DIAPHRAGMACTUATED VALVES

	DIAPHRAGM ACTUATED VALVES	RAF MODELS	RAF General Information
\| Description \| Applications \| Available Models \| Installation \| Typical Application \| Specification Form \|	RAF 90/93 Anti-Burst Control Hydraulic Valve

Description RAF 90 & RAF 93 are piloted hydraulic valves activated by line pressure. Normally the valve is open. Only in case of flow rate higher than a preset maximum, due to a burst or excessive demand downstream, the RAF 90/93 are automatically closed down & can reopen manually. The actual flow rate through the RAF 90 is determined by comparing the headloss across an orifice plate. The valve is closed down by a hydraulic relay. The RAF 93 closes automatically whenever the upstream pressure drops below a preset point. It reopens manually.	Applications Use Anti-Burst Control valve to eliminate water loss & damage due to piping burst. The valve is best in networks susceptible to burst due to old piping, vandalism or pressure surge. The RAF 90 features a metal pilot valve & hydraulic relay to ensure precise & reliable response in general use. The RAF 93 with an all-plastic pilot valve is best for agricultural applications, features a cost effective, simple & reliable command loop.
Available Models RAF 90 - General Application two-way Anti-Burst Control Hydraulic Valve. Pressure rating up to 16 bars. Hydraulic relay guarantees tight closing & manual reopening. RAF 93- Three-way Anti-Burst Control Hydraulic Valve, for agriculture. Pressure rating up to 10 bars.
Installation RAF 90 Anti-Burst Control Valve is activated by line pressure & controlled by a pilot valve. The pilot includes a spring-loaded membrane. An orifice plate is installed down- or upstream of the RAF 90. The orifice size is prepared in advance to suit the specified maximum allowable flow rate. The headloss across the orifice is proportional to flow rate through the RAF 90. This headloss is transferred to the opposite sides of the pilot membrane. When it exceeds the preset point of the pilot’s spring, a hydraulic relay is operated to close down the RAF 90. The RAF 90 is reopened only manually. The RAF 93 operate in a different mode. The RAF 93 is normally open, closes when the upstream pressure drops below a preset point. It reopen only manually. 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 90 - Two-way pilot		RAF 93 - Three-way pilot
RAF 90- control mode Manual: Use the manual override option of the hydraulic relay. Automatic: Set the manual override handle of the hydraulic relay on automatic position (designated R2). In normal flow rate, The pilot is closed, as shown. The RAF control chamber is allowed to drain out through the relay’s vent. The RAF 90 is fully open. When the headloss across the orifice exceeds the preset level, the pilot membrane is pushed upward with its plunger. The line pressure flowing via pilot ports 3-4 flips the hydraulic relay to its other position (designated R1). The line pressure is then directed to the RAF’s control chamber. The RAF closes. After the problem is fixed, reopen the RAF by resetting the hydraulic relay manually & shift back to auto position.		RAF 93- control mode Manually: Use the three way selecting cock to close or open the RAF by positioning the handle on C or O, respectively. Automatic: Open the RAF manually as explained above. Position the three way selecting cock valve on A. When downstream pressure drops due to burst in downstream line, so does the pilot membrane. The RAF closes by line pressure via port 4-2 in the pilot. It remains closed until reopened by hand (after repairing the main line). Typical Application RAF 90 valve controls a water supply network downhill of a reservoir.
Adjustment Use the needle valve a to control the RAF 90 operational speed. Adjust the operational set point by the adjusting screw. See the list of available springs on the next page.

Standard RAF 90	Standard RAF 93	Special Features RAF 80/83
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)	-
Self-cleaning screen filter	Self-cleaning screen filter	External heavy duty screen filter
Orifice Plate		-
Hydraulic Relay (3-way)		-
Four cock valves	Three-way Selecting cock	-
Two Needle valve		-
3/8" Reinforced Plastic tubes	8 mm Plastic tubes	Copper or stainless steel tubes