When an operation relies on hydraulic hose, evaluating it for potential abrasion is paramount. Industry and user experience agree 70% of failures are a direct result of abrasion or external damage—yet many could be prevented. Since hose is critical to performance and other operational metrics, hose design and accessories that protect it become critical. Often this makes one wonder which hose cover or accessory is the best. And, as is often the case with so many variables in an operation, the answer is “it depends.” While some standards, such as ISO 6945, can be poor indicators because of variability, human judgment and field experience seem to be better guides. Let’s walk through the options:
- Assess the application. Abrasion will not occur without relative movement. Products, such as looms, keep hoses separate from one another and can prevent hose-to-hose rubbing. “Elbow pads” found in high-density plastic can be strapped on the hose at strategic points. Passages through which a hose is inserted can be protected with isolators of plastic or rubber. These separate the relative motion created between the surface causing the abrasion of the hose. Brackets supporting the hose can be a good means of controlling rubbing points, but flexure and movement within the bracket can be an issue. Furthermore, the nature of the abrading surface can affect the potential for failure. Determine whether it is a broad surface contact or edge rubbing.
- Evaluate the outside hose cover. Covers can be smooth plastic (nylon thermoplastic hose), a textile such as nylon braid, or more traditional rubber-covered hoses. A smoother cover is less prone to snag. Thermoplastic hoses offer this characteristic, as well. A textile cover can snag easily, but can also be impregnated with plastic resins that decrease friction and increase wear resistance. Rubber covers vary from traditional neoprene to plastic/rubber blends, and the high-end thin polyethylene (UHMWPE) sheath is part of the cover. The latter two cover styles are highly abrasion resistant and benefit from a low coefficient of friction provided by the plastic. The industry typically uses the ratio of 1:8:600+ on the relative abrasion resistance of these categories of rubber covers, with the UHMWPE seen as the premier solution although stiffer and more costly.
Sleeves can supplement the cover and be placed along the length and circumference of the hose. These range from spring coils to woven fabric (typically nylon) to corrugated plastics, with many designed with resistance to chemicals, ultraviolet rays, and ozone attack. The selection criteria will vary by need. A coiled spring-like wire provides protection to blunt-force impacts but is prone to snagging. A woven nylon sleeve can be very abrasion resistant as with a textile hose cover but will be prone to bunching and snagging. These sleeves can have the added capability to resist pinhole sprays of high-pressure fluid.
So while the question of which cover or accessory is best is answered by “it depends,” if the user combines good judgment and practical field experience, effective selections can be made to create a balance in hydraulic flow and abrasion performance.
by Eaton Corp., (www.eaton.com)