Hydraulic System Design: Avoid It Being a Flop with Careful Consideration of Components
It’s no secret that every engineer wants their hydraulic system to run well forever.
During a recent chat with one of our clients we discovered that although they were using our mobile hydraulic power packs quite happily out in the field, back at base they had another hydraulic system that there were considering improving. They wanted to add a highly effective filtration system to it so that the fluid would be as clean as a whistle – or in this case, more like as clean as a fresh coat of paint – excuse the simile! (Even our editor couldn’t come up with anything else!)
Of course, as experienced engineers we are well aware that the cleaner the hydraulic fluid, the longer the service life will be of any component – in the case of all things being equal anyway. Whether taking action would deliver a worthwhile return on investment will also rest on a number of other variables that we won’t cover here. But this situation got us cogitating about something else.
We are fully supportive of the maintenance approach for hydraulic systems, rather than informing somebody of what they should have done a day too late when everything has jammed up and there is a huge repair bill hanging in the future. Although maintenance and design are seen as separate matters, in reality they are closely tied as the design of a hydraulic machine will impact both its reliability and its operating cost.
Taking this into consideration, it becomes clear that the best time to think about what your objectives are with regards to hydraulic system maintenance is before you purchase a machine.
Consider temperature and viscosity
Keeping operating costs in mind, before you order your system, you need to consider what you want when it comes to both reliability and maintenance. You need to avoid buying a flop that will cause more issues than output.
You will also need to consider what targets you have when it comes to contamination control. Ask for a machine that can reach your objectives on reliability because it has been equipped and designed to deliver on them.
Take the hydraulic oil that you plan to use and work out the ultimate running temperature for that oil. Then give directions to the manufacturer that you need your machine to have the right cooling capacity = using the temperature stats that you’ve given to him.
If you’re one to think that the temperature or viscosity of the oil is not all that important, then we’re afraid to inform you that you’re wrong. Based on our experience in hydraulic system repair, we know that failure of lubrication is one of the worst perpetrators when it comes to hydraulic component failure. There are of course other specifics that need to be considered when looking for reliability such as how much oil is in the tank, whether there is a flooded inlet for each of the pumps and what suction strainers are in place for the pump intake lines.
Begin with the end in mind
To clearly demonstrate this point, let’s go back to the viscosity and oil temperature connection. Let’s say you’ve got plans to buy a hydraulic excavator in the 25 ton range. According to directions from the manufacturer, you can expect optimum performance, reliability and longevity from keeping the oil in the range of 25 to 36 cSt with a viscosity index of 100.
The manufacturer has informed you that if you run the excavator at a temperature that is hotter than 70°C then you won’t be able to expect a lot from the machine. The oil won’t last long, the seals will fail and each component will struggle to last a long time.
So you ask the manufacturer to ensure that you cannot even run that machine hotter than 70°C, even on a day that is at 45°C (your local weather). If they do mess up and deliver something that does, then tell them that they will have to fix it at cost to themselves.
So the next time you put an order in for a new machine, have it made to suit how you want it to run, and you’ll be saving yourself and your business a lot of time, trouble and money. If you’ve got any tales to tell, drop us a line.