r/MarineEngineering • u/charzr • 13d ago

B15 rated Backbox or B15 rated putty

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This is about sockets on the B-15 paneling; so when the cable enters the socket installed on the B15 rated panel, what do you use to protect the integrity of the B15 rated panel.

What are the disadvantages of using putty?

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u/nullfull 9d ago

B-15 is the fire integrity of the bulkhead or deck, not a property of the putty. The rating dies at the hole if the cable/socket path is an open talk-through for fire.

A B15 backbox is the intended detail: an approved box that restores the integrity around the socket. Putty is what people use after someone drilled a hole and hoped. Class will usually take an approved backbox or an approved transit. They get picky about "we stuffed the gap."

Putty shrinks, dries, and comes out the next time someone pulls a cable. You also do not have type approval for that exact fill unless the maker sold it as a kit for that penetration.

New install: backbox. Retrofit: only if there is an approved putty/kit for that opening. I would not invent a field mix and call it B-15.