Gates LifeGuard Hydraulic Hose Protects Life and Limb

Protective covers for hydraulic hose assemblies take on a whole new meaning with the Gates LifeGuard line-of-sight sleeving system. The need for higher-pressure systems to power and control ever more compact machine designs have forced design engineers to look for ways to safely protect operators, bystanders, and equipment in the event of a catastrophic hydraulic hose failure.

First and foremost, the best way to protect a hose assembly is to route it away from hose-to-hose and hose-to-metal contact; the second option is to specify a hose made of special hybrid compounds (like Gates MegaTuff hose), some of which can last up to 300 times longer than standard rubber hoses. Further options for abrasion protection employ some sort of protective sleeve, which can include:

Metal spring guard: this is typically used when an exposed hose may encounter flexing, twisting, kinking, tensile or lateral loads, vibrations, or must be bent around a tight radius. The metal spring guard must be fitted before the hose is assembled.

Plastic spring guard: this type of guard is also used on exposed hoses, but unlike the metal spring guard, the plastic variety can be fitted after the hose has been assembled, and in some cases, even after it has been attached to the equipment.

Textile (nylon) sleeving: this type of guard is used on hoses housed within the process equipment, or in places where abrasion is likely to occur. Textile sleeving offers wear resistance second only to certain types of metal spring guards, and can reduce the amount of fluid spillage.

These types of sleeve covers are designed to protect the hose from abrasions and cuts, however it should be remembered that they are designed to protect the hose, rather than the operator, from bursts and pinhole leaks. Excessive pressure surges, flexing, kinking, crushing, and exceeding the minimum bend radius can cause a hose to burst away from the hose ends. Surges that exceed the hose’s maximum operating pressure rating can cause reinforcement failure; excessive flexing, kinking, and crushing can cause the reinforcements to fatigue and eventually fail; exceeding the minimum bend radius will cause excessive strain on the reinforcements and could open large gaps between strands of reinforcing material, severely reducing the ability of the hose to withstand pressure.

Pinhole leaks in a hydraulic hose that is under pressure can release toxic fluid at more than 600 feet per second – over 400 miles per hour – towards operators, bystanders, and sensitive equipment. Although it’s the high-tensile reinforcement of the hose that suffers the majority of this force, the inner tube itself has to bridge the gaps in the braid, which are formed when the hose is bent and stressed. If this compound isn’t strong enough (i.e. not enough tensile strength), which is often the case, it will be blown through gaps in the braid. This causes a scissoring effect and cuts a hole in the tube, resulting in a pinhole leak. The pressure in the hose hasn’t decreased, but now the fluid is forced through a very small opening, which dramatically increases its exit velocity. The resulting fluid jet can act like a hypodermic needle, and can penetrate protective clothing and skin.

To protect operators of hydraulic equipment from catastrophic hose failures and pinhole leaks, several manufacturers have developed specialized versions of “line of sight” textile sleeving. However, specifications regarding 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 50°C, 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. However, 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.

In the absence of specific industry regulation, Gates Corporation has developed its Lifeguard sleeve following a rigorous testing program that could establish future standards for hydraulic hose failure protocols. The LifeGuard sleeve 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 inside sleeve layer is made of nylon fiber that elongates or stretches up to 20 percent. By stretching, it can absorb the energy of a burst or pinhole leak. The outer sleeve contains the fluid and redirects it to the clamped ends. The outer sleeve is resistant to abrasion, but is not specifically designed for abrasive environments. Worker safety within a three-foot line-of-sight of a burst or pinhole leak is the primary benefit. The sleeve is secured at either end of the hose with special “channel” clamps. The clamps allow leaking fluid to escape, so the fluid won’t collect behind the sleeve and cause it to burst. Fluid leaking past the clamps lets the operator know that there’s a leak in the hose.

LifeGuard sleeving protects operators from 3,000 psi pinhole leaks and 6,000 psi bursts on -4, -6 and -8 hose sizes. The sleeving is compatible with a wide range of fluids, including environmentally friendly liquids and biodiesel fuel. It protects up to 212°F, the SAE standard for most industrial hydraulic applications. Gates LifeGuard line-of-sight sleeving is a safe, effective, economical alternative to other costly metal, plastic and nylon shielding.

For more information on LifeGuard line-of-sight sleeving and other Gates hydraulic products, visit www.gates.com/lifeguard.