Section 10. The commissioner shall appoint a board of boiler rules, consisting of the chief of inspections, or a boiler inspector of the division of inspection designated by the commissioner, as chairman and four associate members, one of whom shall be an operating engineer and three shall represent users, manufacturers and insurers of boilers, respectively. Upon the expiration of the term of office of an associate member, his successor shall be appointed for three years by the commissioner. The associate members shall receive as compensation for service and reimbursement for expenses such sums as the governor and council may determine, not exceeding, in all, fifteen hundred dollars a year. Such clerical and other assistants as may be required by the board shall be assigned to it by the commissioner.