Stainless steel tubing, or SS tubing, is a hollow, cylindrical metal form used as equipment components or as the medium through which fluids or gas pass. Manufacturers employ welding or seamless tubing procedures to produce stainless steel pipes and tubing. SS tubes are used in the medical, dental, automotive, petrochemical and semiconductor industries, among others.
Stainless steel tubing is used in applications ranging from and dental implants medical instruments, such as hypodermic tubing like syringes and hypodermic needles, to hydraulic systems, fuel lines and engine conduits. The paper and pulp industry has become increasingly reliant on stainless steel pipes and stainless steel tubes because of the corrosive and aggressive fluids used in the process of paper making. Manufacturers produce different variations of stainless tubing and piping, including stainless steel pipe fittings, which are pipe attachments, corrugated stainless steel tubing which is flexible and made with a PVC outer layer, stainless steel square tubing, which is an alternative to the usual round shape, and seamless stainless steel pipe, which, because of their manufacturing process, are more pressure resistant compared to welded pipes.
Stainless steel tubing and piping is produced via welding, which involves roll forming stainless steel and connecting the formed portions along a seam through fusion, leaving the middle hollow. Welding achieves a higher degree of precision without secondary operations. The degree of precision required of the stainless steel tubing manufacturers depends on the industrial application. It can also be produced through metal spinning, which is a cold worked metal fabrication technique comparable to a potter forming clay, except a metal spinner uses a flat round disc of sheet metal which is rotating on a spinning lathe. However, the metal spinning process is limited to the production of concentric shapes, including tubes and pipes. Perhaps the most easily available type is the seamless stainless steel pipe or tube, which is formed by extrusion. A solid billet is drawn over a piercing rod, which creates a hollow shell without any seams, unlike welding, where seams are unavoidable. Seamless tubing and piping is the most reliable when it comes to retaining high amounts of pressure, as it is much less likely to split. For this reason, hypodermic tubing is made this way.
Although similar, stainless steel pipes and tubes differ in slight manners of properties and applications. All piping is considered tubing and is mostly distinguished by its uses, which are mainly for the transmission of water or gas and used almost exclusively in the plumbing and pipe fitting industries. Different pipe fittings are also often made out of stainless steel. These attachments do a number of different useful things for plumbing and piping. Many connect tubes together, including nipples, which are threaded on both sides, elbows, which turn tubes at a 90 or 45 degree angle, reducers, which allow differently sized pipes to join, and tees, which are able to join 3 different pipes. Caps and plugs cover pipes and keep their contents contained. Tubes, on the other hand, are more diverse in their implementations. They are usually round, but square types are manufactured to make stepladders, display racks and bar foot railings. Corrugated tubing, used in gas heating systems, is made of 2 layers-the exterior is a PVC covering and the interior is stainless steel tubing. Corrugated tubing is easily bent, and therefore needs fewer connections.
A number of stainless steel alloyed tubes such as 304 stainless steel tubing and 316 stainless steel tubing are used because of its excellent corrosion resistance, ease of cleaning, low maintenance and long run cost-effectiveness. Even though stainless steel may require a higher initial cost than other metals, maintenance and replacement costs are lower. Stainless steel tubing is less expensive than titanium, a metal with similar properties and applications. Stainless steel tubing is used very often within the medical industry. This type is referred to as hypodermic tubing, and is the medium for transferring medicine from a bottle to under the skin and into the bloodstream. Stainless steel is used because its smooth and crack-free surface is very easy to sterilize. Hypodermic needles and syringes are very small and considered an example of small diameter tubing. Because these tubes are so tiny, they have their own set of gauge sizes, which are determined by the outside and inside diameter of the tube, instead of wall thickness and outside diameter. Hypodermic tubing can range from .005" to .259" outside diameter and .002" to .239" inside diameter.
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Reducing hardness and stress in a metal, such as stainless
steel, through heating and cooling applications.
- A form of
annealing in which the level of atmospheric gas is reduced in order to
remove surface oxides from the surface of the stainless steel and to prevent
discoloration during the annealing process. This process is responsible
for the bright, shiny appearance associated with stainless steel.
- The internal
pressure limit of stainless steel tubing at which point the tube material will expand
to the point of deformation or bursting.
- A cold forming
process, commonly used in tube and pipe diameter reduction, in which a
tube is drawn through a carbide die. The diameter of the emerging
stainless steel tube
or stainless steel pipe reflects the size of the die.
- A characteristic
of a welded stainless steel tubing in which wall thickness remains consistent throughout
the stainless steel tubing, and the inside and outside diameter centers are equivalent to
one another.
- The decay of metals
by chemical agents, which convert them to nonmetallic products. Stainless
steel has a passive film created by the presence of chromium and often
other alloying elements, such as nickel and molybdenum, that resists
this process.
- The depth
of bend or the sweep of the arc. The minimum degree of bend is about
five degrees, while the maximum degree of bend in rotary-draw bending
is 180 degrees.
- The testing
of stainless steel tubing properties, such as tensile strength, yield strength, hardness,
burst pressure and bending.
- A characteristic
of seamless tubing in which wall thickness is not consistent throughout
the tube.
- A characteristic
of tubular products that is measured on samples of tubing using a standard
Rockwell Penetrator and recording the results on the Rockwell "B"
scale. Hardness is the direct result of annealing temperatures and material
properties; in general, as the hardness number increases, both tensile
and yield strengths increase along with a corresponding decrease in elongation
(ductility).
- A test
in which water is introduced into the stainless steel tubing at high pressure levels in
order to test for holes and porous parts. Because hydrostatic testing
is a nondestructive test, the water pressure level does not surpass the
stainless steel tubing yield strength.
- A term
that refers to the diameter of the interior portion of stainless steel
tubing
and pipes. The measurement of the stainless steel tube or stainless
steel pipe is not included in I.D.
- A pipe specification system that associates certain nominal pipe diameters with standardized wall thickness called "schedules." The same schedule number will have a different fixed decimal inch value for each nominal diameter.
- A term that refers to the diameter of the exterior portion of
stainless steel tubing and pipes. The tube or pipe is included in the O.D. measurement.
- A quantitative measurement
of how "round" a tube is, which is derived by comparing width
to height. Limits of ovality are specified on the appropriate ASTM
specification of a product.
- The creation
of a passive oxide layer on stainless steel, which is responsible for
the high corrosion resistance of stainless steel used in stainless steel
tubing.
- The impurities remaining
in mini-mill stainless steels, which result from the wide variety of metals
entering the process.
- The creation
of stainless steel tubing through the use of a piercing mill. During the process,
a round blank is pierced to produces the stainless steel tubing, which produces inconsistency
in wall thickness throughout the tube that can be fixed through secondary
operations.
- The creation
of stainless tubes through roll
forming and fusing the stainless steel along a seam. Welding provides
consistency throughout the stainless steel tubing.
