Hydraulic quick release couplings

Hydraulic quick couplings

High pressure quick release couplings – general information

Quick release couplings solve the problem of quick connection and disconnection of flexible hose assemblies. The
connection can be made faster and easier than in the case of standard screwed couplings (threaded, flanged) because it is made by hand, with no tools. Usually, it requires only pushing a plug into a socket. Locking occurs automatically, using the spring mechanism. The most often the plug is blocked in the socket with steel balls. In many cases connection and disconnection can be made with one hand only (“one hand operation”).
The use of quick release couplings facilities assembly. It enables fast and easy replacement of interchangeable modules of hydraulic systems, saving time and money.

Construction of the hydraulic quick coupler


Socket: 1 – body 2 – blocking mechanism (sleeve, spring, steel balls) 3 – seal (O-ring, stopper ring) 4 – valve (valve head, spring, valve holder) 5 – – valve seal (O-ring)	Plug: 6 – body 7 – valve (valve head, spring, valve holder) 8 – valve seal (O-ring)

Types of quick release couplings

straight-through	single shut-off	double shut-off	double shut-off, dry-break (leak-free)

no valves	valve only on supply side (most often in socket)	valves on both socket and plug side	valves on both socket and plug side, (flat surface face – “flat face” and appropriate sealing

Standards

Quick release couplings are manufactured according to generally acknowledged standards or according to the manufacturer’s standards. The most common in hydraulics:

ISO 7241-1 A (ISO-A)
ISO 7241-1 B (ISO-B)
ISO 16028 (ISO-F)

Standards define the dimensional requirements for sockets and plugs, strength requirements (working pressure, bursting pressure) and others (flow rate, connection strength, spillage volume, etc.). Dimensional requirements deal with a plug profile in particular (shape and dimensions). Manufacturing according to the same profile standard ensures so called “interchangeability” and allows connection of sockets and plugs from different producers. However, this connection does not guarantee all functional features of an original set of couplers (socket and plug
from the same manufacturer) and should be properly verified.

Other features of hydraulic quick release couplings

Pressure eliminator

The application of a socket or a plug with a pressure eliminator facilities connection of quick release couplings when residual pressure in the system is high. The eliminator, a tiny release valve with two small holes, is built into the socket or plug. Once the quick release coupling is connected, release valve opens, the medium flows out through the holes causing the drop of the static pressure.

socket and plug without eliminator	valve without eliminator

socket and plug with eliminator	valve with eliminator

ISO-F quick release couplings can be fitted with a pressure eliminator at the plug side only. In ISO-F plug with the pressure eliminator, there is an additional space inside the body, into which pressurised oil enters when connecting to the socket. As a result, static pressure drops (in the hose assembly on the plug side) and the quick coupling can be easily connected.

socket without eliminator	plug without eliminator

	plug with eliminator

Protection against accidental disconnection

Disconnection of standard quick release couplings requires backward pull of the plug-locking sleeve in the socket. To prevent accidental disconnection, some of the quick release couplings are equipped with locking sleeve security mechanism preventing backward pull and accidental disconnection. This feature is implemented by an additional safety locking ring (which needs to be moved in the direction of sleeve and turned) or security pin (safety lock- turning of the sleeve is only possible in a proper position of a cut in the sleeve).

safety locking ring	locking pin
quick release coupling unlocked	quick release coupling unlocked
quick release coupling locked	quick release coupling locked

„Push-pull” system

The application of “push-pull” quick release couplings protects flexible hose assemblies from tearing apart in case of accidental strain (e.g. a tractor drives away from a seeder – a mechanical coupler has already been unhooked but hydraulic installation is still connected). The “push-pull” system works properly only if the socket is fixed to the body of equipment (housing) with a knurled locking sleeve (see picture below). When the hose assembly is strained, automatic disconnection of the quick release coupling follows. This prevents damage of the hydraulic installation and possible oil loss. There is also a type of quick release couplings with emergency breakaway function.

szybkozłącze hydrauliczne z mechanizmem push pull

„One hand operation” – connection and disconnection with one hand

To connect standard quick release coupling, locking sleeve must be pulled back and the plug must be pushed into the socket. In order to increase the ease of handling, some of the quick release couplings are connected (disconnected) with one hand. The connection takes place automatically after only pushing the plug into the socket. In order to disconnect such a coupling, the locking sleeve must be pulled back and the plug will pop out.