49 CFR § 195.424 - Pipe movement.
(1) Movement when the pipeline does not contain highly volatile liquids is impractical;
(2) The procedures of the operator under § 195.402 contain precautions to protect the public against the hazard in moving pipelines containing highly volatile liquids, including the use of warnings, where necessary, to evacuate the area close to the pipeline; and
(3) The pressure in that line section is reduced to the lower of the following:
(i) Fifty percent or less of the maximum operating pressure; or
(ii) The lowest practical level that will maintain the highly volatile liquid in a liquid state with continuous flow, but not less than 50 p.s.i. (345 kPa) gage above the vapor pressure of the commodity.
(1) The operator complies with paragraphs (b) (1) and (2) of this section; and
(2) That line section is isolated to prevent the flow of highly volatile liquid.