23 January 2023

Hydraulic couplers hard to connect

Hydraulic couplers hard to connect

Different connection systems for quick-couplings

The various series of quick-couplings available on the market are characterized by different connection systems, here are the most common ones: thrust of the nipple with simultaneous retraction of the female coupler sleeve (“Sleeve Retraction”), thrust of the nipple (“Push to Connect”), thread connection (“Screw to Connect”) and lever (for multi-Couplings). These systems give the quick couplings series different characteristics and make them more or less suitable for the applications where these items are used.


Difficulty in connecting quick-couplings due to trapped pressure

However, they have one aspect in common: in the absence of a dedicated pressure relief mechanism, it will be increasingly difficult to complete the quick-coupling connection maneuver when there’s trapped pressure, up to the point of being practically impossible beyond a certain pressure threshold, which depends on the product series and on the size. 

The presence of pressure inside the hydraulic circuit is a pretty common event which can mainly depend on a missed release after the quick-coupling disconnection or on a progressive increase resulting from a rise in the external ambient temperature: due to the rigidity of the hoses, designed to resist at high or ultra-high pressure values, fluid cannot naturally expand its volume, therefore the thermal expansion leads to a pressure increase. 


Reasons for trapped pressure

Circuits of hydraulic power units are always equipped with pressure relief systems, and consequently it is easy for operators to relieve internal pressure (most often by acting on a joystick connected to a hydraulic distributor). 

However, the same cannot be said about implements connectable to power units; the most frequent situations in which an operator struggles to connect a quick coupling are in fact those where there’s residual pressure inside the hydraulic circuit of an implement preventing the quick-coupling valve from moving back in order to open the circuit. 

Another recurrent root cause of difficult connections is the presence of external debris stuck to external surfaces of quick couplings; learn more about this topic here: How to do hydraulic quick coupler maintenance.


Pressure relief mechanisms in advanced quick-couplings

The most advanced series of quick-couplings offer various systems allowing the relief of pressure and often these mechanisms are completely automatic, not requiring operators (who may even be unaware of the presence of pressure inside the hydraulic circuit) to execute any special maneuver aimed at the connection of the quick-coupling. 


Dangers of using empirical solutions

End users who have to connect quick couplings not equipped with pressure relief systems in presence of residual pressure into the circuit, often end up forcing the retraction of valves in different ways or try to loosen the union fitting between hose and quick coupling in order to let a small amount of fluid out to bring down the pressure. 


Importance of considering pressure requirements when selecting quick-coupling 

However, the use of empirical solutions to overcome connection issues is highly discouraged as it involves a high risk of damaging quick-coupling seals (thus significantly reducing their lifetime) and above all it jeopardizes personal safety of people who operate or stay near working machines.  

Faster website helps to easily select the most proper product for each specific application depending on the expected pressure regime before connecting and disconnecting a hydraulic line: in fact, after ticking correct CUP (Connection Under Pressure) feature boxes, web users view only product series whose characteristics match the pressure requirements of that application.