SAFETY DEVICE FOR LIQUID FEED PIPE

PROBLEM TO BE SOLVED: To provide a safety device for a liquid feed pipe, which is free from breakage of the feed pipe or from damage to a coupling metal fitting or a pump, even if the fluid within the feed pipe is interrupted suddenly. SOLUTION: In a safety device, a valve mechanism 5, which discharges the liquid to the outside if the pressure increases, is attached to a coupling cylindrical body 1, which is connected to a space between a pump and a liquid feed pipe having a water discharging nozzle at its tip end. In this case, the total area of the opening of a liquid discharging port 4 of the valve mechanism 5 should be larger than the area of the opening of the water discharging nozzle. In the middle part of the coupling cylindrical body 1 having coupling parts 2, 3 connected to the feed pipe, the liquid discharging port 4 communicating with the outside is formed, while an annular valve seat 8 of the valve mechanism 5, which opens/closes the liquid discharging port 4 to/from the fluid passage, is formed in such a manner that it is directed to the direction of the flow at the stepped part of an annular groove 6 of the coupling cylindrical body 1. In addition, an annular valve element 9, which is attached/detached to/from the valve seat 8, is energized toward the valve seat 8 by means of a spring 10. In this case, the pressure receiving area of the valve element 9 on the outflow side should be larger than that on the inflow side.