HIGH PRESSURE BUlTERFLY
VALVES WITH OFFSETDESIGN
Standard Practice
Developed and Approvedby the
Manufacturers Standardization Societyof the
Valve and Fittings Industry, Inc.
127 Park Street,NE
Vienna, Virginia 221 80
(703) 281 -6613
COPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
Licensed by Information Handling Services
MSS STANDARD.PRACTICE SP-68
An MSS Standard Practice is intended as ? practice by the manufacturer, the user, and
the general public. The existence of an MSS Standard Practice does not in itself preclude the manufac-
ture, sale, or use of products not conforming to the Standard Practice. Mandatory conformance is
established only by referencein ? tion, sales contract, or public law, as applicable.
U.S. customary units in this SP are the standard; themetric units are forreference only.
Substantive changes in this1997 edition are“flagged” by
parallel barsas shown on the marginsof this paragraph.
The specific detail of the change may be determined by
comparing the materialflagged withthat in the previous
I edition. I
Unless otherwisespecifically noted in thisMSS SP, any standard referredto herein is identified by the date of
issue that was applicable to thereferenced standard(s) at the dateof issue of this MSS SP. (See Annex A.)
Any part of this standard may be quoted. Credit lines should read ‘Extractedfrom MSS SP-68, 1997, with
permission of the publisher, theManufacturers Standardization Society.’ Reproduction prohibited under
copyright convention unless written permission is granted by the ManufacturersStandardization Society of the
Valve and Fittings Industry, Inc.
Originally Approved October 1984
Copyright O, 1984 by
Manufacturers Standardization Society
of the
Valve and Fittings Industry, Inc.
Printed in U.S.A.COPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
Licensed by Information Handling Services
STD*MSS SP-b8-ENGL L977 5770b40 0500954 3T7
MSS PRACTICE STANDARD SP-68
CONTENTS
Section Page
CONTENTS .......... ii
1. SCOPE ............... 1
2 ? NTS ......... 1
3 ? ENSIONS ........... 2
4 ? .... 2
5 ? ...... 2
TABLEAl DISC TO PIPEMINIMUM NOMINAL RADIAL CLEARANCES ..... 4
FIGURE Al NOMENCLATURE AND EXPLANATION OF NOMINAL
RADIALCLEARANCE ........... ? ARANCE ........... 4
ANNEXBREFERENCEDSTANDARDS ........... 5
ii
COPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
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MSS. PRA.CTICE STANDARD SP-68
~ ~~ ~~ ~~
HIGH PRESSURE BUlTERFLY VALVES WITH OFFSET DESIGN
1. SCOPE 2.3.1 The valvedisc will upon rotation project
beyond the body flange gasket surfaces and there-
1.1 This standard practicecovers design require- fore requires care on the part of the user to insure
ments, test performance, marking requirements,and that, when installed, there is no interference between
nomenclature for butterfly valves designed for high the valve disc and adjacent components such as pip-
pressureperformance, having ? ing, strainers, check valves and other valving. Also
from the plane of the stem centerline. mating pipe flanges should be carefully aligned
prior to tightening of the companionflange bolts.
1.2 This standard practice covers flangeless (wafer
type) and singleflanged (lug type)body designs, 2.3.2 The valves shall be designed to be compatible
Compatiblewith ASME/ANSI B16.5flanges for with Schedule 40 pipe for all sizesof Class 150
sizes NPS ? NPS 24 (DN 600)and (PN 20); with Schedule 80 pipe for all sizes of Class
ASME/ANSI B16.47 Series ? es 300 (PN 50) and with Schedule 80 pipe for the
(DN 750)
NPS 30 through NPS 48 (DN 1200). NPS ? NPS ? and
Reference Tables ? 100 for sizes NPS ? h
NPS 24 (DN 600) of Class 600 (PN 100).
1.3 This standard practicecovers valveshaving
bodypressure temperature ratings in accordance
with ASME/ ANSI B16.34. 2.3.3.All valves shall be designed for disc-pipe
clearance accordingto the requirements of Annex A.
