Understanding CGA numbers and port connections

Why connections are gas-specific

Cylinder valve outlets are standardised so that a regulator intended for one gas family cannot be fitted to another. Thread diameter, pitch, handedness and seat design all vary deliberately.

Left-hand threads, for example, commonly indicate a flammable gas. The intent is that an incorrect assembly is physically impossible rather than merely discouraged.

Reading a CGA number

A CGA number such as 580 or 540 identifies one specific outlet geometry, and each is assigned to a defined group of gases — 580 for inert gases such as nitrogen and argon, 540 for oxygen, and so on.

The number is not a size. Two CGA connections with similar thread diameters can still be incompatible in seat design, which is exactly the point.

Outlet connections

• NPT — tapered pipe thread, sealed on the threads; general industrial service.
• Compression tube fittings — a ferrule seals against the tube; repeatable and widely used for panel and instrument work.
• Face-seal fittings — a metal gasket compressed between polished faces; used where leak-tightness and cleanliness are paramount.

Specifying connections in an order

A complete order names the inlet connection, the outlet connection, and the size of each. Where a regulator has several ports, each is specified separately.

In this catalog, configurable products assemble their part number from exactly these choices, so a complete selection produces the manufacturer's own ordering code.