What is a quick-disconnect fitting?
A quick-disconnect fitting is a watertight connection made between different types of tubing and water filtration systems that can be put together or taken apart quickly and easily. The fitting gives any user the ability to add a break in a line of tubing for any application requiring quick removal of tubing from another connector. Because of their ability to remove quickly, quick-disconnect fittings are used in systems where regular disconnections are needed.
How does a quick-disconnect fitting work?
Unlike a quick-connect fitting, quick-disconnect fittings can be removed easily because they do not provide a permanent seal. Because of this characteristic, quick-disconnect fittings are commonly used in fluid transportation applications, where a change in the system requires disconnection of the fittings. QD fittings have two different components that help them function: the coupling body and the insert. The insert connects with the coupling body, snapping together to make a watertight seal. Quick-disconnects can be released by pressing down on the latch and pulling the two ends apart.
Do quick-disconnect fittings come with a shut-off valve?
In special applications where it is imperative that no fluids drip out, like flavor bags in beverage dispensers or IV bags in the hospital, you may consider using a quick-release fitting that has a valve. A valve fitting, when disconnected, closes the valve when the insert is removed from the coupling body to prevent fluids from dripping out. QDs can contain zero, one, or two valves depending on their application. Single-valve fittings only contain a valve on one side of the coupling, so they are not as good at leak prevention as fittings with two valves.
What is a quick-disconnect fitting used for?
Quick-disconnect fittings are used in a variety of applications. They are made in an assortment of different sizes with many different configurations and tube connection types.
Connection types
- Hose barb
- Threaded
- Compression
These fittings come barbed, threaded, or threaded on one end and barbed on the other. Typically, you will find most threaded ends of a quick-disconnect to be a male thread.
This type of fitting is frequently used in the medical industry. Quick-disconnect fittings are used to handle IV bags with water, medication, and other bio-fluids. Most of the time, however, you will see a quick-release fitting being used on water treatment products related to quick connect. For example, you might see a quick-release fitting on the inline filter for a refrigerator. This is usually something that you're going to take apart every six months when it's time to change the filter.
Quick-disconnect fittings are more often used in commercial applications than residential systems. Currently, the strongest demand for quick-disconnect fittings comes from OEM manufacturers for commercial applications.
Quick-disconnect vs quick-connect fittings
Unlike quick-connect fittings, quick-disconnect couplings can be easily released and reconnected many times. Quick-connect fittings provide a permanent seal, while QD fittings are used where frequent changes to a system are needed over time. QD fittings are commonly used in commercial fluid transportation, where frequent line changes or other alterations must be made regularly. Quick-connect fittings, on the other hand, are ideal for situations that do not require regular maintenance.
Types of quick-disconnect fittings
The most common types of quick-disconnect fittings include:
- Ball-latching (snap-type) quick disconnects are the most common type of QD. They feature a spring-loaded ball latching mechanism that locks the two ends of the fitting when they are pushed together. The quick-release sleeve on ball-latching QDs enables swift and simple operation. In fact, these fittings can typically be connected and disconnected with one hand. These fittings are commonly used where frequent connections and disconnections are made, such as fluid transportation, pneumatic tools, and hydraulic machinery.
- Non-latching quick disconnects are used in applications where space is limited or safety issues are a concern. These fittings can also be called screw-type QDs because they often connect via threads.
- No shut-off quick disconnects provide higher flowrates than other shut-off QDs, but they do not prevent leaks when the fitting is disconnected. Because of this, they are not used to transport toxic or otherwise dangerous liquids and gases.
- Single shut-off quick disconnects contain a valve on one end of the coupling that prevents fluid or gases from escaping upon disconnection. Eye protection is recommended when disconnecting a single shut-off fitting because only one-half of the coupling contains a shut-off valve.
- Double shut-off quick disconnects contain a valve in both sides of the coupling. As a result, they prevent leaks upon disconnect from both ends. The fluid lines on both ends of the coupling maintain their pressure when the fitting is connected and disconnected.
- Dry break quick disconnects prevent spills from occurring during connection and disconnection, so they are typically used in lines that transport toxic or expensive gases and liquids.
Popular quick-disconnect fitting brands
Colder Products and LinkTech are two popular manufacturers of quick-disconnect fittings.
Colder Products quick-disconnect fittings are used in a wide variety of industries, including pharmaceutical, liquid cooling, and medical applications.
LinkTech fittings are most often used for medical purposes, but they are also commonly found in food and beverage, analytical devices, and other applications.
How do you connect and disconnect a quick-disconnect fitting?
Quick-disconnect fittings are installed differently depending on the configurations of your water treatment system. For example, a standard compression fitting would be used with a copper tubing configuration. When using a plastic compression fitting, with a compression nut, you would connect it with plastic tubing. Once you have the components attached to the tubing, copper pipe, or directly into a manifold, make sure you leave enough room to make the connection. If you have a valved quick-disconnect fitting, you will need to establish water flow once it is connected. If you have a non-valved fitting, the water will flow openly, so you do not need to bother turning on or shutting off the valve. To connect the fittings, push the insert into the coupling body and push them together until it snaps. To release them, push the latch and pull the two ends of the fittings until they come apart.
How much pressure can a quick-disconnect fitting withstand?
The amount of pressure that a quick-disconnect fitting can withstand varies depending on the series variety of sizes and shapes of the fitting. Some of the smaller plastic fittings can handle up to 100 psi. The same sized fittings made of brass are stout but can handle up to 250 psi. The variety of fittings provide an array of pressure tolerances.
Quick-disconnect fittings are normally rated for operation with certain pressures and temperatures. Depending on the heat of the liquid being fed through your system, the temperature may play a role in the amount of pressure that the fitting can withstand. That has more to do with the type of tube connection that the fitting is making than the actual fitting. A barb connection, for example, is not going to withstand as much pressure as a threaded connection. When selecting the appropriate fittings for your application, ensure you know accurate details of what your fittings will be exposed to.