Developing a Large Hydraulic Cylinder Repair Program

A set of spares could remove downtime risks

By Steve Fiscor, Editor-in-Chief

Hydraulic shovels are critical path production tools for open-pit mines. A mine may have a fleet of six to eight haul trucks or more working in tandem with a large hydraulic shovel. One of those trucks could be taken out of rotation for a repair and, while the operation would likely suffer a productivity loss related to haulage, it would continue to operate. If the shovel goes down, that production unit is offline until the shovel is repaired and all the trucks sit idle.

Shovels can go down for a whole host of reasons, but issues with the large hydraulic cylinders can be especially problematic. When it comes to failures with hydraulic cylinders, shock loading is usually the main culprit, followed closely by excessive heat. Large rocks, or a poorly blasted toe could create problems when the shovel crowds the muck pile. Shock loading will rip threads, buckle rods, and destroy seals. Sometimes the seals are damaged by pressure spikes when the bucket strikes a large rock or the side of a haul truck. The heat from the hydraulic oil can also affect the seals. Heat damage can varnish the rods and everything else in the system.

Logan Industries, located near Houston, Texas, repairs large hydraulic cylinders. For years, the company has performed major repairs for the oil and gas sector. They routinely repair the direct-acting tensioners for offshore oil rigs. These 50-ft long x 2-ft-dia. bore, hydraulic cylinders are used as tension pullers to keep the large drill pipe risers connecting the rig to the seafloor. When the seas get rough, the tensioners bear the brunt of the forces at play, and they withstand incredible loads until they fail and then Logan Industries gets a call.  

More recently, the company started providing repair services for Nevada gold miners operating large hydraulic shovels. What would probably be the largest hydraulic cylinders on the mine site would be considered relatively small for Logan. When the OEMs make the large hydraulic cylinders used on mining class excavators and drill rigs, they do a good job, obviously, because the cylinders do last a while, explained Dean W. Carey, P.E., technical director for Logan Industries. “The mines need an equally-skilled repair shop to provide replacements that will last as long,” Carey said.

A hydraulic cylinder has one axis of motion; it goes in and out. While that may be an oversimplification, to make that happen regularly and reliably, Logan employs a lot of technology. “Seal packages must be properly designed,” Carey said. “Wear pads or bands must be made from the right materials and have the proper tolerances, so that steel doesn’t touch steel. The tolerances need to be nearly perfect or within several thousandths of an inch for it to work properly. And, when you’re talking about a cylinder that’s 20-ft long, with an 18-in. bore, and you’re trying to get clearances within a couple of thousandths of an inch, that’s difficult work. It takes some particular know-how to make that happen.”

Production concerns with oil and gas are somewhat similar to mining, especially when it comes to downtime. If an oil rig or a mine is down, the company that operates it is likely losing millions of dollars a day or more. Working in that type of service environment is where Logan cut its teeth. An oil company would approach them with a repair job and a seemingly unreasonable deadline, and they would work 24/7 to get the job done. More recently the company has invested in a quality control program that is helping them further improve their level of service.

Taking On Mining Jobs

Acknowledging that everything is relative, Carey said, “repairing the hydraulic cylinders for large mining equipment is in our sweet spot.” Logan claims it is qualified for large hydraulic cylinder repair and hydraulic system rebuilds for the Hitachi 5600s, the Cat 6060s, the Komatsu PC 8000s, Liebherr R 9800, as well as the cylinders used for the masts on large rotary blasthole drills. “We rebuild cylinders that are larger than any of those every day and we’re pretty good at it,” Carey said. “That’s why we feel qualified to chase the large hydraulic cylinders in the mining business.” He said he understands that there are some local shops that do great work but when it comes to large bore cylinder work, this is where our interest is and we are very good with them.

Working with Kinross Gold, Logan began providing repair services for the Round Mountain and the Bald Mountain mines in Nevada. “They take a long view and they have got some good ideas about how to maintain their fleet and how to make sure that they have uptime on their machines — they are smart miners,” Carey said. “We have repaired half a dozen cylinders for them and we’re just getting started.”

With the critical importance of the primary loading tool, mines would ideally want to have a set of spares especially if they were operating more than one shovel, Carey explained. “This is something we discuss with mines whenever we are on site,” Carey said. “What does the spare set situation look like? Do you need help with some of that? And, the answer is all over the map. Some do, some don’t. Others have thought about it, and they have a plan. That’s fantastic. In that case, all we can really offer is to do the repair work when it’s time.”

For those that do not have a plan, Carey said Logan can really offer something special. They will pull the damaged cylinders apart and reverse engineer them. The Logan engineering team will make a set of drawings, repair the cylinders, and make a set of spares. “Put some spares aside,” Carey said. “How crazy is that? Let us design a few and sell you some, it’s a fairly simple concept.”

Carey said he would go so far as to offer to put a set of spares on the mine site, if the mine would give Logan the repair work. When the mine uses them, they pay for them. None of the mines have taken him up on that offer yet. “We provide this type of service all the time,” Carey said. “We’re doing it now with the for Caterpillar 6060 front shovel booms. We think our cylinders are better. We have found flaws with the OEM cylinders. This is what we are trained to do. The cylinders that we build for those drill rigs will last much longer and they will operate more efficiently.” Logan followed a similar strategy when it started repairing the direct-acting tensioners for the offshore rigs and they are modifying that program for the mines.

