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Hope you are doing good.

Can anyone please explain to me why actuators are mounted in inverted position on some excavators?

Please see the image for better understanding of my question. click here for image

Another question is, why on some excavators there is a mix of rigid and flexible piping instead of having completely flexible piping to supply hydraulic power to the actuators?

Thank you in advance for your answers.

pj0909
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  • some folks like to only fix one thing at a time; they tend to be able to adjust schedules around one machine being down. others are better off doing extra preventative maintenance since the cost of unplanned downtime exceeds the cost of spare parts and labor. can you tell which is which in your pictures? – Abel Nov 14 '21 at 13:18
  • Initially, I thought you were asking why not all the hydraulic cylinders were mounted to be in tension (i.e. running along the top side). – DKNguyen Nov 15 '21 at 02:03
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    look at the hydraulic line routing – jsotola Nov 15 '21 at 02:56
  • @jsotola , I dont have the hydraulic pipe routing. It was a general question. – pj0909 Nov 15 '21 at 17:56
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    @Abel, could you please explain a bit your question? – pj0909 Nov 15 '21 at 17:57
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    @pj0909 ??? ... the routing is seen in the first image – jsotola Nov 15 '21 at 17:58

3 Answers3

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The cylinder will be mounted where it is easiest to get the hydraulic lines to it.

Tiger Guy
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Piping: Flexible is used where needed - to accommodate joints and movement.

Fixed pipes are used as they are cheaper and also need to have less fixings per length.

As for “inverted” which of those is inverted obviously excluding the one horizontal… So, given how the actuator works - as it is double acting then it makes no difference apart from the required space around each end. However, it can be seen that the cylinder end is always closest to the supply point in the right hand image, while in the left hand image the cylinder end is likely being kept away from a riskier place of damage.

A single acting actuator is ususally positioned so the hydraulic force opposes gravity or the “normal” closed position or rest position.

Solar Mike
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  • could you please explain how the cylinder in the left hand image is been kept away from getting damage? Usually the cylinders are more strong than piston. In both the pictures hydraulic forces are opposing gravity, am I right? – pj0909 Nov 15 '21 at 18:03
  • @pj0909 left hand image - you circled, in red, two cylinders not one. The end with the pipes is up high away from any material being moved... I mentioned gravity with single acting - which of those are single acting in your images? – Solar Mike Nov 15 '21 at 18:06
  • I think none of the actuators are single acting in the image. – pj0909 Nov 18 '21 at 04:31
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Everyone keeps mentioning ease of hydraulic connections, but one could alternatively design the hydraulics to fit the cylinder orientation, yet it is almost never done. This is partially because there is little difference for the cylinders themselves. Consider at least one more step in why the hydraulics might be designed as they are. Here is one possible consideration.

For the Caterpillar pictured, the circled cylinder and associated hoses are easy to service. The adjacent one might be slightly more difficult.

If however you had to replace all sets of hoses, then the Liebherr design might actually come out ahead compared to an equivalent sized machine built in the Cat configuration. This is because a lot more is in a common area to all 3 cylinders on the Liebherr.

Why would someone prefer one over the other?

Mine/quarry bottleneck can be the transportation of material out, meaning missing a single shipment is a considerable cost compared to hoses. Delaying a train by a few hours to make your quota? It could affect the whole line and everyone using those tracks. Delaying a truck? It'll take the same amount of time to make the round trip anyway so it will remain behind forevermore. If you're replacing one, might as well replace even slightly worn ones rather than using the full life of the hose.

Renting out or owning construction equipment? Even if someone has to fix a down machine, work (or rentals) can still go on as long as your plan was flexible enough. Using the full life of equipment just makes sense.

Abel
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