Low pressure quick release couplings (maximum working pressure up to several tens of bar) are designed to connect hoses with different system elements and equipment in industrial applications handling air, gases and fluids. The quick release couplings for compressed air tend to be the most popular in an endless range of applications such as connecting systems by hoses or air compressors with pneumatic tools e.g. blow guns, pneumatic spanner etc. The quick release couplings fall into the following groups:

• free flow quick release couplings, have no valves either in the plug or the socket;
• single shut-off quick release couplings, with a valve built into the socket as a standard, this valve opens when the plug is inserted, the plug has no valve;
• double shut-off quick release couplings, both the socket and the plug contain valves, these valves open when the socket and the plug is connected;
• dry brake quick release couplings, double shut-off, flat face of both the socket and the plug ensures minimum or no spill during connection or disconnection.

The plug is locked in the socked body by a locking mechanism (usually by the balls pressed against the external plug profile). There are many plug profiles, some of them conform to international design standards, some conform to the standard of one or numerous manufacturers, more or less popular in the industry. The interchangeability of quick release couplings from different manufacturers may be considered as the ability to connect the socket with the plug of the same profile but from different manufacturer and each time requires verification. It is recommended to use both the socket and the plug of the same manufacturer.
The main features of quick release couplings, except for the working pressure, are as follows:

• nominal diameter DN (defined as the inner diameter of a quick release coupling flow path, in mm) and flow rate (capacity) – for air and gases given in l/min (litres under atmospheric pressure, normal pressure) at inlet pressure pe = 6 bar and specific pressure drop in the quick release coupling Δp = 0,5 bar or 1 bar. It is important to compare the flow capacity of quick release couplings at the same pe and Δp.
• sealing material, its working temperature range and chemical resistance – e.g. for air, at ambient temperature, NBR seal is the most appropriate.
• material of the quick release coupling elements, its mechanical resistance and chemical resistance – e.g. brass is suitable for air, but the plugs made of brass wear down faster due to frequent connecting and vibrations, than stainless steel plugs.
• easy and strong connection – to connect and disconnect the quick release couplings sometimes both hands are needed and sometimes only one (one hand operation).
• protection against uncontrolled discharge of residual air when e.g. a pneumatic tool is disconnected – this safety device is a feature of the quick release couplings disconnected without pressure.

Tubes International offers a wide range of quick release couplings of all kinds, from the most trusted manufacturers across the world.