Product standards requirements for explosionproof and flameproof tapered threaded connections

Recent hazardous locations electrical product standards revisions have impacted the thread designs used for the explosion flame path in explosionproof equipment. These revisions are a result of the International Electrotechnical Commission (IEC) standards requirements impacting the product standards used in North America. The mating of threads in a hazardous location is a critical component to ensure both the integrity of the mechanical strength and ingress protection of the enclosure as well as the flame extinguishing performance of the male and female thread mating area. Newer hazardous locations product thread designs can appear to be much longer in thread availability. Inter-changeability of new design threads with older design threads can have a visual appearance of fewer threads of engagement as the longer thread length can result in the same amount of threads engaged as the older design with fewer available threads. However, not all threads are engaged into the female entry. This paper provides an overview of the industry standards revisions, the product design impacts, and the inter-mating of new thread designs compared with old thread designs. Graphic illustrations and photographs of these designs provide readers the guidance for applying hazardous locations electrical products into Class I environments. An overview of the design implications while maintaining National Electrical Code minimum thread engagement criteria is provided.