What does “S2” mean?

The stenciled marking on T316L ASTM A270 tubing is often marked with “S2” following ASTM A270. So, what does this mean?

ASTM International Standards include at the end of each published standard, as necessary, Supplementary Requirements that are not specifically addressed in the body of the Standard, but are available as optional requirements by the request of the purchaser, or by a referring specification.  These requirements are identified as S1, S2, etc.  The subject of each supplement varies depending on the Standard in which it is found. For example, in A249 S1 addresses stress relief anneal heat treatment, while in A270 it involves an intergranular corrosion test.

ASTM A270 currently has three such supplementary requirements.  S1 is an intergranular corrosion test, S2 contains pharmaceutical grade tubing requirements and S3 addresses passivation.

S2 specifically pertains to sulfur content when UNS S31600 and S31603 tubing is ordered. The sulfur must be controlled within 0.005-0.017% under the S2 requirement.

S2 is pharmaceutical quality tubing, however; it is not BPE certified tubing. It is important to note that there is a distinct difference between ASTM A270/S2 and ASTM A270/S2 BPE Tubing. ASTM A270/S2 is not 100% borescope inspected, however; Rodger Industries Inc. offers Certified BPE tubing that is 100% borescope inspected.  It should also be noted that borescope inspection of tubes is not a requirement of the BPE Standard, so not all suppliers provide this added assurance.

Rodger Industries stocks a wide range of sanitary process tubing from 3/8” to 12” for a wide range of industry applications. Please contact us today with your tubing needs.