1353

6.23 Valve Types: Sliding Gate Valves

C. S. BEARD (1970, 1985) B. G. LIPTÁK (1995, 2005)

Types: A. Knife gateB. V-insertC. Plate and disc (multi-orifice)D. Positioned disc

Sizes: A. On/off; 2 to 120 in. (50 mm to 3 m)B. Throttling: 1/2 to 24 in. (12 to 600 mm)C. Throttling: 1/2 to 6 in. (12 to 150 mm)D. Throttling: 1 to 2 in. (25 and 50 mm)

Design Pressures: A and B. Up to ANSI Class 150; higher with “wedge within wedge” designC. Up to ANSI Class 300D. Up to 10,000 PSIG (69 MPa)

Design Temperatures: A and B. Cryogenic to 500°F (260°C)C. −20 to 1125°F (−29 to 607°C)

Rangeability: A. 10:1B. 20:1C. Up to 50:1 is claimed; see Section 6.7

Characteristics: See Figure 6.23a

Capacity: A. Cv = 45 d2

B. Cv = 30 d2

C. Cv = (6 to 10) d2

See Table 6.23b

Leakage: A and B. ANSI Class I or II with metal seat; better with soft seat or liningC. ANSI Class IV; see Table 6.1gg for definitions

Materials of Construction: A and B. Ductile iron, cast iron, carbon steel, 304, 316, 317 stainless steel, Alloy20, Hastelloy B or C. Seating can be metal to metal, nylon, or RTFEC. Body: Ductile iron, bronze, carbon steel, stainless steel, aluminum, MonelTrim: Stainless steel is standard, which can be chrome-plated for hardness or Teflon-coated for corrosion resistance; Monel or Hastelloy trims are also available

Costs: The cost of V-insert-type slide gate valves is similar to, but generally less than thatof, single-seated globe valves, which are given in Figure 6.19b. The cost of plateand disc valves is given in Table 8.23j.

Partial List of Suppliers: Anchor/Darling Valve Co. (www.flowserve.com)DeZurik/SPX Valves (www.spxvalves.com)ITT Industries, Engineered Valves (www.engvalves.com)Jordan Valve (www.joprdanvalve.com)Kurimoto Valves (www.kurimoto.co.jp)Red Valve Company Inc. (www.redvalve.com)Richards Industries (www.richardsind.com)Stockham Valves & Fittings (www.stockham.com)Zimmermann & Jansen Inc. (www.zjnc.com)

Flow sheet symbol

© 2006 by Béla Lipták

1354 Control Valve Selection and Sizing

INTRODUCTION

The knife gate-type slide gate valves are relatively inexpen-sive, have high capacity, and are suited for slurry and dirtyservices. On the other hand they have poor control charac-teristics, do not provide tight shut-off, and are not suited forcorrosive services. The V-insert type variation of this designhas similar features, but as illustrated in Figure 6.23a, hasbetter control characteristics.

The positioned sliding disc designs are ideal for high-pressure (up to 10,000 PSIG), cavitating, abrasive, or erosiveservices, but are relatively expensive and are not suited forsludge, slurry, viscous, or fibrous services. The multiportplate and disc type valves are similar, but provide superiorcontrol characteristics. These valves are available as pumpgovernors or as unusually high rangeability (> 200:1) controlvalves in sizes from 0.5 to 6 in.

SLIDING GATE VALVE DESIGNS

Knife Gate Valves

Changing the process fluid’s flow rate by sliding a plate pasta stationary hole is one of the oldest and most basicapproaches to throttling flows. The most common valve, thesliding gate valve, operates like this. Although occasionallyused for automatic control, it is not considered to be a throt-tling control valve. It is a form of “guillotine”-type gate valve(Figure 6.23c) and is much used in the pulp and paper indus-try due to its shearing ability and nonplugging body design.

The “slab-type” sliding gate is provided with a roundopening (Figure 6.23d) and therefore its characteristics aredetermined by the two converging circles. Its characteristics

approximates equal-percentage behavior up to about 70% ofits flow capacity, and above that it becomes nearly linear. Theflow rate of 70% is reached by opening the valve to about30% of its stroke.

