Interpretation Response #22-0011

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 07/28/2022

Company Name: Betts Industries, Inc.

Individual Name: David J. Adams

Location State: PA Country: US

View the Interpretation Document

Response text:

July 28, 2022

Mr. David J. Adams
Director of Design Engineering
Betts Industries, Inc.
1800 Pennsylvania Ave W.
Warren, PA  16365

Reference No. 22-0011

Dear Mr. Adams:

This letter is in response to your February 23, 2022, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the venting capacity of pressure relief systems for cargo tanks, specified in § 178.345-10(e). You state that "Table 1 - Minimum Emergency Vent Capacity" in paragraph (e) includes a note which allows for interpolation of the values on the table for intermediate sizes of cargo tanks, specifically exposed area in square feet. However, you note that it is not stated whether one can extrapolate the data on the table for cargo tanks larger than 1,000 square feet. You have provided an additional table showing data that you have interpolated and extrapolated from Table 1 in § 178.345-10(e). Lastly, you state that you are not aware of any regulation which limits the size of a cargo tank to less than 1,000 square feet of exposed area.

We have paraphrased and answered your questions as follows:

Q1. You ask whether there is any regulation that limits the size of a cargo tank to being no greater than 1,000 square feet of exposed area.

A1. Although the HMR do not limit the size of a cargo tank, the Federal Highway Administration (FHWA) regulates commercial vehicle weight and size requirements, in conjunction with state enforcement agencies. More information on the federal commercial vehicle size and weight program can be found on FHWA's website at the following web address: https://ops.fhwa.dot.gov/freight/sw/overview/index.htm.

Q2. You ask what venting capacity is required if the cargo tank has an exposed area of greater than 1,000 square feet.

A2. As you have stated in your email, the table for minimum emergency vent capacity in § 178.345-10(e) does not have a corresponding value for cargo tanks with an exposed area of greater than 1,000 square feet. It is the opinion of this Office that for cargo tanks with greater than 1,000 square feet of exposed area, extrapolation would be acceptable to determine the value of the cubic feet free air per hour. However, the extrapolation calculation should be verified by the Design Certifying Engineer responsible for determining compliance of the cargo tank design.

Q3. You ask whether extrapolation of the data from Table 1 in § 178.345-10(e) is permitted.

A3. Please see answer A2.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

178.345-10(e)

Regulation Sections