Fortunately, the wide acceptance of welded stainless steel

tubing and standardization within the metals fabrication industry

has simplified tube selection. Outside diameter and gage is used

to specify sanitary tubing. Sixteen-gage tubing is used for the vast

majority of applications, except those with large-diameter and/or

higher product pressures. Specifications for 310 Stainless Steel Pipe Welding are

shown in table 4. Tubing is manufactured according to ASTM

A270 "Specification for Seamless and Welded Austenitic Steel

Sanitary Tubing."

Sanitary Pipeline Fittings are manufactured by a long list of

companies utilizing a number of joint styles and sealing techniques

including (in no particular order): Tri-Clamp or "clamp," Butt-weld,

Bevel Seat, DC, H-Line, HDI-Line, John Perry, S-Line, and I-line.

Fitting types have been developed specifically for certain industries,

manufacturers and user groups. Adaptors to connect different types

of fittings are sometimes available, as well as adaptors to connect

fittings to non-sanitary piping such as flanges, pipe thread, pipe OD

(compression fitting) and other items. The system designer must

select carefully, especially when mating new piping to existing

piping and equipment.

Tube is manufactured to a set outside diameter and wall

thickness (e.g. 1.5" OD, 0.065" wall), while pipe is specified by a

"nominal" (not actual) inside diameter. The wall thickness of pipe

is described by the "schedule". For example, schedules 5 and 40

pipe have wall thicknesses of 0.065" and 0.109" respectively.

Food-Grade Gasket Materials

As specified by the 3-A standards, food-grade rubber and

plastic material can be used for gaskets in sanitary joints. Table 6

lists selected 3-A approved commercial gasket materials and their

working temperature range.