Glossary of Technical Terms

  1. Anti-extrusion Ring
  2. A ring used to support a softer sealing ring and prevent it from extruding.
  3. Back-up Ring
  4. Anti-extrusion ring or support ring.
  5. Bearing
  6. See Wear Ring
  7. Bi-directional Seal
  8. A seal that prevents leakage from both directions.
  9. Cold Flow
  10. Continued deformation under stress
  11. Composite Material
  12. Materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure.
  13. Compression Set
  14. The permanent deformation of a seal after release of a compressive load.
  15. Copolymer
  16. A copolymer is a polymer derived from two (or more) monomeric species.
  17. Creep
  18. Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses.
  19. Double acting Seal
  20. A seal designed to take pressure from two sides.
  21. Dynamic Seal
  22. A seal designed to prevent leakage between two moving surfaces.
  23. Elasticity
  24. The property of a substance that enables it to change its length, volume, or shape in direct response to a force effecting such a change and to recover its original form upon the removal of the force.
  25. Elastomer
  26. An elastic substance occurring naturally, as natural rubber, or produced synthetically, as butyl rubber or nitrile.
  27. Extrusion
  28. Distortion or flow of part of a seal into an extrusion gap under pressure.
  29. Extrusion Gap
  30. The clearance on the low pressure side between two parts, which house the seal.
  31. Face Seal
  32. A seal that is compressed in a direction parallel to its axis.
  33. Flash
  34. Extruded material on the partially finished product formed during the molding process.
  35. Flex Cracking
  36. A surface cracking induced by repeated bending or flexing.
  37. Free Height
  38. The height of a seal in its free-state.
  39. Friction
  40. Friction is the force resisting the relative motion of two surfaces in contact.
  41. Gasket
  42. A rubber, metal, or other material, for packing a piston or placing around a joint to make it seal a fluid or gas.
  43. Gland
  44. A cavity into which a seal is installed. Component at the working end of a cylinder which contains seals.
  45. Hardness
  46. The measured resistance of a material to indention, abrasion, deformation, or machining.
  47. Housing
  48. A rigid component which contains a seal assembly.
  49. Hydraulic Seal
  50. A hydraulic seal is usually a relatively soft, non-metallic ring captured in a groove or fixed in a combination of rings, forming a seal assembly, to block or separate fluid in reciprocating motion applications.
  51. Leakage Rate
  52. The rate at which a fluid passes a seal in a given time.
  53. Lip Seal
  54. An elastomeric seal that prevents leakage in rotary seal applications through the use of one or more contact lips operating on the shaft surface. These seals are commonly called shaft seals, oil seals or rotary lip seals.
  55. O-ring
  56. A toroidal shaped sealing device usually made from an elastomeric material, may also be made from metal or PTFE.
  57. Perfluoroelastomer
  58. An elastomer with high temperature and chemical resistances.
  59. Permanent Set
  60. Permanent deformation of spring or elastomer upon release of load.
  61. Permeation
  62. The passage of a fluid under pressure through a solid material by diffusion.
  63. Polymer
  64. A material formed by the joining together of many (poly) units (mer) of one or more monomers.
  65. Porosity
  66. Quality or state of being porous.
  67. PTFE
  68. Polytetrafluoroethylene.
  69. Rubber
  70. See “Elastomer.”
  71. Scraper
  72. A seal used to keep dirt or other foreign matter out of a hydraulic or pneumatic device.
  73. Seal
  74. A device designed to prevent the passage of a medium (fluid or solid).
  75. Single acting Seal
  76. A seal designed to take pressure from only one side.
  77. Spring
  78. A machine element capable of restoring energy and releasing it.
  79. Static Seal
  80. A seal between two non moving parts.
  81. Tensile Strength
  82. Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material.
  83. Thermal Expansion
  84. Expansion caused by increase in temperature.
  85. Uni-directional Seal
  86. A seal that prevents leakage from only one direction.
  87. Vacuum
  88. An enclosed space that is occupied by a gas at less than atmospheric pressure.
  89. Vulcanization
  90. Refers to a specific curing process of rubber involving high heat and the addition of sulfur or other equivalent curatives.
  91. Weepage
  92. A minute amount of liquid passing by a seal.
  93. Wiper Ring
  94. See “Scraper.”
  95. Wear Ring
  96. Element used to protect moving parts from wear.
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