Hydraulic hose is the medium that conveys fluid throughout a hydraulic system. These conveyed fluids are usually at extremely high pressures, from 3000 psi to as much as 10,000 psi. Exposure to high-pressure fluids is dangerous and can cause serious injury and even death, so great care must be taken when designing hose systems and working with them. The hose itself can also be a danger, if not contained and secured properly.
Keep an eye on pressure
Hydraulic hoses are available in a variety of styles and pressure ratings for different applications. It is critical that the correct hose is chosen because a hose designed for a 1000-psi system and used in a 1500-psi system could quickly and easily fail. Proper selection reduces the risks of hose burst and catastrophic failure. If a hose bursts, it can cause injection leaks, burns and other potential injuries.
In addition, hoses should be inspected regularly for leaks. One should never check for leaks or damage to a hose by feel; even small pinhole leaks at 3000 psi can puncture the skin. Fluid injection wounds like these can cause serious injury, amputation and even death if the wound is not treated immediately.
In this vein, slow hydraulic leaks should also be prevented. Safe options exist for checking hose leaks—these can include something as simple as inserting a colored dye into the hydraulic system and checking it with a UV light. If you see colored fluid at any connections or elsewhere on a hose, shutdown is critical.
In addition, if the pressure is higher than the hose can handle or if the hose is not installed correctly and/or secured properly, hose whip can occur. Hose whip is extremely dangerous, as it can strike operators or other personnel near the machine and cause damage to other equipment as well. Proper installation can help prevent this—for example, specifying the correct length helps give the hose enough room to flex and provides a proper bend radius so it is not pulled beyond its limits. During operation, hose may lengthen by up to 2% and shorten by up to 4%. Most manufacturers list their minimum bend radius in their spec sheets. Minimum bend radius is half of the smallest diameter the hose can be bent without internal damage or kinking. Finally, something as simple as installing the hose along its natural bend radius so it does not contract unnaturally will help maintain hose life.
Along these lines, when assembling couplings and fittings onto a hose, one must ensure they are inserted fully into the hose. Coupling blowoff not only means you have a small metal item that becomes a high-speed projectile, but it can cause pressure and fluid leaks at high pressures, as well as hose whip. Use the right tools to measure how far a coupling must be inserted to ensure it is properly and fully crimped onto a hose.
Check the temperature
When running, a hydraulic system operates on average at about 150° to 180° F. To avoid burns, be careful not to touch the hose or fittings when the system is operational. In addition, most hydraulic fluids are flammable. If a leak or spray of fluid is exposed to an ignition source, it can catch fire. Take caution when routing your hose. It should not be near electrical sparks, flames, exhaust manifolds, or engine blocks, etc.
Heed manufacturers’ instructions
When designing a hose assembly, one of the first things you must know is that mixing hose and couplings from different manufacturers is not allowed. Manufacturers design their hose and couplings to work together. Reading all manufacturers’ spec sheets and installation instructions is critical. And keeping those instructions and spec sheets is just as critical to guarantee that replacement parts are consistent.
Finally, electrical shock is not unheard of with hydraulic hose. Boom lifts and other equipment that are used around electrical lines require the use of non-conductive hydraulic hose. If a normal hydraulic hose is used, it more than likely features wire reinforcement, so is inherently conductive.
Special thanks to Eaton Corp. and Gates Corp. for help with this article, as well as NAHAD’s Hose Safety Institute Handbook. For more on hose safety, visit NAHAD or the Hose Safety Institute at www.nahad.org.