Stud Bolts and Fasteners for Pipelines and Flanges

Flanged joints in pipelines, valves and pressure equipment are held by stud bolts and nuts. The right grade depends on temperature, pressure and what the line carries. JMIKS Fasteners supplies ASTM A193 B7, B8 and B8M studs and the fasteners below from Ahmedabad.

Fasteners Used on Pipelines and Flanges

B7, B8 or B8M?

• B7 is quenched and tempered chromium-molybdenum steel: minimum 860 MPa tensile and 720 MPa yield up to 64 mm diameter. It is the standard stud for carbon steel flanges on oil, gas, steam and process lines, commonly up to about 400 °C.
• B8 (SS 304) and B8M (SS 316) are chosen for corrosion resistance. In class 1 they reach only 515 MPa tensile and 205 MPa yield, so check with your piping engineer before replacing B7 with B8. Strain hardened class 2 is stronger; state the class you need. Both stay tough at very low temperatures.
• L7 (ASTM A320), also in our range, is the same steel family as B7, impact tested at -101 °C, for cold service.

How Flange Stud Length Is Worked Out

Stud length, measured first thread to first thread without the chamfered points, generally adds up:

• both flange thicknesses, including the raised face where the flange table leaves it out
• the compressed gasket thickness (for ring joints, the gap between the flange faces)
• two nut heights (a heavy hex nut is about as high as the stud diameter)
• a short projection beyond each nut, often two or three threads

Round up to the next standard length, and add about one stud diameter on one side if hydraulic tensioners will be used. ASME B16.5 lists stud lengths for each flange size and class; your piping specification has the final word.

Nuts, Washers and Threads

Piping specifications normally pair A193 studs with ASTM A194 heavy hex nuts: grade 2H with B7, grade 8 with B8 and grade 8M with B8M. Name the nut standard from your specification in your enquiry. Many flange joints need no washers; where the specification asks for them, use the type it names.

ASME B16.5 bolting uses UNC threads up to 1 inch and 8UN above, and metric flanges use metric studs. JMIKS lists B7 and B8 studs from M6 to M36 and ¼” to 1-1/4″ BSW, 20 to 500 mm long, so tell us the thread form you need.

Half Threaded Studs and Threaded Rods

Half threaded studs have a plain shank for shear and location, and suit tapped holes in valve bodies and pump casings. For pipe supports, threaded rods with long nuts carry hangers, and U bolts clamp the pipe: match the inside width of the U to the pipe’s outside diameter.

Pipeline and Flange Fastener FAQs

What is the difference between B7 and B8 stud bolts?

B7 is quenched and tempered alloy steel, at least 860 MPa tensile, for high temperature and pressure. B8 is SS 304, chosen for corrosion resistance, and in class 1 reaches only 515 MPa.

Which nut goes with a B7 stud bolt?

Piping specifications normally call for ASTM A194 grade 2H heavy hex nuts. Name the nut standard from your specification in your enquiry.

How is stud bolt length measured?

From first thread to first thread, without the chamfered points. Say how you measure it in your enquiry.

When should I use B8M instead of B8?

Use B8M (SS 316) for chlorides, sea water, coastal air or aggressive chemicals: its molybdenum resists pitting better than the SS 304 in B8. See our SS 304 vs SS 316 guide.

Get a Quote for Stud Bolts

Send the grade, diameter, length, thread form and quantity. Message us on WhatsApp at +91 90333 11425 or use our enquiry form, and we reply within one working day. See the full range in our catalogue (PDF).