49 CFR § 390.38 - Exemptions for pipeline welding trucks.
(a) Federal requirements. A pipeline welding truck, as defined in paragraph (b) of this section, including the individuals operating such vehicle and the employer of such individual, is exempt from the following:
(5) Any requirement relating to hours of service of drivers, including maximum driving and on duty time, found in 49 CFR part 395.
(b) Definition. “Pipeline welding truck” means a motor vehicle that is travelling in the State in which the vehicle is registered or another State, is owned by a welder, is a pick-up style truck, is equipped with a welding rig that is used in the construction or maintenance of pipelines, and has a gross vehicle weight and combination weight rating and weight of 15,000 pounds or less.