© 2000 Yarway Corporation

InletNozzle Seat

Cascade Shaft

PistonLobe

Bushing Seal

CascadeBushing

Body

InletNozzle

Stem forpneumatic,hydraulic orelectric actuator

Turbo-Cascade®

High Pressure Control Valve

Potentially destructive erosive forcesexist in high velocity flow through avalve. Their effects can show up asgrooves cut into the valve’s internalsurfaces by an erosive process calledwiredrawing.

Or the pressure drop can causecavitation damage which occurs as aconsequence of the collapse of vaporbubbles in the fluid flow stream. Thebubbles are formed when the fluidpressure is reduced below its vaporpressure at a given temperature.When the system pressure againrises above the vapor pressure, thebubbles collapse or implode.Accompanied by a cracking noise,the implosions release vast amountsof energy which can tear holes in thewalls of the valve body and destroyinternal parts.

The Need ForHigh Pressure Valves

Control of erosive and cavitationalforces is a primary objective of thedesign of high pressure valves.Various stacked disc designs, forinstance, operate on the principle offixed orifices, or flow paths, in paral-lel. As such a valve opens, the fixedflow areas are progressively uncov-ered by the valve plug. Individual flowarea does not increase.

These small flow areas act as fluidstrainers and the valve can becomeclogged with debris causing a loss ofboth flow and control.

Other designs take an approachbased on multiple orifices only one ofwhich is variable. But this means thatthe single variable orifice must handlethe entire pressure differential acrossthe valve.

Yarway’s Design Approach

Yarway’s Turbo-Cascade controlvalve, on the other hand, is based onthe principle of multiple variable ori-fices in series. In this design, whichhas the benefit of more than adecade of refinement by Yarway engi-neers, the total flow area increases asthe valve modulates toward the openposition. Angular passages or flutes,in a bushing, direct the fluid throughthe flow areas or stages whichincrease in area toward the valve out-let, thus providing higher pressuredrop on the inlet stages of the valveand a decreasing pressure drop ineach stage toward the valve outlet.

In this design, all pressure dropsand pressure recovery occur abovethe vapor pressure, so no cavitationwill occur within the valve.

Turbo-Cascade valves are manu-factured from forged steel bar toassure homogeneity. Connections areavailable to match inlet and outlet linesizes. In many applications, pipelinereducers or expanders can be elimi-nated.

FEATURES AND BENEFITS

• Incorporates three separatefunctions of (1) positive fluidshutoff, (2) regulation, (3)pressure letdown.

• Designed and constructedto accept pressure drops ofthe highest magnitude.

• Assured disc-seat alignmentthrough above and belowseat guiding element.

• Suitable for modulating oron-off services.

• Can be provided with pneu-matic, hydraulic, or electricactuators.

• Choice of forged bodymaterials.

• Rigorously tested andproven successful.

• Successful performancerecord in scores of utilitysteam plants.

• Need for reducers can beeliminated. Normally, inletand outlet end connectionscan match existing linesizes.

• Quiet operation resultingfrom velocity control.

• Meet NACE requirements forcorrosive service; “N” stampcapability.

Turbo-Cascade

®high p

ressure control valve

Typical Applications

Liquid Service1. Centrifugal pump recirculation

systems.

2. Pressurizer relief valves.

3. Pressure reducing systems.

How It Works

The valve divides the fluid flow intomultiple streams and breaks downthe high pressure in separate stagesby inducing 90-degree changes inflow direction to dissipate energy.

As shown in Figure 2, the totalpressure drop of 2800 psi is brokendown into four successive break-downs of 1297 psi (first stage), 793psi (second stage), 465 psi (thirdstage), and 245 psi (fourth stage).

Because the reducing pressurespike at no time goes below thevapor pressure of 35 psia, cavitationwill not occur.

Each stage of pressure letdown isat right angles to the following stage.This causes the fluid passing throughthe valve to change flow direction asit cascades down through the valve,dissipating additional energy. In addi-tion, each Turbo-Cascade valve has afixed orifice in its outlet to provide yetanother stage of pressure drop that

eliminates the possibility of cavitationin the last stage.

