Service experts offer 12 tips for keeping the electrons and hydraulic fluids in your machines flowing properly for maximum production at minimum cost.
Ever since the earliest magnetos and spark plugs were used to crank an engine and the first hydraulic pumps were connected to the lift arms of dozer blades, keeping electrical and hydraulic systems of construction equipment in good repair has always been a key to making money when moving dirt. But, with state-of-the-art electronics and finely engineered hydraulic system components found in today’s equipment lineup, proper maintenance of these systems has never been more critical for maximizing production and profits from earth-moving machines.
“If your hydraulic system isn’t performing well, the rest of your machine won’t perform well,” says Ron Gruber, product support consultant for Caterpillar. “Over the years, construction equipment has evolved from having no hydraulic system to where hydraulics can represent as much as 30% of a machine’s components. Because hydraulic systems are doing more and more of the work, they are having a much greater impact on ownership and operating costs.”
Meanwhile, the increasingly sophisticated technology of today’s electrical systems for controlling the hydraulics has given operators the ability to operate these machines with a degree of ease, speed, and precision that previous generations of equipment operators only dreamed of.
Electronic Networking
At the heart of the latest electrical systems for operating excavators, dozers, and other earth-moving machines is a controller-area network (CAN). It consists of sensors, actuators, and on-board computing devices or controllers, which control the machine’s engine, hydraulics, and other systems, and a electrical bus that allows the different electronic control units to communicate with one another.
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Photo: Caterpillar
Collecting a sample of oil for analysis |
It was developed to provide the precise control of the machine needed to meet the more stringent federal engine emission control requirements of the last decade or so.
“These electronic controllers change everything,” says George Wacaser, director of product support for Martin Equipment in Rock Island, IL, a John Deere dealer serving contractors from locations in Illinois, Iowa, and Missouri. “You now have a fly-by-wire system that connects you to the hydraulic function you want to operate, instead of cables and mechanical linkages.”
Before, you changed engine speed by moving a throttle that was connected by cable to a lever that operated a pump that controlled fuel flow to the injectors. With the latest CAN-Bus system, you still control engine speed with a throttle. Only now, moving the throttle sends an electrical signal over a wire to the engine control unit. That controller, in turn, sends an electronic command to the injector pump to produce the desired engine speed. In a similar manner, moving a lever or pushing a button in the cab tells the hydraulic control unit how to operate control valves to perform the desired hydraulic function. At the same time, logic sequences included in the software that runs the controller can override the operator and prevent running the machine in a way that could exceed design limits and possibly damage the machine.
In addition to improving your ability to operate the machine comfortably and productively, this CAN-bus system is much more durable and trouble-free than the older mechanical control systems. Jim Pipkorn, a product support representative for American State Equipment, a Liebherr dealer based in Milwaukee, WI, explains: “Before, there may have been 10 to 20 switches and gauges on the dash using 20 to 30 wires to control various hydraulic and electrical functions. Eventually, these mechanical switches would fail due to wear and tear. Now you have software mounted on circuit boards with sealed soft-touch buttons that will connect with other circuit boards using just four wires. This results in a huge reduction in the amount of wires in a machine.
All this technology, however, comes at a price—trouble-shooting any electrical problem requires a different set of skills than it once did.
“In the past, you could trace a complete circuit using a electrical schematic from start to finish to solve the problems,” he says. “Now with a CAN-Bus machine, you need to know what type of output you expect from any input and then you trace a circuit from both ends. A huge advantage of today’s technology is that the machine will generate error messages to help you find problems. A lot of machines will show the technician the error messages along with inputs and outputs right on the monitor in the machine, eliminating the need for special equipment. Others need the laptop to interface with the machine’s software.
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Photo: John Deere
John Deere’s Ultra Clean System cleans hydraulic lines and hoses. |
Engines are a little different and require laptops with the proper software for you to see the errors and to troubleshoot. With today’s emission standards, you need to have a electronically controlled engine and properly trained dealer technicians to help.”
Preventing Electrical Problems
Here are some suggestions to help keep your electrical system performing properly:
Cleanliness counts—Electronic circuits are fussier about their environment than the older style systems of wires, switches, and gauges. “Many of our customers don’t realize how moisture and dirt can affect electronic components,” he says. “For example, a buildup of dirt on electronic components can cause them to overheat and then strange things happen.
“In addition to minimizing accumulation of dirt-catching oil, keep cab air filters and any electronic box filters clean to help protect electrical devices from dirt while allowing air to circulate and cool electrical devices.”
