Although not common, hydraulic cylinder failure can occur for various reasons. The below list highlights some of the potential reasons for faults and can help to determine corrective action. However, in all circumstances listed below we would recommend that you contact Valley Hydraulics to discuss the issues and return the cylinder for analysis and/or repair.

Issue

Sign that this is happening

Potential Cause

How to check if this is the issue

External oil leaks near seals

Visibly see external oil leakage around the components fitted with seals

  • Seals are damaged


  • Inspect seals for signs of damage

   

  • Contamination in oil has damaged seals


  • Inspect seals for signs of damage and inspect fluid for evidence of debris


   

  • Piston rod is damaged and has damaged seals


  • Fully extend the piston rod and inspect the surface for damage, also inspect seals for signs of damage


   

  • Air trapped in the cylinder


  • Bleed the cylinder whilst looking for signs of air bubbles


   

  • Over pressurisation


  • Check seal rating & check forpotential pressure intensification within the cylinder


   

  • Seals not compatible with fluid media


  • Inspect seals for signs of damage and check the compatability of seal material with fluid

   

  • Damage to the surface finish of the seal housing grooves due to corrosion


  • Inspect seal grooves for signs of corrosion


   

  • Seal housing sizes incorrect


  •  Dimensionally check and compare the seal groove sizes against manufacturers specification

   

  • Incorrect seals fitted


  •  Check seal part codes and ensure they match the manufacturers specification

   

  • Metal to metal clearances around the seals are incorrect


  • Inspect all metal components for signs of wear then dimensionally check components against manufacturers specification


   
  • Excessive side loading



  • Visually inspect metal components, bearing rings and seals for signs of excessive wear which will generally appear in one area


Piston rod damaged/bent

 

Visibly see external oil leakage where the rod enters the cylinder body, the movement during actuation may not be smooth and the pressure may need to be increased to actuate the cylinder

  • Debris in cylinder


  • Fully extend the piston rod and inspect the surface for scoring along the length and inspect the oil for signs of debris


   
  • Excessive side loading


  • Fully extend the piston rod and inspect the surface for signs of excessive wear/damage in one area


   
  • Structure or external part hitting the piston rod during operation


  • Fully extend the piston rod and inspect the surface for localised damage then observe the cylinder during actuation


   
  • Cylinder loading greater than the piston rod rating


  • Check piston rod for signs of bending and check manufacturers operating parameters of cylinder against actual loadings


   
  • Not enough overlap in the cylinder


  • Check piston rod for signs of bending and check for signs of wear on the surface of the rod where it has come into contact with other metallic components.


   
  • Corrosion on the surface of the piston rod


  • Fully extend the piston rod and inspect the surface for signs of pitting, check the compatibility of rod material with environmental conditions


External oil leak near weld


Visibly see oil leakage around the weld


  • Shock loading

  • Visually check for oil leakage around the weld then check the operating parameters


   
  • Defect in weld

  • Visually check for oil leakage and signs of cracking around the weld, there may be a slight pinhole causing the leak

Main tube bore scored


Cylinder may not hold pressure, the movement during actuation may not be smooth and the pressure may need to be increased to actuate the cylinder


  • Debris in cylinder


  • Inspect the tube bore, piston and piston seal for scoring along the length and signs of debris,  also inspect the oil within the cylinder for debris


   
  • Excessive side loading


  • Inspect the tube bore for signs of excessive wear in one area, also inspect the tube and piston for signs of metal to metal contact


   
  • Clearance between metallic components


  • Inspect the tube bore for signs of excessive wear then dimensionally check components against manufacturers specification


Cylinder tube bore corroded

Cylinder may not hold pressure, the movement during actuation may not be smooth and the pressure may need to be increased to actuate the cylinder


  • Condensation due to temperature fluctuations in non-oil side of single acting cylinders

  • Inspect tube bore for signs of corrosion and check the tube material/coatings are suitable for the environmental conditions

   
  • Water in the oil


  • Inspect the tube bore for signs of corrosion and inspect the oil in the hydraulic system for water


Main tube ballooning


Cylinder may actuate until it hits the ballooned area and then will not move or build pressure, a bulge may be apparent externally on the tube


  • Pressure intensification inside the cylinder


  • Check for signs of blockage on output ports, ensure no pressure spikes can occur during operation


   
  • Cylinder tube rating is lower than the system pressure


  • Check manufacturers pressure rating for the hydraulic cylinder

Broken spherical bearing/bush


Visibly see damage to the bearing/bush

  • Overloaded
  • Check manufacturers operating parameters for the bearing against actual loadings

   
  • Excessive side loading


  • Assess side loading and check figures/angles against manufacturers operating parameters for the bearing


Piston rod will not move


No movement of the piston rod when pressure is applied


  • Blockage in a port

  • Remove hoses and visually inspect the cylinder ports for signs of a blockage and check oil is present within the cylinder

   
  • Valve failure

  • Replace the valve then check the piston rod moves


   
  • Pilot line blocked in a pilot operated valve block


  • Replace the valve with a blanking plug and actuate the cylinder

Unable to build pressure in the cylinder


Cylinder may operate slowly, unable to build pressure in the cylinder or the cylinder will not hold its position when locked


  • Seal failure

  • Visually inspect cylinder externally in areas near to seals for signs of leakage and inspect all seals external and internal for signs of damage

Air in the hydraulic cylinder


Motion of the cylinder will not be smooth and it may appear to jump during actuation, cylinder may creep when locked off under load


  • System not fully bled during commissioning

  • Fully bleed the hydraulic system and re-test

   
  • Not been bled following system components being replaced


  • Fully bleed the hydraulic system and re-test


   
  • Faulty system components


  • Fully bleed the hydraulic system and re-test, ensure all system components are air tight and there are no faults with the equipment