Butterfly Valve

Butterfly valves go from open to closed in 90° of shaft rotation, and there are “quarter-turn” actuators used to operate them.

From: An Applied Guide to Process and Plant Design, 2015

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Meters and Valves

E. Shashi Menon, in Transmission Pipeline Calculations and Simulations Manual, 2015

15 Butterfly Valve

The butterfly valve was originally used where a tight closure was not absolutely necessary. However, over the years, these valves have been manufactured with fairly tight seals made of rubber or elastomeric materials that provide good shut off similar to other types of valves. Butterfly valves are used where space is limited. Unlike gate valves, butterfly valves can be used for throttling or regulating flow as well as in the full open and fully closed position. The pressure loss through a butterfly valve is small in comparison with the gate valve. The L/D ratio for this type of valve is approximately one-third of that of a gate valve. Butterfly valves are used in large and small sizes. They may be hand wheel–operated or operated using a wrench or gearing mechanism. A typical butterfly valve is shown in Figure 12.12.

Figure 12.12. Butterfly valve.

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Butterfly valve applications and design

Karan Sotoodeh, in A Practical Guide to Piping and Valves for the Oil and Gas Industry, 2021

Installation direction

Concentric butterfly valves are bidirectional. Double offset and triple offset butterfly valves are also bidirectional but with preferred flow (pressure) direction, such as flow from the stem side. Fig. 2.96 shows the preferred flow direction of a flanged end double offset butterfly valve. Flow direction is marked on the body of the valves refer to Fig. 2.97.

Fig. 2.96. Flanged end double offset butterfly valve with the preferred flow direction.

Courtesy: Westad.

Fig. 2.97. Preferred flow direction on the body of the butterfly valves.

Courtesy: Westad.

Fig. 2.98 shows an example where the actuated butterfly valve was installed in the wrong direction in the construction yard.

Fig. 2.98. Wrong installation of a double offset butterfly valve in the yard.

This butterfly valve installation is wrong because the flow was incorrectly assumed to be in the opposite direction in the piping modeling program (PDMS) as shown in the small picture on the bottom left of Fig. 2.119. Therefore, it was the recommendation from the valve manufacturer to remove the valve from the line, rotate it 180 degrees, and install it in the preferred flow direction. One reason for the valve supplier manufacturer is that the fluid helps in closing the valve in the preferred flow direction, so it is not possible to get fluid sealing force for closing the valve in the opposite flow direction. Even if a butterfly valve has passed the test on the opposite flow direction, the sealing of the valve may not be effective after a period of time. Insufficient sealing of butterfly valve can be intensified due to bearing wear and emergency cases like fire or water hammering. However, to avoid extra jobs in the construction yard and save time, some engineers may recommend leaving the butterfly valve as it is, since the valve is designed to be bidirectional and is tested from both sides in the valve factory.

Fig. 2.119. Seat design for cryogenic application.

Courtesy: Westad.
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Valves and Meters

Malcolm J. Brandt BSc, FICE, FCIWEM, MIWater, ... Don D. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM, in Twort's Water Supply (Seventh Edition), 2017

18.8 Butterfly Valves

Butterfly valves tend to be cheaper than gate valves because they require less material and less civil works. They are also easier to operate against unbalanced water pressures as the disc pivots about an axis on or near the pipe axis. Consequently butterfly valves are now commonly used in water distribution systems. Butterfly valves can be metal seated or resilient seated; in the latter case the seat is usually made of natural or synthetic rubber and is commonly fixed to the body of valves of smaller sizes or to the disc. Plate 28(b) shows a resilient seated butterfly valve.

Resilient seated valves can remain virtually watertight, even after prolonged use in silty water. Therefore, resilient seats are usually specified for isolating valves in distribution systems. Resilient seated valves may also be used for control purposes but, if operated at small openings, the seal may be damaged. Solid rubber is the material usually used for resilient seatings: inflatable seals have been used on very large valves but not always with success. Metal seated butterfly valves do not have tight shut-off characteristics and are mainly intended for flow control purposes where they need to be held in the partially open position.

Distribution network pipe systems are now designed to produce self-cleaning velocities at least once every 24 hours and should not need swabbing as part of normal operation. A transfer pipeline may need to be swabbed periodically. Butterfly valves on the line prevent the passage of foam swabs (except for very soft ones) but this does not usually pose a problem if the valves are spaced sufficiently far apart to allow the pipe to be cleaned in sections. Short lengths of pipe either side of the valve are made removable so that the cleaning apparatus can be inserted and removed.

