초록 ▼

A backflow preventer apparatus designed for connection between a supply pipe having liquid under pressure and a service pipe, the backflow preventer apparatus comprising a pair of check valves in series and defining a zone therebetween, a relief valve operable upon a change in differential pressure

A backflow preventer apparatus designed for connection between a supply pipe having liquid under pressure and a service pipe, the backflow preventer apparatus comprising a pair of check valves in series and defining a zone therebetween, a relief valve operable upon a change in differential pressure across the upstream check valve, and a vacuum breaker operable upon a drop in pressure in the zone to a predetermined pressure supply above atmospheric pressure. The differential pressure operable relief valve, when opened upon certain operating conditions, causing the zone to drain to atmosphere. The vacuum breaker operates independent of supply pipe pressure or service pipe pressure but solely on a drop in pressure in the zone.

대표청구항 ▼

A backflow preventer apparatus having an inlet adapted to be connected to a supply pipe having liquid under pressure therein and an outlet adapted to be connected to a service pipe, said backflow preventer apparatus comprising: a body member having a flow passage therethrough; a first check valve an

A backflow preventer apparatus having an inlet adapted to be connected to a supply pipe having liquid under pressure therein and an outlet adapted to be connected to a service pipe, said backflow preventer apparatus comprising: a body member having a flow passage therethrough; a first check valve and a second check valve in series in said passage and defining therebetween a zone, said first check valve and said second check valve being operable to open position to permit flow of liquid from said supply pipe to said service pipe when there is a demand for liquid in said service pipe; a differential pressure operable relief valve assembly communicating respectively with pressure of liquid in said supply pipe and in said zone between said first and second check valves, said relief valve assembly having a passage from said zone terminating in an outlet to atmosphere and having a valve therein operable to open position upon a predetermined drop in differential pressure between said supply pipe pressure and said zone pressure caused by backsiphonage in said supply pipe or by backpressure in said service pipe whereby liquid in said zone discharges to atmosphere through the outlet of said relief valve assembly; and a vacuum breaker means communicating directly with said zone between said first and second check valves adjacent the highest point therein, said vacuum breaker means having a valve element therein normally closed by pressure of fluid in said zone when pressure of fluid in said zone is greater than a predetermined pressure slightly above atmospheric pressure, and said valve element in said vacuum breaker means being opened completely independently of pressures of liquid in said supply pipe and said service pipe and only when pressure of fluid in said zone drops to said predetermined pressure slightly above atmospheric pressure.