What is in this article?:
- Hose installation
- Other important considerations
You can make equipment more reliable and easier to maintain simply by following hose installation guidelines prescribed by manufacturers.
Other important considerations
Most hydraulic hose is wire reinforced, which makes it an electrical conductor. For equipment that may be used near power lines or where hose will be in close proximity to flammable solutions that could be ignited by static electricity discharged from the hose, manufacturers offer non-conductive hose.
In other applications, static electricity sometimes may be discharged through the hose wall to surrounding surfaces. This is caused by conducting electrostatic charges from the fluid through the hose's metal reinforcement and cover to adjacent surfaces. Consequences can include localized burning that weakens the hose or even produces pin-size holes in the hose wall. In this case, hose with a conductive tube may be called for to conduct electrostatic charges to hose end fittings rather than through the hose.
Just as twisting can dramatically shorten hose life, so can excessive heat. Heat from external sources, such as exhaust components on mobile equipment, can quickly soften or embrittle the hose wall from the outside in. Therefore, it is important to keep hose away from external sources of heat. If this is not possible, manufacturers offer insulated protective sleeves to partially block heat transmitted to the hose.
However, heat from an internal source — the hydraulic fluid itself — also can reduce the service life of the hose. Pumping hydraulic fluid at a temperature of only about 18° F over the maximum recommended temperature for a hose can cut its expected life in half. What makes this problem even more serious is that machine operators often are unaware that fluid temperatures may exceed manufacturers recommendations - especially if the high temperatures occur only intermittently.
Finally, strive for neat appearance when routing hoses, Figure 8. This not only prevents tangling, twisting, and rubbing together (which can cause abrasive wear), but aids maintenance by making it easy to remove and re-install hose assemblies and trace circuit routing.
Use adapters sparingly because they add to the number of components in an assembly. This increases assembly time, cost, and the number of potential leak points. However, when properly applied, adapters can simplify hose assemblies that use angled fittings (such as 90° elbows) at each end. Hose-end fittings on these assemblies must be carefully oriented to prevent twisting the hose during installation. So using an angled hose coupling at one end of the hose and a straight coupling connected to an angled adapter fitting on the other eliminates the need to carefully align hose ends during assembly.
Clean hose prevents early contamination troubles
When cutting hose to length, either a serrated or abrasive blade is used. Serrated blades cut one- and two-wire braid and textile-reinforced hose cleanly and efficiently, but usually are not recommended for use on spiral-reinforced hose because the blades would wear quickly or become damaged. Abrasive wheels cut all types of hose efficiently, but produce abrasive debris that usually finds its way into the hose. If not flushed from the finished hose assembly, this debris holds potential for serious wear and damage to sensitive components of the hydraulic system. Skiving and crimping can also produce debris that must be removed before putting the finished hose assembly into service. Skiving involves cutting a length of the outer jacket from the hose to prepare it for accepting a hose-end coupling. Crimping squeezes the coupling onto the hose's inner and outer surfaces, so some residual plating material could come off and find its way into the hose.
Compared to skiving and crimping operations, storage can introduce more and a wider variety of contaminants. During storage, dirt, water, metal particles, rust, abrasive particles, and any number of other types of contaminants may migrate into a hose sitting on a shelf. It should be obvious, then, that all hose assemblies should be cleaned before being put into service. At the very least, finished hose assemblies should be cleaned with a strong blast of compressed air. Naturally, this air should be clean and dry.
The most effective cleaning technique is high-velocity, bidirectional flushing. This floods the hose assembly with cleaning fluid until the fluid comes out of the hose as clean as when it went in. However, the cost of this equipment and the time required to flush an assembly makes it impractical for many potential applications.
A relatively new cleaning technique offers an effective and practical alternative to these procedures by using sponge-like projectiles that are shot through hose and tubing assemblies by a blast of compressed air. Equipment for this procedure is much more affordable than that for high-velocity flushing. Perhaps more importantly, though, it cleans assemblies much more effectively than compressed air alone and in a fraction of the time it takes for high-velocity flushing.
Once the hose assembly has been cleaned, be sure to install protective caps or plugs at both ends to prevent contamination from entering the assembly. These should not be removed until the hose assembly is being installed on the equipment.