Minimum Thickness for Stainless Steel Drums
Pipeline and Hazardous Materials Safety Administration · Dec 9, 1997 · Reference No. 97-0165
Reggie’s quick take
A company asked about minimum wall thickness for stainless steel drums used for nitric acid under the Hazardous Materials Regulations. The agency said the capacities in the § 173.158 table are maximums, so a 200-liter stainless steel drum must be at least 1.5 millimeters thick. Where § 173.28 and § 173.158 both set a thickness, the stricter one (the greater minimum) applies. On specific gravity, a drum marked 1.8 may hold a material of 1.805 only if it was tested with that material, or one at least as heavy, and the test report is on hand.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your letter regarding the minimum thickness requirements for stainless steel drums under the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180). I apologize for the delay in responding to you inquiry and hope we have not caused you any inconvenience. Your questions are paraphrased and answered as follows:
Q. Section 173.158 has a table of thickness that seems to be unclear as to the thickness required in between the liter capacities listed. For instance, if a container's marked capacity is 200 liters, what is the required minimum thickness?
A. The capacities listed in § 173.158 for the minimum thickness for stainless steel drums for nitric acid are maximum capacities. Therefore, the minimum thickness for a stainless steel container with a marked capacity of 200 liters is 1.5 millimeters.
Q. Section 173.28 has a table of thickness that is used to determine if a packaging can be reused without retesting. The packaging in this case is required to be 1½ times the thickness in the table. Which one takes precedence?
A. For stainless steel drums to be used for nitric acid, the minimum thickness requirements that takes precedence is the more restrictive requirement (i.e., the one that requires the greater minimum thickness).
Q. Is the specific gravity marked on non-bulk containers the absolute maximum that is allowed? In other words, a product has a specific gravity of 1.805 is it allowed in a container marked for a specific gravity of 1.8?
A. If a packaging has been tested using the actual hazardous material, or a product with the same specific gravity, and the specific gravity marking is rounded down to the nearest tenth in accordance with § 178.503(a)(4)(i), the packaging may be used for that hazardous material provided the test report is available. Therefore, a material with a specific gravity of 1.805 may be loaded in a container with a specific gravity marking of 1.8 if the packaging has been tested with the actual material, or a product with the same or greater specific gravity, provided the test report is available.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.