Protect the wires—Usually wires are routed out of harm’s way to prevent abrasions or shielded to protect them from heat sources. Put wires back in place if they get dislodged from their original locations and replace any damaged or missing shields, advises Mike Moseley, vice president of customer support for Heavy Machines Inc. The company sells Liebherr and LeTourneau equipment from its headquarters in Memphis, TN, and locations in Florida, Georgia, Maine, Texas, and West Virginia. “Most electrical components have water tight seals of some sort, such as a rubber boot or plug, that need to be replaced if damaged, to maintain good electrical connections,” he says.
Weld with caution—To avoid damaging electronic components, Moseley notes, be sure to isolate the electrical system before doing any welding on the machine.
Making the most of fluid power—Just as electrical systems have become more complex, so have hydraulic systems. Manufacturers have gone from using simple pressure-regulated pumps that give you full flow to using electronically controlled pressure-regulated pumps and in some applications electronically controlled load-sensing pumps.
With the pressure-regulated pump flow, you can control the flow electronically—fine control, full power, or for running options such as a hydraulic hammer. These pumps use remote-mounted proportional valves that get their signal from the CAN-Bus system. Remote mounting of the solenoid valve removes it from the heat and vibration when mounted on a pump, resulting in much more reliable regulation of the pump.
Load-sensing hydraulic pumps are becoming quite popular also. These pumps supply just the amount of oil needed. By eliminating wasted energy, it reduces fuel costs. A load-sensing control valve allows for multifunction operation. You can boom up, curl the bucket, and push the stick out, all at a different pressure, all at the same time, without losing any of the functions.
In their continuing quest to move more dirt in less time at less cost, manufacturers are designing hydraulic valves, cylinders, motors, and pumps to withstand hydraulic pressures as high as 6,000 pounds per square inch. This requires producing components to meet the much more demanding specifications and extremely tight tolerances now needed. That, in turn, has heightened the need for proper maintenance.
Poor maintenance leads to poor machine performance. Often, however, this loss of performance isn’t immediately obvious. “In most cases, an operator doesn’t notice any maintenance-related performance problems until the machine has lost about 20% of its capabilities,” says Gruber. “Losing 20% of your production is like taking five days to do four days’ worth of work. Adding to the expense is the cost of the extra fuel burned as the machine takes longer to complete a job.”
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Photo: Caterpillar
Assembler uses a hose gun to clean hydraulic lines. |
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Photo: JCB
Good access to hydraulic components is important. |
Here are some tips to help minimize such waste of time and money.
Prevent particle pollution—The single most important practice for minimizing hydraulic problems is to keep foreign material, including dirt, metal particles, and water, as well as air, out of the system. About 75% to 85% of hydraulic pump, cylinder, and valve failures are due to contamination, which accelerates wear, Gruber reports.
“Usually it’s not the large particles but the very small ones that you can’t see with your eye that cause the vast majority of damage to hydraulic systems,” he says. “These particles measure no more than about 5 microns in size. But, they can get wedged in-between tight spaces between pistons and cylinder walls to score the inside surfaces or in valves, causing them to stick.
Foreign material can invade hydraulic systems in several ways. “Every time the system is opened up, there’s an opportunity for contaminants to get inside,” Gruber says. “If oil is coming out, then dirt is going in.”
Dirt and other contaminants can get in through openings like those created by worn or damaged seals and a dirty or bent rod that wears the cylinder as the rod moves in and out. Dirt around the opening of the hydraulic oil filler tube can enter the system when refilling the machine’s reservoir. Adding unfiltered fluid from a dirty or contaminated container to the hydraulic tank can be another source of foreign material. So can debris left inside a new replacement hose during the manufacturing process. In that case, the contaminants should be removed by shooting a cleaning projectile through the hose using high air pressure. Once cleaned, the hose should be capped before it leaves the hose assembly area at the shop.
Using the relatively new extended-life hydraulic fluids can minimize opening up the hydraulic system. “Caterpillar now recommends and factory fills hydraulic oil that can be used up to 6,000 hours between changes,” Gruber says. “It can also be used in older equipment.”
Regardless of type of hydraulic fluid, he recommends analyzing samples every 250 hours in terms of its lubricating properties and the type and amount of contaminants and correcting any problems.
