0E0-GB PRESSURE REDUCING VAVES MAIN FEATURES The pressure reducing valve is able, by varying its pressure drops, to hold the downstream pressure of the fluid at a constant level against changes in the upstream pressure and flow rate. The pressure reducing valve is used: - in water/plumbing systems: to hold a constant water pressure in the water supply main after the pressure reducing valve; - in plumbing systems/sanitary appliances: to maintain the water pressure constantly below the max. permissible value; - in water/plumbing systems: to save water. By controlling the pressure to the taps, excessive withdrawal of water from the taps is avoided; - in compressed air systems: to keep the air pressure constant in the main, regardless of fluctuations in pressure supplied by the compressors; - after tanks or storage cylinders: to reduce and stabilize the pressure in the main, which is normally lower.
GENERA The WATTS Cazzaniga pressure reducing valves Series DRV, DRVN and DRVD are of balanced seat type. This means that the inlet pressure, when acting on the two openings A and B with the same section, is compensated. Therefore it does not exert any force on the pin-plug system when the degree of valve opening changes. Instead, the outlet pressure acts on the diaphragm and hence on the pin-plug system which, therefore, is subjected to two opposing forces, namely: the force exerted by the outlet pressure tending to close the plug, and the pressure exerted by the spring tending to open it. This results in the pressure reducing valve acting like a balanced seat type having the outlet pressure almost unaffected by variations in upstream pressure. SETTING The difference between the downstream pressure P measured with zero flow rate and the same pressure measured with a general flow rate Q represents the pressure drop DP across the pressure reducing valve. It depends on the flow rate as shown in the pressure drop diagrams. If it is required for the upstream pressure not to exceed a given value P, this should be adjusted to value P when the flow rate is zero. At flow rate Q, the downstream pressure will be below the value P by an amount equal to pressure drops DP. When the pressure reducing valve is installed to ensure that the downstream pressure reaches a given value P at a certain flow rate Q, this pressure should be adjusted to value P + DP when the flow rate is zero. At flow rate Q the downstream pressure will be equal to P. SIZING The valve selection criterion consists in determining the diameter so that the speed of the fluid does not reach excessive levels, at nominal flow rate, thus causing excessive pressure drops and noisy effluent which are transmitted to the supply main. The flow rate-speed diagrams provide a guide for selecting the valve diameter in the case of liquids (see water) or gases with pressures of to 0 bar (see air). EXAMPES OF SIZING Example (cavitation) Pressure reducing valve with: Inlet pressure P = bar Outlet pressure P = 3 bar From the cavitation diagram it can be seen that the pressure reducing valve works constantly in the red zone. To avoid rapid deterioration, two valves can be used, one connected upstream to the other. Upstream valve: pressure change from to bar (green zone) Downstream valve: pressure change from to 3 bar (green zone). Example (flow rate) Pressure reducing valve DRV/N with: Inlet pressure (min.) P = bar Outlet pressure P = bar Max. flow rate Q = 0 l/min From the flow rate-speed diagram it can be seen that a diameter of 0 or can be used. The pressure drop diagram shows that in the two cases: DRV0/N Q = 0 l/min DP =. bar DRV/N Q = 0 l/min DP = 0. bar DRV Diaphragm pressure reducing valve with single balanced