Proper coupler selection is important because of the variety of media for which they are used.
Four basic factors should be considered to assure proper selection:
All couplers consist of two basic components; a socket and a plug. The type of coupler varies by the valving arrangements in these two components.
One Way Shut-Off
In a one way shut off only the socket has valving to shut off the flow when disconnected. It is therefore, installed on the pressure side of the line. The plug has no valving and exhausts the downstream line at disconnect.
Two Way Shut-Off
The two way shut-off provides valving in both the socket and the plug, thereby shutting off flow at both of the disconnected ends. Originally developed for hydraulic lines, they are suitable for many other media because of the variety of metals and seal components offered.
Straight-thru couplers as the name implies, do not have valving in either the socket or the plug. Therefore, both ends of the line are exhausted at disconnect.
Operation refers to the action required to connect and disconnect a coupler. Operation is a function of the socket only and does not vary for plugs.
Manual pockets require manual retraction of the sleeve to both connect and disconnect the plug.
Automatic Sockets accept the plug by simple insertion into the socket and do not require retraction of the sleeve to connect.
Safety Sockets are a variation of automatic operation. The socket accepts the plug by insertion. The sleeve is moved straight forward to lock and turn on the air. The sleeve is moved back by rotating first to the left and then to the right. This shuts off the supply line exhausts the downstream line and the releases the plug.
The most important factor in properly sizing couplers is the flow.
The media flowing through the coupler will usually determine the type. compressed air, many other gases, and some liquids can be handled by one way shut-off couplers. Hydraulic fluids as well as many other liquids and some gases require two way shut-off. Straight-thru couplers are suitable where there is no pressure in the line at connect or disconnect and loss of media at disconnect does not matter.