1.4 Definitions may be found in MSS SP-96.
2.3.4 When the user elects to use ? br>2. DESIGN REQUIREMENTS ule pipe than listed in 2.3.2, it shall be his responsi-
bility to insure disc/pipe clearance.
2.1Valve Flange Gasket Surfaces. The flange gas-
ket surfaces of the valve body (against the mating 2.4. Minimum Wall Sections. All valves shall have
flanges)shall be flushwitli or. raised from other ? ickness as required by ASME/
body surfaces within the outside diameters of the ANSI B16.34 for the rating marked on the identif"i-
mating flanges. cation plate.
2.2Flange Bolting
2.5 Special Requirements for Single Flange (Lug
Type) Valves. Single flange (lug type) valves may be
2.2.1 Threaded holes used for flange bolting shall designed for closure in dead-end pipingwhen
provide for full thread engagement to ? stalled against ? Such condition
less than 1.O times the nominal bolt diameter. may also óccur after removing the companion
flange and piping from one side of the valve. Single
2.2.2Unless otherwise specified by the customer, flange (lug type) valveswhich have every flange
threaded holes for flange bolting shall be tapped in bolt hole threaded shall be designed such that all
accordance with ASME B1.l Coarse Thread Series parts which are necessary to support pressure loads
Class 2B for bolts ? and shall be acting across the seating element safely support the
I tapped to the 8-ThreadSeries Class 2B for bolts ? ntial pressure rating of the valve.
1'h1' and larger. Examples of such parts areseat seal retaining plates
and their bolting or retaining means. In the event
2.3. MinimumDisc-Pipe Clearance that the valvedesign cannot accommodate theseCOPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
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STD*MSS SP-b8-ENGL L777 ? L7T
MSS PRACTICE STANDARD SP-68
pressure loads, the valve shall be marked to show ? O-FACE DIMENSIONS(^) I
installation or application restrictions.
Valve Type2 ? ternal Disc Position Indicator. Allvalves Size
shallhave ? te the disc position.
NPS DN in mm in mm ' in mm
The design shall be such that the components can-
not beassembled to falsely indicate the open or 30 750 6.50 165 9.05 191230 7.50
200 8.00 9.50 241
closed position of the valve. 7.88 900 36 203
9.68 1100246 42 229 9.0011.81 300
48 10.88 1200276 10.00 254 350 13.78
3. FACE TO FACE DIMENSIONS b, Note: Tolerance/variance not to exceed ? mm).
3.1Valve body face-to-face dimensions for sizes
NPS ? NPS 24 (DN 600) flangeless 4. MARKING
(wafer type) and single flange (lug type) valves and
tolerance or variances are'listed in Table 1. 4.1 Valves shall bemarked in accordance with
MSS SP-25. When the maximum differential shut-
I TABLE 1. FACE-TO-FACE DIMENSIONS(^) ? any temperature is less than the
body pressure rating at that temperature, this limit
shall also beshown on the permanently affixed
Valve Class 150 Class 300 Class 600 identification plate.
Size (PN 20) (PN 50) (PN 100)
IPS DN in mm in mm in mm 4.2 Valves designated for shutoff in ? 31.88 48 48 1.882.12 54 direction (one way valves) shall be clearly and per-
4 100 2.12 54 2.12 54 2.50 64 manently marked to identify the high pressure side
6 150 2.25 57 2.31 59 3.06 78 or direction of flow.
8 200 2.50 63 2.88 73 4.00 102
10 71 2.813.25 250 4.62 83117 4.3 Valves conforming to the requirements of this
3.19 30081 12 92 3.625.50 140 Standard Practice maybe marked SP-68 on the
350 143.62 92 117 4.626.12 155 identification plate.
