The United States Pipeline and Hazardous Materials Safety Administration (“PHMSA”) addressed in a December 22, 2025, Interpretive Letter the application of the Hazardous Materials Regulations (“HMR”) to the transportation of propane in a specification MC 331 cargo tank motor vehicle (bobtail). See Reference No. 19-0025R.
PHMSA was responding to a meeting and May 19, 2025, correspondence with Westmor Industries, LLC (“Mestmor”).
PHMSA initially states that after further review, Reference No. 19-0025 has been superseded by this December 22, 2025, Interpretive Letter.
Westmor describes a scenario in which propane deliveries require drivers to reverse into unfamiliar locations to complete the delivery of propane to customers. This is stated to present safety concerns due to limited visibility and blind spots.
Westmor is stated to be considering mounting a reel to the structural support at the front of the bobtail chassis. The company wants to avoid installing a protection device. Based on a design drawing that was submitted by Westmor, the company is asking whether the proposed configuration is allowed by the HMR?
PHMSA responds in the negative, stating:
… While there is not a restriction against mounting the hose reel and piping to the front of the MC 331 chassis, § 178.337-10(a) requires “[a]ll valves, fittings, pressure relief devices, and other accessories to the tank proper shall be protected in accordance with paragraph (b) of this section against such damage as could be caused by collision with other vehicles or objects. . .”
§ 178.337-10(f)(2) is also cited, requiring each internal self-closing stop valve, excess flow valve, and check valve must be shielded by a shear section or other sacrificial device. Such protection device is required to be placed in the piping system outboard of the stop valve and within the accident damage protection device to prevent any accidental loss of lading.
PHMSA concludes that Westmor’s design would not meet the accident damage protection requirements prescribed in § 178.337-10.
A copy of the Interpretive Letter can be found here.
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