Omnisafe fittings
Omnisafe fittings are used in ultra-high-purity plumbing and propulsion systems to join tubes and/or components together. This flight qualified, all metal, face seal, Compression fitting, is used in gas or liquid fluid delivery systems. Integral opposing torque eliminators prevent twist or "wind up" during mate up. Anti-torque couplings subsequently, resist loosening under thermal cycling or shock & vibration.[1] Omnisafe fittings are used primarily in fluid delivery applications such as aerospace propulsion, nuclear and Semiconductor device fabrication. These ultra high purity systems typically specify extremely low leak tolerance.
Omnisafe fittings allow fluid delivery system modularity due to simplified threaded connection and disconnection. This removes the logistic issues of fabricating an all welded system by enabling 1) work on independent subsystems 2) Component replacement due to failure or upgrade, 3) Subsystem or Component test, or 4) Late component integration.
How they work[edit]
Before the tightening of the Omnisafe fitting, a new gasket is placed inside the female nut assembly. As the male and female nuts are threaded together the two torque eliminators engage. When the nuts are brought to finger tight. Using two opposing wrenches, the male and female nuts are tightened 1/6th of a turn past finger tight. The Toroid shaped surfaces of the glands are indented into the gasket, linearly with no rotation, creating a high purity, high pressure or high vacuum seal.
In the standard configuration the threads of the female nut are silver plated to prevent thread galling. In certain aerospace applications where plating is not permitted a small amount of Krytox or light oil applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of fitting. When using unplated female nuts it is advisable to tighten 1/8" turn past finger tight and only tighten more as necessary to prevent the threads from galling.
Types of fittings[edit]
Omnisafe fittings come in standard sizes to connect systems of 1/8", 1/4", 3/8", 1/2", 3/4, & 1" tubing. The standard material for all component parts of the fitting is 316L Stainless Steel. Other materials used for the wetted surface include Inconel, Hastelloy, Incoloy 800HT, Phosphor Bronze and Titanium.
Aerospace NASA[edit]
1.DAWN [2] - Omnisafe fitting are used in the Xenon Ion Propulsion (XIPS) on Dawn a mission to explore the building blocks of the Solar System in the Main Asteroid Belt.
2.MSL (Curiosity Rover) [3] - 42 Omnisafe fittings connect components of the Heat Rejection System (HRS) - Mars Rover exploring Gale Crater.
3.MSL 2020 (Perseverance Rover) [4] - 42 Omnisafe fittings connect components of the Heat Rejection System (HRS) - Mars Rover exploring Jezero (crater).
Semiconductor[edit]
3.Process Module Technology Center[5] - Used in piping connections that deliver high purity process gases from supply tanks to process tools for Semiconductor device fabrication
Nuclear[edit]
4. National_Ignition_Facility [6] - Fittings used to connect the vapor supply to a chamber for Crystal growth.
5. Thorium Molten Salt Reactor[7]
Advantages[edit]
Omnisafe fittings are utilized because they are flight qualified and offer a high integrity seal in critical fluid delivery system where leaks are catastrophic. These systems include spacecraft propulsion and process equipment where the working fluid is toxic, corrosive or pyrophoric. Standard Omnisafe fittings allow hundreds of mate/demate cycles. High purity - Omnisafe fittings do not generate particles due to galling of the sealing surfaces observed in face seal fittings with out torque suppression. If the gasket is inadvertently missing during tightening the glands are not damaged as with face seal fittings with out torque suppressors.
Disadvantages[edit]
For the standard Omnisafe fitting the gasket is a consumable and must be replaced each time the fitting is opened. The Omnisafe fitting must be orbitally welded on to tubing or a component during the fabrication of a fluid delivery system.
See also[edit]
References[edit]
- ↑ "New Torque Suppressor Solves Problems of Metal Face Seal Fittings" (PDF). Solid State Technology. 1997.
- ↑ "Flight Qualification of Omnisafe Anti-Torque, MultiMate/Demate Fitting" (PDF). Joint Propulsion Conference 2005. 2005.
- ↑ "Mechanically Pumped Fluid Loops for Spacecraft Thermal Control" (PDF). Joint Propulsion Conference 15th Annual Thermal & Fluid Analysis Workshop 2004.
- ↑ MSL 2020 - Mars Rover Perseverance
- ↑ "Torque Elimination Fittings Add to Gas Handling Safety 2002" (PDF). Semiconductor International. 2002.
- ↑ "Torque Elimination Fitting Prevent Ultra High Purity Gas Corrosion Site". MDS – Material Performance, September 1999. 1999.
- ↑ "High Performance Metal Face Seals @ TEAC6". Thorium Energy Alliance Conference 6. 2014.
External links[edit]
- "Jointing Copper Tubes: Compression Joints" (PDF). UK Copper Board.
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