Butterfly valves should normally be mounted with the spindle horizontal since this allows debris in the pipe invert to be swept clear as the valve is closed. Where the spindle is vertical solids can lodge under the disc at the spindle and cause damage to the seal. Disc position indicators are useful and strong disc stops integral with the body should be specified, so that the operator can feel with certainty when the disc is fully closed or fully open.

Butterfly valves have been made to very large diameters (10 m or more) operating under very high heads and at high water velocities (20 m/s or more) and have proved successful in use. However, when a butterfly valve is to be used for flow control purposes the maximum velocity of approach to the valve should be limited to 5 m/s. Resilient seated valves can be specified to have no visible leakage on seat test but the range of acceptable seat leakage rates for metal seated valves varies from about 0.004 to 0.04 l/h per 100 mm of nominal diameter (DN), at the specifier’s choice. However, a low rate for a high pressure differential would be expensive to achieve and difficult to maintain with metal seats. For some control applications, an acceptable seat leakage rate of about 0.4 l/h per 100 mm DN may be appropriate.

If a valve may be required to remain in place closed on removal of the pipe on one side for a temporary operation, it must be flanged for bolting to a pipe flange on the other side. ‘Wafer’ butterfly valves whose bodies are sandwiched between pipe flanges do not achieve this. Use of such valves for isolation of air valves allows maintenance to be carried out on the air valve in situ with the pipeline in service but does not allow removal and replacement of the air valve under pressure. Since replacement of air valves is likely to be cheaper than in situ refurbishment, flanged isolating valves are preferred in such situations.

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Control Valves

Alireza Bahadori PhD, CEng, MIChemE, CPEng, MIEAust, RPEQ, in Oil and Gas Pipelines and Piping Systems, 2017

16.5 Control Valve Body Size and Flange Rating

16.5.1 Globe Body Valves

16.5.1.1 Body Sizes

Nominal body sizes for the globe body should be selected from the following series:

(Inches) 1 1½ 2 3 4 6 8 10 12 etc.

The use of odd sizes such as 1¼″, 2½″, 5″, 7″, 9″, etc., should be avoided. 1½″ and 3″ valves are less common in petroleum industries.

The minimum globe control valve body size to be used should be one inch screwed, unless flange type is specified, and the internal trim size should be in accordance to the requirements as specified in data sheet.

Body sizes smaller than 1 in. may be used for special applications, and pressure regulation services. For valve sizes smaller than 1 in., reduced trim in 1 in.-size bodies normally will be preferable.

Flange-rating-globe-control valves should normally have flanged ends, but flangeless bodies may be considered for special applications.

The flange rating should generally be in accordance with the piping class, but for carbon steel bodies the flange rating should be class 300 minimum.

For the pressure–temperature rating of globe-body control valves reference should be made to relevant standards.

All globe-body, control-valve manifolds, and bypass valves should follow the piping class and ratings. The dimensions, however, should be in accordance with the recognized standard such as ANSI/ISA RP-75.06 (Fig. 16.13).

Figure 16.13. Illustrations of end types and external bolting options.

16.5.2 Butterfly Body Valves

Lug type and wafer type butterfly valves should have body pressure–temperature ratings for the selected American Society of Testing and Materials (ASTM) material specification in accordance with the applicable ANSI B-16 standard.

The wafer type butterfly valves, other than lugged type, should be provided with or without holes for the passage of bolts securing the connecting flanges dependent upon valve design.

Lugged type, wafer valves should be supplied with threaded or drilled holes the lugs to the size, nominal pressure rating, and type of connecting flange.

The end flanges of double-flanged steel butterfly control valves should be cast or forged integral with the body.

For other types of valves such as eccentric rotating plug valves or butterfly valves flanges should be a wafer type, i.e., suitable for installation between flanges.

Butterfly valves should be one of the following types shown in Figs. 16.14–16.17, with metal or resilient seating or linings:

Figure 16.14. Butterfly valve: double-flanged type.

Figure 16.15. Butterfly valve: single-flange wafer type.

Figure 16.16. Butterfly valve: flangeless wafer type.