4.00 400101 16 5.25 133 7.00 178
18 450 4.50 114 5.88 7.88 149
20 500 5.00 127 6.25 159 8.50 ? 600 154 6.067.12 9.13 181232
(a) Note: Tolerance/variance not to exceed ? ell Test. Each valveshall be given ? m). test at ? less than 1.5 times the
100°F (38°C) rating, rounded off the next higher 25
3.2Valve body face-to-face dimensions for sizes psi (1 bar) increment. The test shall be made with
NPS 30 (DN 750) through NPS 48 (DN 1200) Class water, which may contain ? itor, or
150 (PN 20) valves and tolerances or variances are with kerosene, or with other suitable fluid (liquid
listed for three body types in Table 2. These body or gas),provided such fluid hasviscosity not
face-to-face dimensions are an adaptation of MSS greater thanthat of water, ata temperature not
SP-67Wide, API 609 Category B, and ASME above 125°F (52°C).Visually detectable leakage
B16.10Wide for Type 1, IS0 5752 Series 20 -for through pressure boundary walls is not acceptable.
Type 2, and IS0 5752 Series 16 for Type 3. Test duration shall not be lessthan shown in Table 3.COPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
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MSS PRACTICESTANDARD SP-68
I TABLE3. SHELLTEST DURATION ? furnished forshutoff’or isola-
tion applications, where seat leakage is permissible,
t
i Valve Size Shell Test Duration shall be testedas specified in 5.2.2 except that leak-
NPS DN Seconds, Minimum age past the sealshall not exceed the maximum
leakage allowance specifiedby thepurchaser.
3-8 ’ 80-200 30
10-18 250450 60
2048 500-1200 120 5.2.4 Each valve furnished for services other than
shutoff or isolation shall be testedat ? >with seat leakageallowance as agreed upon by
manufacturer andpurchaser.
The test shall be made with the valve in the partially
open position. Leakage through the stem packing 5.2.5 Leakage detection devices, e.g., pressure decay
shall not be cause for rejection if the manufacturer devices may be used for detecting leakage provided
can demonstrate that the shaft seal design is capa- that they are used at the pressures required for the
ble of sealing at 1.1 times the maximum rated pres- shell and closure tests of paragraphs 5.1 and 5.2.
sure of the valve. When used, the valvemanufacturer shall have
demonstrated that the test results are equivalent to
5.2 SeatTesting the requirements of paragraphs 5.1 and 5.2.6.
5.2.1 Each valveshall be tested in accordance 5.2.6 For automatic leak detectionmethods, the
with 5.2.2, 5.2.3, or 5.2.4 as appropriate. For bi- term “no visibleleakage” is as ? br>directional valves, the test pressure shall be applied greater than ? (8 ? er
across the disc in the direction producing the most valve NPS(’); Test duration shall be as shown in
adverse seating condition. Valves limited to closure Section 5.2.2.
against differential pressure in one direction (see
4.2) shall be tested inthat direction.
5.2.2 Each valve furnished for shutoff or isola-
tion service shall be subjected to ?
fluid as described in 5.1. at 1.1 times the shutoff
differential pressure rating of the valve at ambient
temperature. No visible leakage through the body NOTE The footnote below is for supplementary purposes
or the disc or past the seat shall be allowed. Test and is not part of the standard.
duration shall not be lessthan shown in Table4.
’This leakage rate is based on the measured leakage of
nitrogen gas from ? th ? br>I TABLE4.SEATTEST DURATION ? tube discharge submerged in water to ? The tube end was cut square and smooth with no
Valve Size Seat Test Duration chamfers or burrs and the tube axis was parallel to the
NPS DN Seconds, Minimum surface of the water. Leakage was adjusted to ? -200 30 equal to 40 bubbles in 10 minutes at 90 psi. The 40 bubbles
10-18 250450 60 equaled 1.6 ml or, ? ing thesedata,
a leak rate equivalent to ? nute is found
2048 500-1200 120
to be4.1 ? YRIGHT Manufacturers Standardization Society of the Valve and Fittings
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STD-MSS SP-b8-ENGL L777 5770b'iO 0500758 T'i2
MSS PRACTICESTANDARD SP-68
ANNEX A
DISC TO PIPE CLEARANCE
In accordance withparagraphs 2.3.2 and 2.3.3 of this Standard Practice, butterfly valves shall be designedto have clearance
with the inside diameterof adjacent pipe.
Minimum nominal clearances are shown in Table AIof this Annex.
