic technology used in the manufacture of excavators across the world. An excavator comprises the following key components;

• The boom - This is the long arm of the excavator which extends in front. The boom is a critical component of the machine because this is where all attachments get hooked to. The boom has the stick and the attachment. Though booms may vary in design and technology employed by respective manufacturers, they all work the same. The boom is attached to the upper structure and the cab. All these excavator parts rotate around the track at a 360^o angle.
• The undercarriage - This part of the excavator consists of the track or wheels, and it is where the upper structure and the boom sit on and rotate over. The swing bearing connects the undercarriage with the upper part of the excavator.
• The slewing bearing - This is the part where the magic happens. The behind-the-scenes part makes it possible for the upper carriage to swing around in a 360^o. The swing bearing is connected to hydraulic hoses that control the excavator's rotation. The swing bearing has cogs, making it possible for the smooth rotation of the excavator.
• Rotary manifold - The rotary manifold which connects to the hydraulic hoses is the one responsible for the 360^o angle rotation of the excavator. The rotary manifold transfers the power of hydraulic fluid between the upper carriage and the excavator's undercarriage, all while the excavator rotates at 360^o. In an excavator, the hydraulic fluid in the rotary manifold makes it possible to drive the excavator.
• Cab or the house - This is where the excavator is controlled from.

The excavator unscrewing itself

In search of the truth, people have gone to great lengths to find out whether an excavator can actually unscrew itself. Before we go any further, the short answer to this query is, No. If you go to some online sites, you will find people actually trying to demonstrate how an excavator can unscrew itself. It is a pervasive myth that the excavator can unscrew itself.

According to the myth or people purporting that an excavator can unscrew itself, you only need to enter the cabin and make this happen. Start the excavator's engine and turn the boom 360^o continuously 16 times. In other words, we can simplify the theory by assuming that if some hand with mighty power they'd unscrew the cab, and it would detach itself from the track. It would be more like opening a bottle of water or coke.

From the above description of excavator parts, you will notice that the joint between the upper part of the excavator and the track or the undercarriage is more complicated than just a single screw.

Why an excavator can't unscrew itself

To understand why an excavator cannot unscrew itself, we need to take a look at how the rotary manifold and the slewing ring work.

The slewing ring or bearing of an excavator, which can be anything between a few feet to more than 7 meters in diameter, forms the base of the upper carriage and the excavator's cab. The large diameter helps at ensuring a loaded boom is properly and firmly pivoted. A slewing ring works the same way as a standard bearing and employs friction-reduction elements.

It has an outer and inner ring and a gear integrated into either inner or outer rings. The gears on the ring make contact with those in the slewing ring, which causes the free rotation of the upper part of the excavator. One thing to note, though, is that there is a lot of movement between the inner and the outer rings of the slewing ring, and this is the space that needs ample lubrication.

On the other hand, the rotary manifold is a large shaft that can be said to be a large pin. This large pin is drilled and grooved and rotates inside a high-pressure cylinder inside the slewing ring. There are grooves and ports along the shaft length through which hydraulic fluid flows.

In simpler terms, the rotary manifold is a large round grooved shaft that has numerous O rings separating the grooves where high-pressure hydraulic fluid flows through. It is imperative to note here that the joint between the track and the cab works is that it can't unscrew. Detaching the excavator from the track requires you to follow some not-so-easy steps.

How can you know if the rotary manifold is faulty?

Since we have established it is the rotary manifold on which the excavator rotates, we can now safely try and understand what problems this mega pin can encounter. Let us look at the symptoms of when this pin malfunctions. These symptoms may indicate a deteriorating rotary coupling or a dead one;

1. Having to adjust the blade up since it keeps creeping down constantly.
2. Oil leaks to the ground or onto the machine's belly.
3. The lazy drive means you could push both drive levers, yet the excavator veers off the intended path. At times, being forced to apply less power to operate a powerful function.
4. The blade moves up and down at high speed for a particular function.

How to detach the upper carriage from the lower structure of the excavator?

The rotary manifold can be removed from the machine. This happens after you have disconnected the slewing bearing and the hydraulic hoses, bolts, and adaptors. It is quite a process. Let us take a look at how this is done.

1. The slewing bearing is held in place by several bolts. You will need to unfasten and remove all of these bolts first. Removing the slewing bearing is mainly done when you want to replace it.
2. You can now disconnect the hoses to the rotary manifold. The hoses can be five, but the number can change depending on the model of the excavator. Remember to cap the bolts where the hoses were.
3. Place some large stumps under the upper carriage to ensure the excavator remains supported and stable once you pull out the undercarriage.
4. Start the excavator's engine and detach the upper part from the track.
5. Pull the now free track from under the excavator, and you will have uninterrupted access to the ring and the rotary manifold.

How to avoid the excavator slewing bearing and rotary manifold from damage

The slewing bearing is the one responsible for the continuous 360^o rotation of the excavator. It must be well-lubricated to enable it to perform its functions without any interruptions. The service must be done regularly with heavy-duty, extreme-pressure grease. Remember to remove all debris stuck between the bearing and the upper body after every operation.

Because of the intensity of the pressure exerted on the bearing, lubrication should be done at least after every 100 hours of operation. Some operators of these machines do the lubrication exercise after every day of operation. Regular lubrication ensures the bearing is at optimal performance state and the gears aren't overstressed.

On the other hand, the rotary manifold is responsible for the smooth powering the excavator. This unique pin where hydraulic fluid hoses go must be taken good care of. Check for leakages, change the hydraulic fluid as advised by the manufacturer, and avoid overstressing the machine because otherwise, you will essentially be overworking this small complex component.

Conclusion

An excavator cannot unscrew itself. The failure of the rotary manifold, as we have seen above, will lead to the excavator ceasing to function in a matter of seconds. We have also seen that the excavator's upper part and track are connected by the slewing bearing, which does not unscrew itself. But to avoid any issues with the turning of the excavator at 360^o angle, you will need to maintain these two components regularly.