Compression Fittings: How They Work and Where They're Used

Compression fittings are one of those ingenious yet simple inventions that quietly power many of the systems we rely on every day, from the water running through your taps to the hydraulic systems lifting heavy machinery. 

In simple terms, stainless steel compression fittings are couplings that connect two pipes or tubes by compressing them together. They’re commonly made of durable materials like brass, copper or stainless steel. 

Compression fittings are generally suitable for low to medium-pressure applications, ranging from -5 psi to about 125 psi. However, depending on the materials and design, some high-quality compression fittings can withstand much higher pressures, particularly when made from stainless steel. 

For instance, a stainless steel fitting might handle pressures above 10,000 PSI. In plumbing and residential gas systems, the typical pressure will fall well within this range, which means compression fittings are a perfect choice for them. 

The Design of Compression Fittings

Compression fittings feature three main components that govern how compression fittings work: the fitting body, a compression ring (often referred to as a ferrule), and a compression nut. Here’s a breakdown of each:  

• The fitting body acts as the main connector, typically featuring a threaded opening where the tubing or piping will fit. It can come in various shapes (such as tees, elbows, or straight connectors) to suit different system layouts.
• The ferrule is a small ring, usually made of brass, copper, or stainless steel, that is squeezed tightly during installation to create the seal. Depending on the application, the ferrule may be a single or double component.
• The compression nut is the part you tighten down, which applies pressure to the ferrule and forces it to grip the tubing or pipe snugly.
  
  

How a Compression System Works

How compression fittings work is relatively simple. When the tubing is inserted into the fitting body and the compression nut is tightened, the ferrule is squeezed. The tapered design of the fitting body ensures that the ferrule is forced inward onto the pipe. This creates a seal that is tightly pressed around the pipe, which prevents any leaks from escaping.

Compression fittings rely on precision engineering. The angles of the ferrule, fitting body, and nut are all designed to work in perfect harmony to distribute pressure evenly. The key to a compression fitting’s function is that when the compression nut is tightened, the ferrule is forced into the fitting body, and its angled edges compress the ferrule onto the outer diameter of the tube or pipe.

Compression fittings are especially valuable because they don’t require additional sealing materials. The sealing is accomplished solely through the mechanical action of the ferrule compressing against the tubing. 

Because of this, it has become a more reliable and straightforward connection compared to other joint types, like those that require gaskets or o-rings.

The Installation Process

Here is a detailed guide on how to properly install stainless steel compression fittings: 

Cut the Pipe

First, you need to measure and cut the pipe to the desired length. The cut should be clean, with no jagged edges. A rotary pipe cutter works best because it gives you a smooth and precise cut.

Deburr the Pipe

After cutting the pipe, use a deburring tool to smooth the edges. Even the smallest burrs can prevent a proper seal and allow debris into the system, which is something you definitely want to avoid.

Assemble the Compression Fitting

Place the compression nut onto the pipe with the open end facing outward. Thereafter, slide the ferrule (or olives) onto the pipe, ensuring it sits flush with the end. Insert the pipe into the fitting body and be sure to press it until it hits the backstop inside the fitting. This ensures the pipe is seated properly for the best connection.

Tighten the Compression Nut

With one hand holding the pipe and fitting together, screw the compression nut onto the fitting body with your other hand, tightening it as much as you can with your fingers.

Tighten Further with Adjustable Wrenches

Use adjustable wrenches to securely tighten the compression nut. Hold the fitting with one wrench and use the other to tighten the compression nut. Be careful not to overtighten, as this could damage the pipe or the fitting. Stop when the nut no longer turns.

Test the Connection

After everything is connected, turn on the water supply (or whatever fluid the system uses) and check for leaks. If you notice a small leak, tighten the compression nut a little further. For larger leaks, you may need to disassemble the joint and inspect it for any damage or assembly issues.

Applications of Compression Fittings in Different Industries

Compression fittings are used across a broad spectrum of industries. In each industry, it requires different materials, pressures and pipe types. 

Here are some examples:

• Plumbing: In your home, compression fittings are used for water supply lines, often connecting copper or plastic pipes. They’re used in situations where pipes need to be joined without the need for welding or soldering.  
• Gas Systems: Gas lines, especially in residential settings or smaller commercial systems, also rely heavily on compression fittings. Since these fittings don’t need any additional sealing materials, they are particularly well-suited for systems that need to remain leak-free under pressure. Compression fittings are also used in larger systems such as refineries where safety cannot be compromised.
• Hydraulic Systems: In industrial and manufacturing applications, hydraulic systems rely on compression fittings to join pipes that carry pressurised fluids. These fittings need to withstand high pressures and temperature variations.
   

Conclusion

Stainless steel compression fittings are an elegant solution to the everyday problem of joining pipes and tubes securely. Their design, functionality and ease of installation make them a cornerstone in low-pressure applications and industries ranging from hydraulics down to plumbing.

What makes compression fittings so universally valued is their balance of simplicity and reliability. They’re easy to install, don’t require specialised tools, and can be reused in many cases. Also, they work with a variety of materials, including copper, plastic and of course, stainless steel.

Hopefully, we’ve simplified how these fittings work enough for you to appreciate just how much they simplify complex systems.