Flow Limiting Valves
The model 1300 limiting Valve is a hydraulically operated ACV, diaphragm actuated, control valve that prevents excessive flow by limiting flow to a preselected maximum rate.
The pilot valve senses the pressure differential across the specially sized orifice plate. When the pressure differential is less than the set point, the valve opens, allowing flow to meet predetermined demand. At the desired maximum set point, the pilot reacts to small changes in sensing pressure and controls the main valve position by modulating the pressure above the diaphragm.
When the pressure drops across the orifice exceeds the set point, the valve closes slightly, limiting the flow to the pre-set maximum. The orifice is usually sized to generate a pressure differential of 0.3 bars at the desired flow. Adjusting the pilot setting permits the maximum flow to be changed in the field above or below the original point.
Operating Principals of ACVs
Valve Closing: When the pilot closes water is trapped inside the bonnet and the main valve disc will be forced to close.
Valve Opening: When the pilot opens water is released from the bonnet allowing the main valve disc to open.
Valve Modulating: The main valve will mimic the small pilot valve. When the latter partially closes the main valve does the same and vice versa. The pilot valve reacts to a change in external signal received from the system. This signal might cause the pilot valve disc to partially close (hence closing the main valve) or to partially open.
Material of Standards
1. Body —— Ductile Iron EN-GJS-500/7 Or Ductile Iron EN-GJS-400/12
2,6,8. Isolation valve —— Nickel plate copper alloy (Optional SS316)
3. Strainer —— Stainless steel SS316
4. Restriction —— Stainless steel 316
5. Needle Valve —— Stainless steel 316
6. Flow Control Pilot —— Stainless steel 316
7. Orifice Plate —— Stainless steel 304