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Interpretation Response #16-0183

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

Interpretation Response Details

Response Publish Date:

Company Name: HazMat Resources, Inc

Individual Name: Daniel Shelton

Location State: TX Country: US

Response text:

September 5, 2017
 
Mr. Daniel G. Shelton
President
HazMat Resources, Inc.
124 Rainbow Drive, Suite 2471
Livingston, TX  77399-1024
 
Reference No. 16-0183
 
Dear Mr. Shelton:
 
This letter is in response to your October 14, 2016, letter and e-mail requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the installation of Department of Transportation (DOT) 400 series cargo tank vents on Motor Carrier (MC) 300 series cargo tank motor vehicles (CTMV).  Specifically, you ask several questions concerning the application of these requirements.  You also enclose guidance documents from your organization and the Truck Trailer Manufacturers Association; one memorandum from the Federal Motor Carrier Safety Administration (FMCSA); and clarification letters on this topic issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA). 
 
Scenario #1
 
An MC 307 CTMV has a maximum allowable working pressure (MAWP) of 35 pounds per square inch gauge (psig), and a total surface area of 884 square feet.  This CTMV has a pressure relief device (PRD) on it with:  1) a set pressure of 35 psig that is manufactured for a DOT 407 CMTV; and 2) a venting flow rate of 460,443 standard cubic feet per hour (SCFH) at 52.5 psig with an exposed surface area of 1,061 square feet.  A DOT 407 PRD with a set pressure of 35 psig may open between 42 and 46.2 psig.
 
Q1. Is the PRD in the above scenario set at the correct pressure for the CTMV? 
 
A1. No.Sections 173.33(d)(3), 180.405(h)(3), and 180.405(c)(2)(iv) allow the modification of PRDs on MC 307 CTMVs to more recent DOT 407 PRD specifications as long as the minimum venting capacity of the MC 307 and the DOT 407 CTMV requirements in §§ 178.345-10 and 178.345-11 are met.
 
Q2. Is the CTMV in violation of § 180.407(a)(2) if the internal pressure exceeds 35 psig and the PRD does not open until at least 42 psig?
 
A2. No.Section 180.407 addresses requirements for the testing and inspection of specification CTMVs.In this case, § 178.345-10(d) prescribes the setting requirements for CTMV PRDs and permits them to operate within this range.
 
Q3. Is the CTMV in violation of § 180.407(h)(3) for venting capacity for the CTMV specification if the PRD does not open until 46 psig?According to former § 178.342‑4(b) that prescribed the total venting capacity requirements for MC 307 CTMVs, the PRD must limit the internal pressure of the MC 307 CTMV to 130 percent of the MAWP (35 x 130% = 45.5 psig).However, the DOT 407 specification vent installed on the cargo tank is marked with a flow rating at 52.5 psig, not 45.5 psig.
 
A3. No.  PHMSA amended the HMR to discontinue construction of MC 300 series cargo tanks, and to permit the use of DOT 400 series PRDs on the remaining in-service MC 300 series cargo tanks.  FMCSA reports fewer than 300 of these in-service cargo tanks currently exist.  After thorough review of the applicable provisions of the HMR, PHMSA has confirmed that use of the DOT 400 series PRDs on MC 300 series cargo tanks is acceptable under the HMR.  These replacement PRDs on MC-specification cargo tanks must comply with §§ 180.405(c)(2) and 180.405(h)(1)-(3).  Although this means that the minimum venting capacity of the MC 307 PRD you described must be met, the rest of the MC 307 PRD specifications, including the open and/or closing pressures, do not apply.  Instead, these PRD specifications must conform with § 178.345-10.  Further, these PRDs must have a minimum flow rate/flow capacity that conforms to their applicable vent capacity prescribed in Table I of § 178.345-10(e).  The vent capacities prescribed in this table are identical to those prescribed in the outdated MC 307 specification section for total (venting) capacity (former § 178.342-4(b)).  Because your example states the DOT 407 specification flow rate is approximately 460,000 cubic feet free air per hour for an exposed surface area of 1,061 square feet, the minimum venting capacity specification for the MC 307 PRD is met.  Note:  PHMSA has received no incident report data regarding the failure of these upgraded PRDs on MC 300 series cargo tanks for over 20 years.
 
Q4. Is the CTMV in violation of § 173.33(d)(3) for the venting capacity for the MC 307 specification if the PRD does not meet the venting flow rate until 52.5 psig? 
 
