If you run hydraulic equipment or create hydraulic hose assemblies, you’re sure to see some common failures during your career. By understanding what’s causing the hydraulic hose to fail, you’ll be better equipped to make decisions about future use and replacement. If you are or have experienced hose failure, check out the common failures below, along with their solutions
Blisters that have formed on the hose cover can be caused by unsuitable fluids that have permeated the hose tubing and gathered under the cover. Compressed gases can also permeate or flow out through the tube and become trapped under the cover. Solution: Replace the hydraulic hose with one that is recommended as compatible with the fluid being used. If it is compressed gas, the cover can also be torn, allowing the gas to pass thru.
If the equipment has become unresponsive or sluggish, cutting and evaluating the hydraulic hose will probably show that the hose tube is swollen, deteriorated or possible washed out in sections. Incompatible fluid is likely the cause. Excess fluid temperatures can cause the tube to bulge near the end of the coupling. Solution: Replace the hydraulic hose using a hose comprised of the the material recommended for that particular fluid.
Hose twist is evident by a spiraling hose label and bends in two planes. Twisting a high pressure hydraulic hose just 7 degrees could shorten the service life by up to 90%. Solution: Re-route and replace the hose to ensure that bending takes place in only one plane.
A hydraulic hose cover or tube with cracks is typically caused by exposure to excessive heat and/or ozone. Did you know that an increase of just 18 degrees above the maximum hose temperature may decrease the hose life by up to 50%? Cracks can also be cause by flexing. Solution: Select a hose that meets or exceeds the temperature and flow requirements of the application. Also, once the heat source is identified consider re-routing the hydraulic hose away from it to reduce the heat’s effects.
Coupling Blow-off is where the coupling has separated and released from the hose. The most frequent cause of coupling blow-off is improper hydraulic hose assembly. Solution: Inspect and replace the hose assembly to assure proper procedures are followed. Adjust hose length and/or routing to accommodate potential hose length reduction under pressure.
Hose/Coupling Interface Weep
Fluid seeping from the end of the ferrule could be caused by insufficient hose insertion during assembly and/or under crimping. Excessive vibration, flexing and tugging will weaken the interface and reduce the hydraulic hose assembly’s ability to prevent seepage. Solution: If it has been under crimped or the stem has been inserted wrong, the hose assembly must be replaced with one that has been properly assembled and inspected.
Hose Burst at Coupling
A hydraulic hose that has burst at the coupling may be caused by inadequate hose slack, excessive flexing/bending or an over crimped hose end. Solution: Adjust the hydraulic hose assembly’s length to accommodate contraction under pressure and increase the actual bend radius as the hose exits the coupling. Bend restrictors can be used to reduce bending stress at the coupling. Replace the hydraulic hose assembly with an assembly that has been properly crimped.
Hose Burst at Body
A hose bursting some distance from the ends maybe cause by excessive pressure surges, flexing, kinking, crushing or exceeding the minimum bend radius. Solution: Review the operating pressure. Choose a hose that has the proper working pressure rating to handle the maximum pressure, including surges for your application. Reroute the hydraulic hose to end excessive flexing and/or exceeding the minimum recommended bend radius for the use.
Cover abrasion happens when part of the hydraulic hose cover has been removed, exposing the reinforcement section of the hose. This could be caused by using non compatible fluids or rubbing against objects in the operating environment. Exposed hose reinforcement is susceptible to ruse and accelerated damage. Solution: Re-route the hydraulic hose assembly and bundle hose together that flex in the same direction. Protect the hose from abrasion by using sleeves and spring guards.
Other common hydraulic hose failures include: thread leaks, crushed hose, coupling corrosion, hose tube cracks and crimping errors.