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Technical Library > STUD BOLTS > INTRODUCTION TO STUD BOLTS > Length of Stud Bolts
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STUD BOLTS LENGTH


 The length of the required stud bolts depends on the flange diameter and pressure rating. In this article, we show the ASME B16.5 charts that define the stud bolts requirements (lengths, number, diameter) per increasing flanges NPS and ratings.

 

STUD BOLTS LENGTHS ASME B16.5

Stud lengths are measured in inches, from first thread to last thread as shown in the image, assuming ASME B16.5 flanges specifications.

length of stud bolts

CLASS 150 FLANGES – STUD LENGTH (in INCHES)

 Class 150 Flanges ASME B16.5 Length of Stud Bolts 
NPS Outside Diameter of Flange Diameter of Bolt Circle Diameter of Bolt Holes Number of Bolts Diameter of Bolts Raised Face
0.06 in
Ring Joint
1/2 3 1/2 2 3/8 5/8 4 1/2 2 1/4
3/4 3 7/8 2 3/4 5/8 4 1/2 2 1/2
1 4 1/4 3 1/8 5/8 4 1/2 2 1/2 3
1 1/4 4 5/8 3 1/2 5/8 4 1/2 2 3/4 3 1/4
1 1/2 5 3 7/8 5/8 4 1/2 2 3/4 3 1/4
2 6 4 3/4 3/4 4 5/8 3 1/4 3 3/4
2 1/2 7 5 1/2 3/4 4 5/8 3 1/2 4
3 7 1/2 6 3/4 4 5/8 3 1/2 4
3 1/2 8 1/2 7 3/4 8 5/8 3 1/2 4
4 9 7 1/2 3/4 8 5/8 3 1/2 4
5 10 8 1/2 7/8 8 3/4 3 3/4 4 1/4
6 11 9 1/2 7/8 8 3/4 4 4 1/2
8 13 1/2 11 3/4 7/8 8 3/4 4 1/4 4 3/4
10 16 14 3/4 1 12 7/8 4 1/2 5
12 19 17 1 12 7/8 4 3/4 5 1/4
14 21 18 3/4 1 1/8 12 1 5 1/4 5 3/4
16 23 1/2 21 1/4 1 1/8 16 1 5 1/4 5 3/4
18 25 22 3/4 1 1/4 16 1 1/8 5 3/4 6 1/4
20 27 1/2 25 1 1/4 20 1 1/8 6 1/4 6 3/4
24 32 29 1/2 1 1/4 20 1 1/4 6 3/4 7 1/4

CLASS 300 FLANGES – STUD LENGTH (in INCHES)

  Class 300 Flanges ASME B16.5 Length of Stud Bolts 
NPS Outside Diameter of Flange Diameter of Bolt Circle Diameter of Bolt Holes Number of Bolts Diameter of Bolts Raised Face
0.06 in
Ring Joint
1/2 3 3/4 2 5/8 5/8 4 1/2 2 1/2 3
3/4 4 5/8 3 1/4 3/4 4 5/8 3 3 1/2
1 4 7/8 3 1/2 3/4 4 5/8 3 3 1/2
1 1/4 5 1/4 3 7/8 3/4 4 5/8 3 1/4 3 3/4
1 1/2 6 1/8 4 1/2 7/8 4 3/4 3 1/2 4
2 6 1/2 5 3/4 8 5/8 3 1/2 4
2 1/2 7 1/2 5 7/8 7/8 8 3/4 4 4 1/2
3 8 1/4 6 5/8 7/8 8 3/4 4 1/4 4 3/4
3 1/2 9 7 1/4 7/8 8 3/4 4 1/4 5
4 10 7 7/8 7/8 8 3/4 4 1/2 5
5 11 9 1/4 7/8 8 3/4 4 3/4 5 1/4
6 12 1/2 10 5/8 7/8 12 3/4 4 3/4 5 1/2
8 15 13 1 12 7/8 5 1/2 6
10 17 1/2 15 1/4 1 1/8 16 1 6 1/4 6 3/4
12 20 1/2 17 3/4 1 1/4 16 1 1/8 6 3/4 7 1/4
14 23 20 1/4 1 1/4 20 1 1/8 7 7 1/2
16 25 1/2 22 1/2 1 3/8 20 1 1/4 7 1/2 8
18 28 24 3/4 1 3/8 24 1 1/4 7 3/4 8 1/4
20 30 1/2 27 1 3/8 24 1 1/4 8 8 3/4
24 36 32 1 5/8 24 1 1/2 9 10

CLASS 600 FLANGES – STUD LENGTH (in INCHES)

   Class 600 Flanges ASME B16.5 Length of Stud Bolts
NPS Outside Diameter of Flange Diameter of Bolt Circle Diameter of Bolt Holes Number of Bolts Diameter of Bolts Raised Face
0.06 in
Ring Joint
1/2 3 3/4 2 5/8 5/8 4 1/2 3 3
3/4 4 5/8 3 1/4 3/4 4 5/8 3 1/2 3 1/2
1 4 7/8 3 1/2 3/4 4 5/8 3 1/2 3 1/2
1 1/4 5 1/4 3 7/8 3/4 4 5/8 3 3/4 3 3/4
1 1/2 6 1/8 4 1/2 7/8 4 3/4 4 1/4 4 1/4
2 6 1/2 5 3/4 8 5/8 4 1/4 4 1/4
2 1/2 7 1/2 5 7/8 7/8 8 3/4 4 3/4 4 3/4
3 8 1/4 6 5/8 7/8 8 3/4 5 5
3 1/2 9 7 1/4 1 8 7/8 5 1/2 5 1/2
4 10 3/4 8 1/2 1 8 7/8 5 3/4 5 3/4
5 13 10 1/2 1 1/8 8 1 6 1/2 6 1/2
6 14 11 1/2 1 1/8 12 1 6 3/4 6 3/4
8 16 1/2 13 3/4 1 1/4 12 1 1/8 7 1/2 7 3/4
10 20 17 1 3/8 16 1 1/4 8 1/2 8 1/2
12 22 19 1/4 1 3/8 20 1 1/4 8 3/4 8 3/4
14 23 3/4 20 3/4 1 1/2 20 1 3/8 9 1/4 9 1/4
16 27 23 3/4 1 5/8 20 1 1/2 10 10
18 29 1/4 25 3/4 1 3/4 20 1 5/8 10 3/4 10 3/4
20 32 28 1/2 1 3/4 24 1 5/8 11 1/4 11 1/2
24 37 33 2 24 1 7/8 13 13 1/4

