Sealing requirements for electrical equipment connecting to high pressure process systems

Both the National Electrical Code (NEC) and the Canadian Electrical Code (CEC) contain sealing requirements to prevent the migration of flammable fluids from travelling through wiring systems to nonhazardous locations. This paper will review the need for, the intent and the application of these code requirements. Case studies of incidents will be discussed to demonstrate that significant hazards exist, and how they are effectively mitigated by the code requirements. In addition, product standards can be used to meet the intent of the sealing requirements. CSA C22.2 No. 30 Explosion Proof Enclosures for use in Class I Hazardous Locations, and ISA 12.27.03 Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids currently exist and IEEE PAR 1673 Requirements for Conduit and Cable Seals for Field Connected Wiring to Equipment in Petroleum and Chemical Industry Exposed to Pressures Above 1.5 kilopascals (0.22 psi) is under development. The International Electrotechnical Committee (IEC) Technical Committee 31 (TC31) has assigned the task of developing a standard for equipment to Working Group 30 (WG30). This standard is based on the ISA 12.27.03 document and is preparing to release the final draft in 2012. The requirements were added to the NEC in the early 1980 and in 2006 Canada copied those rules into the CEC. In Canada, it became quickly evident that the NEC rules were confusing and that no guidance was on how to apply them was given. A working group was established to the clarify what the new requirements meant, specifically on "secondary seals" and "making primary seal leaking obvious", to provide background information to help answer the question: "Why are these rules needed?", and to give manufacturers (e.g., process transmitters) a path forward to have their products certified (listed) to appropriate standards.