The Leak Test Connector for Smooth Straight Tubes

The FasTest ST is an external, sleeve-actuated leak test connector that seals onto the outside of a smooth straight tube — copper, steel, or aluminum — with no flare, bead, thread, or expanded end required. The operator pushes the connector onto the tube and the sleeve locks it in place, making a leak-tight connection in seconds on a tube exactly as it comes off the line.

Sealing to a featureless tube is the hard part, and it is what the FasTest ST is built around. Pressure-assisted sealing means rising system pressure energizes the seal further and helps the connector resist movement, rather than working to push it off. On a smooth tube that offers no mechanical feature to lock onto, that pressure-assisted behavior is what turns a fast connection into a reliable one.

From deep vacuum at 10 millitorr (micron) all the way to 1,000 psi (69 bar). We cover system evacuation at one end and leak testing, burst testing, and high-pressure work at the other — which is why it is used across refrigeration production, lab, and R&D environments where one connector needs to handle the full process.

Engineered for the demanding requirements of the refrigeration industry, the FasTest ST is now made with stainless steel materials, and its durable main seal can be replaced without disassembling the connector — keeping high-volume stations running with minimal downtime.

The Problem the FasTest ST Solves

A smooth straight tube is one of the harder things to make a repeatable test connection to, and the usual approaches all have real costs:

• There is nothing to grip: A smooth tube has no bead, flare, thread, or expanded end. Connectors that lock onto a tube feature have only the tubing itself to lock onto, so manufacturers often fall back on installing a fitting or brazing a connection — both of which add a costly/time-consuming step and consume/waste a portion of the tube material.

• Pressure pushes the connector off: Without a mechanical feature to retain it, a connector on a smooth tube is fighting system pressure trying to push it away. A system that only relies on a seal to resist that force will have a much lower maximum operating pressure and must often be “fixtured” to prevent the connector or tube from blowing off.   The ST features a gripping collet that mechanical holds the tube in the connector to much higher pressures than are possible with a seal alone doing the gripping.

• Deep vacuum and high pressure in one process: Refrigeration processing runs from deep-vacuum evacuation through charging as well as leak and burst testing. Most connectors cover one end of that span, forcing a tool change mid-process.

• Seal wear is a downtime problem: Seals are consumables (especially the “Main Seal”) in high-volume testing. If replacing one means taking the connector apart, the maintenance time adds up across a fleet of tools.  ST Main Seals are easy to replace and minimize replacement time.

The FasTest ST addresses all of this: it connects to the tube as-is with no preparation, pressure-assisted sealing resists movement as pressure rises, its range runs from 10 millitorr of vacuum to 1,000 psi in one tool, and seals are replaceable without connector disassembly.

Key Features 

Instant Connections to Copper, Steel, and Aluminum Tubes

The FasTest ST connects to smooth straight tubes in copper, steel, and aluminum — the materials used throughout refrigeration systems. The sleeve-actuated connection takes seconds and requires no tube preparation, no fitting installation, and no tools, so operators can move from tube to tube at production speed.

Built for the Demanding Requirements of Refrigeration

The FasTest ST is designed specifically around what refrigeration work demands: deep vacuum, high pressure, repeated cycling, and a leak-tight seal on plain tube stock. Rather than being a general-purpose connector adapted to refrigeration, it is engineered for that environment from the start.

Deep Vacuum Down to 10 Millitorr (Micron)

Deep-vacuum capability down to 10 millitorr (micron) lets the FasTest ST handle system evacuation as well as pressure work. Combined with the 1,000 psi (69 bar) upper limit, a single connector covers evacuation, charging, leak testing, and burst testing without swapping tools between process steps.

Pressure-Assisted Sealing Resists Movement Under Pressure

Pressure-assisted sealing is the FasTest ST’s defining engineering feature. As system pressure rises, it energizes the seal further and helps the connector resist movement instead of being pushed off the tube. On a smooth, featureless tube — where there is no bead or thread to retain the connector — this is what eliminates leaks and keeps the connection stable through the full test.