As shown in the cutaway illustra-tion (Figure 3), the cage or bushingthrough which the cascade pistontravels has cast grooves which pro-vides an increase in flow area as thefluid passes through the valve. Thecascade shaft has preciselymachined lobes that move up anddown inside the fluted bushing.Varying the position of the lobes with-in the fluted bushing varies the areaexposed to flow and thus controlsvalve capacity.

To increase flow area further, thediameter of the cascade shaftbetween the lobes decreases towardthe valve outlet.The increasingly largerflow area forces higher pressure dropon the upper inlet stages. This is toassure that the pressure at all pointswithin the valve remains above thevapor pressure of the liquid, thus pre-venting cavitation.

Pressure Reduction Capacity

The Turbo-Cascade valve’s pressure-reduction capability depends on thenumber of pressure-reduction stagesincorporated into the valve for a givenset of conditions. Normally, 600 psi isthe upper limit for one stage, twostages are used for 1500 psi, four

stages for 3000 psi and six stages forpressures over 3000 psi.

The cutaway section of the bush-ing (Figure 3) shows the fluid flowpassages that provide staged pres-sure breakdown. Three stages areillustrated, but up to six can be pro-vided for very high pressure differen-tials. With the cascade shaft in theclosed position in the bushing (Fig.3a), drop-tight shutoff can beachieved. Throttling position and a fullopen position are shown in Figs. 3band 3c.

With the cascade shaft in the fullopen position, the lobes are at mid-point of the flutes in the bushing andmaximum flow occurs.

Valve Actuation

The valve is designed for compatibilitywith a variety of actuators and posi-tioners—pneumatic, hydraulic orelectric. A simple form of actuator is acylinder for on-off operation. Theposition of the actuator is controlledby a solenoid valve that opens orcloses the Turbo-Cascade on signal.Valves requiring flow modulation areequipped with cylinder or diaphragmactuators and appropriate position-ers.

A hydraulic balancing technique isused in larger Turbo-Cascade valves

4

Use the smaller of ∆Ptrue or ∆Pallowed inequation (1).

QCv = √ ∆P

SG

248Cv = √1168

0.88

Cv = 6.8

Select Class 900 ANSI Valve with 2stages, Trim Number 0903 (Cv = 7.6).Select desired end connections

5

for very high pressures to provideautomatic operation. Smaller valves,with up to 2″ intervals, are unbal-anced and can easily be operated bypneumatic piston or diaphragm actu-ators. In larger sizes, most have bal-anced pistons so that pneumaticactuators can be used.

Turbo-Cascade valves are quiet bydesign. The fluted flow configurationof the internals effectively limits fluidvelocity at all points within the valve,thus preventing a high operatingsound-pressure level in even themost severe pressure letdown situa-tions.

The design of the valve places theseating surfaces on the upstream orhigh pressure side with flow over theseat. A slight deadband protects theseating surfaces, allowing them toseparate before appreciable flowbegins. These features combine toprovide tight shut-off in high pressureservice over extended periods oftime.

Basic Calculations forSizing Turbo-Cascade Valves

Maximum ∆P per stage is 750 psi.

1. Flow coefficient or Cv is calculatedusing the basic equation:

QCv = √ ∆P

SG

where: Cv = Flow Coefficient

∆P = Pressure Drop,Inlet to Outlet

SG = Fluid Specific Gravity

2. Choked flow due to flashingand/or cavitation must also beconsidered using the equation:

∆Pallowable = FL2[P1 - (rc x Pv)]

where: FL = Valve Recovery Coefficient(2 stage = 0.93,4 stage = 0.96,6 stage = 0.98)

rc = Critical PressureRatio (Use Specific Gravity)

P1 = Inlet Pressure(psia)

Pv = Vapor Pressure(psia)

P2 = Outlet Pressure(psia)

∆Ptrue = P1 - P2

In sizing use the smaller of the ∆Pwhich will result in a larger Cvrequired.