CLASS 900 FLANGES – STUD LENGTH (in INCHES)

    Class 900 Flanges ASME B16.5 Length of Stud Bolts
NPS Outside Diameter of Flange Diameter of Bolt Circle Diameter of Bolt Holes Number of Bolts Diameter of Bolts Raised Face
0.06 in
Ring Joint
1/2 4 3/4 3 1/4 7/8 4 3/4 4 1/4 4 1/4
3/4 5 1/8 3 1/2 7/8 4 3/4 4 1/2 4 1/2
1 5 7/8 4 1 4 7/8 5 5
1 1/4 6 1/4 4 3/8 1 4 7/8 5 5
1 1/2 7 4 7/8 1 1/8 4 1 5 1/2 5 1/2
2 8 1/2 6 1/2 1 8 7/8 5 3/4 5 3/4
2 1/2 9 5/8 7 1/2 1 1/8 8 1 6 1/4 6 1/4
3 9 1/2 7 1/2 1 8 7/8 5 3/4 5 3/4
4 11 1/2 9 1/4 1 1/4 8 1 1/8 6 3/4 6 3/4
5 13 3/4 11 1 3/8 8 1 1/4 7 1/2 7 1/2
6 15 12 1/2 1 1/4 12 1 1/8 7 1/2 7 3/4
8 18 1/2 15 1/2 1 1/2 12 1 3/8 8 3/8 8 3/4
10 21 1/2 18 1/2 1 1/2 16 1 3/8 9 1/4 9 1/4
12 24 21 1 1/2 20 1 3/8 10 10
14 25 1/4 22 1 5/8 20 1 1/2 10 3/4 11
16 27 3/4 24 1/4 1 3/4 20 1 5/8 11 1/4 11 1/2
18 31 27 2 20 1 7/8 12 3/4 13 1/4
20 33 3/4 29 1/2 2 1/8 20 2 13 3/4 14 1/4
24 41 35 1/2 2 5/8 20 2 1/2 17 1/4 18

CLASS 1500 FLANGES – STUD LENGTH (in INCHES)

     Class 1500 Flanges ASME B16.5 Length of Stud Bolts
NPS Outside Diameter of Flange Diameter of Bolt Circle Diameter of Bolt Holes Number of Bolts Diameter of Bolts Raised Face
0.06 in
Ring Joint
1/2 4 3/4 3 1/4 7/8 4 3/4 4 1/4 4 1/4
3/4 5 1/8 3 1/2 7/8 4 3/4 4 1/2 4 1/2
1 5 7/8 4 1 4 7/8 5 5
1 1/4 6 1/4 4 3/8 1 4 7/8 5 5
1 1/2 7 4 7/8 1 1/8 4 1 5 1/2 5 1/2
2 8 1/2 6 1/2 1 8 7/8 5 3/4 5 3/4
2 1/2 9 5/8 7 1/2 1 1/8 8 1 6 1/4 6 1/4
3 10 1/2 8 1 1/4 8 1 1/8 7 7
4 12 1/4 9 1/2 1 3/8 8 1 1/4 7 3/4 7 3/4
5 14 3/4 11 1/2 1 5/8 8 1 1/2 9 3/4 9 3/4
6 15 1/2 12 1/2 1 1/2 12 1 3/8 10 1/4 10 1/2
8 19 15 1/2 1 3/4 12 1 5/8 11 1/2 12 3/4
10 23 19 2 12 1 7/8 13 1/4 13 1/2
12 26 1/2 22 1/2 2 1/8 16 2 14 3/4 15 1/4
14 29 1/2 25 2 3/8 16 2 1/4 16 16 3/4
16 32 1/2 27 3/4 2 5/8 16 2 1/2 17 1/2 18 1/2
18 36 30 1/2 2 7/8 16 2 3/4 19 1/2 20 3/4
20 38 3/4 32 3/4 3 1/8 16 3 21 1/4 22 1/4
24 46 39 3 5/8 16 3 1/2 24 1/4 25 1/2

 

STUD BOLTS LENGTH CALCULATION FORMULA

The length of stud bolts can be calculated with a simple formula which takes into consideration parameters such as free threads, the thickness of the nut and the flange, height of the raised face on the flange and the thickness of the gaskets applied on the flanges:

Stud Bolt Length (L) = 2 x (S + he + eb + i) + J

Lenght of stud bolts

 

 

 

 

 

 

 

 

 

 

 

Where:

  • “S”: free threads (1 to 2 pitch)
  • “he”: nut thickness
  • “eb”: flange thickness (with tolerance)
  • “i”: height of raised face (for 150 and 300 flanges rating, the height of raised face is included in “eb” height)
  • “J”: gasket thickness
Interesting to note that “he” (height of the hex nut) equals the diameter of the threaded stud.

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