Replaceable Seals Without Connector Disassembly

The FasTest ST’s seals are durable and replaceable without taking the connector apart. In high-volume testing, where seals are a routine consumable, this keeps a seal change to a quick in-place service rather than a teardown — meaningfully reducing maintenance downtime across a fleet of connectors.

Now Made with Stainless Steel Materials

The FasTest ST is now made with stainless steel materials, supporting durability and corrosion resistance in the refrigeration and lab environments where it is used most.

Technical Specifications

Where the FasTest ST Is Used

Refrigeration Tube Leak Testing

As a leak test connector for smooth straight tubes, the FasTest ST connects directly to the copper, steel, and aluminum tube stock used throughout refrigeration assemblies. Because no fitting or brazed joint is needed, leak testing happens on the tube as-is — which both speeds the test and avoids consuming the tube end.

Evacuation & Charging

The FasTest ST’s deep-vacuum capability down to 10 millitorr (micron) makes it suitable for evacuating refrigeration systems as well as charging them. One connector covers the evacuation and charging steps that would otherwise require separate tooling.

Burst & High-Pressure Testing

With a 1,000 psi (69 bar) rating and pressure-assisted sealing that resists movement as pressure climbs, the FasTest ST is used for burst testing and high-pressure validation of tube assemblies — applications where a connector that creeps or releases under load is not an option.

Laboratory & R&D Testing

In lab and R&D settings, the FasTest ST’s wide vacuum-to-pressure span and tool-free connection make it a practical bench connector for tube testing across a range of conditions, without preparing or consuming sample tubes for each test.

FasTest ST vs. a Compression Fitting or Brazed Test Connection

Frequently Asked Questions

Q: What is the FasTest ST?

A: The FasTest ST is an external, sleeve-actuated connector that seals onto smooth straight tubes — copper, steel, or aluminum — from 10 millitorr of vacuum up to 1,000 psi (69 bar). It connects to the tube as-is, with no flare, bead, thread, or expanded end required.

Q: Is the FasTest ST a leak test connector?

A: Yes. The FasTest ST is used as a leak test connector for smooth straight tubes, and it also handles burst testing, evacuation and charging, and lab processes. FasTest offers a full range of leak test connectors for other tube features, threads, and port types.

Q: What does the FasTest ST connect to?

A: Smooth straight tube. Unlike connectors that grip a bead, flare, or expanded end, the FasTest ST seals to plain tube stock without any feature or preparation.

Q: What tube materials can the FasTest ST connect to?

A: Copper, steel, and aluminum tubes — the materials commonly used in refrigeration systems.

Q: What is the pressure and vacuum range of the FasTest ST?

A: Vacuum 10 mtorr (micron) up to 1,000 psi (69 bar) — a span that covers deep-vacuum evacuation at one end and leak testing, charging, and burst testing at the other.

Q: Why does pressure-assisted sealing matter on a smooth tube?

A: A smooth tube has no mechanical feature to retain the connector, so system pressure works to push it off. Pressure-assisted sealing uses that rising pressure to energize the seal further and resist movement — eliminating leaks and keeping the connection stable through the test.

Q: Is the FasTest ST available in stainless steel?

A: Yes — the FasTest ST is now made with stainless steel materials, supporting durability and corrosion resistance in refrigeration and lab environments.

Q: How are the seals on the FasTest ST replaced?

A: The FasTest ST uses durable, replaceable seals that can be changed without disassembling the connector. Main seal replacement instructions are available for download.

Q: Can the FasTest ST be rebuilt in-house?

A: FasTest does not recommend it. ST Series connectors are complex to rebuild and require customized tooling, so FasTest recommends returning connectors to the factory for rebuild. Contact fastsales@fastestinc.com for assistance. Routine seal replacement, by contrast, can be done in place without disassembly.

Q: What is the difference between the FasTest ST and the JXL?

A: Both are rated to 1,000 psi (69 bar). The FasTest ST connects to smooth straight tubes, while the JXL connects to smooth straight and swaged tubes — so the JXL is the choice when the tube population includes swaged ends as well as plain ones.