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Understanding Air Fittings, Hose Connectors & Quick Release Couplers

Understanding Air Fittings, Hose Connectors & Quick Release Couplers

Despite their compact size air hose fittings and connectors play a very important role in the overall performance of air compressors and the air tools that they are used with. The fittings maintain a constant flow of air and pressure within the hoses so that the performance of the air tools is not compromised. Having durable and reliable air tool fittings and air tool couplers is hugely important for the safe and efficient operation of your air tools. Our superb air tool fittings and couplers can enable you to extend your air supply and/or help you create more complex air systems to suit your needs. To ensure the equipment is in its optimal working condition the fittings must be kept in good working shape.

How are air hose fittings measured?

female quick release coupler

Many of the hoses in our range will come already fitted with some type of end fitting so you can start connecting up to your air compressor and tools, any addition couplers you need will be the same size.

If you're still unsure what size you need, it's simple, the circumference of your hose is the size coupler that you will need. You can use this quick trick to work out the circumference of your hose;

  • Take your hose and a length of string
  • Wrap the string around the hose
  • Keep the string running around the diameter straight and true
  • Mark the string across both ends
  • Layout the sting next to a tape measure
  • Read the length of the string from mark to mark
  • This will give you the circumference of the hose
  • Take this length and divide by PI (3.1416)
  • This will give you the diameter of the hose

There are many different types of air fittings but most air tools use one of just a few types of connector. The main things to consider are the fitting type and the thread size. Common fixing types include ¼” BSP, ¼” PCL and 3/8” NPT.

What is BSPF and BSPM?

The British Standard Pipe (BSP) is a family of standard screw thread types that is used internationally for interconnecting and sealing pipe ends by connecting male with female threads. The thread size is measured and based on the inside of the hose fitting. When couplers are labelled as "Female Quick Release Coupler to 1/4" BSPM" the BSPM translates to British Standard Pipe Male. In turn "F" appears if the coupler connects to female.

Can you connect two air hoses together?

Most hoses come supplied with either a thread fixing or quick release coupling. A male thread would screw into a female thread, whereas a male quick release would plug into a female quick release, so you may need a coupling to connect lines together. Fortunately, we supply a wide range of couplings, and any SGS air compressor or hose would use a ¼” BSP thread or quick release coupling to keep things simple.

By using couplings there is technically no limit to how long you can make the hose. As a general rule, it is always better to have a single, longer hose than to have multiple hoses connected together. The more connections present, the more likely it is you will experience pressure drop.

Should I use Teflon tape on air fittings?

It is a good idea to use Teflon/PTFE tape on threaded fittings. Quick-release fittings are designed to seal using internal o-rings, so any additional sealant or tape is not required. If you are experiencing leaks from a quick-release coupling, it will likely be due to incompatibility or damage/loss of the o-ring. There are many types of fittings out there that look very similar, so if you are experiencing a leak it may just be down to incompatibility.

What are Quick Release Couplings?

Quick-release couplings allow you to easily connect and disconnect airlines from either the air compressor or air tool. As mentioned above, quick couplings are designed to seal when disconnected via an internal o-ring, eliminating the need for a shut-off valve. These connections are made up of a male part and a female part which contain the internal pressures when properly connected.

The connection also allows the joint to move, meaning less kinking and twisting of the hose, better suited for a busy workplace, to keep the area safe.

What is a PCL coupling?

A PCL coupling is disconnected simply by pulling back on the collar whilst holding the air hose, or tool connected. This can cause the air hose to whip as the compressed air escapes, so it's best not to do this in a busy environment. However, it's best to use this design as a single action coupling, ideal for use in a fixed application, such as directly fixed on to the compressor. While they may look similar, a PCL fitting will not properly connect to a BSP fitting.

What are Hose Tails?

Hose tails can be used to connect couplings to hoses, or (potentially), to connect two hoses together. It’s important to make sure that the correct hose tail size is chosen, based on the internal diameter of the hose, and then secured using a jubilee clip.

quick release couplers

What to consider when choosing your coupling

  • The type of coupling you need. Is it ¼” BSP, ¼” PCL or another type?
  • The maximum pressure (in PSI) the air coupler/plug can withstand
  • Some couplers require the use of PTFE tape to form a seal
  • Couplers may come with different temperature ratings
  • Will it last? All SGS couplers come with 2-year warranties!

Still need help?

still need help?

Our in house experts are always on hand for buying advice and to provide bespoke care, regardless of the application.

Call SGS on 01332 576 850 or fill out our contact form today.

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