Is it possible, in the 21st century, to build a hydraulic system that doesn’t break down? Mechanical devices will eventually wear out, of course, so by “break down” we really mean fail unexpectedly. To help us achieve this aim of perfect reliability, we now have systematic tools available, such as proactive maintenance procedures and Design For Six Sigma (DFSS).
The objective of DFSS is to design systems that have a target reliability level of at least 99.99966%, which equates to no more than 3.4 failures in every million opportunities. Proactive maintenance combines many of the techniques of preventive and predictive maintenance into a process also designed to achieve similar levels of reliability. The essence of both tools is to attempt to think of all possible failure mechanisms and then to prevent them from happening, either by design or maintenance.
However, safety experts tell us that between 80% and 85% of industrial accidents are caused by human error, so is perfect reliability already a lost cause? Fortunately, human beings are very predictable animals, so it’s a fair bet that at some time during the life of a hydraulic system, someone will try to start it up with no oil in it. There’s a 50:50 chance that when the electricians first wire up the electric motor, the motor (and pump) will run backwards. If there’s a shut-off valve on the inlet or drain line of the pump, someone’s inevitably going to start the pump up with one or both of the valves closed. If something is adjustable, then as sure as eggs is eggs, at some time or another, someone will adjust it. If there is an accumulator on the system, sooner or later someone will forget to drain it down before starting maintenance work on the system. And one thing that’s 100% certain is that if there’s a pressure-compensated pump on the system with a relief valve to protect it, one day the compensator will be wound up higher than the relief and the oil’s going to boil.
Anyone who’s worked with hydraulics for any length of time could probably come up with a whole page full of such instances. It’s not that maintenance people are fools; it’s just that sometimes we get tired and lose concentration, sometimes our mind is elsewhere, and sometimes we forget things. Sometimes we don’t really know enough about the job we’re doing, so we shouldn’t really be doing it … but someone has to. So there are all sorts of reasons why people sometimes do stupid things; I’ve done enough myself to know.
Engineers therefore need to think about all these things that might (or rather, will) go wrong and try to design them out. Automatic drain valves for accumulators, interlock switches on shut-off valves, float switches in tanks, thermal cut-off switches, lockable adjusters, etc. I know, it all sounds very expensive, but probably not as expensive as the first breakdown, if anyone ever stops to reckon up its true cost. Not only are we talking about lost production, consequential repairs, premium labor rates and shipping costs, clear-up costs, etc., but we may also be talking about people’s well being and even their lives.
To illustrate the point, in 1886 it was decided that a new bridge was required across the River Thames in London, but being downstream of what was then the biggest port in the world, it had to allow tall-masted ships to pass freely beneath it. The result was Tower Bridge, one of the best-known landmarks of the City of London with its two opening sections or “bascules”. The problem was, each 162-foot long bascule weighed around 1,500 tons, and for the bridge to open, each had to tilt through almost 90 degrees in just over a minute then close again once the ship had passed through. To begin with, this would happen more than 20 times a day. The solution was eight 20-gal/rev hydraulic motors (with built-in brakes) operating via a curved rack and pinion arrangement. But being aware of the consequences of a failure of the bridge, the Victorian engineers built in numerous parallel systems and devices, and no doubt when the bridge opened in June 1894, they were confident that they had covered every eventuality.
Unfortunately they were wrong, and one sunny afternoon in July, the bridge suffered a mechanical failure and failed to close. However, this was in July 1968 and in the interim 74-year period, the bridge had hydraulically opened and closed its 1,500-ton bascules 352,713 times.
So is it possible, in the 21st century, to build a hydraulic system that doesn’t break down? Maybe not, but we should be able to get pretty close if they could achieve 99.99972% reliability in the 19th century.
ABOUT THE AUTHOR
Steve Skinner’s 46 years of experience with hydraulics was gained mainly with Vickers and subsequently Eaton in the UK. Although having roles in applications, sales, and product management, for most of his time there he was employed as European training manager. Now a freelance lecturer but still actively involved in BFPA and CETOP fluid power certifications, he will shortly be publishing a book on the history of hydraulic fluid power. Visit www.steveskinnerpresentations.co.uk.
In the words of one of my favorite bands, “What a Long, Strange, Trip it’s been.” Having been elected to serve as the 2014 president of the International Fluid Power Society (IFPS), I can pause and reflect on just how I arrived at this point. Never in my wildest dreams did I imagine this day when I first heard of the organization so many years ago. This is truly an honor, and I am humbled.
There have been a lot of very smart people in this industry with whom I have had the pleasure of becoming acquainted with over the course of my career, and many of them have served a number of roles to help get me where I am today. Some of those roles were as mentors, teachers, peers, co-workers, and students. Yes, I have learned a great deal from my teaching experiences over the years, and I have had the privilege of knowing some of the legendary teachers in the industry, such as George Altland of Vickers. In fact, that is really what I want to focus my comments on—education in our industry.
