The important question is whether the motor was/is required to be explosionproof; it is possible for single phase motors, not likely for three phase.
If is required, it still sounds like it is ok if? the explosionproof flexible fitting (technically it's an explosinproof flexible coupling) is less than 18".
Last edited by rbalex; 09-08-13 at 11:59 PM.
Robert B. Alexander, P.E.
"I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)