A special high-efficiency filter can be used to remove contaminants as small as 5 microns to help keep the hydraulic system clean. Such a filter should be used for no longer than 250 hours before being replaced. A kidney loop or filter cart, which removes and cleans the oil before returning it to the hydraulic system, can be used to restore contaminated hydraulic systems to recommended cleanliness levels. “Once the contaminants have been removed, then a standard hydraulic oil filter should manage filtration very well,” Gruber says.
Use the right attachment—Hooking up and disconnecting dirty hydraulic hose couplings when changing attachments can introduce foreign material into the hydraulic system. Dirt can also sneak into the system when the machine is used with an improperly sized attachment. For instance, using a tool, such as a hydraulic hammer, that requires more hydraulic cooling capacity than the machine can provide, can cause the hydraulic fluid to overheat and, ultimately, damage the machine’s hydraulic pumps. At the same time, a machine with too much power can overwork the attachment. Either way, the result is excessive wear and shorter life of hydraulic components.
Eliminate air—Hydraulic systems can be contaminated and damaged by air mixing with the oil. As aerated oil goes to the pump, the air bubbles implode, eroding the housing or plates. This contamination goes to the control valve, creating wear. Hydraulic reservoirs normally are pressurized. Besides helping to keep dirt and water out, the pressure pushes on the oil to force air bubbles up out of the oil. “You can always tell a machine is cavitated or aerated just by listening to the high pitched whine,” Pipkorn says.
“Air in the servo system can also make a good operator look bad,” he continues. “Unlike oil, air is compressible. If there’s air in the control-valve servo caps, your function will hesitate and then start with a jerk every time. This is caused when air in the hose compresses to the point where it develops enough pressure to push the spool and the spool jumps. The air can get in just by changing a hose on the boom or hooking up attachments like a hammer. Usually, you can bleed the air out by cracking a bleeder loose.”
Installing a new pump without taking the time to put oil in the case to get the air out can be especially costly. “With no oil in the case of the pump to lubricate the moving parts, a new pump self destructs and you’ll find lots of contamination in the hydraulic tank,” Pipkorn explains.
Minimize condensation—Water is another contaminant that can harm the lubricating characteristics of hydraulic fluid. “Keep the hydraulic reservoir topped off with fluid to the OEM's recommended level,” says Moseley. “The more air space in the tank, the greater the likelihood of moisture forming. Proper levels minimize that and, of course, improve hydraulic system performance and longevity by minimizing fluid heat buildup as well.”
Check performance—Manufacturers recommend checking hydraulic pressure, cycle times, and regulation of pumps periodically, such as during a regular 2,000-hour maintenance service.
“This will help to detect any loss in performance over time that may not be obvious on a day-to-day basis,” Pipkorn says.
“It will keep your machine running more efficient. This is something that your own mechanic can do.”
Replace hoses in a timely manner—“Equipment operators tend to run hoses to the point of failure,” reports Moseley. “The sudden loss of fluid from a ruptured hose could damage hydraulic pumps. The same thing could happen if the operator fails to notice a more gradual rupture and loss of oil and continues to run the machine.”
Fix the leaks—Leaking hydraulic systems can cost you in several different ways. Oil dripping onto machine surfaces or pavement can increase the risks of falls and injuries. Oil leaks also attract dirt. When it accumulates on hydraulic system components, it can cause the fluid to overheat. And that can degrade the fluid’s lubricating qualities, causing excessive wear and introducing metal particles, which can lead to even more wear of hydraulic pumps, motors, and such.
Use top-quality parts—When replacing hydraulic consumables, like filters and fluid, or parts of individual components, your best bet is to use OEM parts, since the machine’s manufacturer wants to minimize warranty claims
For example, Pipkorn compares two brands of filter. The one that meets OEM requirements may remove particles as small as 10 microns in size in order to perform properly between recommended oil and filters changes. Another brand may cost less, but it may only remove particles larger than 20 microns, increasing the potential for damaging the system.
Go by the book—The best way to keep your hydraulic and your electrical systems in good repair is to follow the preventive maintenance steps detailed in the equipment owner’s manual, suggests Moseley.
“That should be your starting point,” he says. “All the maintenance recommendations are right there.”
Owners’ manuals often include a list of maintenance items for the operator to check on a daily basis, Moseley notes, If not, he suggests making up your own operator’s pre-shift inspection list. It should include such vital checks as ensuring fluid levels are correct, noting and reporting any fluid leaks and making sure everything is tight.
“It’s easy to assume that operators know to do this,” Moseley says. “But unless you document each of these simple checks, an operator could overlook them.”