I’m sure I am preaching to the choir when I say that education is extremely important in any professional field, but in some aspects, it is uniquely so in the fluid power industry because there is not a widely accepted and consistent set of standards that exist for educating students in the technologies of fluid power. Unlike ABET, which is the accreditation body for engineering and technology degree programs, there are no specific standards that are universally adopted and accepted to ensure that those working within the industry at various levels have consistent core knowledge and skill levels. The closest the fluid power industry has are the various certifications offered through the IFPS.
What is lacking is a consistent and agreed-upon set of teaching standards to ensure that everyone attains at least the same foundational levels of knowledge. A lot of different sources offer hydraulic training with a wide and varied level of instruction. There are programs that propose to teach basic hydraulics in as little as a day to well-structured associate degree programs lasting for two years. A disturbing trend over the past few years is that many of the individuals who say they are seeking knowledge aren’t as concerned about the quality of the instruction and the depth as they are about the length of time they have to lose from “work” and corresponding cost to obtain a “certificate.” As a result, those individuals who take the shortcuts don’t possess enough knowledge to perform optimally.
Because of this, I am a firm believer in IFPS certifications. They offer the best tool currently available to evaluate and substantiate an existing knowledge and skill set. It is a shame that companies within the industry don’t as a whole actively embrace and seek certification for their employees. Certification provides a mechanism of validating that those responsible for the operation, maintenance, and selection of fluid power components and systems have met at least some minimum established standard of knowledge. I encourage all professionals in the industry to take a positive step forward and attain certification at whatever level is appropriate for their job functions. This would go a long way to help improve safety, reduce energy waste, enhance productivity, and promote the professionalism of those within our industry.
By Tom Blansett, CFPAI, CFPS, CFPIHT, CFPCC, Manager of Hydraulics Training Services at Eaton Corp. and 2014 IFPS President
The latest buzzword used within colleges and among many industry leaders is “mechatronics.” If one consults Wikipedia, the definition provided there is: “Mechatronics is a design process that includes a combination of mechanical engineering, electrical engineering, control engineering, and computer engineering. Mechatronics is a multidisciplinary field of engineering; that is to say, it rejects splitting engineering into separate disciplines. Originally, mechatronics just included the combination of mechanics and electronics, hence the word [itself] is a combination of mechanics and electronics; however, as technical systems have become more and more complex, the word has been ‘updated’ during recent years to include more technical areas.”
Given that Wikipedia is not a traditional encyclopedia, this source seems the perfect place to attempt to define this new and changing term. Mechatronics, as it is evolving, includes not only mechanics and electronics, but also such various disciplines as fluid power, control theory, and computer science.
Mr. Tetsuro Mori, a senior engineer at the Japanese company Yaskawa in 1969, came up with the original term “mechatronics.” He got the idea from combining the technologies that had been utilized in industrial robots. This included using mechanics, electronics, and computing to accomplish the robots’ day-to-day jobs.
Engineering cybernetics deals with questions of controls engineering within the mechatronic systems. This application of controls leads to collaboration, and most mechatronics modules are designed to perform the production goals, incorporate machine flexibility, and provide agile manufacturing properties within overall manufacturing systems. Thus, the application of mechatronics leads to what is known as “machine control architecture.”
Applications for implementing mechatronics in industry are many: automotive manufacturing, robotics, motion control, systems integration, intelligent control, systems modeling and design, vibration and noise control, packaging, medical technology, and servo-mechanics. These are just a few examples of where mechatronics can be used. Mechatronic systems may provide a complete production system or may only provide sub-components of that production system.
Students graduating with degrees in this area of study can select from a wide spectrum of industries for career choices. These engineers can choose either small or large companies, primary manufacturers, OEMs, or end users, and they may use their interdisciplinary backgrounds in mechanical, electrical, fluid power (hydraulics and pneumatics), computers, microcontrollers, programmable logic controllers, programming, industrial sensors, electrical drives, and engineering functions. The combination of system technologies and the interdisciplinary approach gives the students a broader vision and understanding of the entire production process.
Mechatronics is yet another avenue for students to gain the theoretical concepts coupled with hands-on applications for current and future global manufacturing arenas. These students can become qualified engineers, technicians, or mechanics—there is a widespread need for interdisciplinary understanding at all levels of industry. Now is the time to apply at your local community college or university for a rewarding future. Good Luck!
Editor’s Note: If you are an instructor at an educational institution or an industry professional involved in mechatronics, we invite you to contribute technical articles to our publication about this growing field. Please contact Kristine Coblitz at email@example.com for more information.
By Jimmy Simpson, CFPAI, AJPP, Chairman of Fluid Power Education Foundation (FPEF) and Adjunct Fluid Power Instructor at Northwest State Community College