18.8 Stainless Steel Sanitary Tubing

18.8 Stainless Steel Sanitary Tubing

Stainless Steel – The  broad  classification  of  iron-base  alloys  (50% minimum  iron)  containing  at  least  10%  chromium  that  are  known  for their excellent corrosion and heat resistance. Other elements are also  added to form alloys for special purposes, in addition to the corrosion resistance imparted by the chromium. Some of these elements are: nickel  for increased corrosion resistance, ductility and workability; molybdenum  for increased corrosion resistance, particularly resistance to pitting, increased creep strength and high temperature strength; columbium and titanium for stabilization; sulfur and selenium for improved  machinability.

Stress-Corrosion Cracking – Catastrophic  failure  by  generally transgranular cracking occurring in stainless steels and other metals. It is caused by combined action of a corrosive environment and stress, often without outward appearance of general corrosion attack.

Tensile Strength – A short form of "ultimate tensile  strength".  The maximum tensile stress which a material is capable of sustaining. Tensile strength is calculated from the maximum load during the tension test carried to rupture and the original cross section area of the specimen.

Tensile Testing – A procedure used to determine the load at which a material will begin to plastically deform (the tensile yield strength) and ultimately at which it will break (the ultimate tensile strength). Resulting test values are a ratio of applied load (pounds) to cross-sectional area of the   test sample (square inches) and are expressed in units of pounds per  square inch (psi) or in metric units of megaPascals   (MPa).

TIG (Tungsten Inert Gas) – A welding process that uses a non-consumable tungsten electrode to provide an electric arc to melt a work piece. Inert gases are used to shield the arc and the weld puddle to prevent oxidation during cooling. Used for heat exchanger, condenser and 18.8 Stainless Steel Sanitary Tubing.

18.8 Stainless Steel Sanitary Tubing Dimensions – O.D.- outside diameter. I.D.- inside diameter.

Wall thickness or gauge.

All tube dimensions are specific; pipe dimensions are nominal.Specific -actual measurements in  inches.

Nominal - theoretical or stated value of a   dimension.

Ultimate Tensile Strength – The stress in pounds per square inch (psi) that causes the material to fracture.

Weld Decay Test- A  corrosion  test  developed  for  the  black  liquor industries (pulp/paper, sugar refining) to detect susceptibility of stainless steel weldments to attack by boiling hydrochloric acid cleaning solutions. Test  results are reported as a ratio of the change in thickness of the weld  to the change in thickness of the base material. A ratio of 1.0:1 indicates  no difference between weld and base metal. A ratio of 1.25:1 indicates   that the  weld  thickness  changed  by  25%  more  than  the  base material did.

Yield Strength – The calculated stress value  at  which  a  tensile  test specimen experiences a plastic change in length with an increase in   applied load. The yield strength of a material must be exceeded to achieve a permanent change in shape (i.e. forming or bending). Applied loads of less than the yield strength result in spring back, or the tendency for a material to return to its original shape when the load is removed.