DIAPHRAGMACTUATED VALVES

	DIAPHRAGM ACTUATED VALVES	RAF MODELS	RAF General Information
\| Description \| Applications \| Available Models \| Installation \| \| Typical Application \| Specification Form \| Animation \|	RAF 70/73 Flow Rate Control Hydraulic Valve

Description RAF 70 & RAF 73 are piloted hydraulic valves activated by line pressure. Normally the RAF 70/73 is partly open to allow a preset constant flow rate. The flow rate through the RAF 70/73 is determined indirectly using an orifice plate. The headloss across the orifice is proportional to the actual flow rate. On rising headloss, the RAF 70/73 is automatically piloted to close. On the other case, the valve opens. Thus the flow rate is maintained constant, regardless of line pressure fluctuations or the downstream demand.	Available Models RAF 70 - General Application two-way Flow Rate Control Hydraulic Valve. Pressure rating up to 16 bars. RAF 73 - Three-way Flow Rate Control Hydraulic Valve for agricultural & domestic applications. Plastic pilot is used for 2"-4" size with pressure rating up to 10 bars. For sizes 6"-12" a metal pilot is provided.
Applications Use RAF 70 /RAF 73 Flow Rate Control valve to maintain a compensated constant flow rate to limit the flow downstream. RAF 70 has two-way metal pilot valve for general use in water supply systems of medium pressure rating. The RAF 73 has a three-way plastic pilot valve featuring a cost-effective option for low pressure irrigation or domestic water supply. Apply RAF 70/73 to eliminate excessive pumping or to limit the water demand.
Installation RAF Flow Rate Control Valve is activated by line pressure & controlled by a pilot valve. The pilot includes a spring- loaded membrane. An orifice plate is installed either downstream or upstream of the RAF. The orifice size is prepared in advance to suit the specified required flow rate. The headloss across the orifice is proportional to flow rate through the RAF valve. This headloss is transferred to the opposite sides of the pilot’s membrane, which moves upward or downward accordingly. These movements open or close the inner ports of the pilot valve, directing the line pressure to control the RAF 70/73. In two-way configurations, the control chamber drains downstream, enabling faster & gradual opening without water spill. In three-way configurations, the control chamber drains out, enabling the valve to open fully.
RAF 70 - Two-way pilot		RAF 73 - Three-way pilot
RAF 70- control mode Manual: To open the RAF 70, close cocks 1 & 2 & open the Vent. To close the RAF open cock 1 & close cock 2 & Vent. Automatic: In normal flow rate the RAF 70 is open. The head loss across the orifice is low, & the pilot membrane is maintained in its lower position, as shown. The line pressure flows through the open pilot, ports 1-2, & drains downstream. When the flow rate through the valve increases, so does the headloss across the orifice. When the headloss is higher than preset, the pilot membrane is pushed upward closing port 2. The RAF is forced to close by line pressure. The flow rate decreases as does the headloss across the orifice. The pilot’s membrane moves back & the RAF gradually reopens.		RAF 73- control mode Manual: Use the three-way cock to close or open the RAF by turning the handle to the C or O positions, respectively. Automatic: The three-way cock should be positioned at A. RAF 73 is normally open. When the headloss across the orifice is normal (in accordance with the required flow rate) the pilot’s membrane is positioned as shown. The RAF’s control chamber drains out through ports 2-4 (vent). When the flow rate increases, the headloss across the orifice rises. The pilot membrane is pushed upward with its plunger. The line pressure is then connected to the RAF control chamber via ports 3-2. The RAF diaphragm pushed downward by the line pressure & lowers the flow through the valve.
Adjustment Use needle valve a to control the RAF 70 operational speed. Adjust the required flow rate using the adjusting screw.
Typical Application RAF 73 valve avoids excessive water demand downhill of a reservoir to minimize shortage.

Standard RAF 70	Standard RAF 73	Special Features RAF 70/73
Complete basic RAF valve as specified above	Complete basic RAF valve as specified above	Enamel/epoxy coating
metal pilot (2-way)	Plastic pilot (3-way) for 2"-4" Metal pilot (3-way) for 6"-12"	-
Self-cleaning screen filter	Self-cleaning screen filter	External heavy duty screen filter
Assembled Orifice Plate	Assembled Orifice Plate	-
Five cock valves	Selecting cock (3-way)	-
Needle valve		-
3/8" Reinforced Plastic tubes	8 mm Plastic tubes	Copper or stainless steel tubes

Plastic Pilots	Metal Pilot
Body & bonnet -Bronze Spring -Music wire. Membrane - Nylon fabric reinforced Natural Rubber. Bolts & nuts - Zinc plated steel. Pressure rating : up to 16 bar. Assembled spring comply with specs.	Body & bonnet -Fiber glass reinforced Nylon. Spring -Music wire. Membrane - Nylon fabric reinforced Natural Rubber. Bolts & nuts - stainless steel. Pressure rating : up to 10 bar. Assembled spring comply with specs.