| 摘要 |
<p>A fire service meter that includes a strainer, a high flow water meter, a low flow water meter and a check valve fluidly coupled together. The check valve includes a sealing member or clapper adapted to seal against a valve seat. A shaft is secured to the clapper via a pivot arm. The shaft has a portion that extends externally of a body of the check valve. A bracket is secured to the external portion of the shaft. Two springs are provided each having one end attached to the bracket and their opposite ends attached to the body. The springs are arranged so that in a first position both springs apply a closing moment to the bracket so as to force the clapper in a closed position. As a pressure differential increases across the clapper and forces the clapper to move away from the valve seat, the position of the springs change so that one of the springs applies an opening moment to the bracket so as to decrease the amount of head loss associated with the opening of the clapper.</p> |
