How Tube fittings, Flare fittings, Medium and High Pressure and SAE O-ring Seals Perform

There are several connections that are used for higher pressure connections where taper seals are not ideal. These connections use either a metal to metal seat or an o-ring seal to make a pressure tight seal at high pressures.

SAE Seal

Design: The SAE (Society of Automotive Engineers) o-ring boss seal uses a male fitting with an o-ring to seal in a female port with an angled section where the o-ring seats. Unlike NPT seals that stretch the female portion, SAE seals use straight threads and therefore do not damage the mating part.

Applications: This seal is popular in automotive applications and in other situations where heating, cooling and vibration are an issue. All ports on Ralston Instruments hand pumps, calibration manifolds, volume controllers and fluid traps use an SAE o-ring boss seal.

Flareless Tube Seal

Design: Flareless tube fitting connections such as those made by Swagelok, Parker, Hoke, Gyrolok and Tylok use a set of ferrules and a nut to dig into a piece of tubing to form a pressure seal on a piece of copper, steel or stainless steel tubing. These are effective because there is no end preparation required to make a good seal.

Applications: This seal is used in the nuclear and process industries. Ralston Instruments makes a full line of Tube fitting adapters to connect to any flareless tube fitting.

37° Flare AN Seal

Design: The 37° flare AN seal is used for sealing tubing to end connections. It requires the end of the tube to have a nut slipped onto it and then flared out using a special tool. To seal properly, the nut is threaded into a flare fitting which clamps the flared tube in between the nut and flare fitting.

Applications: These seals are used predominantly in aerospace, marine applications and in older plants that have not upgraded to flareless tube fittings. Despite their effective sealing method, these fittings are time consuming to prepare. Ralston Instruments carries a variety of 37° flare AN adapters.

High Pressure Seals

Design: High pressure seals such as those made by HIP, Autoclave Engineers or Butech use a metal-to-metal seal that provides the ability to go to very high pressure. These seals work well up to 60,000 psi pressure but require some tube preparation. Each tube must be coned and threaded with two separate tools before they are ready for use.

Applications: Ralston Instruments offers High Pressure Quick-test adapters and High Pressure Quick-test XT adapters to adapt to both Quick-test and Quick-test XT hoses. These allow our customers to connect all Ralston hoses and adapters to High Pressure connections.

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