Stud Bolt and Nuts

A193 B7 Stud Bolt is a bolt with threads on both ends that designed to be screwed into a fixed part at one end, and to receive a nut on the other end. In Petroleum or Chemical industry, they are prominently used for flange connection, so stud bolt used with two nuts on either side is the most common combination which replaces bolt and nut assembly.

As we know that Stud Bolts have many categories, the type for flange connection is called flange stud bolts, which has fully thread with chambered ends. The theoretical length is measured the thread. Continuous threaded stud bolt is very similar to it, except no chambered ends.

Heavy hex nuts are slightly larger and thicker than standard hex nuts. They are come in different grades and heavy pattern, and typically used for large diameter and high strength bolts. It is washer faced.

The diameter and length of bolts is according to flange type and pressure, and the quantity are depending on flange bolt hole.

Stud and Bolt

While Studs and bolts are very similar. They are both threaded fastener and belong to detachable connection. The differences between them as follow.

• Shape

Stud is an external threaded rod with one head. Bolt has thread at both ends without head.

• Usage

Mostly Studs and nuts are working together to connect two objects with through holes.

One end of bolts is screwed into the metal part with internal threaded hole, the other end is passed through the metal part with through hole, and then the nut is screwed to fasten the two or more parts together.

Bolting Dimensions for Class 300 Flanges

A105N Class 300 Flange is quite common used in industries, but this time we would like to show A193 B7 stud bolt dimensions for ASME B16.5 Class 300 Flanges.

NPS	Diameter Bolts inch	Length RF mm	Length RTJ mm	No of Bolts
1/2	1/2	65	75	4
3/4	5/8	75	90	4
1	5/8	75	90	4
1 1/4	5/8	85	95	4
1 1/2	3/4	90	100	4
2	5/8	90	100	8
2 1/2	3/4	100	115	8
3	3/4	110	120	8
3 1/2	3/4	110	125	8
4	3/4	115	125	8
5	3/4	120	135	8
6	3/4	120	140	12
8	7/8	140	150	12
10	1	160	170	16
12	1 1/3	170	185	16
14	1 1/3	180	190	20
18	1 1/4	195	210	24
20	1 1/4	205	220	24
24	1 1/2	230	255	24

What is ASTM A193 B7 Stud Bolt?

ASTM A193 specification covers alloy steel and stainless steel bolting material of pressure vessels, valves, pipe flanges, and pipe fittings for high temperature or high pressure service, it is chromium molybdenum alloy steel and hold the strength to 1000 degrees F. Usually A193 B7 Stud Bolt are engineered to mate with 2 sets of ASTM A194 Grade 2H Heavy Hex Nuts. We will introduce later. Let’s see the bolts chemical and mechanical first.

Tensile strength and yield strength is strength indicators, elongation and reduction belong to plastic and toughness indicators.

While Tensile strength is the maximum tensile that a finished fastener can withstand before it breaks or begins to break. Tensile Load = Tensile Strength X Thread Nominal Stress Cross-Sectional Area

When the A193 B7 Stud Bolt reaches the yield strength, it has entered the plastic deformation range.

Elongation and reduction measure the deform ability before breaking.

A193 B7 Stud Bolt Chemical Composition %

C	Mn	Si	P	S	Cr	Mo
0.37-0.49	0.65-1.10	0.15-0.35	0.035	0.04	0.75-1.20	0.15-0.25

A193 B7 Stud Bolt Mechanical Properties

Diameter	Tensile Strength	Yield Strength	Elongation	Reduction	Hardness
M64 or Below	860 Mpa	720 Mpa	16	50	321 HB
M64 to M100	795 Mpa	655 Mpa	16	50	321 HB
M100 to M180	690 Mpa	515 Mpa	18	50	321 HB

A194 Grade 2H Heavy Hex Nuts

Standard A194 covers a variety of carbon steel, alloy steel and stainless steel nuts. Nuts of this specification are used for high-pressure and high-temperature conditions. They are quenched and tempered carbon steel nut. Quenching and temper are common heat treatment process.

Quenching enhance the hardness of Pipe Fittings. The main processes are heating, heat preservation and quick cooling. Cooling medium generally is brine or oil. High hardness and clear surface can be obtained with brine as the medium, but deform and crack prone to generate. Oil medium is only suitable for stable, Austenite carbon steel or Alloy Steel Fittings under A1 temperature.

Temper helps reduce brittleness and internal stress of hex nut. It can adjust mechanical properties to suit different needs. Hex nuts has high hardness and brittleness after quenching, tempering can reduce hardness and increase toughness or plasticity.

Heavy Hex Nuts Dimension Chart

Basic	Width Across Flats			Width Across Corners		Thickness
Dia	Basic	Max	Min	Max	Min	Basic	Max	Min
1/4	1/2	0.5	0.488	0.577	0.556	15/64	0.25	0.218
5/16	9/16	0.562	0.546	0.65	0.622	16/64	0.314	0.28
3/8	11/16	0.688	0.669	0.794	0.763	23/64	0.377	0.341
7/16	3/4	0.75	0.728	0.866	0.83	27/64	0.441	0.403
1/2	7/8	0.875	0.85	1.01	0.969	31/64	0.504	0.464
9/16	15/16	0.938	0.909	1.083	1.037	35/64	0.568	0.526
5/8	1 1/16	1.063	1.031	1.227	1.175	39/64	0.631	0.587
3/4	1 1/4	1.25	1.212	1.443	1.382	47/64	0.758	0.71
7/8	1 7/16	1.438	1.394	1.66	1.589	55/64	0.885	0.833
1	1 5/8	1.625	1.575	1.876	1.796	63/64	1.012	0.956
1 1/8	1 13/16	1.812	1.756	2.093	2.002	1 7/64	1.139	1.079
1 1/4	2	2	1.938	2.309	2.209	1 7/32	1.251	1.187
1 1/2	2 3/8	2.375	2.3	2.742	2.622	1 15/32	1.505	1.433
1 3/4	2 3/4	2.75	2.662	3.175	3.035	1 23/32	1.378	1.31
2	3 1/8	3.125	3.025	3.608	3.449	1 31/32	2.013	1.925
2 1/4	3 1/2	3.5	3.388	4.041	3.862	2 13/64	2.251	2.155
2 3/4	4 1/4	4.25	4.112	4.907	4.688	2 45/64	2.759	2.647
3	4 5/8	4.625	4.475	5.34	5.102	2 61/64	3.013	2.893
3 1/4	5	5.375	5.2	6.207	5.928	3 7/16	3.506	3.37
3 1/2	5 3/8	5.375	5.2	6.207	5.928	3 7/16	3.506	3.37
3 3/4	5 3/4	5.75	5.562	6.64	6.341	3 1/16	3.76	3.616
4	6 1/8	6.125	5.925	7.073	6.755	3 5/16	4.014	3.862

A194 2H Hex Nut Chemical Components %

C	Mn	Ph	S	Si
0.40 min	1	0.04	0.05	0.4

A194 2H Hex Nut Mechanical Properties

Size	Tempering Temp Fahrenheit	Proof Load Stress, ksi	Hardness
1/4-1 1/2	850	175	248-327
1 1/2-4	850	175	212-327