seat. Ensures min. pressure drops with high flow rates. Downstream pressure set by means of the setting screw () and is locked with lock nut (3) DRVM ike DRV, but with pressure gauge Ø0 for reading downstream pressure /speed diagram DRV - DRVN Speed (m/s) 30 0 0 0, 0, 0, 0, 00 / MM 000 3/ MM 00 MM 003./ MM 000./ MM 000 MM 003 / MM 0030 3/ MM 003 MM 0033./ MM 0030./ MM 0030 MM DN DN0 DN DN3 DN0 DN0 Air Water 0, 0, 0, 0, 0, 0, 0 0 0 0 00 00 00 00 000 m3/h 0 0 00 00 000 000 0000 l/min /speed diagram DRVD Speed (m/s) 0, 0, 0, 0, DN0 DN DN0 DN00 DN DN0 DN00 0, 0 0 0 0 00 00 00 00 000 m3/h 3 0 0 30 0 0 00 00 300 l/s
CAVITATION The cavitation diagram shows three zones of valve operation in relation to the upstream and downstream pressures, namely: zone C: normal duty, no cavitation zone B: medium duty, possible cavitation zone A: heavy duty, the valve cavitates. Continuous operation in the red cavitation zone causes rapid deterioration of the internal parts. If the pressure reducing valve is to be used in the red zone, please contact the WATTS Cazzaniga Engineering Department. APPICATION APPROVAS - DVGW approval (Arbeitsblatt W 3) - GA approval (DVR to 3) according to DIN 0 class I (noise below 0 db) - SVGW approval (W/TPW0). - TIN approval (Poland) - CSTB approval (NF P 3-00) (DRV, DRV0). - KTW certification for all materials in contact with water. 3 0 Overall dimensions (mm) DRV / DRVM Key:.. 3. ock nut. Setting screw.. Diaphragm. Inlet connection. Pin. Plug 0. Guide bushing. Filters. Outlet connection Cavitation diagram A Cavitation zone B Transition zone C Work zone (bar) Inlet pressure 0 0 Plug Inlet / outlet connections Diaphragm Seal and O-ring Setting screw and lock nut Filters A 0 0 3 Downstream pressure B C (bar) TECNICA CARACTERISTICS bar Downstream pressure (outlet). to bar Connections to M / M tailpiece Downstream pressure adjustment (screw ) Clockwise rotation: increase in pressure Downstream pressure gauge (DRV-M only) Pressure gauge Ø0, scale 0 to bar Max. operating temperature 0 C Shot-blasted brass OT Shot-blasted brass OT with nylon fabric - diagram [ bar ] 0,0 0, / 3/././ 0 0 0 0 3 0, 0, 0, 0, DRV0/N DRV0/N DRV3/N DRV/N DRV0/N DRV/N 3 0 0 30 0 0 0 00 00 00 [l/m]
APPICATION APPROVAS - DVGW approval (Arbeitsblatt W 3) - GA approval (DRV/N to DRV3/N) according to DIN 0 class I (noise below 0 db) - CSTB approval (NF P 3-00) (DRV/N, DRV0/N). - KTW certification for all materials in contact with water 3 0 Key:.. 3. Adjusting knob. Setting screw.. Diaphragm. Inlet connection. Pin. Plug 0. Filters. Outlet connection Overall dimensions (mm) DRVN / DRVMN Plug Inlet / outlet connections Diaphragm Seal and O-ring Setting screw Filters DRVN Diaphragm pressure reducing valve with single balanced seat. Ensures min. pressure drops with high flow rates. Downstream pressure set by means of knob (3) with adjustment scale to bar. DRVMN ike DRVN, but with pressure gauge Ø0 for reading downstream pressure. 00 / MM 000 3/ MM 00 MM 003./ MM 000./ MM 000 MM 00 / MM 000 3/ MM 00 MM 003./ MM 000./ MM 000 MM Shot-blasted brass OT Reinforced plastic with nylon fabric TECNICA CARACTERISTICS bar Downstream pressure (outlet). to bar Connections to M / M tailpiece Downstream pressure adjustment (knob 3) Clockwise rotation: increase in pressure Downstream pressure gauge (DRV-M/N only) Pressure gauge Ø 0, scale 0 to bar Max. operating temperature 0 C - diagram [ bar ] 0,0 0, / 3/././ 0 0 0 0 3 0, 0, 0, 0, DRV0/N DRV0/N DRV3/N DRV/N DRV0/N DRV/N 3 0 0 30 0 0 0 00 00 00 [l/m]
