SPECIFICATION FOR liNE PIPE 141
Table G-1-Guided-bend Test Jig Dimensions (Continued)
(1 ) (2) (3) (4) (5) (6) (7) (8) (9) (10) (1 1)
Size Specified Dimension A
Wall Grade
80
80 Thickness A B&X42 X46 X52 X56 X60 X65 X70 X80
80 t in. mm In. mm In. mm in. mm in. mm in. mm in. mm in. mm in. mm
80 5.2 132.1 5.2 312.1 5.2 132.1 6.2 157.5 6.2 157.5 6.2 157.5 7.4 I R!W K8 223.5
80 in. mm 3.7 94.0 5.2 132.1 6.2 157.5 6.2 157.5 6.2 157.5 7.4 188.0 7.4 188.0 7.4 188.0 K8 223.5
80 4.4 111.8 6.2 157.5 6.2 157.5 6.2 157.5 7.4 188.0 7.4 188.0 7.4 188.0 8.8 223.5 10.5 266.7
80 0.6R8 17.5 4.4 111.8 6.2 157.5 7.4 188.0 7.4 188.0 7.4 188.0 8.8 223.5 8.8 223.5 8.8 223.5 10.5 266.7
80 0.750 19.1 5.2 132.1 7.4 188.0 7.4 188.0 7.4 188.0 8.8 223.5 8.8 223.5 8.8 223.5 10.5 266.7 12.6 320.0
80 0.812 20.6 5.2 132.1 7.4 188.0 7.4 188.0 8.8 223.5 8.8 223.5 10.5 266.7 10.5 266.7 10.5 266.7 12.6 320.0
SO 0.875 22.2 6.2 157.5 7.4 188.0 8.8 223.5 8.8 223.5 10.5 266.7 10.5 266.7 10.5 266.7 12.6 320.0 12.6 320.0
0.938 23.8 6.2 157.5 K8 223.5 8.S 223.5 10.5 266.7 10.5 266.7 10.5 266.7 10.5 266.7 12.6 320.0 15.1 383.5
1.000 25.4 6.2 157.5 8.8 223.5 8.8 223.5 10.5 266.7 10.5 266.7 12.6 320.0 12.6 320.0 12.6 320.0 15.1 383.5
1.062 270 7.4 188.0 10.5 266.7 10.5 266.7 10.5 266.7 12.6 320.0 12.6 320.0 12.6 320.0 15.1 383.5 18.1 459.7
1.125 28.6 7.4 18S.0
1.188 30.2
1.250 31.8
APPENDIX H-PURCHASER INSPECTION (NORMATIVE)
H.1 Inspection Notice H.3 Compliance
Where the inspector representing the purchaser desires to The manufacturer is responsible for complying with all of
inspect pipe or witness tests, reasonable notice shall be given the provisions of this specification. The purchaser may make
of the time at which the run is to be made. any investigation necessary to be satisfied of compliance by
the manufacturer and may reject any material that does not
H.2 Plant Access comply with this specification.
The inspector representing the purchaser shall have unre- H.4 Rejection
stricted access, at all times while work on the contract of the
purchaser is being performed, to all parts of the manufac- Unless otherwise provided, material that shows defects on
turer's works that will concern the manufacture of the pipe inspection or subsequent to acceptance at the manufacturer's
ordered. The manufacturer shall afford the inspector all rea- works, or material that proves defective when properly
sonable facilities to satisfy the inspector that the pipe is being applied in service, may be rejected and the manufacturer so
manufactured in accordance with this specification. All notified. If tests that require the destruction of material are
inspections should be made at the place of manufacture prior made, any product proven not to have met the requirements of
to shipment, unless otherwise specified on the purchase order, the specification shall be rejected. Disposition of rejected
and shall be so conducted as not to interfere unnecessarily product shall be a matter of agreement between the manufac-
with the operation of the works. turer and the purchaser.
143
APPENDIX I-MARKING INSTRUCTIONS FOR API LICENSEES (NORMATIVE)
1.1 General 1.3.1 MANUFACTURER'S API LICENSE NUMBER
The marking requirements in this appendix apply to The manufacturer's API license number shall be marked.
licensed manufacturers using the API monogram on products
covered by this specification. (The manufacturer's name or mark is optional.)
Pipe and pipe couplings manufactured in conformance (t)1.3.2 API MONOGRAM AND DATE
with this specification may be marked by the licensee as spec-
ified in Appendix I or Section 10. Products to which the The API monogram (~), immediately followed by the
monogram is applied shall be marked as specified in Appen- date of manufacture (defi~ as the month and year when the
dix I.
monogram is applied), shall be applied only to products com-
1.1.1 The required marking on pipe shall be as stipulated plying with the requirements of the specification and only by
hereinafter. authorized manufacturers.
1.1.2 The required marking on couplings shall be die 1.3.3 COMPATIBLE STANDARDS
stamped unless otherwise agreed between the purchaser and
the manufacturer, in which case they shall be paint stenciled. Products in compliance with mUltiple compatible stan-
dards may be marked with the name of each standard.
