Guidelines for Proper Hose Installation

Hydraulic hose failures take several forms: failure of the cover and wire reinforcement, pulling loose from the fittings, bursting from over-pressures, and abrasion.

When selecting hose for use on an application, itís essential to know the system pressure, including pressure spikes. Pressure spikes greater than the published working pressure will shorten hose life and must always be taken into consideration. Typically minimum burst pressure rating is four times that of the maximum working pressure.

When fabricating hose assemblies, it is significant to note that hose manufacturers do not necessarily test their product with other manufacturerís fittings or fabrication and assembly equipment. Interchangeability of hose, fittings and assembly equipment is beyond the scope of most hose designs and could lead to hose failure.

Twisting a high-pressure hose only 7 degrees may reduce its service life up to 90%. When hose installation is straight, allow enough slack in the hose line to provide for length decreases, which occur when pressure is applied. If hose assemblies are too short to permit adequate flexing, service life will be reduced.

Hose can elongate by 2% or contract by 4%, depending on hose construction. Length contraction will occur under pressure impulses. Routing must take this into account.

Improperly assembled fittings can separate from hose and cause injury and/or property damage. Elbows and adapters should be installed so as to relieve strain on an assembly and still be reasonably accessible for inspection and maintenance.

When routing near hot engine manifolds, a heat shield is advisable.

The illustrations indicate proper hose routing. Following these recommendations should keep your hoses in good condition and maximize your hose's life.

- Article excerpted from Hydraulic and Pneumatics, May,1997, and Off-Highway Engineering, October 1997

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