Contactor Replacement Question

No, you cannot replace ANY component in a fire pump controller without violating the UL listing, and if there is a fire and the pump fails and an insurance adjuster finds that, your insurance may become nullified.

Absolutely not, apart from the legal and liability problems, a standard 20A contactor would never tolerate this duty. The contacts would probably disintegrate at the first operation due to the DC in inrush current.

There would also a be a real danger of the contactor contacts welding together, preventing the starter from disengaging.

Further in most countries installing uncertified electrical equipment in to an explosion proof situation is a a criminal offence, with the ultimate possibility of gaol.

Thanks but still my question in technical what the problem only inrush current and if I found DC motor contactor is it be fine ?

Not to belittle the liability issues, but most components that are mounted inside of the exsplosion proof housing are often standard parts. It is the enclosure that has to meet the ratings not the individual devices "inside". So strictly from a practical sense if you can find a contactor with the right ratings and it fits onto the space in the enclosure, you should be ok. But checking with your local inspector in writing would be a good idea.

"... but most components that are mounted inside of the exsplosion proof housing are often standard parts."

Irresponsible posting.

You are focusing only on the issue of it being in an explosion proof enclosure. IT IS A FIRE PUMP CONTROLLER!!!! You should NEVER mess with re-engineering ANY component within a fire pump controller. You have NO IDEA what the consequences could be, and if you make a mistake, YOU ONLY FIND OUT WHEN YOUR FACILITY BURNS DOWN!!!!