A pinhole leak in a hydraulic hose under pressure releases toxic fluid at more than 600 ft/sec - approaching the muzzle velocity of a gun. The fine jet of pressurized fluid acts like a hypodermic needle. At short distances it can penetrate both protective clothing and skin. Although it creates a seemingly superficial wound, the poisoning that results can threaten life and limb if not immediately treated.
Hearing about such accidents, many users of hydraulic tools, including railroads, utility line crews and construction companies, are motivated to explore ways to better protect employees who work in close proximity to exposed hydraulic hoses. One of the tools commonly used by workers in these industries is a pole tamper. The pole tamper is connected to a hydraulic whip hose about 5 ft long, which in turn connects to the hydraulic line. Operating pressure inside the hose can reach 2,000 psi. The whip hose is often used as a handle to maneuver the pole tamper, so it's subject to over-flexing and kinking, exceeding the minimum bend radius requirement. While the hose is not designed to be used in this manner, it happens frequently in the field. Even when operators are not holding the hose itself, the line can be within inches of their face or body as they work the pole tamper by the shaft.
Ordinary nylon sleeving and protective hoses are often attempted as solutions, but neither can contain a pinhole leak. So many companies have discovered Gates' LifeGuard(TM) Line-of-Sight Sleeving System. Unlike other types of hose guards, wraps and sleeving, LifeGuard sleeving is a safety product. It protects hoses from 3,000 psi pinhole leaks and 6,000 psi bursts on -four (1/4 inch), -six (3/8 inch) and -eight (1/2 inch) hose sizes. The sleeving is compatible with a wide range of fluids, including environmentally friendly liquids and biodiesel fuel. It protects up to 212F, the SAE standard for most industrial hydraulic applications.
LifeGuard sleeving is comprised of two nylon layers. During manufacture, the two sleeve layers are continuously woven at the same time, one inside the other, but they are not attached to one another. The inner layer is made of tightly woven, extruded filament nylon designed to absorb the energy of a hydraulic hose burst or pinhole leak by stretching or elongating up to 20 percent. The outer layer is a bolt-cut, air-textured nylon material that contains escaped fluids and redirects them to the clamped ends of the hose. The outer sleeve is resistant to abrasion, but is not specifically designed for abrasive environments. The primary benefit is worker safety within a 3-ft line-of-sight of a burst or pinhole leak.
The sleeve is secured at either end of the hose with special "channel" clamps. The clamps allow leaking fluid to safely escape, so the fluid won't collect behind the sleeve and cause it to burst. Fluid leaking past the clamps lets the operator know there's a leak in the hose.
Current standards and specifications relating to hydraulic hose protection are vague. ISO 3457 and EN474-1 state, "Hydraulic hoses containing fluid with a pressure of more than 5MPa (50 bar) and/or having a temperature over 50C, and which are located within 1.0 m of the operator, shall be guarded."
Mining industry equipment must conform to Mine Safety and Health Administration (MSHA) standards and be certified. MSHA's Accident Prevention Program simply says, "Install abrasion protection such as spiral wrapping, sleeves and guards." ISO and European standards don't specify a test method for sleeving products.
While there are no current industry regulations, Gates Corp. developed its LifeGuard (patent pending) sleeve following a rigorous testing program that could likely be used to establish future standards for end-user applications. The LifeGuard sleeve has been tested both in the lab and in the field to verify its performance and capabilities at typical fluid pressure and temperature levels.