Choosing the correct hose has a major impact on downtime. “Equipment operators and technicians can reduce, if not eliminate, premature hydraulic hose failure by giving maximum consideration to hose assembly selection and installation,” says Deans. “Yet, with all of the different types of hoses on the market, choosing the right one can be difficult. Gates suggests using the ‘STAMPED’ method to ensure you get the right hose assembly for the job. STAMPED stands for Size, Temperature, Application, Material to be conveyed, Pressure, Ends or couplings, and Delivery.”
Be wary of adapters that let you use a different size hose. “Adapters allow field operators to change OEM hose with a different size or type that may not be appropriate for the OEM equipment,” Deans cautions. “For example, to save money, or because a parts store doesn’t have the exact replacement hose in stock, an operator may replace a -12 hose (3/4-in. ID) with a -8 hose (1/2-in. ID), using an adapter to drop down a size.” This can have negative results. “Using the smaller size could increase the fluid velocity inside the hose, generating heat, crimping the hose, or exerting excess pressure on the coupling — all of which could lead to premature hose failure.”
Many users can be tempted to use adapters due to lack of hose availability. “The biggest offender is -10 hose (5/8-in. ID), which is not prevalent in North America,” says Deans. “Operators typically want to drop down to a -8 (1/2-in. hose ID) to save money. On a drive or control mechanism, doing so could cause the equipment to behave unpredictably.”
Also keep track of any trouble spots on the machine. “One often overlooked factor in hose replacement is frequency of failure at a particular location on the equipment,” notes Jahnke. “If a particular hose fails or requires replacement more often than average for all of the hose on that piece of equipment, it may be prudent to upgrade to a stronger or more durable product.”
He adds, “It is particularly important to follow proper installation procedures, as well as guidelines regarding minimum bend radius, twist and orientation, securement and storage. Most hose will carry either a generic SAE or ISO specification on the ‘Layline’ or a manufacturer’s product designation. For example, a SAE EN856 Type R12 is a four-spiral high-pressure hose specification, which prescribes certain levels of performance no matter who manufactures it.”
All manufacturers provide cross references between generic designations and their proprietary product numbers. “However, in some cases, a manufacturer will exceed the specification, providing even higher levels of service and longer life,” says Jahnke.
Keep the system clean
Today’s high-performance hydraulic systems utilize extremely tight tolerances that can easily be damaged by even small amounts of contamination.
“Before removing hose from equipment, spray it down with brake cleaner to remove all the oil, grease and debris,” says Deans. “This will minimize the chance of dust, dirt or grime falling into the port when you remove the hose. Use a cap or plug to close the ports on the machine while you are servicing the hose or waiting for a replacement to prevent dust or debris from being blown into the ports. If you have a replacement hose on hand, you can forego capping the ports and simply install the new hose. Use brake cleaner to clean the threads and surfaces that the replacement hose will mate to in order to avoid introducing contaminants into the hydraulic system.”
Gruber advises, “When a broken hose assembly is removed, the preferred method to keep contamination from entering the system is to install clean plastic or metal plugs and caps to cover all open hose ends, tube ends and related ports. Wrapping exposed hose ends, tube ends or related ports with clean plastic is also acceptable.”
Don’t leave anything exposed longer than absolutely necessary. “Any system port exposed to the atmosphere is a potential entry point for contaminants, so the duration of that exposure should be as short as possible,” says Jahnke.
New doesn’t mean the same as clean. In some instances, the new hose can have debris left over from the manufacturing process. “It is very important to clean new hose assemblies prior to installation,” notes Gruber. “An unclean hose assembly is an easy way to introduce contamination into the hydraulic system.”