1.1.3 Additional markings, including those for compatible
standards following the specification marking, are allowed 1.3.4 SPECIFIED DIMENSIONS
and may be applied as desired by the manufacturer or as
requested by the purchaser. The specified outside diameter and the specified wall thick-
ness shall be marked, except that, for the specified outside
1.2 Location of Markings diameter, any ending zero digits to the right of the decimal
need not be included in such markings.
The location of identification markings shall be as speci-
fied in 1.2.1 - I.2.3. 1.3.5 GRADE AND CLASS
1.2.1 SIZES 1.900 AND SMALLER The symbols to be used are as follows:
The marking is die stamped on a metal tag fixed to the bun- Grade (see Note) Symbol
dle, or may be printed on the straps or banding clips used to
tie the bundle. Grade A25-Class I A25
1.2.2 SEAMLESS PIPE IN ALL OTHER SIZES AND Grade A25-Class II A25R
WELDED PIPE SMALLER THAN SIZE 16
Grade A A
Paint stencil on the outside surface starting at a point
between 18 in. and 30 in. (460 and 760 mm) from the end of Grade B B
the pipe, and in the sequence shown in 1.3, except when
agreed between the purchaser and the manufacturer, some or Grade X42 X42
all of the markings may be placed on the inside surface in a
sequence convenient to the manufacturer. Grade X46 X46
1.2.3 WELDED PIPE SIZES 16 AND LARGER Grade X52 X52
Paint stencil on the inside sllli"ace starting at a point no less Grade X56 X56
than 6 in. from the end of the pipe in a sequence convenient to
the manufacturer, unless otherwise specified by the purchaser. Grade X60 X60
1.3 Sequence of Markings Grade X65 X65
The sequence of identification markings shall be as speci- Grade X70 X70
fied in 1.3.1 - I.3.IO.
Grade X80 X80
Note: See 1.3 for limitations on downgrading.
For grades intermediate to X42 and X80, the symbol shall
be X followed by the first two digits of the specified mini-
mum yield strength in U.S. Customary units.
By agreement between the purchaser and the manufacturer
and when so specified on the purchase order, the grade shall
be identified by color in accordance with SR3.
145
146 API SPECIFICATION 5L
1.3.6 PRODUCT SPECIFICATION LEVEL paint stenciled as follows, using the values that are appropri-
The symbols to be used are as follows: ate for the pipe dimensions specified on the purchase order:
a. PSL I PSLl 5LXXXX.X ~ (MO-YR) 6.625 0.280 B PSLl E
b. PSL 2 PSL2
5LXXXX.X ~ or 168.37.1 B PSLl E
(MO-YR)
The PSL marking shall be placed immediately after the c. Size 4 1/2, 0.237 in. (6.0 mm) specified wall thickness,
grade symbol. Grade A25, Class I, continuous welded, threaded-end pipe
should be paint stenciled as follows, using the values that are
1.3.7 PROCESS OF MANUFACTURE appropriate for the pipe dimensions specified on the purchase
order:
The symbols to be used are as follows:
5LXXXX.X ~ (MO- YR) 4.5 0.237 A25 PSLl F
a. Seamless pipe S
b. Welded pipe, except continuous E or
welded and laser welded F 5LXXXX.X ~ (MO-YR) 114.3 6.0 A25 PSLI F
c. Continuous welded pipe L
d. Laser welded pipe d. Size 14, 0.375 in. (9.5 mm) specified wall thickness,
Grade X70, PSL 2, seamless, quenched and tempered, plain-
1.3.8 HEAT TREATMENT HN end pipe should be paint stenciled as follows, using the values
that are appropriate for the pipe dimensions specified on the
The symbols to be used are as follows: HS purchase order:
HA
a. Normalized or normalized HQ 5LXXXX.X ~ (MO-YR) 140.375 X70
and tempered
PSL2 S HQ
b. Subcritical stress relieved
c. Subcritical age hardened or
d. Quench and Tempered
5LXXXX.x ~ (MO-YR) 355.69.5 X70
1.3.9 TEST PRESSURE
PSL2 S HQ
When the specified hydrostatic test pressure is higher than
the tabulated standard pressure (Tables 4, 5, 6A, 6B, 6C, E- e. Size 123/4, 0.330 in. (8.4 mm) specified wall thickness,
6A, E-68, or E-6C, whichever is applicable), the word Grade X42, PSL 1, seamless plain-end pipe should be paint
"TESTED" shall be marked, immediately followed by the stenciled as follows, using the values that are appropriate for
specified test pressure (in pounds per square inch for pipe the pipe dimensions specified on the purchase order:
ordered in U.S. Customary units, or in hundreds of kilopas-
cals for pipe ordered in SI units). 5LXXXX.X ~ (MO-YR) 12.750.330 X42
1.3.10 SUPPLEMENTARY REQUIREMENTS PSLI S
See Appendix F for supplementary requirements.
