Hydraulic Piston Actuation Failure Modes 1

[adjalabi]

What are the possible reasons for a hydraulic bind occuring in the lock chamber of an hydraulically actuated piston designed to stroke a mandrel behind locking segments which then expand over a load shoulder to grip a groove profile on a seperately standing hub. This situation is relevant to the functioning of subsea flowline connectors for subsea completions. Sometimes a secondary release mechanism is employed, but what brought this question up is even if you use a secondary release mechanism, how will that overcome the hydraulic bind in the primary piston locking chamber without being able to vent that chamber. If you could vent the chamber that would bleed it off and eliminate the bind... unless my understanding of a bind is inaccurate in which case, I stand to be corrected.

 

[budt]

If I understand your question, you are asking what might cause a cylinder to bind (NOT BE ABLE TO MOVE WHEN SIGNALLED TO DO SO AT THE PRESENT AVAILABLE PRESSURE AND WORK)

In my experience I have come across these situations where a cylinder is mechanically resisted enough that the available hydraulic pressure against its area was not enough to make it either Extend or Retract or both.

Damaged Tube wall such as a dent that kept the piston from passing the damaged area.

Damage tube walls from lack of lubrication that caused scoring and galling of the tube.

Seals that were extruded into the clearance between the piston and tube wall. This usually happens when the piston clearance is too much due to over honing.

Side load on the Piston Rod causing the piston to contact one side of the tube so much that hydraulic pressure could not move it.

Over sized piston of a material that expands from heat more than the tube and causes binding after a length of run time.

Mechanical binding of the driven device.

There may be other reasons but these are the ones I have seen.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us