On critical services, such as in catalytic cracking, reform-ing, isomerization, or coal gasification applications, the “dou-ble” gate valves are often considered (Figure 6.23e). In this

FIG. 6.23a The characteristics of the various types of sliding gate-type valvedesigns.

Positioneddisc

Plate &disc

V-insert

0

20

40

60

80

100

% Fl

ow o

r Cv

0 20 40 60 80 100% Lift or rotation

TABLE 6.23b Valve Capacity Coefficients of Open Gate, V-Insert, or Plate-and-Disc-Type Slide Gate Valves

Size in. (mm)

Valve Design

Plate and DiscOpen Knife

GateV-Insert

Type

0.5 (12.5) 0.0005 to 2.5

1.0 (25.4) 0.0005 to 9

1.5 (38) 9.0 to 17.5

2 (51) 17.4 to 30.5 161 88

3 (75) 362 196

4 (100) 646 353

6 (150) 1450 794

8 (200) 2570 1410

10 (250) 3450 1935

12 (300) 5060 2850

14 (350) 6630 3725

16 (400) 8680 4870

18 (450) 11,350 6370

20 (500) 14,000 7850

24 (600) 20,550 11,550

30 (750) 31,900 17,900

36 (900) 45,700 26,200

FIG. 6.23c The guillotine-type sliding gate valve.

Inspectionwindow

© 2006 by Béla Lipták

6.23 Valve Types: Sliding Gate Valves 1355

design a “wedge” is provided within the wedge-shaped slid-ing gate. This inner wedge forces the two sliding gates on itstwo sides against the two seats, thereby guaranteeing tightclosure.

V-Insert Type The addition of a V-shaped insert (Figure 6.23f)in the valve opening creates a parabolic flow characteristic.As shown in Figure 6.23a, this characteristic is somewhatsimilar to that of the V-ported globe valve. The performance

of these valves is much dependent on the type of actuatorand positioner used, because the quality of control is depen-dent upon the ability to provide very accurate positioning ofthe sliding gate.

Positioned-Disc Valves

Rotation of a movable disc with two holes, which if rotatedcan progressively cover two holes in the stationary disc, cansuccessfully throttle flow (Figure 6.23g). This variable chokewas designed to control flow from high-pressure oil wells.

The use of ceramic or tungsten carbide discs allows it tohandle pressures up to 10,000 PSIG (69 MPa). Such valvesare presently furnished in 1 and 2 in. (25 and 50 mm) sizeswith areas from 0.05 in.2 with 0.25 in. hole (32 mm2 with6.3 mm hole) to 1.56 in.2 with two 1 in. holes (1006 mm2

with two 25 mm holes).An angle version of this valve design is used for propor-

tioning control, with an actuator capable of controlling thedischarge flow at quarter-turn movement. Both linear androtary type actuators can be used. The valve opening (therelationship between the discs) remains in the last positionif power fails.

A stepping actuator (Figure 6.23h) positions the innervalve disc in 1° increments as a function of a pneumaticcontroller input to a double-acting, spring-centered piston.Rotation occurs through a rack and pinion assembly. Limit

FIG. 6.23d The design of a slab-type sliding gate valve.

FIG. 6.23e The design of the double gate valve, which is also called the “wedgein the wedge” design. (Courtesy of Zimmermann & Jansen Inc.)

FIG. 6.23f Sliding gate valve with V-insert.

FIG. 6.23g High-pressure process streams can be throttled by the positioned-disc-type slide gate valve.

Fully open �rottling Fully closed

© 2006 by Béla Lipták

1356 Control Valve Selection and Sizing

switches are provided, and a stepping switch can be used forposition transmission and for position feedback in automaticcontrol systems.

Plate and Disc Valves

A wide variety of flow characteristics are available using astationary plate in the valve body and a disc that is moved

by the valve stem. The plate (Figure 6.23i) is readily replace-able by removing a flanged portion of the body, whichretains the plate with a pressure ring. Areas of the plate areundercut to reduce friction. A circumferential groove pro-vides flexibility and allows the plate to remain flat in spiteof differential pressures or expansion or contraction of thebody. The stem contacts the disc by a pin through a slot inthe plate.

