Stud bolts for pressure-temperature applications conform to the requirements of ANSI/ASME B16.5, Steel Pipe Flanges and Flanged Fittings.
LENGTH-FIRST TO FIRST
The length of stud bolt, measured parallel to the axis, is the distance from first thread to first thread. First thread is defined as the intersection of the major diameter of the thread with the base of the point. Please see the drawing above-this is confusing to most users!! Stud bolts are normally available in 1/4 inch length increments. Length tolerances, all stud bolt sizes, shall be as tabulated below:
Length, in. Length Tolerance, in.
to 12 +/-0.062
over 12 to 18 +/-0.125
over 18 +/-0.250
Points shall be flat and chamfered, or sheared at option of the manufacturer. When points are flat and chamfered, the diameter of the flat shall not exceed the minor diameter of the thread, and shall be not less than one or more than two complete threads as measured from the extreme end parallel to the axis.
Threads shall be Unified inch coarse thread series (UNC), Class 2A, for all stud bolt sizes 1 in. and smaller, and Unified inch 8 thread series (8 UN), Class 2A, for all stud bolts larger than 1 in., in accordance with ANSI/ASME B1.1. Acceptability of screw threads shall be determined based on ANSI/ASME B1.3.
Chemical and mechanical requirements shall be specified by the purchaser and shall be in accordance with applicable ASME, ASTM, and ANSI codes and specifications current at the time of ordering.
It is recommended that stud bolts be designated in the following sequence: product name, nominal size, threads per inch, length, material, and protective finish, if required.
Example: ANSI/ASME B16.5 stud bolt,
5/8-11 x 3-1/2, ASTM A193, Grade B7, Zinc & Clear Chromate Plated
D Diameter – Nominal Stud Sizes
L Length – Measured end to end
T For 6B & 6BX studded flange connections with R, RX & BX gaskets, thread length maximum on end = 1 diameter + 1.5 pitch + 1/16-0
N Nut end thread length for 6B & 6BX studded flange connections with R, RX & BX gaskets shall be 2-1/2 diameters of full thread minimum.
* Class of Threads – Tap end threads may be furnished in any class thread specified. Nut end threads shall be American Standard Coarse or Fine series, Class 2A or 8 UN.
When ordering, please specify:
Diameter (D); Length (L); End-to-end dimension. (If length is figured first thread to first thread, order
must so specify.)
Tap end thread length (T) and thread series
Nut end thread length (N) and thread series
Double End or Tap End Studs are available in either rolled or cut threads. When the threads are rolled,
the full thread dimensions will increase slightly, and the diameter of the bodies will be undersized to the
pitch diameter of the thread.
Tap End Studs are available in ASTM A193 Grades of material or special materials. Sigma stocks the most
frequently used sizes of tap end studs in ASTM A193 Grade B7. Tap end studs can also be plated or
coated if allowances are made for coating thickness and thread fit.
Prints should be furnished on Double end or Tap End studs whenever possible.
** American Association of Wellhead Manufacturers -
TECHNICAL REPORT TR9501 Revision A
The ASME B16.5 – 1996 Pipe Flanges and Flange Fittings, flange bolt and gasket standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings.
The standard includes flanges with rating class designations 150, 300, 400, 600, 900, 1500, and 2500 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S units. The Standard is limited to flanges and flanged fittings made from cast or forged materials, and blind flanges and certain reducing flanges made from cast, forged, or plate materials. Included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints. The standard covers the required number of bolts, diameter of the stud bolts, length of stud bolts and ring size in R, 1RF, RTJ, and RX gaskets.
API 6A is an International Standard which specifies requirements and gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling, storing, shipment, purchasing, repair and re-manufacture of wellhead and well tree equipment for use in the petroleum and natural gas industries.
Covering bolts on Wellhead Equipment, Valves and chokes, and loose flanged connectors.
TORQUE FOR FLANGE BOLTING (B7/L7 STUDS)*
ANSI / API 6A / ISO 10423:2003 Feb. 1, 2005
|ASTM A193 Grade B7 Tensile and Yield Strength
2 1/2″ and under – tensile 125 ksi; yield strength 105 ksi
Over 2 1/2″ to 4″ – tensile 115 ksi; yield 95 ksi
Over 4″ to 7″ – tensile 100; yield 75 ksi
ASTM A320 L7 Tensile and Yield Strength
Source: API 6-A, 19th Appendix D, Table D1 &
|Stud Diameter||Tension||PTFE Coated Bolt coefficient of Friction||Plain Bolt coefficient of Friction|
|Inch||Nm||Ft. lbs||Nm||Ft. lbs|
*This chart is for general practice purposes only and should not be in the engineering or design of any products. The most current edition of the API specification may be obtained on the API Standards website to make sure you have the most current edition of API 6A. For most the accurate references in critical situations torque values should be replaced with field measured tension values. Accurate stud tension is difficult to attain using torque, because friction has a significant effect on the torque–tension relationship. Any thread damage (however minor), additional lubrication, or standard deviations within the range can change friction and thereby the expected outcome.
ASTM A193 Grade B7M Bolt
B7M bolts for High Temperature and/or High Pressure service are modified in our tempering furnace to meet the ASTM A193 /A193M – B7M standard for bolting covering both metric and inch bolting products. The A193 B7M standard covers threaded rod, bolts, studs, and stud bolts. In accord with the A193 standard the final modification is the tempering at 1150° F minimum performed after all machining, roll threading and any type of cutting. The tempering furnace recording chart is kept on record with your order maintaining complete traceability of your final product. Tensile and 100% hardness records are also available and kept with your order.
