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Single ferrule or double ferrule compression fittings?

Compression fittings - Out door installation.
Compression fittings are often used to withstand high temperatures, pressures and vibration levels.

Demanding industrial applications require utmost precision and secure technologies in order to safeguard from influences which could ruin a project. These may include leakage from thermal vibration or pulsation within an application. In all cases, the safety of the operator and their working environment is business-critical.

Senior project managers are often presented with an abundance of options when choosing fittings for instrumentation, process and control systems and other equipment. At the end of the day, users just need a solution that is risk-free, leakage-free, and simple enough to use without breaking the budget.

Compression fittings generally do just that. These fittings are generally used to connect two imperial tubes, two metric tubes or, the connection of a metric tube to an imperial tube.

The common size range is between 1/8 to 2 inches / 4mm to 50mm. Compression fittings are rated to the optimal working pressure of the tubing it connects to.

Stainless steel compression tube fittings are used for a range of applications in different industrial settings. Twin ferrule are preferred for higher working pressures and harsh applications. This also makes twin ferrule fittings a safe choice for the full gamut of low pressure operation right through to high pressure. So, what are the main differences between single ferrule and double ferrule tube fittings?

Single ferrule compression fittings

Single ferrule fittings have comparatively less pressure rating than its twin-ferruled counterpart. These compression fittings are designed with the consideration of the operators’ ease of use, having one less part than twin ferrule fittings and are generally difficult to be installed incorrectly.

Despite its benefits, double ferrule fittings are generally the preferred option.

Single ferrule stainless steel compression fitting
Single ferrule stainless steel compression fitting

Why are single ferrule compression fittings still used in industry?

While the high pressure rating and perfect connection of double ferrule fitting make them a favourable option in the industry, single ferrule compression fittings are slightly cheaper for low pressure applications where there is no risk of pressures increasing or mistakenly mixing of the two fitting types.

Double ferrule compression fittings

Double ferrule (or two-ferrule, twin-ferrule depending on the manufacturer) compression fittings are produced in various materials, but the size ranges are identical to single ferrule fittings. Double ferrule compression fittings provide a perfect connection thanks to its strong mechanical grip design. The fittings can be used for tubing with various thickness and different hardness levels.

Design of double ferrule tube fittings

The basic design of a double ferrule tube fitting consists of four main pieces:

  1. Nut
  2. Front ferrule
  3. Back ferrule
  4. Body
Double ferrule stainless steel compression fitting
Double ferrule stainless steel compression fitting

Some very advanced fittings may have additional parts such as a tightness indicator (such as the VIS-LOK Stainless Steel Compression Tube Fitting above).

Double ferrule compression systems are designed to give the tight grip around the tubing, minus any damage to the wall. The ferrule inside is designed to perform as the locking ferrule, while the outer ferrule provides its sealing capability.

Due to its robust design to withstand high temperatures, pressures and vibration levels, it is without question one of the best choices for applications within an industrial setting.

As Australia’s leading industrial pipe fitting supplier, we supply premium grade stainless steel compression tube fittings to industries with applications in:

  • Oil and Gas Upstream
  • Oil and Gas Downstream
  • Industrial Gases
  • Mining
  • Power and Energy
  • Research and Development in Universities
  • Metal Processing
  • Medical Gas Applications
  • Natural Gas Distribution
  • And much more

For more information, call us on 1300 85 45 20 03 8318 4090

* Pipe and tube lengths can vary by +/- 2%
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