When working with instrumentation systems, one of the most common challenges is distinguishing between fractional and metric tube fittings. Even a marginal difference in size can lead to leaks or unsafe connections. At Super Engineering Works, we simplify this process by providing metric fittings with a stepped shoulder on both nut and body, making identification quick and accurate.

Identification of Tube Fittings

  • Metric Tube Ends → Stepped shoulder on nut & body
  • Fractional Tube Ends → Smooth design (no step)

This unique design feature ensures that users can easily avoid mismatches between fractional and metric fittings, preventing costly errors in assembly and operation.

Installation Instructions

Super Engineering Works Tube Fittings are supplied fully assembled, finger-tight, and ready for immediate use. To achieve a leak-proof seal, follow these three simple steps:

Step 1: Tube Insertion

Insert the tubing into the fitting until it rests firmly on the shoulder. The nut should be snug-tight so that the tube does not rotate by hand.

Step 2: Marking

Before tightening the nut, make a scribe mark at the 6 o’clock position.

Step 3: Tightening

While holding the fitting body steady with a backup wrench, tighten the nut one and one-quarter turns. For smaller sizes like 1/8”, 3/16”, and 3 & 4 mm, only three-quarter turns are required.

Pro Tip: After tightening, the scribe mark should move to the 9 o’clock position.

High-Pressure Applications

For high-pressure systems, use a wrench to snug the nut until it no longer turns by hand. Then, tighten one and one-quarter turns further. This ensures the fitting holds pressure well above the working pressure of the tubing.

Re-tightening Instructions

Connections can be disconnected and re-tightened multiple times without losing their leak-proof performance. This makes Super Engineering Works fittings ideal for long-term use in demanding industries.

Pre-Swaging Method

In tight spaces (like cramped quarters or overhead ladders), pre-swaging helps simplify installation:

  • Assemble the nut and ferrules onto a pre-swaging tool.
  • Tighten one and one-quarter turns, then loosen the nut.
  • Insert the tubing (with pre-swaged ferrules) into the actual fitting body, then snug and tighten as per instructions.

This ensures accurate ferrule positioning and faster installation.

Pressure Ratings

Super Engineering Works Tube Fittings are rated for working pressures higher than the tubing itself (depending on tubing size and material).

Note: As temperature increases, material strength and pressure tolerance decrease.

Tubing Selection Guidelines

For best performance:

  • Use Stainless Steel 304 & 316 seamless tubing (ASTM A269 or equivalent).
  • Ensure hardness ≤ Rb80 (per ASTM standards).
  • Operating range: −20°F to +100°F (−29°C to +37°C).
  • Tubing should be free from scratches and suitable for bending/flaring.

Do not use tubing beyond its maximum allowed working pressure.

Conclusion

By using Super Engineering Works Tube Fittings, you ensure:

  • Easy identification of fractional vs. metric fittings.
  • Hassle-free installation with three-step tightening.
  • Reliability in high-pressure systems.
  • Flexibility through re-tightening and pre-swaging methods.

Our fittings are engineered for precision, safety, and durability — making them the trusted choice across oil & gas, petrochemical, power, and hydraulic industries.