We have discussed hydrostatic testing of all sorts of containers, most notably our SCBA cylinders and our process piping. But one very important cylinder I do not mention near enough is the 1-ton Chlorine cylinders. All chlorine cylinders, except DOT 3E 1800, MUST BE HYDROSTATICALLY TESTED EVERY FIVE-YEARS from the date of the previous hydro test (49 CFR Parts 100-185). The DOT 3E 1800 cylinders are those sample size cylinders, like the cylinders of calibration gases we use on our direct reading instruments. Granted this testing is usually done by the “owner” of the cylinder(s) – BUT IT IS OUR RESPONSIBILITY to ensure we are NOT using cylinders PAST their testing due date.
A cylinder may not be filled after it reaches the month and year five years past its last test date. However, a cylinder filled before the requalification becomes due may remain in service until it is emptied.
Retesting is also required after any reheat treatment or if the cylinder shows any signs of weakness, such as a LOSS IN WEIGHT OF 5% OR MORE.
Additionally, each time a cylinder is retested it must also be visually inspected, internally and externally, in accordance with CGA C-6, Standard for Visual Inspection of Steel Compressed Gas Cylinders.
Upon expiration of the test period, a cylinder may be requalified at any time during or before the month and year the requalification is due (See 49 CFR 180.205).
A ton container may be requalified at any time during the calendar year the prequalification retest is due (See 49 CFR 180.519).
No cylinder or ton container may be filled with a hazardous material and shipped in commerce once the requalification is overdue. However, a cylinder or ton container that is filled before the qualification expires may remain in service and can be shipped after expiration to the customer destination to be used and then returned to the original supplier/shipper for requalification.
Here is an image of how the 1-tonner’s are stamped after their testing – much like what we are accustomed to seeing on our SCBA cylinders.
Source: The Chlorine Institute’s Pamphlet 17 – Packaging Plant Safety and Operational Guidelines, Edition 5