Reliable Fan Operation At 1450 Rpm

Dear Sirs,

We intend to install ID and FD fan on the new Combustion Air System for Primary Reformer of our Ammonia plant.We have got offers for both 1450 rpm fans and for 900 rpm fans. Some personnel feel that 900 rpm machine should be preferred as such low rpm machine shall be more reliable compared to 1450 rpm machine. I shall be grateful if you could kindly share your experince and advise whether 900 rpm fans are more reliable for such critical service as compared to 1450 rpm fans and whether 1450 rpm machines are being used in Primary Reformer service in Ammonia Plants.

I shall be obliged to recive your advise on this matter,
With warm regards,
Ashwani