A sample calculation follows:

Flow Q = 248 gpm

Inlet Pressure P1 = 1500 psia

Outlet Pressure P2 = 250 psia

Shut-off Pressure PSO= 1500 psia

Temperature T = 364 F

Vapor Pressure Pv = 164 psia

Specific Gravity SG = 0.88

Critical PressureRatio rc = 0.88

Recovery Factor FL = 0.93(since a 2 stage ischosen for 1250∆P)

True ∆P = P1 - P2

= 1500 - 250

= 1250 psi

∆Pallowed = FL2[P1 - (rc x Pv)]

= [1500 - (0.88 x 164)]

= 1168 psi

Fig. 3a Fig. 3b

Figure 3 – Yarway technique for pressure letdown.

Fig. 3c

Item Part Material

1 Body/Inlet Connection ASME SA105

2 Actuator Adapter ASME SA105

3 Packing Gland ASME SA105

4 Gland Bushing ASTM A479 Type S21800

5 Cascade Shaft ASME SA479 Grade 410

6 Cascade Seat ASTM A747 CB7 CU-1 (17-4PH)

7 Spacer Sleeve AISI Type 416 Stainless Steel

8 Pin Type 18-8 Stainless Steel

9 Stem ASME SA564 GR 630 (17-4)

10 Orifice AISI Type 316 Stainless Steel

11 Stud ASME SA193 Grade B7

12 Hex Nut ASME SA194 Grade 2H

13 Name & Date Plate Type 18-8 Stainless Steel

Item Part Material

14 Drive Screws Type 18-8 Stainless Steel

15 Pipe Plug ASME SA182 Grade F316

16 Gland Stud ASME SA193 Grade B7

17 Hex Nut ASME SA194 Grade 2H

18 Lantern Ring AISI Type 416 Stainless Steel

19 Packing Carbon Yarn & Graphite

20 Seal TFE/Egiloy

21 Upper Gasket Spiral Wound Inconel w/Grafoil

22 Piston Ring AISI Type 420 Stainless Steel

23 O-Ring Fluoraz (TFE-Propylene)

24 Locknut Carbon Steel

26 Vent Ring 17-4PH Stainless Steel

27 Belleville Washer 17-4PH Stainless Steel

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Recommended spare parts for service inspection (on hand).

NOTES:1. Valve constructed in accordance with ANSI B.16.34 & B.16.5 with tolerances per B.16.112. Temperature limitation: 500F.3. Install any valve with minimum straight piping 6″ upstream, 18″ downstream. Install any reducers at end of straight runs.

Nominal Dimensions, in. (mm)Valve Sizes A B C D E

1 (25) 14-1/16 (357) 6-1/2 (165) 9-13/16 (250) 28-7/16 (722) 9-1/2 (241)1-1/2 (40) 14-1/16 (357) 7-3/4 (197) 10-1/2 (267) 42-5/16 (1074) 12-1/2 (318)

2 (50) 17 (432) 8-1/4 (210) 11-1/6 (281) 42-5/16 (1074) 12-1/2 (318)

Dimensions (Unbalanced Turbo-Cascade Valve)

*Actuator height depends on application and accessories required. Consult Yarway.

Parts/Materials (Unbalanced Valve)

How to SpecifyTurbo-Cascade Valves

Control valve forservice, Tag No. , inaccordance with data sheet attached,shall be a Yarway Turbo-Cascadevalve, Series 5400, forged steel body,incorporating separate elements fortight shutoff and throttling. Pressurereduction shall be accomplished in

stages to dissipate pressure and con-trol velocity by directing the fluidthrough a series of variable orificeswhose individual flow area increasesas the valve is opened. The fluidpressure breakdown shall take placethrough a series of characterizedpassages between the stem and the

bushing whose flow area will be ofsufficient cross-sectional area to pre-clude the possibility of obstruction byforeign particles. Valve shall operatewith a sound pressure level of 90dBA or less measured three feet fromthe valve, three feet downstream.

