195.106—Internal design pressure.
(a)
Internal design pressure for the pipe in a pipeline is determined in accordance with the following formula:
Code of Federal Regulations
P=Internal design pressure in p.s.i. (kPa) gage.
S=Yield strength in pounds per square inch (kPa) determined in accordance with paragraph (b) of this section.
t=Nominal wall thickness of the pipe in inches (millimeters). If this is unknown, it is determined in accordance with paragraph (c) of this section.
D=Nominal outside diameter of the pipe in inches (millimeters).
E=Seam joint factor determined in accordance with paragraph (e) of this section.
F=A design factor of 0.72, except that a design factor of 0.60 is used for pipe, including risers, on a platform located offshore or on a platform in inland navigable waters, and 0.54 is used for pipe that has been subjected to cold expansion to meet the specified minimum yield strength and is subsequently heated, other than by welding or stress relieving as a part of welding, to a temperature higher than 900 °F (482 °C) for any period of time or over 600 °F (316 °C) for more than 1 hour.
(b)
The yield strength to be used in determining the internal design pressure under paragraph (a) of this section is the specified minimum yield strength. If the specified minimum yield strength is not known, the yield strength to be used in the design formula is one of the following:
(1)
(i)
The yield strength determined by performing all of the tensile tests of API Specification 5L on randomly selected specimens with the following number of tests:
| Pipe size | No. of tests |
|---|---|
| Less than 65/8 in (168 mm) nominal outside diameter | One test for each 200 lengths. |
| 6 5/8 in through 123/4 in (168 mm through 324 mm) nominal outside diameter | One test for each 100 lengths. |
| Larger than 123/4 in (324 mm) nominal outside diameter | One test for each 50 lengths. |
(ii)
If the average yield-tensile ratio exceeds 0.85, the yield strength shall be taken as 24,000 p.s.i. (165,474 kPa). If the average yield-tensile ratio is 0.85 or less, the yield strength of the pipe is taken as the lower of the following:
(2)
If the pipe is not tensile tested as provided in paragraph (b) of this section, the yield strength shall be taken as 24,000 p.s.i. (165,474 kPa).
(c)
If the nominal wall thickness to be used in determining internal design pressure under paragraph (a) of this section is not known, it is determined by measuring the thickness of each piece of pipe at quarter points on one end. However, if the pipe is of uniform grade, size, and thickness, only 10 individual lengths or 5 percent of all lengths, whichever is greater, need be measured. The thickness of the lengths that are not measured must be verified by applying a gage set to the minimum thickness found by the measurement. The nominal wall thickness to be used is the next wall thickness found in commercial specifications that is below the average of all the measurements taken. However, the nominal wall thickness may not be more than 1.14 times the smallest measurement taken on pipe that is less than 20 inches (508 mm) nominal outside diameter, nor more than 1.11 times the smallest measurement taken on pipe that is 20 inches (508 mm) or more in nominal outside diameter.
(d)
The minimum wall thickness of the pipe may not be less than 87.5 percent of the value used for nominal wall thickness in determining the internal design pressure under paragraph (a) of this section. In addition, the anticipated external loads and external pressures that are concurrent with internal pressure must be considered in accordance with §§ 195.108 and 195.110 and, after determining the internal design pressure, the nominal wall thickness must be increased as necessary to compensate for these concurrent loads and pressures.
(e)
The seam joint factor used in paragraph (a) of this section is determined in accordance with the following table:
| Specification | Pipe class | Seam joint factor |
|---|---|---|
| ASTM A53 | Seamless | 1.00 |
| Electric resistance welded | 1.00 | |
| Furnace lap welded | 0.80 | |
| Furnace butt welded | 0.60 | |
| ASTM A106 | Seamless | 1.00 |
| ASTM A 333/A 333M | Seamless | 1.00 |
| Welded | 1.00 | |
| ASTM A381 | Double submerged arc welded | 1.00 |
| ASTM A671 | Electric-fusion-welded | 1.00 |
| ASTM A672 | Electric-fusion-welded | 1.00 |
| ASTM A691 | Electric-fusion-welded | 1.00 |
| API 5L | Seamless | 1.00 |
| Electric resistance welded | 1.00 | |
| Electric flash welded | 1.00 | |
| Submerged arc welded | 1.00 | |
| Furnace lap welded | 0.80 | |
| Furnace butt welded | 0.60 |
The seam joint factor for pipe which is not covered by this paragraph must be approved by the Administrator.
[Amdt. 195-22, 46 FR 38360, July 27, 1981; 47 FR 32721, July 29, 1982, as amended by Amdt. 195-30, 49 FR 7569, Mar. 1, 1984; Amdt 195-37, 51 FR 15335, Apr. 23, 1986; Amdt 195-40, 54 FR 5628, Feb. 6, 1989; 58 FR 14524, Mar. 18, 1993; Amdt. 195-50, 59 FR 17281, Apr. 12, 1994; Amdt. 195-52, 59 FR 33396, 33397, June 28, 1994; Amdt. 195-63, 63 FR 37506, July 13, 1998]