BERMAD Control Valves Presents:

Basic Control Valves

Goals and AgendaGoalsGetting to know more about:What a control valve is.How a control valve operates. Various kinds of control valves.

AgendaBasic concepts and termsVarious valve body patternsComparison of actuatorsValve operation characteristics as determined by actuator

Definitions PressureThe ratio of hydraulic force acting perpendicularly on unit area of surfacePressure Unitsatm., bar, m.w.h., psi, kpaFlowThe amount of liquid supplied /consumed in a given period of time. Flow units: m/h, l/sec, gpmKvFlow factor - Describes the flow rate in m/h at 1 bar pressure drop

DefinitionsUpstream pressureInlet pressureDownstream pressureOutlet pressureWorking pressureThe available inlet pressure measured upstream of the valve.Maximum pressureThe rated pressure of the valve/system.

Control Valves in Agriculture System

QQP3A2P1A1P2A1P1P2TerminologyA1 = Seat areaA2 = Actuator effective areaP1 = Upstream pressureP2 = Downstream regulated pressureP3 = Upper control chamber pressureP = P1-P2Q = Flow

Principle Equation of Control Valve OperationP (pressure) x A (area) = F (force)Pressure: atm, bar, kps, psi, mwh, etc.Area: cm, mm , inch, etc.Force: kgf, N (Newton) etc.

How do changes of these variables effect the control valve?

Operational ModesClosedOpenModulating

Closed ValveA2 > A1 P3 x A2 > P1 x A1P3 = P1P2 = 0Q = 0A1A2

Closed ValveF2 - F1= Net force for drip- tight closingF2 = A2 x P3F1 = A1 x P1P1P2A2A1

Fully OpenWhich of the variables can be controlled, to modify the relative forces and thus the state of the control valve? Answer: P3

Fully Open P1 x A1 > P3(0) x A2 P2 = P1 - PP3 = 0 Q= working flowP1P2A1A2P3

Fully OpenF1 = A1 x P1P1P2A1F1= Net Force for Opening

A = D / 4 2r = DD / 4 = D x HThus for unrestrictedflow H = D1/4How Open is Open?HHH2r = D

Control Valve Basic Patterns Y-Pattern Globe Saunders Angle In-Line

Y Oblique Pattern700200

Y ObliqueAdvantages Saves energysemi-straight flowLow head lossHigher cavitation resistanceOne piece actuator unitfast serviceadvantage in vertical installationDisadvantagesHigh level of skills required for assembling & maintainingRelatively expensive

Globe Pattern200900

GlobeAdvantagesEasy to assemble & maintainLower cost

Disadvantages Loss of energyHigh head - lossTurbulent flow

AngleAdvantages Easy to assemble & maintainSaves space and accessories

All BERMAD Models are available in Angle pattern

AdvantagesSaves energy - almost full bore Low cost

DisadvantagesUnbalanced diaphragmTends to drawShort lifeDifferent types for different pressuresNo linear indication to valves position Cavitation jet to body and diaphragm at low flow conditionSaunders

In-line ValvesAdvantages Saves energy- straight flowGood performance at high differential pressureHigh cavitation resistance ProtectedDisadvantagesRequires dismounting from line for maintenanceSensitive to parts in fluidRequires up-stream filterHigh Level of skills required for assembling and maintainingExpensive when becomes commercial

In-line ValvesDisadvantages (continuance)Several Dynamic seals (stem+pistons)Requires high pressure to start opening and closing procedureIncreases leakage risk Increases body and seal erosion damageMonoblocklow diameter, long and internal tubesA small control chambersmall control orifice causes Increased reacting time at P drop

In-line ValvesDisadvantages (continuance)Double chambered only - Continuous drainingPlastic constructionrelatively low strain resistanceCumbersome, complicate and long installation

Balanced diaphragmSame diaphragm for the entire range of pressuresFull support to the flexible partSealing - resembles radial seal disc Dynamic guiding proportional to PLinear indication to valve positionSaves energy - semi straight flow 400 Series

Closing/Opening Speed Depends on:The type of actuatorPaths & control tube sizeFlow, downstream and upstream pressure

Actuators Double-chambered Single-chambered

Single and Double-Chambered ActuatorsCharacteristicDoubleSingleStructureComplicatedSimple?ClosingFast with Slow EndSlow & SlamOpeningFast with Slow EndSlow & AccelerateConversionConverts to SingleComplicate/ ImpossibleControl OptionManyFew

Single-Chambered Actuator ConversionImpossibleComplicated

Double-Chamber Actuator StructureRelatively complicatedMany partsAssembly must be exactHigh level of skills required for assembling & maintaining

Control Valves

diaphragm valve valve valvePilot valve Hydraulic Diaphragm Valve

Pressure Reducing Valve Downstream valve - valve

Pilot valve Pressure Valve ( Diaphragm )Needle valve ( main valve )Pressure gauge ( Downstream ) Valve Main valve Main valveDiaphragm - Vent

Up (down)Down (up)

(upstream) (pressure relief) (surge) (pressure sustaining) 730 () () Pressure Sustaining/Pressure Relief valve

Pressure Sustaining valve

Pump Control Valve : Model 7431. 4 52. 6 7 3.

Pump Control Valve

(surge) (surge) (shock wave) #2 Anticipating Control Valve( Surge Control valve)

Surge Solutions Surge Control Valve

735 Function Power Failure

Surge control valve

Flow Control Valve

1. Orifice

Flow Control ValveModel 772-U

Altitude Valve 3 (altitude pilot) 2

Altitude Valve

Modulating Float Valve :

GS 1

OperationModulating Float Valve

Modulating Float Valve

Non Modulating Float Valve :

Non Modulating Float Valve

GS 1

OperationNon Modulating Float Valve

Altitude Valve :

GS 1 Drain

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