[Code of Federal Regulations] [Title 30, Volume 1] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 30CFR18.98] [Page 129] TITLE 30--MINERAL RESOURCES CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR PART 18_ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES--Table of Contents Subpart E_Field Approval of Electrically Operated Mining Equipment Sec. 18.98 Enclosures, joints, and fastenings; pressure testing. (a) Cast or welded enclosures shall be designed to withstand a minimum internal pressure of 150 pounds per square inch (gage). Castings shall be free from blowholes. (b) Pneumatic field testing of explosion-proof enclosures shall be conducted by determining: (1) Leak performance with a peak dynamic or static pressure of 150 pounds per square inch (gage); or (2) A pressure rise and rate of decay consistent with unyielding components during a pressure-time history as derived from a series of oscillograms. (c) Welded joints forming an enclosure shall have continuous gastight welds.