The PRD ( pressure triggered ) of Class 6 , shall be so designed to operate at temperatures as specified in the Annex 5O . 7.2.4 . The burst pressure of the PRD ( pressure triggered ) of Class 6 shall be at least 1.5 times working pressure at ambient temperature and at the maximum operating temperature as indicated in Annex 5O . '' Paragraph 7.4.2.2.2. ,