the fitting is screwed into a boss and orientated as needed, an additional nut tightens the fitting, washer and o-ring in place. Flare fittings, are metal to metal compression seals deformed with a cone nut and pressed into a flare mating. Face seal, metal flanges with a groove and o-ring seal are fastened together. Beam seals are costly metal to metal seals used primarily in aircraft. Swaged seals, tubes are connected with fittings that are swaged permanently in place. Primarily used in aircraft. Elastomeric seals (O-ring boss and face seal) are the most common types of seals in heavy equipment and are capable of reliably sealing more than of fluid pressure. See also Automatic transmission Brake fluid Fluidics Hagen–Poiseuille equation High-density solids pump Hydraulics Hydraulic brake Hydraulic drive system Hydraulic analogy National Fluid Power Association Sidelifter Hydraulic press Pascal's law [[Oil Hydraulics]] References and notes Hydraulic Power System Analysis, A. Akers, M. Gassman, & R. Smith, Taylor & Francis, New York, 2006, External links Facts worth knowing about hydraulics, Danfoss Hydraulics, 1.4Mb pdf file On-line re-print of U.S. Army Field Manual 5-499 Information about Fluid Power is also available on the National Fluid *Power Association web-site nfpa.com Engineering vehicles Fluid dynamics Machinery, Hydraulic