17. The of a vapor is the temperature at which the vapor ignites spontaneously from the energy of the environment. 18. For the balanced-bellows design of a spring-operated relief valve, the bellows on the backside of the valve seat ensures that the pressure on that side of the seat is always 3 19. Pressure relief valves are needed on the discharge side of pumps. 20. According to Probability Theory for processes in series configuration, the failure of any one component results in the failure of the