It shall be the duty of the board to make written findings of fact and conclusions of law and to promulgate a written decision and order upon the issue or issues presented in each case. In making such findings the board shall consider only, and be bound only, by the evidence submitted. When a valid contract is in effect defining the rights, duties and liabilities of the parties with respect to any matter in dispute, the board shall have power only to determine the proper interpretation and application of the contract provisions which are involved. Any investigation made by less than the whole membership of the board shall be by authority of a written directive by the chairman and such investigation shall be summarized in writing and considered by the board in reporting its findings and making its recommendation.

The board shall hand down its findings, decision and order (hereinafter referred to as its order) within sixty (60) days after it is called into session. If all three (3) members of the board do not agree, the order of the majority shall constitute the order of the board. The board shall furnish to each of the parties a copy of its order and a certified copy thereof shall be filed in the office of the clerk of the circuit court. Unless such order is reversed upon a petition for review filed pursuant to the provisions of Section 65-2-15, such order, together with such agreements as the parties may themselves have reached, shall become binding upon and shall control the relationship between the parties from the date such order is filed with the clerk of the circuit court, as aforesaid. However, such order may be changed by mutual consent or agreement of the parties.