Figure 16.17. Butterfly valve: U-section wafer type.

1.

Double flanged: A valve having flanged ends for connection to pipe flanges by individual bolting.

2.

Wafer: A valve primarily intended for clamping between pipe flanges using through bolting:

a.

single flange;

b.

flangeless;

c.

U-section.

Note:

This type of valve when supplied with threaded holes may be suitable for terminal connections.

Note:

This type of valve when supplied with threaded lugs may be suitable for terminal connections.

Notes:

1.

This type of valve may be suitable for the individual bolting of each flange to the pipework, but this cannot be assumed.

2.

This type of valve may be suitable for terminal connections.

16.5.3 Face-to-Face Dimensions

Face-to-face dimensions of flanged-bodied globe-style control valves should comply with the recognized standard such as ANSI/ISA-S 75.03 (Table 16.2).

Table 16.2. Face-to-Face Dimensions for Flanged Globe-Style Control Valves

Nominal Valve Size (ANSI Classes 150) (ANSI Classes 300) (ANSI Class 600) Tolerance
Dimension “A” Dimension “A” Dimension “A”
Inches mm Inches mm Inches mm Inches mm Inches
½ 184 7.25 190 7.50 203 8.00 ±1.6 ±0.062
¾ 184 7.25 194 7.62 206 8.12 ±1.6 ±0.062
1 184 7.25 197 7.75 210 8.25 ±1.6 ±0.062
1½ 222 8.75 235 9.25 251 9.88 ±1.6 ±0.062
2 254 10.00 267 10.50 286 11.25 ±1.6 ±0.062
2½ 276 10.88 292 11.50 311 12.25 ±1.6 ±0.062
3 298 11.75 318 12.50 337 13.25 ±1.6 ±0.062
4 352 13.88 368 14.50 394 15.50 ±1.6 ±0.062
6 451 17.75 473 18.62 508 20.00 ±1.6 ±0.062
8 543 21.38 568 22.38 610 24.00 ±1.6 ±0.062
10 673 26.50 708 27.88 752 29.62 ±1.6 ±0.062
12 737 29.00 775 30.50 819 32.25 ±3.2 ±0.125
14 889 35.00 927 36.50 972 38.25 ±3.2 ±0.125
16 1016 40.00 1057 41.62 1108 43.62 ±3.2 ±0.125

Face-to-face dimensions of butterfly valves should be in accordance with the recognized standard such as BS-5155 (Table 16.3).

Table 16.3. Face-to-Face Dimensions of Butterfly Valves

1 2 3 4 5 6 7
Nominal Size (in.) Double Flanged Short Double Flanged Long Wafer Short Wafer Medium Wafer Long Wafer
Face-To-Face Dimension For Nominal Pressures Not Exceeding Face-To-Face Dimensions For Nominal Pressures Not Exceeding Class 300
Class 150 Class 300 Class 150 Class 150 Class 150
mm mm mm mm mm mm
1½ 106 140 33
2 108 150 43
2½ 112 170 46
3 114 180 46 64 49
4 127 190 52 64 56
5 140 200 56 70 64
6 140 210 56 76 70
8 152 230 60 89 71
10 165 250 68 114 76
12 178 270 78 114 83
14 190 290 92 127 127
16 216 310 102 140 140
18 222 330 114 152 160
20 229 350 127 152 170
24 267 390 154 178 200
28 292 430 229
32 318 470 241
36 330 510 241
40 410 550 300
48 470 630 350
56 530 710 390
64 600 790 440
72 670 870 490
80 760 950 540

Note: Wafer type valves may not be available in all combinations of materials and face-to-face dimensions.

Tolerances on face-to-face dimensions for butterfly valves should be in accordance with BS-5155 standard (Table 16.4).

Table 16.4. Tolerances on Face-to-Face Dimensions of Butterfly Valves

Face-to-Face Dimension Tolerance
mm mm
Up to and including 200 ±1
Above 200 up to and including 400 ±2
Above 400 up to and including 600 ±3
Above 600 up to and including 800 ±4
Above 800 ±5

Flange dimensions of butterfly valves Class 125 should be in accordance with the recognized standard such as BS-5155 (Table 16.5, if a flange type is specified).

