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 | The OCV Pressure-Reducing Valve is used in many applications worldwide. The primary function of the 127 series is to reduce ageater upstream pressure to a lesser. more manageable downstream pressure,operating with out regard to either upstream supply or downstream demand. SERIES FEATURES ▲Reduces higher inlet pressure to a constant lower outlet pressure. ▲Outlet pressure is accurate over wide range of flow. ▲Piiot-operated main valve is not subject to pressure fall off characteristic of direct-acting PRV's. ▲Outlet pressure is adjustable over complete range of control spring (see pilot features). |
VALVE FEATURES ▲Operates automatically off line pressure. ▲Heavy-duty,nylon-reinforced diaphragm. ▲Rectangular-shaped,soft seat seal provides drip-tight Class VI closure. ▲Diaphragm assembly Guided top and bottom ▲Throttling seat retainer for flow and pressure stability. ▲Easily maintained without removal from the line. ▲Replaceable seat ring. ▲Alignment pins assure proper reassembly after maintenance. ▲Valves are factory tested. ▲Valves are serial numbered and registered to facilitate replacement parts and factory support. | Regardless of the source of high pressure,the 127-3 reduces that pressure to a constant discharge pressure，despite fluctuations in the demand or inlet pressure. Here,a parallel valve arrangement is used to handle a wide range or demand.
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VALVE OPERATION Maintains a constant downstream pressure despite fluctuations in demand and inlet pressure. Assumining proper sizing and adjustment the 127-3 will maintain downstream pressure at the set point ±2 psi. 1.) Model 65 Basic Control Valve , a hydraulically-operated , diaphragm-actuated globe or angle valve which closes with an elastorrer-on-metal seal. 2.) Model 1340 Pressure-Reducing Pilot,a wo-way, normally-open pilot valve which senses down stream pressure under its diaphragm and balances it against an adjustable spring load. An increase in downstrearn pressure tends to make the pilot close. 3.) Model 126 Ejector,a simple "tee" fitting with a fixed orifice in its upstream port It provides the proper pressure to the diaphragm chamber of the main valve, depending on the position of the pressure-reducing pilot. 4.) Model 141-3 Flow Control Valve, a needle-type valve which provides adjustable，restricted flow in one direction and free flow in the opposite direction. On the 127-3, the flow control valve Is connected as an opening speed control. 5.) Model 159 Y Strainer,(standard on water service valves}. the strainer protects the pilot system from solid contaminants in the line fluid. 6.) Two Model 141-4 Ball Valves, (standard on water service valves, optional on fuel service valves), useful for isolating the pilot system for maintenance or troubleshooting. |  |
| ▲Accurate sensing of outlet pressure. ▲simple,single adjustment. ▲All parts replaceable while mounted on valve. ▲Rubber-to-metal seat for positive shut-off. | ▲Large area diaphragm for quick,precise throttling. ▲Visual indication of diaphragm condition. ▲Bronze and stainless steel construction. |
 | The Model 1340 & 2420 Pressure Reducing Pilot controls the amount of pressure in the upper chamber of the main valve (hence,the degree of opening or closing of the main valve). The downstream system pressure is sensed under the pilot1o close,increasiing the amount of pressure in the upper chamber of the main valve causing It to close a proportionate amount to maintain a constant discharge pressure. As the downstream pressure decreases,the pilot begins to open, allowing the pressure in the upper chamber of the main valve to decrease ,caus ing the main valve to open. This ls a constant modulating action com pensating for any change In down- stream system pressure. MODel 1340 / 2420 Pressure Reducing Pilot 1. Adjusting Screw Cover |
SIZING PRESSURE REDUCING VALVES
For the most comprehensive procedure in sizing pressure reducing valves, it Is best to use our ValveMaster software or the Performance Charts in the Engineering Section of the OCV catalog. In the absence of these. the following procedure will get you where you need to be,and enable you to avoid the most common error in sizing PRV's:an oversized valve.
Procedure
The following procedure takes both factors (flow rate/pressure drop) into account through the use ot the flow coefficient,or Cv.The theory is simple:for best results，a PRV should be sized to operate between 10% and 90% of its capacity, or in other words, between 10% and 90% of Its wide open Cv.It Is a four-step procedure:
Step 1. Calculate Cv Minimum
| Step 2: Calculate Cv Maximum
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Step 3: From the table,find the size that includes both the Cv min. and Cv max. you have calculated in either the globe or angle valve column. Occasionally, the flow range Is so wide that and Cv max. will not fit in the proper range for any one size valve.In such cases, a parallel valve installation,with a smaller valve by passing around a larger one, should be given strong consideration. The valves should be sized so that: | Step 4: From the table check that the velocity (GPM) at the calculated Q max. does not exceed 5 ft/sec .
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