Device for damage protection against local flooding caused by sprinkler failure

A valve for isolating a sustained abnormal elevated fluid flow and allowing normal flow and temporary flow surges to pass therethrough comprising

• a valve housing having an flow passage therethrough, an inlet and an outlet ports for connection to upstream and downstream conduits respectively, and a valve seat near said outlet port;
• a closure means housed in said housing and being moveable along the longitudinal direction of said flow passage, the cross-section of said closure means being substantially smaller than the cross-section of said flow passage such that a flow gap is formed between the inner walls of said housing and the outer walls of said closure means so that said fluid can flow freely through said gap;
• a spring means exerting a mechanical force on said closure means against the motion of said closure means towards said valve seat, said mechanical force being so predetermined such that it can withstand the hydraulic force of said normal flow and being overcome by the hydraulic force of said sustained abnormal elevated fluid flow to cause a closure;
• a dashpot means connected to said closure means for producing damping force upon a closure motion of said closure means, said damping force being so predetermined that it can prolong said closure motion to a sufficient time period to prevent closures responding to aaid temporary flow surges;
• said dashpot means being formed by a piston means housed in a circular cylindrical cavity of said closure means such that a motion of said closure means towards said valve seat generating a sliding motion of said piston in said cylindrical cavity, a small flow path being provided for communicating the interior and exterior of said spaced;
• said sliding motion of said piston pressurizing the fluid in said cylindrical cavity and forcing said fluid in to exit through said small flow path;
• the resistance force of the flow through said small flow path transmitting to said plug and consequently providing damping action on said plug.