TABLE Al. DISC TO PIPE MINIMUM NOMINAL RADIAL CLEARANCES
Valve Size Minimum Nominal Radial Clearance with Valve
NPS DN Centered with Pipe Using L/ 16 Inch (1.5 mm) Thick Gaskets
up to ? nch (1.5 mm)
8 through 20 200 through 500 0.12 inch (3.0mm)
24 and larger 600 and larger 0.25 inch (6.5mm)
Note a: The minimum clearance condition may exist when the disc is either in ? or the full open position
depending on the design.
Note b: Larger discs may be used for designs that allow for alignment of the pipe with the disc provided that it can be
demonstrated by worst case calculations that the pipe will not interfere with discrotation.
Note c: See Figure Al for typical illustration and nomenclature.
FACE TO FACE DISC CENTERLINE
DIMENSION
STEM CENTERLINE
PICTORIAL REPRESENTA1IONS
SEAT RETAINER " OFFSET SEAT ARE FOR ILLUSTRATIVE
PURPOSES ONLY AND DO NOT
STEM CENTERLINE STEM _-DESIGN. IMPLYCENTERLINE ,PIPE
(AXIS OF ROTATION)
SECTION A-A
STEM OFFSET ~r-
DISC CENTERLINE
STEM CENTERLINE
DISC
CLEARANCE IN THE FULLY
OPEN DISC POSITION (SEE
NOTE ?
SECTION B-B
FIGURE Al. NOMENCLATURE AND EXPLANATION OF NOMINAL RADIAL CLEARANCECOPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
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MSS PRACTICESTANDARD SP-68
ANNEX B
REFERENCED STANDARDS
This Annex is an integral part of the Standard Practice which is placed after the main textfor convenience.
List of standards and specifications referenced in thisStandard Practice show the yearof approval.
ASME. ANSIIASME. ANSI. ASMEIANSI
B1.l-1989Unified InchScrew Threads (UN ? )
B1.5-1988 Acme ScrewAcme B1.5-1988 Threads
B16.34-1996Valves ? 16.47-1996 LargeDiameter Steel Flanges: NPS 26 Through NPS 60
-MSS
MSS SP-96-1996Guidelines onTerminology for Valves and Fittings
Publications of the following organizationsappear on the above list:
ANSI American National Standards, Inc.
11 West 42nd Street, New York, NY 10036
ASME The American Societyof Mechanical Engineers
345 East 47th Street, New York, NY 10017
MSS Manufacturers Standardization Societyof the Valve and Fittings Industry, Inc.
127 Park Street, NE, Vienna,VA 22180COPYRIGHT Manufacturers Standardization Society of the Valve and Fittings
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List of MSS Standard Practices
(Price List Available Upon Request)
Nunber
SP8-1996 Standard Finishesfor Contact Facesof pipe Flanges andConnectintEnd Flanges of Valves and Fittings
SP-9-1997 Spot Facingfor Bronze. Iron and Steel Flanges
W-251993 Standard Marking System for Valves, Fittings, Flanges and Unions
SP42-1990 (R95) Class 150 Camsion Resistant Gate, Globe, Angle and Check Valveswith Flanged and Butt Weld Ends
SP43-1991 (R 96) Wo@t Stainless Steel Butt-welding Fittings
SP+1996 Steel Ppdine Flanges
SP4-1992 Bypass and Drain Connections
spa-1991 (R 95) Chss 150LW Conosion Resistant Cast Flanges and Flanged Fittings
SP-53-1995 Quality Standard forSteel Castings and Forgingsfor Valves, Flanges andFittings andOther Piping Components- Magnetic Particle
Exminatan Method
SP-54-1995 Quali Standard for Sleel Castings for Valves, Flanges. and Fittings and Other Piping Components- Radiogaphic Examination Method
SPs6-I996 Qual! Standad for Steel Castingsfa Valves, Flanges and Fittings andOther Piping Canponents- Visual Method forbal. of Surface
IrreguMties
