An introduction to Vis-Lok

An Introduction to Vis-Lok

Vis-Lok stainless-steel twin ferrule compression fittings are rapidly becoming the industry standard for reliability and strength.

In the realm of twin ferrule compression fittings, the qualities of robustness, strength, reliability and performance are of paramount importance. These critical attributes ensure the safety and integrity of piping systems, providing a dependable foundation for sustained operations under all conditions. This is especially important in industries and applications where failure can result in significant hazards. Twin ferrule fittings such as Vis-Lok are designed to withstand the rigours of extreme conditions, providing reliable, secure, leak-proof connections that will maintain system efficiency and minimise operational downtime.

Advancements in fittings technology — such as the Vis-Lok Twin Ferrule Compression Fittings — now give industries access to solutions that not only meet the stringent demands of high-pressure applications but exceed them.

In this blog post, we will introduce you to Vis-Lok’s twin ferrule fittings and give you an insight into how this product can ensure that your systems operate at maximum efficiency and with minimal downtime.  

What is Vis-Lok?

Vis-Lok has rapidly emerged as a standout product, renown in the industry for being robust and reliable. Vis-Lok’s distinctive check ring system provides an easy visual tightness indicator which guarantees the perfect connection every time. This feature simplifies the installation process and ensures a consistently reliable setup, even for contractors who are new to the system.  

1. Stainless steel 316 durability

The durability of the Vis-Lok system is evident in high quality materials used. The 316 stainless often has a higher percentage of chromium and nickel than competing products, which gives it greater resistance to corrosion and pitting in harsh environments such as marine, manufacturing and outdoor conditions.

2. A wide variety of applications

Vis-Lok’s use of high quality materials makes it suitable for a wide range of industries and applications. These are just some of the situations where Vis-Lok products can be used.

• Oil and gas production and distribution

• Industrial gases

• Mining

• Power generation

• Research & development facilities, universities, and laboratories

• Metal processing

• Medical gases and equipment

• Defence force including naval forces

• CNG vehicles and supply stations

• Chemical manufacturing

• Dairy factories

• Aerospace and aeronautical

• Pulp and paper manufacture

• Luxury yachts and marine

• Water and wastewater treatment

• Valve actuation

• Hydraulics

Additional Information on Vis-Lok.

Vis-Lok’s reputation for innovative design, quality assurance and ethical manufacturing standards make it the preferred choice across a range of industries. Here are some of the unique features of this product.

1. Innovative Features of Vis-Lok

A standout feature of Vis-Lok is the coloured indicator ring on each fitting. These rings show the user when the fitting is correctly tightened, eliminating the need for a gauge therefore reducing installation errors. This feature is particularly useful in maintaining system integrity and preventing leaks, common issues when twin ferrule compression fittings are not installed correctly.

Here is how the installation process works.

1. Tighten the nut. Once the tube has been cut, deburred, witness marked, and inserted into the fitting, the nut is the tightened, and the coloured check ring compresses.
2. Visually confirm tightness. When the fitting is tightened to the correct torque, the ring will automatically fall off. This ensures the perfect connection has been achieved.
3. Reduced installation errors. The visual cue provided by the rings eliminates the possibility of an installer missing the gauge step and therefore over or under-tightening the nut. This is a common cause of leaks in other twin ferrule compression fitting systems.
4. Reusable check rings. The plastic check rings are fully recyclable and can be reused multiple times.

2. Ethical manufacturing standards

Ethics in manufacturing is a priority for Vis-Lok. We can provide a 3.1 material test report (based on the European Standard EN1024 Type 3.1) for each of our fittings and tube. This ensures full traceability across the supply chain: from the raw material to the final product. This traceability reflects Vis-Lok’s commitment to responsible manufacturing practices and reassures our customers about the quality and ethical sourcing of each component.

3. Product specifications

Vis-Lok accommodates both imperial and metric sizing, although the imperial range is more readily available here in New Zealand. The Vis-Lok system’s pressure rating is determined by the pressure rating of the tube being used, not that of the fitting itself. A crucial part of this is the wall thickness and size of the tube. For example, a ¼” tube with a wall thickness of 0.049” will have a higher pressure rating than that of a 1” tube with the same wall thickness.

By way of comparison, these are the pressure ratings of ¼” and 1” tube.

• ¼” tube with a wall thickness of 0.049” = 8,100 PSI operating pressure.
• 1” tube with a wall thickness of 0.049” = 1,800 PSI operating pressure.

To find out more about the different pressure ratings view the pressure rating chart in our vis-lok brochure.

4. Bright, shiny and strong

All Vis-Lok tube undergoes a bright annealing process. This enhances the stain and corrosion resistance of the material. Vis-Lok tube contains a significant amount of molybdenum which also improves its corrosion resistance. The double ferrule fitting design ensures a secure and reliable installation, capable of withstanding high pressure without the risk of O-ring degradation.

Comparing the Vis-Lok and Swagelok Systems.

While the quality and function of both Vis-Lok and Swagelok systems are similar, they have some distinct differences. Vis-Lok’s indicator ring simplifies the installation process, ensuring a correct and secure system of a consistently high standard.

1. Swagelok does not have the indicator ring; however, it is a well-established brand with a good reputation earned over many years. The lack of an indicator ring does add complexity to the installation process.
2. Both brands have a silver coating on the inside threads on the nut to eliminate or reduce galling, this is also beneficial when reusing and re-installing fittings. This never comes into contact with the medium being transferred through the system.
3. Both brands also have rolled threads. This gives a much higher shear strength and higher resistance to galling when compared to a cut thread.
4. The back ferrule on Vis-Lok is leading edge hardened, rather than case-hardened, for ease of installation and high sealing integrity. The front edge of the back ferrule can bite down and grip the tube, which prevents an uneven transfer of torque and protects the system from leakages. The back ferrule can “hinge” or ‘flex” downwards, giving a better swaging action.
5. Both brands are known for their high-quality products and features that enhance installation integrity and reduce the risk of leaks.

Make Vis-Lok Your Preferred System.