MIL-STD-1411B
service pressure. These cylinders are marked with a "+" sign following the last periodic test date, and shall be equipped with an CG-1 type PRD with a rated burst pressure not to exceed the minimum required test pressure of the cylinder with which the device is used.
5.2.3.1.4 PRD CG-7 (spring loaded, reseating PRD). Cylinders with CG-7 type PRDs shall be inspected for evidence of leakage. CG-7 type PRDs are utilized in government service on cylinders in LPG and fluorocarbon gas service. Faulty PRDs shall be cause for valve rejection and shall be scheduled for replacement in accordance with A-A-59860 and the PID.
5.2.4 Inspection of flanges. Flanges on high-pressure cylinders shall be inspected for tightness of fit. These flanges are either pressed into place, sweat fit, or peened tight. Heat cannot be applied to the cylinder in resweating these accessories due to the possibility of annealing. Flanges shall be scheduled for peening, or for flange replacement when peening would deform the cylinder neck to fill a stretched flange. Any cracked flange or a flange with damaged threads shall be replaced in cylinder maintenance. Flanges on low-pressure cylinders, including acetylene cylinders, are welded to the base metal of the cylinder shell. Acetylene cylinder flanges provide drilled and tapped holes for removable PRDs in their shoulders (see
5.2.3.1). The removal and repair of flanges on low-pressure cylinders shall be a major rebuild operation carried out by shops registered and approved by the Associate Administrator for Hazardous Materials Safety. When approved services are not available to the contractor, the cylinder shall be rejected, tagged, and returned to the government agency empty for repair or disposal.
5.2.5 Inspection of footrings. DOT specifications provide for welded or brazed seams in the fabrication of low-pressure cylinders, and due to the thin construction in the bottom areas they are provided with footrings welded in place. Footrings shall be inspected and scheduled for
maintenance when they are deformed or when rings are cracked or broken in any place where the seam is not a part of the cylinder proper. Welding or brazing of the footring is permissible so long as the cylinder is only subject to heat controlled by water or steam. Welded seams on the cylinder proper shall be repaired only by shops approved by the Associate Administrator for Hazardous Materials Safety of the Office of Hazardous Materials Safety. Maintenance of
flanges shall be performed in accordance with 49 CFR 173.34. If authorized repair or rebuild services are not offered by or available to the contractor, the cylinder shall be rejected, tagged, and returned to the government agency. High-pressure cylinders are not provided with footrings, as welding or brazing is not allowed in DOT specifications 3A or 3AA for cylinders with service pressures above 500 psig. These cylinders have round bottoms and require fixtures to hold them in upright position, or the crown of their bases are bumped back to provide a ring at the side wall as a standing surface for upright stability. Seamless 3A and 3AA cylinders of thin wall construction with service pressures under 500 psig are provided with welded footrings for cylinder bottom protection and shall be repaired only by authorized services or by a
manufacturer of similar cylinders.
5.2.6 Periodic test date inspection. Each cylinder shall have its periodic test date inspected for serviceability. Cylinders with serviceable test dates shall be forwarded to general cylinder inspection and cylinders with expired dates shall be grouped for retest as specified herein. Cylinders in high pressure service classified as DOT 3A and DOT 3AA are hydrostatic
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