APPICATION APPROVAS - ASSE, ANSI, CSA, UPC (USA) approvals - WATTS Patent, U.S. Patent N 3.. 0 3 WATTS Patent, U.S. Patent N 3.. BY-PASS 3 Key:.. 3. Setting screw. ock nut.. Inlet connection. Diaphragm. Valve seat. Outlet connection 0. Filter. Filter cap. Plug 3. Guide bushing. By-pass EXPANSION Plug Inlet connection Diaphragm Seal and O-ring Setting screw and lock nut Filters UB (WATTS Patent, U.S. Patent N 3.. ) Diaphragm pressure reducing valve, single seated, with spring. Ensures min. pressure drops with high flow rates. Provided with upstream filter having ample surface and separate connection for easy cleaning. Downstream pressure set by means of screw (3). Fitted with by-pass valve, it allows freeing on the upstream main any overpressure at downstream side (generated, for example, by expansion of water in the water heaters). 0 / FF 00 3/ FF 0 FF 03./ FF 00./ FF 00 FF Cast iron Nordel with nylon fabric UPSTREAM PRESSURE Overall dimensions (mm) UB PUG REDUCED PRESSURE TECNICA CARACTERISTICS 0 bar Downstream pressure (outlet) Adjustable. to bar Upstream connection to F threaded tailpiece Downstream connection F threaded Downstream pressure adjustment (screw 3) Clockwise rotation: increase in pressure Max. operating temperature 0 C - diagram [ bar ] 0,03 0,0 0,0 / 3/././ 03 03 3 3 3 0,0 0, 0, 0, 0, 0, DN0 DN0 DN DN0 DN DN3 000 000.000.000 0000 0000 0000 [ l/h ]
APPICATION DRVD Flanged pressure reducing valve with single balanced seat and spring. Ensures min. pressure drops with high flow rates. Downstream pressure set by means of screw (). Nodular cast iron body faced with epoxy resins. DRVD ike DRVD but with max. inlet pressure: bar. DRVD0 ike DRVD but with max. inlet pressure: 0 bar. PN: bar Pout:.- bar 0003 DRVD0/ " DN0 000 DRVD/ "/ DN 0003 DRVD0/ 3" DN0 0003 DRVD00/ " DN00 00 DRVD/ " DN 003 DRVD0/ " DN0 0003 DRVD00/ " DN00 Pout: - bar 000 DRVD0//- " DN0 000 DRVD//- "/ DN 000 DRVD0//- 3" DN0 000 DRVD00//- " DN00 00 DRVD//- " DN 00 DRVD0//- " DN0 000 DRVD00//- " DN00 Pout: - bar 000 DRVD0//- " DN0 0000 DRVD//- "/ DN 000 DRVD0//- 3" DN0 000 DRVD00//- " DN00 0030 DRVD//- " DN 00 DRVD0//- " DN0 000 DRVD00//- " DN00 PN: bar Pout:.- bar 0000 DRVD0/ " DN0 000 DRVD/ "/ DN 0000 DRVD0/ 3" DN0 0000 DRVD00/ " DN00 00 DRVD/ " DN 000 DRVD0/ " DN0 0000 DRVD00/ " DN00 Pout: - bar 000 DRVD0//- " DN0 000 DRVD//- "/ DN 000 DRVD0//- 3" DN0 000 DRVD00//- " DN00 00 DRVD//- " DN 00 DRVD0//- " DN0 000 DRVD00//- " DN00 Pout: - bar 000 DRVD0//- " DN0 000 DRVD//- "/ DN 000 DRVD0//- 3" DN0 000 DRVD00//- " DN00 00 DRVD//- " DN 00 DRVD0//- " DN0 000 DRVD00//- " DN00 PN: 0 bar Pout:.- bar 000 DRVD0/0 " DN0 000 DRVD/0 "/ DN 000 DRVD0/0 3" DN0 000 DRVD00/0 " DN00 003 DRVD/0 " DN 00 DRVD0/0 " DN0 Pout: - bar 000 DRVD0/0/- " DN0 000 DRVD/0/- "/ DN 000 DRVD0/0/- 3" DN0 000 DRVD00/0/- " DN00 003 DRVD/0/- " DN 00 DRVD0/0/- " DN0 Pout: - bar 000 DRVD0/0/- " DN0 0003 DRVD/0/- "/ DN 000 DRVD0/0/- 3" DN0 000 DRVD00/0/- " DN00 0033 DRVD/0/- " DN 00 DRVD0/0/- " DN0 Plug (ND 0 to 00) (ND to 00) Seal ip seal Seal ring Guide bushings Setting screw and lock nut Finish Nodular cast iron GS00- Nodular cast iron GS00- Brass Faced steel Epoxy resins (blue RA 0) TECNICA CARACTERISTICS Downstream pressure (outlet) Downstream pressure adjustment - - 0 bar (ND00 only up to bar). to bar (standard) to bar (optional) to bar (optional) Clockwise rotation: increase in pressure Connections Flanged according to UNI3 (NP - - 0) ND00 only NP and NP Pressure gauge connections G / " ND0 to ND (upstream and downstream) G 3/" ND0 to ND00 Max. operating temperature 0 C
Overall dimensions (mm) - diagram DRVD [ bar] 0, 0, 0, 0, 0, DN00 DN0 DN DN00 DN0 DN DN0, 0 0 0 00 00 300 00 00 00 000 000 3000 000 [ l/min] 0 0 00 0 00 30 0 30 30 00 0 0 33 0 0 3 3 0 00 3 B PN 00 0 0 30 B PN 00 3 0 300 30 B PN0 00 3 0 300 -- 0 3 Key:.. 3. Plug. Seal.. Seal ring. Guide bushings. ip seal. Setting screw 0. screws