The director of state police shall hold the rank of colonel. Within the division of state police there shall be not less than one major, 2 field officers with the rank of captain, 7 troop commanders with the rank of lieutenant, and 7 assistant troop commanders with the rank of sergeant. Every police employee shall have had not less than 2 years’ service within the division to become eligible for promotion of any type except from probationary status to trooper. No member of the division shall be eligible for promotion in any event unless his or her record is free from the commission of any major infraction of divisional discipline within the last 7 consecutive years of such service. In addition to the foregoing, the personnel commission, with the advice of the director, shall establish suitable classification for additional grades, positions and ranks and for each classification shall fix standards of health, education, training and experience, as well as the conduct and manner of taking of competitive examinations for promotion within the division.