11. The Chief Inspector may at time withdraw or revoke any certificate or provisional order on the report of an Inspector or otherwise-(a) if there is reason to believe that the certificate or provisional order has been fraudulently obtained or has been granted erroneously or without sufficient examination; or(b) if the boiler in respect of which it has been granted has sustained injury or has ceased to be in good condition; or(c) where the Government has made rules requiring that boilers shall be in charge of persons holding certificates of competency, if the boiler is in charge of a person not holding the certificate required by such rules; or(d) where no such rules have been made, if the boiler is in charge of a person who is not, having regard to the condition of the boiler, in the opinion of the Chief Inspector competent to have charge thereof: Provided that where the Chief Inspector withdraws or revokes a certificate or provisional order on the ground specified in clause (d), he shall communicate to the owner of the boiler his reasons in writing for the withdrawal or revocation, and the order shall not take effect until the expiry of thirty days from the receipt of such communication.