Table 16.5. Dimensions of Class 125 (Cast Iron) Flanges of Butterfly Valves

1 2 3 4 5 6 7
Nominal Size of Valve Diameter of Flange Minimum Thickness of Flange Diameter of Bolt Circle Number of Bolts Diameter of Bolt Holes
Inches mm mm mm mm Inches
1½ 127 14.3 98.4 4 15.9 5/8
2 152 15.9 120.6 4 19.0 ¾
(2½)* 178 17.5 139.7 4 19.0 ¾
3 190 19.0 152.4 4 19.0 ¾
4 229 23.8 190.5 8 19.0 ¾
5 254 23.8 215.9 8 22.2 7/8
6 279 25.4 241.3 8 22.2 7/8
8 343 28.6 298.4 8 22.2 7/8
10 406 30.2 362.0 12 25.4 1
12 483 31.8 431.8 12 25.4 1
14 533 34.9 476.2 12 28.6 1⅛
16 597 36.5 539.8 16 28.6 1⅛
18 635 39.7 577.8 16 31.8 1¼
20 698 42.9 635.0 20 31.8 1¼
24 813 47.6 749.3 20 34.9 1⅜

Note:

This size has been retained only for the purpose of replacing existing valves. Its use for new construction on piping systems using BS 1560: Part 2 flanges, should be avoided.

Class 125 (cast iron) valves should be used on special applications such as slurry and utility services.

Flange dimensions of butterfly body control valves should be in accordance with the recognized standard such as of BS-1560: Part 2.

For pressure–temperature rating of butterfly control valves reference should be made to relevant standards.

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Piping system components

Maurice Stewart, in Surface Production Operations, 2016

4.2.8.5 Butterfly valves

4.2.8.5.1 General considerations

The butterfly valve is a rotary valve in which a disk-shaped seating element is rotated 90° to open or close the flow passage. They are used in throttling service, particularly where large-size valves with automatic actuators are required. Butterfly valves cannot be used where a nonobstructed, full opening is needed. They offer a size and weight advantage over plug and ball valves.

4.2.8.5.2 Types

4.2.8.5.2.1 Wafer-type

The wafer-type butterfly valve is installed between two flanges. It requires both flanges to be in place (Figure 4.62).

Figure 4.62. Wafer-type butterfly valve.

(Courtesy of Rockwell International and WKM)
4.2.8.5.2.2 Lug-type

The lug-type butterfly valve is constructed with threaded lugs around the valve's circumference (Figure 4.63). This allows one flange to be removed and the valve can still operate for “dead end” service.

Figure 4.63. Lug-type butterfly valve.

(Courtesy of Rockwell International and WKM)

4.2.8.5.3 Classifications

4.2.8.5.3.1 Conventional

Conventional butterfly valves are used mainly in low-pressure water service and throttling applications. The seats, disk, and shaft are in the same plane. The seat is obtained by an interference fit between the disk and resilient (flexible) liner. This type of fit is shown in Figure 4.64. The tightness of the seat is limited by the operating torque of valve and the seal between the shaft and the liner. The sealing characteristics of this valve are poor and leakage usually occurs.

Figure 4.64. Conventional butterfly valve.

4.2.8.5.3.2 High performance

The high-performance butterfly valve provides good sealing characteristics and a tight shutoff. The disk is essentially an off-center slice of a ball, and the seating mechanism of this valve is similar to that of a ball valve. The disk and seats of this valve are offset from the shaft and shaft sealing in this valve is not critical. Many valves offer a primary seat made of a resilient material and a secondary metal-to-metal seal making them “fire-safe.” High-performance butterfly valves are available in pressure classes as high as ANSI 900 and can be used in applications requiring tight shutoff.

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Valves

Roy A. Parisher, Robert A. Rhea, in Pipe Drafting and Design (Third Edition), 2012

Butterfly Valve

The butterfly valve has a unique body style unlike the other valves we have discussed. The butterfly uses a circular plate or wafer operated by a wrench to control the flow. A 90° turn of the wrench moves the wafer from a fully open position to a fully closed position. The wafer remains in the stream of flow and rotates around a shaft connected to the wrench. As the valve is being closed, the wafer rotates to become perpendicular to the direction of flow and acts as a dam to reduce or stop the flow. When the wrench is rotated back to the original position, the wafer aligns itself with the direction of flow and allows the commodity to pass through the valve (see Figure 5.17).

Figure 5.17. Butterfly valve.