Parts/Materials (Balanced Turbo-Cascade Valve)

Item Part Material

1 Body/Inlet Connection ASME SA105

2 Actuator Adapter ASME SA105

3 Packing Gland AISI 4140

4 Gland Bushing ASTM A479 Type S21800

5 Cascade Shaft ASME SA479 Grade 410

6 Cascade Seat ASTM A747 CB7 CU-1 (17-4PH)

7 Spacer Sleeve AISI Type 416 Stainless Steel

8 Nameplate Type 18-8 Stainless Steel

8A Nameplate Type 18-8 Stainless Steel

9 Valve Stem ASME SA564 GR 630

11 Stud ASME SA193 Grade B7

12 Hex Nut ASME SA194 Grade 2H

13 Drive Screws Type 18-8 Stainless Steel

14 Jam Nut Carbon Steel

15 Pipe Plug ASME SA105

16 Gland Stud ASME SA193 Grade B7

17 Hex Nut ASME SA194 Grade 2H

18 Lantern Ring AISI Type 416 Stainless Steel

19 Packing Carbon Yarn & Graphite

20 Seal TFE/Egiloy

21 O-Ring Fluoraz (TFE-Propylene)

Item Part Material

22 Venting Ring 17-4 PH Stainless Steel

23 Piston Ring Type 420 Stainless Steel

25 O-Ring Fluoraz (TFE-Propylene)

29 Gasket Graph-Lock

30 Pilot Seat AISI Type 410 Stainless Steel

31 Orifice AISI Type 316 Stainless Steel

32 Actuator —

33 Belleville Washer 17-4 PH Stainless Steel

34 Pin Type 304 Stainless Steel

35 Cap Screw Type 18-8 Stainless Steel

36 Lockwasher Type 410 Stainless Steel

37 O-Ring Fluoraz (TFE-Propylene)

38 Collar ASTM A583 Type 416 St. Steel

39 Pilot Valve AMS 5385—Stellite

40 Spacer ASME SA479 Grade 410

41 Warning Label —

42 Pipe Plug Type 18-8 Stainless Steel

43 Nozzle Stellite

44 Piston Type 17-4PH Stainless Steel

45 Locknut Type 18-8 Stainless Steel

46 Stem Retainer ASME SA564 GR 630 (17-4)

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NominalDimensions, in (mm)

Valve A B

Size1&2 4 Stages 6 1&2 4 6 C D H

Stages 1500 2500 Stages Stages Stages Stages

3″ 21-3/4 21-3/4 21-3/4 28 13-3/8 13-3/8 13-3/8 17 33-9/16 10-1/4(552) (552) (552) (711) (340) (340) (340) (432) (852) (260)

4″ 25-5/8 25-5/8 25-1/8 32-1/2 13 13 14-7/8 17-1/2 33-9/16 10-1/4(651) (651) (638) (826) (330) (330) (378) (445) (852) (260)

6″ 20-3/8 Consult — — 12-3/8 Consult — 16-3/4 33-9/16 10-1/4(518) Yarway (314) Yarway (426) (852) (260)

Dimensions (Balanced Turbo-Cascade Valve)

Recommended spare parts for service inspection (on hand).

Dimensions listed are typical for max. trim sizes*Actuator height depends on application and accessories required. Consult Yarway.NOTES:1. Valve constructed in accordance with ANSI B.16.34 & B.16.5 with tolerances per B.16.112. Temperature limitation: 500F.3. Install any valve with minimum straight piping 6″ upstream, 18″ downstream. Install any reducers at end of straight runs.

8

Balanced Turbo-Cascade Valve

9

Unbalanced Turbo-Cascade Valve

105 Rev. 7/00 6M 700C Printed in U.S.A.

Class, TrimCv Kv Stages

*End ConnectionsANSI No. Standard Inlet/Outlet

0941 3.8 3.3 1 1, 1-1/20942 7.3 6.3 1 1, 1-1/2, 20943 15.9 13.6 1 1-1/2, 20944 31.0 26.6 1 2, 30945 43.0 36.9 1 2, 3

900 0951 94.5 81.1 1 3, 40901 2.3 2.0 2 1, 1-1/20902 4.4 3.8 2 1, 1-1/2, 20903 7.6 6.6 2 1-1/2, 20904 18.0 15.5 2 2, 30905 26.5 22.7 2 2, 30930 56.0 48.1 2 3, 4

