Following requalification, each cylinder must be plainly and permanently marked as per the CSA B339-14 (Cylinder, Spheres, and Tubes for the Transportation of Dangerous Goods) Standard.
Clause 24.6.4.1 states that “Except as provided in Clause 24.6.4.4, any marking becoming illegible shall be remarked on the container or reproduced on a metal plat permanently secured to the cylinder or any permanent part of the container, excluding the sidewall.”
Clause 24.6.4.4 states that “Where the space originally provided for marking requalification dates becomes filled, the expired requalification dates, except the last one, may be removed by peening, provided that
(a) Permission to do so has been obtained from the owner of the container;
(b) The design minimum wall thickness is maintained; and
(c) The original manufacturing test date is not removed.”
TDG standards such as the CSA B339 Standard can be viewed on the CSA Group website. Simply register or log in and scroll down to “TDG Standards” under “View Access”.