Courtesy of Crane Co.

Butterfly valves have minimal turbulence and pressure drop. They are good for on − off and throttling service and perform well when controlling large flow amounts of liquids and gases. However, these valves do not normally create a tight seal and must be used in low-pressure situations or where some leakage is permissible. Drawing symbols for the butterfly valve are shown in Figure 5.18. A dimensioning chart for the butterfly valve is included in the appendix.

Figure 5.18. Butterfly valve drawing symbols.

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Control valves

In Handbook of Valves and Actuators, 2007

Butterfly valve

Traditional butterfly valves now work at high pressure drops across the disc which can be both metallic and “soft”. Upper and lower temperature limits are the same, by and large, as those for globe valves, depending on duty and material of construction. The butterfly construction is especially suitable for high temperatures. Bodies can be fabricated from bar and plate and the seals can be mounted on cooling extensions away from the main flow. The upper temperature limit can be extended by using a refractory lining. A standard butterfly valve is shown in Figure 6.38.

Figure 6.38. Standard wafer butterfly valve with actuator

Butterfly valves can be used as a control valve and also as a shut-off valve, as discussed in Chapter 3, Section 3.3.3, against high pressure drops of regularly up to 415 barg. Depending upon the materials of construction and the seat design a butterfly control valve may have very limited shut-off pressure drops. Some 100 barg valves are only rated for 4 barg shut-off differential.

A butterfly valve should have a range of possible shaft diameters for each nominal valve size in order to handle the variation in torque due to various operating pressure conditions and packing box friction. Shafts should not be made of material prone to creep, such as some austenitic stainless steels. In these situations a precipitation hardening stainless steel such as 17-4PH is preferred. The corrosion resistance of such materials, equivalent to AISI 304, must be borne in mind. The disc must withstand high differential pressures. Some valves do have restrictions on the maximum throttling differential pressure, 35% of pressure rating in some cases.

Figure 6.39 shows the pressure distribution caused by the fluid flowing through a standard butterfly valve. The disc can be considered as an aerofoil, where greater forces are applied on the upper side than on the lower. The pressure is therefore relatively low where the velocity is high and relatively high where the velocity is low. These dynamic pressures generate an unbalanced torque which tends to close the valve. This torque varies from zero when the valve is closed, to a maximum at about 80° open, returning to zero again when the valve is fully open. It is this torque which imposes the pressure drop limitations which can be tolerated by the valve. It also determines the required actuator thrust. Furthermore, unbalanced torque reduction in these valves increases their range of applications.

Figure 6.39. Pressure distribution on a standard butterfly valve disc

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Treated Water Storage

Malcolm J. Brandt BSc, FICE, FCIWEM, MIWater, ... Don D. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM, in Twort's Water Supply (Seventh Edition), 2017

Valves

Stop valves (gate or butterfly) must be provided on inlets, outlets, drain down pipes and the reservoir bypass but must not be provided on the overflow or on any wall or underfloor drainage systems. Gate valves become impracticable for normal reservoir use above about 600 mm diameter, when resilient-seated butterfly valves should be provided (Section 18.8). The valve size can be less than that of the pipeline, though the saving in cost of the valve is at least partly offset by the need for tapers and the increased space occupied by the pipework in a valve house. If a smaller size of valve is selected, a check should be made that the maximum velocity through the valve does not exceed that recommended by the valve manufacturer.

Autonomous over-velocity valves, designed to close automatically when the water velocity in the pipeline exceeds a predetermined rate, have fallen out of general favour because of their high cost and infrequent use. They may still be appropriate in special circumstances, for example where a large reservoir provides the major supply to a distribution area, or where the loss of water from a failed outlet main would be severe because of high head. The possible need for such valves should therefore be reviewed in reservoir planning and electrically operated butterfly valves should be considered as an alternative.

Wherever they are located, all butterfly valves and special control valves should preferably be installed in chambers or houses so that they are accessible for maintenance. Important gate valves (such as the isolating valves on any pipes connecting into the reservoir) should also be placed in chambers but others can be buried.

Isolating valves on pipes leading into or out of the reservoir should be bolted to flanged pipes cast into the reservoir wall. Otherwise any differential movement between reservoir and valve could cause a joint to fail and release of the entire reservoir contents. The same principles apply to outlet or drain pipework built into the reservoir floor.

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