When selecting the right coupling, the frequency of hose connection and disconnection is a major factor in the type of coupler that should be used. For example, at workstations where pneumatic tools are being changed many times throughout a shift, a quick connect coupler allows rapid tool replacement and provides a significant increase in productivity.
Another example is hydraulic testing processes. Quick couplings significantly reduce the time required to test each assembly. If technicians were required to tap into systems using a wrench to connect and disconnect, valuable time would be added to each testing procedure. Again, productivity increases with the use of quick couplings.
Many industries are rapidly adopting quick couplings for this very reason, realizing the increase in efficiency far outweighs the increased costs.
A quick coupling, often referred to as a quick coupler, QD or quick-acting coupling, is a mechanical device that provides a fast, easy, sure way to repeatedly connect and disconnect almost any fluid or gas line. All quick-connect couplings have two parts: a plug and a socket. The plug is the male half and the socket is the female half. When connected properly, these parts seal and lock the joint effectively to contain internal pressures and resist any tensile forces that tend to pull the joint apart.
The most significant advantages of a quick couplings over standard hydraulic connections are:
Time of connection/disconnection
Prevention of fluid leakage
Cost is a factor that prevents quick connect couplings from being more widely used. These couplings contain many more components such as valving and locking mechanisms, which means higher material and assembly costs.
Secondly, there is an issue of pressure drop. Media flowing over the internal valves causes turbulence in the media - either fluid or gas. Think of the effect rocks have on the flow of a river. This can cause a slight drop in pressure that can be measured as ‘pressure drop’ (PSID).
Before selecting a coupling, important questions must be answered regarding performance:
What are the functional requirements of the coupling?
What is the maximum working pressure of the application?
Which seals and body material are compatible with the system’s fluid?
Is the application static or dynamic?
What size coupler/hose is required?
What is the maximum pressure drop suitable for the application?
Does the application require the ability to connect and disconnect under pressure?
What is the media temperature and ambient temperature?
What end configurations are required?
Is an industry interchange coupler required?
Are air inclusion and fluid loss concern in the application?
Once these questions have been answered, a preliminary selection of coupling type can be made: one, two or no shutoff valves, and the type of connecting and disconnect mechanism. Keep in mind that one style may offer the greatest convenience in service, but a different model's lower pressure drop may be more desirable for the application.
Single shut-off couplings are primarily used for pneumatic or gas applications, connecting air tools, hoses or other implements to compressed air and gas supplies. In these applications, the coupler half (female) is valved while the nipple half (male) is un-valved or “straight-through.” Upon inserting the nipple, it opens the valving on the coupler, which allows flow. When disconnecting the nipple, the valve on the coupler automatically closes which stops the flow from the coupler.
Both coupling halves are frequently valved in the case of hydraulic applications. Double shut-off couplings minimize fluid leakage while limiting the amount of air, dirt, and water that can become trapped between valves during reconnection. To address these concerns, many manufacturers offer flat-faced couplings that reduce fluid spillage to a drop or less every time the coupling is disconnected.
The impact of employing quick connect couplings will make a difference in any operation where reliability, time and productivity are of the utmost importance. Parker’s Quick Coupling Division is the largest quick coupling manufacturer in the world, providing quick disconnects and accessories that are appropriate for use in countless applications across widespread markets where fluid lines are connected and disconnected. These markets include aerospace, subsea gas and oil exploration, agriculture, electromechanical, filtration, thermal management and all others that require reliable, safe connections.
Many of Parker’s coupling products are available with unique non-standard options well suited to very specific applications. Examples of unusual end-use applications might include: high temperatures (above 250° F), extremely caustic/corrosive solutions passing through the coupling, external/environmental corrosion situations or other high wear and tear situations such as dragging the product along the ground.
Article contributed by Anthony Mistretta, product sales manager, Quick Coupling Division, Parker Hannifin.