A4. No.See Answer A3.
 
Q5. If the PRD is bench tested and conforms to § 180.407(j)(1)(ii)(B), is it permissible to operate the PRD on this CTMV with no further alterations? 
 
A5. Yes, provided testing requirements in § 180.407(j)(1)(ii)(B) are met.See Answer A1.
 
Q6. Do the HMR allow a Registered Inspector to change the set pressure of a PRD for a specification CTMV?  If the answer is yes, what equipment would be required to determine the flow rating of that vent at that set pressure, and what training is required to perform these operations? 
 
A6. The HMR do not state who is allowed to set the PRD or what equipment must be used, only that testing and setting requirements must be met (see § 180.407(j)(1)(ii)(B)).This information may be found in the PRD owner’s manual or may be obtained by contacting the PRD manufacturer.See § 180.409(a) for the applicable training and experience requirements.
 
Q7. If a Registered Inspector bench tests the PRD and finds that it complies with § 180.407(j)(1)(ii)(B), then changes the set pressure to 35 psig to match the MAWP of the CTMV, does the Registered Inspector have to use § 180.407(j)(1)(ii)(A) or (j)(1)(ii)(B) to re-bench test the PRD to determine its suitability? 
 
A7. Section 180.407(j)(1)(ii)(B) must be used to bench test a modified PRD of DOT 407 specification to be used on an MC 307 CTMV.
 
Scenario #2
 
An MC 306 CTMV has a MAWP of 5 psig. 
 
Q8.      If the PRD is bench tested and conforms to § 180.407(j)(1)(i), is it permissible to operate the PRD on this CTMV with no further alterations? 
 
A8.      Yes.  If the PRD is of the MC 306 specification and is tested in conformance with § 180.407(j)(1)(i)(A), it is permissible to use.  This is due to the venting requirements of former § 178.341-4(d)(2) not prohibiting the PRD from opening below the MAWP.  If the PRD has been modified in accordance with § 180.405(c)(2)(ii) and is tested in conformance with § 180.407(j)(1)(i)(B), it is also permissible to use.  In the second example, the PRD must be tested to open at not less than 110 percent (5.5 psig) of the MAWP and not more than 138 percent (6.9 psig) of the MAWP as prescribed in § 178.346-3(c)(1).
 
Scenario #3
 
An MC 312 CTMV has a MAWP of 120 psig.  The HMR do not mandate self-closing PRDs or specify a set pressure for PRDs for MC 312 CTMVs.
 
Q9.      If the PRD is set at 95 psig, is this CTMV in violation of the HMR?  If so, under what section?  If not, how do I comply with § 180.407(j)(1)(iii) for bench testing? 
 
A9.      If the PRD has not been modified per § 180.405(c)(2)(vi), it must meet the requirements of an MC 312 CTMV and is not in violation of the HMR.  With that being said, when mandated by the HMR to bench test the PRD, it will have to conform to the requirements of § 180.407(j)(1)(iii)(A) and must open between 100 and 110 percent of the MAWP and must reseat at no less than 90 percent of the MAWP.  If the PRD has been modified in accordance with § 180.405(c)(2)(vi), then it is in violation of the HMR.  Section 178.345 10(d) states that the set pressure of the PRD must be no less than 120 percent of the MAWP and no more than 132 percent of the MAWP.  When mandated by the HMR to bench test the PRD, it must conform to the requirements of § 180.407(j)(1)(iii)(B).
 
 
I hope this information is helpful.  Please contact us if we can be of further assistance.
 
Sincerely,
 
 
 
Shane Kelley
Acting Director
Standards and Rulemaking Division
Office of Hazardous Materials Safety
 
173.33(d)(3), 180.405(h)(3), 180.405(c)(2)(iv), 178.345-10, 178.345-11, 180.407, 178.345-10(d), 180.407(h)(3), 178.342‑4(b), 180.405(c)(2), 180.405(h)(1)-(3), 178.345-10(e), 173.33(d)(3), 180.407(j)(1)(ii)(B), 180.407(j)(1)(ii)(A), 180.407(j)(1)(i), 180.409(a), 180.405(c)(2)(ii), 178.346-3(c)(1)

Regulation Sections

Section Subject
173.33 Hazardous materials in cargo tank motor vehicles
178.345-10 Pressure relief
178.345-11 Tank outlets
178.346-3 Pressure relief
180.405 Qualification of cargo tanks