SP-58-1993 Pp Hangers and Supports ? gn and Manufacture
SPGO-1991 Cannecting Flange JointBeWn Tapping Sleeves and Tapping Valves
SP8l-1992 Pressrre Testing of Steel Valves
SP-651994 High presslre Chemical lndusby Flangesand Threaded Stubs for Use with Lens Gaskets
SP87-1995 ButWy Valves
SP88-1997 H@ Presswe Butterffy Valves WithOffset Design
SP89-1996 Pipe Hangers and Slpports ? !ition
SP-70-1990 Cast Iron Gate Valves, Flanged and ThreadedEnds
SP-71-1990 Cast lm Swing Check Valves. Flanged and Threaded Ends
SP-72-1992 Ball Valves with Flanged or Butt-welding Endsfor General Service
SP-73-1991 (R 96) Brazing Join6 for Wrought and CastCopper Alloy Solder Joint Pressure Fittings
SP-751993 Specificationfor High Test Wrought Butt Welding Fittings
SP-771995 Guidelines for Pipe Support Conlractual Relationships
W-70-1987 (R 92) Cast Iron Plug Valves. Flanged and Threaded Ends
SP-79.1992 Socket-Weldng Reducer Inserts
SPW1997 Emme Gate, Globe. Angleand Check Valves
SP-81-1995 Stalnless SW.Bonnetless. Flanged, Knife Gate Valves
SP-82-1992 Valve Ressue Testing Methads
SP43.1995 Class 3OOO Steel Pipe Unions, Socket-Welding and Threaded
!Y851994 Cast Iron Globe& Angle Valves. Flanged and Threaded Ends
Spa1987 (R 92) Guidelines for Mebic Data in Standards fw Valves, Flanges, Fittings and Actuatws
SP-87-1991 (R 96) Factory-Made Butt-welding Fittings for Class ? Applications
SP881993 Diaphragn Type Valves
spa-1991 Pipe Hangers andSuppats ? Installation Practices
W-90.1986 (R 91) Guidelines on Terminology for Pipe Hangers and Suppwts
SP-91-1992 (R 96) Guidelines for Manual Optionof Valves
SP-92-1987 (R 92) MSS Valve User Guide
W-93-1987 (R 92) Quality Standard for Steel Castings and Forginsfor Valves, Flanges, and Fittings andOther Piping Components- Liquid Penelrant
Examination Method
SP-94-1992 Quality Standardfw Ferricc and Martensitic Steel Castingsfor Valves, Flanges, and Fittings andOther Piping Components- Ulhsonic
Exmination Method
SPg51986 (R 91) Sugge (d) Npplesand Bull Plugs
W-96-1996 Guidelines on Terminology for Valves and Fittings
SP-97-1995 lntegally Reinforced Forged Branch Outlet Fittings- Socket Welding, Threaded and Buttwelding Ends
SP-98-1996 protective Coatings for the Interior of Valves,Hyhnts. and Fittings
SP-99-1994 Insbunent Valves
SP-100-1997 Qualification Requirementsfor Elastwner Diaphraps for Nuclear ServiceDiaphqn Type Valves
SP-101-1989 Part-Tm Valve Actuator Attachment- Flange and Driving Canponent Dimensions andPerfmance Characteristics $19.00 each. Same quantity discounts applyon total ader.
SP-1131994 Connecting &!nt between Tapping Machines and Tapping Valves
SP-114-1995 Cwrosion Resistant Pipe Fittings Threaded and Socket Welding, Class 150 and 1000
SP-1151995 Excess Flow Valvesfor Natural Gas Savice
SP-116-1996 Secvice tine Valves and Fittingsfor Drinking WaterSystems
SP-117.1996 BelWSeak for Glabe and Gate Valves
sP-1ta1996 Canpact Steel Globed Check Valves- Flanged, Flangeless. Threaded& Welding Ends (Chemical& Petroleun Refinery senrice)
SP-119-1996 Belled End Socket Welding Fittings,Stahless Steel and C- Nkkel
SP-120-1997 Flexble mitePacking System for Rising Stem Steel Valves (Design Requiemenk)
SP-121-1997 Qualification Testing Methodsfor Stem Packingfa Rising StemSteel Valves
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