Fig. 1
Hydraulic hoses such as these are subject to high pressure, sometimes between 3,600 psi and 5,000 psi or higher. Preventing the hoses from being compromised is a critical component of maintaining the equipment.

Hose Replacement: Do it Right the First Time

Hydraulic hoses are tricky, but here are some tips if no fluid-transfer pro is available in your area.

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All of those excavators, loaders, bulldozers, and other heavy machinery typically working at a construction site have a common vulnerability: They’re only as reliable as the hoses through which all of that hydraulic fluid travels. A sudden rupture not only halts work abruptly, but can also cause a spill that endangers the surrounding environment. It can happen without warning. And even if the hose doesn’t rupture, high-pressure hydraulic fluid leaks can seriously injure workers.

When a hydraulic hose does fail, you have two options. One is to have a member of the team carefully attempt to replace the hose. The other option—and the one that’s more reliable and far safer—is to have a hose professional come out and replace the hose. The hose pro knows the ins and outs of hose replacement and has the right equipment experience to get the job done according to specifications.

Some equipment managers keep a stock of hoses and a crimper for such emergencies as this. But simply having those tools isn’t enough. Knowledge and attention to detail are critical. Improper technique in replacing a hydraulic hose can lead to a host of future problems with the equipment.

Anyone who attempts to replace a hydraulic hose must have the proper training. It may seem like a simple, straightforward procedure, but there’s more to it than people think. If your supplier provides such training, take advantage of it. Make sure the person replacing your hoses knows how to do it properly.

If you do opt for a do-it-yourself remediation of a ruptured hydraulic hose, proceed with care. Educate yourself, because there’s more at stake than just the hose. Anyone at your company working with hydraulic hose should have a Fluid Power Connector & Conductor Certification from the Fluid Power Society. This program is intended for those who fabricate, assemble, and test hose and assemblies. Connector & Conductor Certification requires a three-hour written and a three-hour, hands-on job performance test.

Keep it Clean

Cleanliness should be a top priority. The close tolerances in hydraulic valves, pumps, and actuators make clean parts critical when fashioning a hose assembly. Contamination is always a danger during hose replacement. This has held especially true since the advent of sophisticated electronics in pump systems—it now takes considerably less contamination to trigger a failure.

These contaminating particles come from a variety of sources. Some originate in the tank and make their way into the hydraulic hoses. Others result from erosion within the system, whether from chemical breakdown or friction over time. One of the most serious and prolific sources of contamination remains the hose-cutting process itself, but more on that later.

Even when the person doing the work is careful, fine particles can end up in the hydraulic fluid. In addition to keeping the hose itself clean, make sure the entire bench is free of grit and contaminants.

PIRTEK technicians fire foam pellets straight through the inside of the hose, wiping it as clean as it can be. But in the absence of such technology, take every precaution to ensure the inside and outside of each hose is as free from particles as possible. Blowing compressed air through the hose can remove many of these particles. Some technicians also have a system in place that vacuums up debris during the cutting process to minimize contamination of the hose’s interior.

Flushing with liquid is another common method of cleaning a hose. Use a solvent that is compatible with the hose materials and the hydraulic fluid to avoid damaging the hose or contaminating the hydraulic fluid. Proper fluids are designed to evaporate quickly, and some even remove lubricants left behind by the manufacturing process.

Age takes its toll on hydraulic hoses. Sunlight and heat can accelerate damage to the outer covering, which exposes the reinforcement to the elements and can lead to hose failure.

The Newer, the Better

A second consideration is the age of the hose stock. Be sure the hoses are relatively new, not several years old. Rubber dries out over time, as evidenced by tires, which carry a date of manufacture. Aged rubber becomes susceptible to cracking and begins to deteriorate, losing much of its integrity. This degrading of a rubber hose is hastened by overheating. Heating and cooling over time—the wide span of temperatures—can punish the inside of a hose, creating fissures that lead to failure. Therefore, be sure to use hoses with ratings consistent with the fluid temperatures.

As hydraulic hose assemblies age, the outer cover can deteriorate with extended exposure to sunlight or heat. This cover is designed to protect the reinforcement, which must withstand a high-pressure flow of oil. Hydraulic systems commonly have working pressures between 3,600 PSI and 5,000 PSI, and in some cases, much more. If the cover is compromised, the wire reinforcement is exposed to the elements. This leads to rust, creating a weakness that these high pressures soon expose. The resulting failures usually occur without warning.

The stiffening of a flexible hose is one warning sign that a hose is too old or is succumbing to heat-induced failure. Sometimes you can bend it and hear cracks forming inside. Obviously, you should discard such a hose. An old hose can look fine on the outside while the inside is honeycombed with cracks. That’s because the inside and outside of the hoses are made of different materials. So, don’t rely solely upon visual inspections. A hose should have information printed on it indicating its date of manufacture. Check this information before using the hose for replacement.

Use the Right Tools

When cutting hose, avoid using a normal serrated blade. This kind of abrasive cutting can and will leave particles in the assembly that ultimately end up in the equipment’s hydraulic fluid. Instead, use a saw made specifically for hydraulic hose. Two basic designs are available. One is a blade with teeth that appear to face backwards when compared to a saw blade for, say, wood. The other is similar to a knife blade without teeth. Both are designed to cut the hose cleanly without any grinding and residue.

Also, the cut should be at a 90-deg. angle. The end of the hose should lie flat inside the fitting, making a tight seal. A diagonal cut compromises the fit by preventing the end of the hose from fitting over the entire length of the mating surface on the fitting.

The next consideration is crimping, which must be consistent with the manufacturer’s specifications. Maintaining modern equipment is important because each hose requires a certain die set for the crimping process. These die sets can wear and no longer meet specifications over time. An improper crimp—even with a small variation—introduces yet another risk factor to your expensive equipment.

Ken Adair is the owner of PIRTEK O’Hare, PIRTEK McKinley Park, and PIRTEK Bolingbrook, all in the Chicago area.

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