If you have a front end loader on your tractor, you’ll know how handy hydraulics are. Pressurized oil can lift amazing weights and allow you to operate large equipment with a degree of accurateness that can be measured in inches, maybe less. But, if you’ve ever had a hydraulic hose fail, you’ll know how quickly all work stops.
During regular operation hydraulic systems on the pieces of equipment are stressed with expansion and contraction, and it is the weakest link that most often fails. Hoses are usually the weak link as they are positioned at the flex points of the system and commonly in a vulnerable position. Combined with the strains of the pressure there are all the environmental issues (mud, sun light, branches, etc.) and hoses are often overlooked on the maintenance check.
Testing hydraulic hoses can be as easy as holding a piece of paper several inches from the line while the equipment is running and looking for evidence of a spray pattern. I have found that a thorough visual check is just as effective. Wiping the hose clean while flexing it with your hands will usually reveal cracks or deterioration. Failing that, your daily walk-around will reveal oil on the surface of lines or at fittings and a drop of the fluid level in the reservoir.
While operating my tractor I caught the view of one of my hoses with a long split revealing the pink inner wrap—time for a replacement. For replacement I start with positioning (when possible) the damaged hose in an “unloaded” position which means articulating the cylinder so that the minimum amount of oil is loaded in the hose end where the replacement is to take place. This prevents a minimum amount of oil loss.
The equipment should be immobilized, meaning that the weight of the equipment is transferred from the cylinder to blocks or stands preventing cylinder pressurizing. Next, with my catch basin in place and wearing a face shield and heavy gloves, I slowly undo the fittings starting with the JIC and then the NPT (see sidebar). Remove the hose and let it drain. It is a good idea to cap the cylinder ports with something to prevent contaminants from entering. Replacement is just the reverse starting with the NPT and then the JIC with a couple of don’ts:
--don’t over tighten the hose fitting to the cylinder ports;
--don’t use any pipe sealants; you want metal-to-metal contact in the fittings.
There are three types of cylinder actions: single, double and telescopic, bleeding air from the system is not necessary in double acting cylinders but may be needed in single acting cylinders if the reservoir is above the bottom end of the cylinder.
Your equipment manual will provide the oil type. It is essential that you follow this recommendation as the different pumps use different viscosities. Using the wrong oil will cause damage to the components.
Safety and hydraulics
Last winter my cousin, Barry was snow plowing with his tractor in the dark and was forced indoors suffering from severe cold. As it turned out one of his hydraulic hoses had split and saturated his insulated work wear with quarts of oil which had seeped through to the skin.
Luckily for Barry, the break in the line discharged the high pressure fluid onto his thick work wear instead of onto bare skin as the trauma (medically called hydraulic injection injury) may have resulted.
This uncommon life-threatening injury requires immediate emergency surgery and can be incurred with pressure as low as 100 PSI. Victims often complain of feeling a prick sensation that they associated with being stabbed with a wire.
Never touch a pressurized hose bare handed if you suspect a leak; when checking for leaks a full face shield is a must along with heavy leather gloves. It is recommended that a data sheet for the hydraulic oil you use be kept on hand where you use it in the event of an accident so that it can accompany you in an emergency.
Hydraulic fittings
There are four basic types of fittings for hydraulics:
Compare replacement hose (left) to old hose (right) to ensure proper ends
National Pipe Thread (NPT), Joint Industry Council (JIC), O-Ring Face Seal (ORFS) and O-Ring Boss (ORB) all available with male and female ends. It is imperative that when replacing lines you marry the types together as this ensures a proper seal which prevents leakage. To the unfamiliar eye some look like the proper type and will attach together, but will not seal. The photo shows two different types that look similar, the new line (NPT) and the old line (JIC).
- Dan Kerr