Factor of Safety (FOS)

Hydraulic Hose Assemblies have a rated maximum working pressure (MWP) of the lesser of the MWP of the hydraulic hose and the MWP of the connector terminations.

Hydraulic Hose has a finite life. The lifespan of Hydraulic Hose Assemblies is affected by many factors (see ‘Hose Selection’and ‘Safety Guide’ pages 488 to 493, and RYCO HALP. program page 23). Three limiting factors are working pressure, temperature and impulse pressures (pulses). High Impulse Pressures will fatigue hydraulic hose and consume their life.

Fatigue life is specified by a logarithmic P-n curve, where P = Pressure and n = Impulses. Hydraulic hose assemblies require a FOS (Factor of Safety) of 4:1.

Factor of Safety Impulse Curve

Impulse Curve for EN853-2SN (SAE 100R2AT)

This implies that an unused hydraulic hose assembly has to be able reach four times its MWP (4 x MWP) once only (one pulse).

Depending upon the specification requirements of the hydraulic hose, the Hydraulic Hose Assembly (be sure to use couplings that are MATCHED to the hose) must pass an Impulse Test (fatigue life test) at a specified percentage of the hose

MWP for a specified number of pressure impulses. In the example above we see that EN853-2SN requires 200,000 impulses at 133% of its MWP (rated pressure). Impulse Tests are generally conducted with fluid heated to the maximum rated operating temperature of the hose.

RYCO Hydraulics Connector Terminations have a FOS of 4:1.

Factor of Safety Hose Assembly