Issues regarding the sealing of connections between G-threaded explosion-proof wire glands and galvanized steel pipes or flexible pipes

Sealing and explosion protection are unrelated to wood. The thread clearance meets the requirements, satisfying the explosion-proof standards – perfect.

Explosion-proof electrical equipment (d): refers to electrical equipment in which the components that could ignite explosive mixtures are enclosed within a housing capable of withstanding the explosion pressure from such mixtures inside, and which prevents the spread of explosion to the surrounding explosive mixtures. Therefore, explosion-proof wire glands ensure that even in the event of an explosion inside, it will not ignite the flammable gases outside the gland, thus preventing any safety hazards in case flammable gases leak inside. Secondly, cables generally have no joints when passing through wire boxes; otherwise, explosion-proof junction boxes would be used. In the absence of joints, the possibility of sparks igniting flammable gases is extremely low. However, the explosion-proof enclosure for instruments is different; it must be sealed. Normally, we use gland fittings as sealing elements to prevent combustible gases from entering, with the aim of protecting the equipment. For example, short circuits in the instruments inside the explosion-proof enclosure can generate sparks, and if combustible gases are present, this could damage the equipment and cause unnecessary losses. There is no problem with using Exe II as shown in your diagram for Zone 1 and Zone 2

Why don’t domestic manufacturers of explosion-proof wire glands prefer NPT threads with threaded sealing functionality?

Thank you for your reply. Since you say that explosion-proof junction boxes are designed to prevent an explosion inside the box from igniting the flammable gases outside it, then G-threaded connections do not have a sealing function. If an explosion does occur inside the box, how can we ensure that sparks do not leak out through the threads, or that flammable gases do not leak into the box through those threads?

Since G threads are widely used in China, and although various standards state that G threads do not provide a sealing effect, this is because all the thread-forming machines in China use G-threaded cutters, and it is also easier to form threads with G threads. Now, let’s talk about explosion protection. Generally speaking, it is not the cable conduit itself that provides explosion protection; just as cable trays do not offer such protection, the concept of explosion protection relates to the cable itself, rather than the cable conduit or cable tray. Meters or rotating equipment are generally sealed using flexible hoses or gland heads, with the sealing gasket playing the key role, rather than the flexible hose or gland head itself.

I forgot to mention that in this type of wire gland, connections should not be made inside it; connections can be made within the junction box. As the name implies, a wire gland is simply a container used to assist with wiring. Explosion protection refers to the fact that the interface threads are usually tapered threads, but I don’t think this provides any real explosion protection… Combustible gases can still enter the conduit through gaps in the cable trays or pipes. So don’t point at this explosion-proof one. . . Is it the cable that is explosion-proof?……

There is a slight difference between a junction box and a wire gland. Connection boxes are used to facilitate the connection of connectors, while wire passing boxes are commonly employed in situations where there are bends in the wire conduits, tees, or when the straight sections are too long to allow easy wire passage

G-thread is easier to thread; for NPT tapered threads, there’s no need to use special lathes for processing. I understand that protective tubes and cable glands serve a protective purpose – even if flammable gases get inside, the cable itself, having no joints, won’t catch fire. So, when bidding for or quoting prices for chemical processing plants, we usually calculate the cost of our galvanized steel pipes based on the assumption that they are explosion-proof pipes. However, now many clients claim that these aren’t explosion-proof pipes, and I don’t have sufficient evidence to convince them; there’s nothing I can do about it

There are also two different types: junction boxes and wire passing boxes. Junction boxes are primarily used in electrical lighting systems, and they usually come equipped with terminals. For explosion-proof junction boxes, high standards are required; when using intermittent piping, armored explosion-proof connectors must be employed, while conductive paste should be applied in the case of continuous piping. A cable gland is used for passing cables that are relatively long or have many bends. If someone tells you that a protective tube combined with a cable gland is not explosion-proof, then ask them whether the cable tray needs to be explosion-proof as well; after all, they’re all used to hold cables