Logistics and Cylinder Repair

Houston may seem distant from the mining districts, but that hardly factors into the repair time. Granted, it’s two days travel time from Elko to Salt Lake City and then to Houston via Albuquerque and Amarillo. Of the total turnaround time to repair the cylinders, four or five days are used transporting them from the mine to the Logan shop.

To properly repair a large hydraulic cylinder, the mines are looking at a 6- to 8-week turnaround, depending on how much is wrong with them. The process requires materials and considerable engineering. “Re-chroming the rods can be time-consuming process,” Carey said. “If we don’t re-chrome them the turnaround time could be a couple of weeks, depending on the amount of damage. These cylinders are not coming to us because they’re working correctly.”

Logan outsources the re-chroming process. “There are three re-chroming facilities in Houston that we use,” Carey said. “The mines prefer hard chrome or an HVOF chrome coating. We have guys in Houston that can do that. They have the grinding facilities, so they can remove the varnish, re-chrome and polish the rods.”

Even though, Logan is hiring a specialist to do the work, they still provide guidance as far as the tolerances, the type of chrome and how it’s applied. “We’re still dictating how we want the job done, and we closely monitor the process with written specifications our vendors are required to follow.” Carey said.

The Logan machine shop has CNC lathes and mills and manual lathes and mills. The cylinders usually require considerable machining to return to OEM specifications “We perform a lot of machining and inspection work to make sure we are meeting OEM specs,” Carey said.

Logan engineers the seals to make sure they are right. “We also have seal specialists that talk with seal manufacturers,” Carey said. “There are three in the world that are of the caliber that we need to make sure the repaired cylinders last — Trelleborg, System Steel, and Merkel. They make the best seals in the world. If a customer asks us to use an OEM kit, we will order them. If they leave it up to us, we will install what we think is best and has served us well for a long time. 

The company has the same policy for wear bands. “The wrong type of wear band could compress more than it should, risking steel-on-steel wear,” Carey said. “Because we’ve been doing this for so long, we know what works and what doesn’t.”

Beyond the machining, there are threads and bearings that need inspection and cleaning. “If material is missing, our fabricators will butter it up, put more steel where there is none, so that we can then machine it to the proper tolerances,” Carey said. “We will often find that bearings, bearing seats, knuckle-ends, clevises, pins, etc. have also seen extreme wear.”

The company follows a similar process for damaged threads. “They lay some beads to build the steel back up, make sure it’s compatible so it doesn’t just shuck off and then re-machine everything,” Carey said. “Then it’s time to polish and hone to a smooth, mirror finish, so that the seals can do their job. After that, it’s time to assemble it.”

Assembling large cylinders versus small cylinders is a totally different ballgame, Carey explained. “When you are working with things that are big, they have mass and momentum that cannot be changed or ignored,” Carey said. “When you’re putting a large cylinder together and you start feeding them into the seals, if they are misaligned, you will be doing it again, because the seals will get destroyed. These are valuable lessons that we’ve learned over the years.”

Once the cylinder is reassembled, it needs to be tested. Logan has two tests stands and three guys dedicated to the process. “That’s all they do is test cylinders,” Carey said. “We will put a chart on them. We will hold pressure on them, sometimes overnight. Once the testing is complete, we ship them back to the mine. We pack them in crates and shrink-wrap them so that they arrive at the mine nice and shiny.”

Continuous Improvement

A little more than seven years ago, Logan began investing considerable time and training with quality control. Carey describes the process as a cultural shift that is now paying dividends. “We can show you how we control quality throughout the repair process,” Carey said. “We have a process we follow for each aspect of the repair. We also employ people to verify that we do what we’re telling customers we do.”

The quality management process drives Logan’s business. “We have all of processes documented,” Carey said. “We can put a new employee in a training class and make them productive on the floor, performing quality work quickly. Trusting that process was a hard thing to do at first, but now we’re used to it and it just makes sense.”

The company records its mistakes, how they fixed them and publishes that information for its customers. “Everybody makes mistakes,” Carey said.

Carey is an engineer and he formed the engineering department that’s working miracles at Logan today. “Over time, you gain the experience and the expertise to do this type of work,” Carey said.

Earlier this year, one of Logan’s oil-and-gas customers was performing a critical inspection. They encountered cylinders with thin walls that would not hold pressure. “Nobody had noticed it, and the rig was going into service and they were scrambling,” Carey said. “They called us. All the cylinders would have to be repaired and replaced, and that seemed pretty straightforward, and normally it would be, but they needed it done in five days. There were eight of these suckers and that’s a lot of pipe. We needed to source the pipe. We found 250 ft of it and bought it. They gave us a purchase order and the trucks started showing up.”

Working 24 hours a day, Logan completed the repairs in four days and the customer was able to make the activation date. “We have done that several times and won some loyal customers,” Carey said.

Carey recalls his career path. “When I started making machinery, I thought engineering was the end all be all,” Carey said. What really gets him going these days is working with customers to develop a solution for a particular problem. “I’m pretty good at that and I like doing it,” Carey said.