As they are frequently under high pressure, need to withstand vibration or are subjected to pulsating pressure changes, it is imperative that hydraulic connections are secure. Here Stäubli offers some advice on how to select hydraulic connectors for any application

There are numerous types of connectors available from a wide range of potential suppliers, and as such selecting the most suitable connectors for any hydraulic circuit is not straightforward. The choice is made even more tricky by the fact that incorrect selection could lead to unreliability, poor performance, circuit failure and leakages.

In recognition of these difficulties, Stäubli, specialists in connection technology, offer step by step selection advice – making recommendations on the choices available and working closely with the user to ensure that the optimum connection solutions are chosen that will perform reliably over many years with minimal maintenance.

Thorough evaluation

The specific connector requirements for any application are often viewed in isolation with flow, pressure and temperature being the main (and often the only) factors considered. Selection of the most suitable connector calls for a much deeper evaluation, taking into account all the anticipated requirements and considering how these may interact with each other.

How the connection will be made needs close consideration. Is a facility for blind mating required? Is indication of successful connection needed? Will the connection be made in difficult to reach positions? Is automatic locking with single handed connection required? Will the connection be made under pressure? Would mounting several connectors onto a plate to make all connections in one be an option? Defining these requirements identifies the model of connector required, e.g. a compact CBX connector for difficult access conditions and for automatic connection or an SPX for blind connection.

Any leakage obviously needs to be avoided, but is any spillage on disconnection permissible? If not, then a non-spill, clean break connector is required such as Stäubli’s HPX. The flat faced design of this connector also ensures that there is no ingress of air or contaminates into the circuit on both connection and disconnection.

The environmental conditions in which the connectors will be used are also important, such as temperature, atmosphere, corrosion, shock loading and vibration. These requirements may lead to selecting a stainless steel connector if corrosion is a concern or a connector with a secure robust bayonet or screw locking system to withstand vibration.

Maximum working pressure is obviously important in the selection and Stäubli have connectors capable of working at higher pressures. The required flow rate will also be a major factor – full bore, unrestricted flow connectors offer the highest flow rate within any specified coupling diameter. Choice of seal is equally important too, particularly when operating at higher temperatures – it is possible to select from nitrile, fluorocarbon, ethylene-propylene or perfluoroelastomer to suit the application.

Possible Applications

What are the typical applications for hydraulic connectors? These are fairly widespread right across industry from robust high pressure connectors on steel rolling mills to compact spill-free connectors on the brake lines of Formula One cars.

For applications where pulsating hydraulic pressure or vibration is present, such as on hydroforming which is frequently performed at a pressure of 2000 bar, Stäubli recommend its range of hydraulic couplings which can withstand these difficult operating conditions. The two stage locking system – an initial screw thread followed by an automatically applied claw type locking sleeve – ensures a positive and secure connection under pressure, while the pre-guiding system of the plug into the socket makes connection easy. Dust caps are securely fastened to each coupling to protect the connection face on tools not in use.

Selecting the most suitable hydraulic connector calls for evaluation of many parameters in the planned application. Stäubli engineers are trained to fully consider all aspects of the application and are skilled in evaluating the combination of requirements. They will provide advice from the design stage onwards on the most suitable connection solution for any hydraulic application to ensure performance, long term reliability and minimum maintenance.

Stäubli (UK)

T: 01952 671 918