1501 2.3 2.0 2 1, 1-1/21502 4.4 3.8 2 1, 1-1/2, 21503 7.6 6.6 2 1-1/2, 21504 18.0 15.5 2 2, 3

1500 1505 26.5 22.7 2 2, 31506 1.1 0.9 4 1, 1-1/21507 2.2 1.9 4 1, 1-1/2, 21508 4.8 4.1 4 1-1/2, 21509 9.0 7.7 4 2, 31510 16.5 14.2 4 2, 3

2501 2.3 2.0 2 1, 1-1/22502 4.4 3.8 2 1, 1-1/2, 22503 7.6 6.6 2 1-1/2, 22504 18.0 15.5 2 2, 32505 26.5 22.7 2 2, 32506 1.1 0.9 4 1, 1-1/2

2500 2507 2.2 1.9 4 1, 1-1/2, 22508 4.8 4.1 4 1-1/2, 22509 9.0 7.7 4 2, 32510 16.5 14.2 4 2, 32511 0.87 0.75 6 1, 1-1/22512 1.6 1.4 6 1, 1-1/2, 22513 3.5 3.0 6 1-1/2, 22514 7.0 6.0 6 2, 32515 13.0 11.2 6 2, 3

Flow Coefficients (Unbalanced Valve)

Class, Trim Cv Kv StagesEnd Connections

ANSI No. Inlet Outlet

946 94 80.69 1 3,4,6 3,4,6,8947 140 120.17 1 3,4,6,8 3,4,6,8,10948 190 163.10 1 4,6,8 4,6,8,10949 255 218.88 1 6,8,10 6,8,10,12

900 950 360 309.01 1 6,8,10 6,8,10,12916 53 45.49 2 3,4,6 3,4,6,8917 78 66.95 2 3,4,6,8 3,4,6,8,10918 112 96.14 2 4,6,8 4,6,8,10919 148 127.04 2 6,8,10 6,8,10,12920 190 163.10 2 6,8,10 6,8,10,12

1516 53 45.49 2 3,4,6 3,4,6,81517 78 66.95 2 3,4,6,8 3,4,6,8,101518 112 96.14 2 4,6,8 4,6,8,101519 148 127.04 2 6,8,10 6,8,10,12

15001520 190 163.10 2 6,8,10 6,8,10,12

1521 27.5 23.61 4 3,4,6 3,4,6,81522 42 36.05 4 3,4,6,8 3,4,6,8,101523 58 49.79 4 4,6,8 4,6,8,101524 81 69.53 4 6,8,10 6,8,10,12

2516 53 45.49 2 3,4,6 3,4,6,82517 78 66.95 2 3,4,6,8 3,4,6,8,102518 112 96.14 2 4,6,8 4,6,8,102519 148 127.04 2 6,8,10 6,8,10,122520 190 163.10 2 6,8,10 6,8,10,12

2500 2521 27.5 23.61 4 3,4,6 3,4,6,82522 42 36.05 4 3,4,6,8 3,4,6,8,102523 58 49.79 4 4,6,8 4,6,8,102524 81 69.53 4 6,8,10 6,8,10,12

2526 21 18.03 6 3,4,6 3,4,6,82527 31 26.61 6 3,4,6,8 3,4,6,8,102528 42 36.05 6 4,6,8 4,6,8,10

Flow Coefficients (Balanced Valve)

*Standard inlet and outlet 1″ through 2″ flanged or socketweld, 3″ and largerbuttweld end. Nominal Line Size - Inches.

Yarway Corporation reserves the right to change thedesigns and materials of its products without notice.

Yarway Corporation • 480 Norristown Road • P.O. Box 350 • Blue Bell, PA 19422Phone 610-825-2100 • Fax 610-825-1235 • www.yarway.com

North American Regional Offices: Eastern 800-523-6248 • Southeast 800-561-5816Southwest 800-561-5819 • Midwest 800-561-5814 • Western 800-561-5813

Inquiries from other than North American Locations should be addressed to the International Department, Blue Bell, PA