| 摘要 |
<p>A device having pressure independent control and balancing valves, suitable for use in a hydronic system, comprises a seat, a plug having an upstream surface and a downstream surface, and a piston, wherein the seat, plug and piston are aligned coaxially, a controller determines the size of a first flow restriction between the upstream surface of the plug and the seat, the piston is operable to move in response to differential pressure across the first restriction and a predetermined force, the position of the piston relative to the downstream surface of the plug determining the size of a second flow restriction thereby in use maintaining a substantially constant differential pressure across the first restriction.</p> |