Typical use for B7M bolting includes sour gas service where Hydrogen Sulfide gas exposure may lead to Hydrogen embrittlement problems in hard alloys.
All B7M bolting which has been 100% hardness tested must be marked B7M and will have the Sigma Trademarked S for manufacturer’s identification.
B7M bolts are 100% indentation hardness tested to ensure conformance to the standard. Tensile Tests are performed after tempering.
ASTM A194 2HM heavy hex nuts are most commonly used with ASTM A193 B7M bolts.
Xylan Coated Stud Bolts
Xylan 1010, 1070, 1014, 1052 and now 1424 have been used as bolt coatings for almost a quarter century now. Most major Oil and Chemical Companies recognizing that maintenance is a huge issue have made coated bolt specifications for bolted high pressure flange connections. The various properties on the Xylan give excellent make up and brake out torque and reduce the need for high risk cutting torches or high cost bolt cutting when maintenance is required.
Xylan 1014 in bolt coatings used for its good lubricity, chemical and abrasion resistance.
Xylan 1052 for coated bolts used for its excellent lubricity.
Xylan 1070 and 1010 where the pioneers in the field – used for the lubricity and chemical inertness.
With VOCs an ever present issue these days Whitford has made a low VOC version 1424 which Sigma applies to achieve the results need in a coated bolt connection and to stay complaint in a green economy.
Xylan coated bolts come in many tints and the coated bolts are often coordinated with standard corporate color branding schemes. While very light shades are possible most of the popular hues range from a Dark Yellow to black with Reds and Blues and greens being the most widespread.
Sigma Fasteners manufactures Tap End Stud bolts to your print, Tap End Stud Bolt Standard or AWHEM Standard in all ASTM grades.
Tap end studs have a short thread length on the tap-end side typically threaded tor Class UN-3A fit. This side is screwed into a tapped hole. The nut end of the stud is threaded with a Class UN-2A fit. Length of the stud is measured form end to end. The tap end has a chamfered point, but the nut end may have either a 30° or 45° chamfered end or round raduised end, at the customers option.The tap end can be measured from the end to last scratch, end of the chamfer to the last full thread or any combination of last scratch, last full thread, end or end of chamfer.
Tap-end studs with multiple finishes:
Unfinished or black, zinc plated, Xylan coated, PTFE coated. Moly coated, Cad Plated for export.
Sigma can lower your cost for tap end studs with contract pricing and managed inventory.
Catalog: Tap End Stud
Double End Studs – Double ended studs
At Sigma Fasteners we provide mission critical bolting products for the nations leading manufacturers of pressure control equipment for controlling pressures during drilling and oil production.
Double-end studs used by many of these manufacturers have equal-length threads on each end to accommodate a nut and are threaded to a Class 2A fit. Length of stud is measured overall. Both ends have chamfered points, but round points may be furnished on either or both ends at the manufacturer’s option, This style is furnished in the same four types listed for tap-end studs. Double-end studs are used for flange bolting or other applications where torching from both ends is necessary or desirable.
Most steel grades not heat treated or quenched and tempered can be furnished on special order for production quantities. Only the Type 2 continuous thread studs made to specification ASTM A193 grade B7 are stocked in a full range of sizes.
Moly Coated Bolts
Molybdenum disulfide coated bolts are commonly used to improve the performance in extremes of load carrying capacity, operating temperature and coefficient of friction. This coating provides effective lubrication in a wide range of loads, in many cases exceeding 250,000 psi. Moly coatings lubricate sacrificially by transferring lubricant between the two mating surfaces, which helps to reduce both wear and the coefficient of friction.
Moly coatings are a combination of molybdenum disulfide lubricant and high performance resins. The coating is thermally cured to bond thoroughly with the base metal of the coated part.
Moly coated bolts can solve problems associated with corrosion, chemical exposure, and abrasion. offer excellent corrosion and chemical resistance and a barrier protection better than phosphate. With Moly’s exceptional barrier protection, it is appropriate for more severe environments and is often used in chemical processing and oil field equipment.
Stud bolts are available in ASTM Grades B7, L7, B16, B16M, L7M, B8, 660 and B8M; they are also available exotic metals such as Monel, Titanium, Inconel, Alloy 20, and Hastelloy, 17-4PH. These studs are also available with industrial coatings such as SermaGard, Xylan, PTFE, Fluoropolymers and other coatings.
Stud Bolts for Pressure-Temperature Piping
- Continuous Thread Studs (Fully Threaded Studs)
Stud bolts are threaded end to end and are often used for flange bolting with two nuts on either end.
There are two types of these studs.
- Type one – usually for general purpose; the length of stud is measured from end to end. Threads are UNRC-2A.
- Type two – studs for high temperature pressure piping. These studs are made to dimensional standard requirements of ANSI B16.5 the length of this stud is measured from first thread to first thread, exclusive of points. Threads are UNRC-2A for sizes 1 inch and under and 8 UNR-2A for sizes over 1 inch. The length of stud bolt, measured parallel to the axis, is the distance from first thread to first thread. First thread is defined as the intersection of the major diameter of the thread with the base of the point.