Cracking pressure and pressure override. The globe valve generally has a __________ pressure drop when fully open; and is __________ commonly used for throttling system flow. Power Engineering MCQ Power Engineering Chapter 94 How many pressure relief valves shall a hot water heating boiler have? Which one of the following could cause this condition? Denis Papin is credited by many sources as the originator of the first pressure relief valve (circa 1679) to prevent overpressure of his steam powered “digester”. Subject: Hydraulics and Pneumatics 5. B) The handwheel will turn, and the valve stem will move toward the closed position because the clutch is automatically engaged when the breaker is opened. The relief valve setting can be adjusted by clicking on and dragging the "% set" slide bar. c. The valve is opened by pressure in the line surpassing a preset pressure set on the spring in the valve d. The valve is automatically closed when the water line pressure drops below the spring pressure setting e. The relief valve may be isolated from the vessel it serves by means of a gate valve… B) reduce system pressure. Which one of the following describes the position of the gate valve? Which one of the following types of similarly sized valves in an operating water system produces the least frictional head loss when fully open? B) The valve is fully open or nearly fully open. B) A hydraulic lock has developed under the valve disk. Over time, hydraulic systems are being operated at higher and higher pressures. A) The relief valves are installed to prevent unnecessary opening of the safety valves during a steam pressure transient. C) the tortuous path through a gate valve body can make flow control difficult. The development of the safety relief valve has an interesting history. Parker’s pressure relief valves are designed to limit the upstream pressure by opening at a preset value and discharging the medium. A) excessive stem leakage will result unless the gate valve is fully open or fully closed. A typical motor-operated valve (MOV) has just been opened from the main control room, and the breaker for the MOV has been opened. 1 like Like. 2. Comment. C) The valve stem packing gland was overtightened after the packing material was replaced. Which one of the following is the type of valve used to control the direction of fluid flow through a system and prevent backflow? B) blowdown. D) smaller; less. (Assume that each valve has a non-rising stem. A compound pressure relief valve is one which operates in two stages. D) The valve was packed with improved packing material having a lower friction coefficient. Good luck! A) produce a larger pressure decrease when fully open. B) pump runout by providing a constant backpressure. Accept Read More. B) The operator placed the valve in the wrong position for adjusting the packing gland. A) pump cavitation by keeping nonoperating systems filled. How will a typical motor-operated valve respond to a loss of electrical power to the valve actuator? Engines - Two-Stroke & Non-Conventional Engines, Theory of Machines - Friction Clutches, Breaks, Dynamometer, I.C. B) globe; gate The entire external valve stem is threaded, except for a 1-inch section that becomes smooth just before the valve stem enters the packing gland. knf-flodos.ch. D) Ball. C) Removes pressure from the packing/stuffing box and is typically used when needed to isolate packing leakage. A) larger; less Minimize downtime this year with AccuTEST’s high-tech pressure relief valve testing system. Which one of the following describes the function and use of the backseat on a manual valve? A) maintain system integrity. A) Gate valve How many pressure relief valves shall a hot water heating boiler have? C) The handwheel will turn, and the valve stem will move toward the closed position because the clutch is automatically engaged when the handwheel is turned. Which one of the following describes a major design consideration for installing both types of valves in the same system? They are designed to accommodate higher pressures than direct acting relief valves at the same flow rate capacity. Answer: B. As the fluid is diverted the pressure inside the vessel will stop rising. Reverse flow of fluid is not possible 2. D) The actuator closing spring on a relief valve is in a compressed state whereas the actuator closing spring on a safety valve acts in tension. Relief valves should be located nearest to the point where the increased pressure can occur. When the valve was remotely opened and closed to verify operability, the measured valve stroke time in each direction was 15 seconds, which is shorter than normal for this valve. D) The valve is fully closed or nearly fully closed. 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