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10-Minute Hydraulic Inspection Plan
Tim Deans holds what is left of a hydraulic hose. He is making a point: The exploded section of hose (shown at right) illustrates what happens when a hydraulic system is taken for granted, the engineer with Gates Corporation says. “Hydraulic hose, for example, is built with a four-to-one safety factor. It is built to operate even if severely deteriorated, like when its cover is gone and the underlying wire braid is rusting. That’s why hose is often taken for granted. It keeps working even when it needs to be replaced.”
When such a hose blows in the field, hours or even an entire day could be lost making repairs. But imagine something worse. What if that hose supplies the transport wheels’ cylinders on a piece of tillage implement running between fields? “Or worse yet, what if it fails with you standing next to it?” Deans queries.
Avoiding such disasters is really quite simple, Deans suggests. “Grab a pad, pen, and paint marker and walk every piece of equipment prior to the season. Inspect all the components on their hydraulic systems to look for problems,” he advises. “Better to find and fix a problem in the shop than in the middle of a field.”
A thorough inspection of most implements shouldn’t take more than 10 minutes. Begin by always releasing the pressure in any system. And then starting at the hitch, work your way back to the component (cylinder, orbit motor, etc.) being supplied.
Mark needed repairs such as a crushed hose or cracked fitting with the paint marker. “Use the pad and pen to write down developing problems not needing immediate repair. You can check those items the following winter in the shop,” Deans explains.
Abraded, cracked, and crushed hose
The arteries of any system, hoses are often the most abused and overlooked component on implements. During your inspection, examine the length of all hoses looking for wetness “which can indicate a puncture into the hose,” Deans explains. “You will also want to look for abraded, cracked, crushed, or punctured hoses, all of which call for replacement.”
Cracking of the cover – either by weather or high operating temperatures – indicates the hose cover is jeopardized. “These three hoses are all suspect,” says Deans, referring to the hoses shown in image 1. “Starting from the right, I would characterize them as fair, worse, and terrible.”
The fair hose (on the right) shows the beginning of weather checking, where the sun has started to leach out plasticizer compounds in the rubber cover, making it brittle. “Unless it is leaking, it won’t need replacing. Certainly reexamine it next year,” Deans says.
High operating temperatures can also lead to leaching. “You would see this in an area where the hose was crushed or pinched,” he says. “That restriction increases the heat in that area, which leads to the cover cracking. An increase of just 18°F. above the maximum rated operating temperature can decrease hose life by half.”
The cover on the “worse” hose (in the center) has become extremely brittle. Its cover will start flaking off, eventually leading to the condition presented by the “terrible” hose. “That is an automatic replacement. The steel braiding, which is the structure of the hose holding in pressure, has started to rust. This hose is primed to fail at any time,” Deans says.
When inspecting hoses, look for cracks (like those shown in image 2) as well as abrasions. In the latter case, look around to determine what is abrading, or scraping, the hose, “and eliminate it. It could be hoses rubbing against each other or against metal parts on the implement or vehicle mounting points,” Deans explains.
Another inspection point is to see if the hoses are mismatched as shown in image 3, “particularly if you bought the equipment used and the hoses were replaced at some time. It is crucial that hoses are sized to that implement’s needs,” Deans says. “Find that information in its operating manual. Or you can call a Gates engineer (gates.com) for help figuring out hose sizing.”
The last item during the hose inspection is to watch for twisted or distorted hoses, as shown in image 4. Twisting misaligns the steel reinforcement of a hose, reducing its ability to withstand pressure, Deans warns. Twisting a high-pressure hose by as little as 7° can reduce its service life by as much as 90%.
The solution here is not replacement but rather loosening the hose to eliminate the twist. “If the twist is happening during movement, such as when the implement is being folded, then use elbows and adapters to eliminate the twist,” he advises.
Finally, for a hose not showing obvious distress, check the condition of its cover by pressing a ballpoint pen into the rubber, Deans says. The pen shouldn’t permanently indent or penetrate the cover. “If it leaves a mark, then write it down in the pad for reinspection next year.”
Size up couplers and fittings
Deans admits the example shown in image 5 is an exception. “Obviously, these fittings came off a hardware store shelf. Someone was making due at the time, grabbing what was available. Galvanized water pipe fittings are never acceptable on hydraulic systems,” he warns.
Primarily what you are looking for with fittings is leaking. “Now, you may not consider a leak to be a big thing,” Deans says, “but any leak is lost horsepower and a reduced ability for the hydraulic system to do work.”
A fitting leak such as that shown in image 6 can also introduce dirt into a hydraulic system. There are any number of causes for a fitting leak. “It may be simply that the fitting has loosened over time by use and vibration. Retightening may solve the problem,” Deans advises.
Another cause of leaks could be a missing or damaged O-ring, damaged threads or seat angle, thread misalignment, or incompatible thread ends or seat angles.
You can remove the coupling and inspect it with these five steps:
- See if there is a missing O-ring (if the coupler uses an O-ring). Check for damage caused by installation or material breakdown from heat.
- Check threads and or seat angle for damage that may have occurred during installation. Any ding or burr in the threads may be a potential leak path.
- Examine if the coupler was misaligned during installation. In this case, the threads may have been damaged, which will require that the coupler be replaced.
- Determine if any incompatible components were employed. Use a thread identification kit to identify mating components.
- Finally, look for signs of overtorquing. This can cause threaded connections to stretch as well as damage mating seat angles. Overtorquing also damages the staking area of the nut and causes cracking of either the nut or seat. “Undertorquing, on the other hand, does not allow proper sealing,” Deans warns. “Always use a torque wrench when installing or retightening any coupling.”
Finish your inspection by sizing up cylinders and orbit motors. “With these items, you’re mostly looking for leaks (shown in image 7),” Deans says. “You may need to replace the cylinder whipper seals, for example. The point is to eliminate leaks.”