The disc is held in contact with the plate by upstreampressure and by retaining guides. The contacting surfacesof the disc and plate are lapped to light band flatness. Thechrome-plated surface of the stainless steel plate has a hard-ness comparable to 740 Brinell to resist galling and corro-sion and obtain smooth movement of the disc. The material,with the registered name of Jordanite, is reported to havean extremely low coefficient of friction, is applicable tohigh-pressure drops, and has great resistance to heat andcorrosion.

Flow occurs through mating slots in the disc and theplate. Positive shut-off occurs when the slots are separated(Figure 6.23i). Flow increases on an approximately linearrelationship until the slots are lined up for maximum flow.Capacities are about Cv = 6.5 d2 through the 2 in. (50 mm)size and about Cv = 12 d2 through the 6 in. (150 mm) size.

Stem travels to obtain full flow are very short due to theslot relationship, and low-lift diaphragm actuators can beused for positioning. Forces needed for positioning are low,requiring only sufficient power to overcome friction betweenthe plate and disc, which is right-angle motion and notopposed to the direction of flow.

Valve bodies are offered in sizes between 1/4 and 6 in.(6.3 and 150 mm) and with ratings through 300 PSIG (2.1MPa), depending on the material, with a selection of trimsand packings. Many styles of actuators are used, includingone with a thermal unit and cam actuation. This body designhas been adapted for extensive use in self-contained pressureor temperature regulators.

This valve is also used to control the steam flow to steam-driven pumps, so as to maintain the pump discharge pressureconstant. The sizes and costs of these pump governors aregiven Table 6.23j.

FIG. 6.23h The actuator of a positioned-disc-type angle valve. (Courtesy ofWillis Oil Tool Co.)

FIG. 6.23i This throttling control valve provides wide rangeability by the useof a plate-and-disc inner valve. (Courtesy of Jordan Valve, a divisionof Richards Industries.)

Controlsignal

Cap

Plate

Disc

Pressurering

Lower rodassembly

Body

Locknut

Open Closed

TABLE 6.23jMultiple-Orifice, Plate- and Disc-Type PumpGovernor Steam Valve Costs*

Valve Size (Inches) Carbon Steel Stainless Steel

0.5 $2,000 $2,600

1.0 $2,300 $3,300

1.5 $2,700 $3,600

2.0 $3,100 $4,000

* All valves are provided with 150# RF connections(Courtesy of Jordan Valve.)

© 2006 by Béla Lipták

6.23 Valve Types: Sliding Gate Valves 1357

Bibliography

Arant, J. B., “Fire-Safe Valves,” InTech, December 1981.Ball, K. E., “Final Elements: Final Frontier,” InTech, November 1986.Bialkowski, B., Coughran, M., and Beall, J., “Control Valve Performance

Update—The Last 10 Years,” Pulp Pap-Canada, (102):21-22,November 2001.

Bishop, T., Chapeaux, M., Jaffer, L., et.al., “Ease Control Valve Selection,”Chem Eng Prog, 98 (11): 52–56 November 2002.

Carey, J. A., “Control Valve Update,” Instruments and Control Systems,January 1981.

Control Valve Handbook, 3rd edition, Marshalltown, IA: Fisher ControlsInternational Inc., 2001.

Control Valve Seat Leakage, FCI 70-2-1998, Cleveland, OH: Fluid ControlsInstitute, Inc., 1998.

Borden, G. and Friedmann, P. G. (eds.), Control Valves — Practical Guidesfor Measurement and Control, Research Triangle Park, NC: ISA, 1998.

“Control Valves—Globe, Plug, Pinch, Needle, Gate,” Measurements andControl, February 1994.

Fernbaugh, A., “Control Valves: A Decade of Change,” Instruments andControl Systems, January 1980.

Monsen, J. F., “Valve Wars—Rising Stem vs. Rotary,” Plant Services,January 1999.

Rahmeyer, W., “The Critical Flow Limit and Pressure Recovery Factor forFlow Control,” InTech, November 1986.

Whatever Happened To… A Guide to Industrial Valve and ActuatorCompaniess—Past and Present, Washington, D.C.: Valve Manufactur-ers Association, 1997.

© 2006 by Béla Lipták