By Josh Cosford
Because it is impossible to physically stack every component of a hydraulic system like a Jenga tower, plumbing is required to direct hydraulic energy through the circuit. Pipe, tube and hose are required to channel fluid through the system, and the requirements of the system must be reflected in the choice of conduit.
Hydraulic hose is the most commonly used conduit, especially on mobile machinery, and is mandatory should any bending or movement in the mechanism require it. Hoses are multi-layer construction, most often with synthetic rubber such as Nitrile and strengthened with braided steel, although synthetic and textile braids are used as well.
The pressure rating of hydraulic hose is a result of the number of braid layers and the nature of their construction. The SAE has created standards for hose construction, which dictate specifications for pressure, temperature and type of fluid being used. As you would imagine, the more layers of braided material used, the higher the pressure the hose can withstand. Consequently, hose with four or six layers of steel braiding is quite stiff, so consideration should be taken for bend-radius requirements when choosing hose.
Consideration should be taken for diameter when selecting hose to ensure pressure drop remains in check; pressure drop is so often overlooked in a hydraulic system, and the energy wasted can be extensive. However, just as the layering of braids can affect the rigidity of hose, so too can its diameter. Hose manufacturers publish the bend-radius of their hose, and most manufacturers carry a short bend-radius hose in their product line, although it is often more expensive.
Specialty hose is available for demanding applications, such as for use in high heat or with exotic fluids. Steel braiding in a hose transmitting high water-based fluid is bad news, as internal corrosion will occur and will go unnoticed. Hose can also be had with non-conductive construction, to ensure the hose does not transmit electricity when installed on a machine working on electrical utility jobs.
The most common hydraulic hose is the 100R1 and 100R2 construction types, with one or two layers of braided steel respectively. These hose types are not suitable for every application, so consult with industry professionals when choosing your hydraulic hose.