If, after examination thereof, the commissioner shall find that such rating plans filed by, or on behalf of, an insurer provide for, result in or produce rates that are unreasonably high or excessive, or are not adequate for the safeness and soundness of the insurer or are unfairly discriminatory between risks in this state involving essentially the same risks, he shall issue an order to such insurer, or to the rating organization of which such insurer is a member or subscriber, directing that such rating plans be altered in the manner, and to the extent, stated in such order to produce rates that are reasonable and adequate and not unfairly discriminatory. If the commissioner shall find that such rating plans provide for, result in or produce rates that are not unreasonably high, are not inadequate for the safeness and soundness of the insurer and are not unfairly discriminatory between risks in this state, he shall approve such rating plans and rates, and such approval shall continue in effect until he shall, by order, direct that such rating plans and rates be changed or modified as in this section provided. As soon as reasonably possible after the filing has been made, the commissioner shall, in writing, approve or disapprove the same; provided, however, that unless disapproved within 30 days such rating plans and rates shall be deemed to be approved by him. Whenever the commissioner shall find that rating plans theretofore approved by him or which pursuant to Section 27-13-75 are effective without approval, provide for, result in or produce rates which are unreasonable or inadequate or which discriminate unfairly between risks in this state, he shall issue an order to all insurers employing such rating plans, or to the rating organizations of which such insurers are members or subscribers, directing that such rating plans be altered or revised in the manner, and to the extent, stated in such order to provide for, result in or produce rates which are reasonable, adequate and do not discriminate unfairly between risks in this state. Rating plans and rates filed with the department on, or before, January 1, 1972, pursuant to the provisions of this section, shall be deemed to have been approved by the department, such approval to continue in effect until the commissioner shall, by order, direct that such rating system be altered or modified as in this section provided. Changes in rates resulting from an order of the department directing or approving alterations or revisions in rating plans shall become effective following the date of such order as fixed by the commissioner and shall be applied to policies written on, or after, such effective date. Under such rules and regulations as he shall adopt, the commissioner may, by written order, suspend or modify the requirement of filing as to any kind of insurance, subdivision, or combination thereof or as to classes of risks, the rates for which cannot practicably be filed before they are used. Such orders, rules, and regulations shall be made known to insurers and rating organizations affected thereby. The commissioner may make examination as he may deem advisable to ascertain whether any rates affected by such order are excessive, inadequate, or unfairly discriminatory.