or
1.3.11 EXAMPLES
5LXXXX.x ~ (MO-YR) 323.9 8.4 X42
a. Size 14, 0.375 in. (9.5 mm) specified wall thickness,
Grade 8, PSL 2, seamless, plain-end pipe should be paint PSLl S
stenciled as follows, using the values that are appropriate for
the pipe dimensions specified on the purchase order: f. Size 65/8, 0.216 in. (5.5 mm) specified wall thickness,
Grade X42, PSL 1, laser welded, plain-end pipe should be
5LXXXX.x ~ (MO-YR) 140.375 B PSL2 S paint stenciled as follows, using the values that are appropri-
ate for the pipe dimensions specified on the purchase order:
or
5LXXXX.X ~ (MO-YR) 6.625 0.216 X42
5LXXXX.X ~ (MO-YR) 355.69.5 B PSL2 S
PSLl L
b. Size 65/8, 0.280 in. (7.1 mm) specified wall thickness,
Grade B, PSL I, electric welded, plain-end pipe should be or
5LXXXX.x ~ (MO-YR) 168.35.5 X42
PSLI L
SPECIFICATION FOR liNE PIPE 147
g. Size 24, OA06 in. (10.3 mm) specified wall thickness, of 0.156 in. (4.0 mm) and less is prohibited, except that by
Grade X42, PSL 2 helical seam submerged-arc welded plain- agreement between the purchaser and the manufacturer and
end pipe should be paint stenciled as follows, using the values when so specified on the purchase order, pipe or plate may be
that are appropriate for the pipe dimensions specified on the cold die stamped. The manufacturer at his option may hot die
purchase order: stamp [200°F (93°C) or higher] plate or pipe, cold die stamp
plate or pipe if it is subsequently heat treated, and cold die
<t>5LXXXX.X (MO-YR) 24 OA06 X42 PSL2 E stamp couplings. Cold die stamping shall be done with
rounded or blunt dies. All die stamping shall be at least I 111.
or (25 mm) from the weld for all grades except Grade A25.
<t>5LXXXX.X (MO-YR) 610 10.3 X42 PSL2 E 1.8 Thread Identification
1.4 Bundle Identification At the manufacturer's option, threaded-end pipe may be
For pipe of size 1.900 or smaller, the identification markings identified by stamping or stenciling the pipe adjacent to the
specified in 1.3 shall be placed on the tag, strap, or clip used to
tie the bundle. For example, size 1.900, 0.145 in. (3.7 mm) threaded ends, wi~ the threader's API license number, the
specified wall thickness, Grade 8, electric welded, plain-end (<&»,API monogram
pipe should be marked as follows, using the values that are immediately followed by the date of
appropriate for the pipe dimensions specified on the purchase
order: threading (defined Qas the month and year the monogram is
<t>5LXXXX.X (MO- YR) 1.90.1458 PSLl E applied), the specified outside diameter of the pipe, and LP to
or indicate the type of thread. The thread marking may be
<t>5LXXXX.X (MO-YR) 48.3 3.7 8 PSLl E applied to products that do or do not bear the AP[ monogram.
For example, size 65/8 threaded-end pipe may be marked as
1.5 Length
follows, using the value that is appropriate for the pipe out-
In addition to the identification markings stipulated in 1.2,
1.3, and [A, the length shall be marked as follows, using feet side diameter specified on the purchase order:
and tenths of a foot for pipe ordered in U.S. Customary units,
or meters to two decimal places for pipe ordered in SI units, 5LXXXX.X ~ (MO-YR of threading) 6.625 LP
unless a different measuring and marking format has been
agreed upon by the purchaser and manufacturer: or
a. For pipe larger than size 1.900, the length, as measured on <t>5LXXXX.X (MO-YR of threading) 168.3 LP
the finished pipe, shall be paint stenciled on the outside sur-
face at a location convenient to the manufacturer, or by If the product is clearly marked elsewhere with the manu-
agreement between the purchaser and the manufacturer, on facturer's identification, his license number, as above, may be
the inside surface at a convenient location. omitted.
b. For pipe of size 1.900 or smaller, the total length of pipe in
the bundle shall be marked on the tag, band, or clip. 1.9 Thread Certification
1.6 Couplings (<t»The use of the monogram as provided in 1.8 shall
All couplings in sizes 23/8 and larger shall be identified constitute a certification by the manufacturer that the threads
with tJrnanufacturer's name or mark and the API mono-
so marked comply with the requirements stipulated in the lat-
gram ( W), immediately followed by the date of manufacture
est edition of AP[ Std 58 but should not be construed by the
(define as the month and year when the monogram is
applied). purchaser as a representation that the product so marked is, in
1.7 Die Stamping its entirety, in accordance with any~[ specification. Manu-
Cold die stamping of grades higher than A25 plate or pipe facturers who use the monogram ( t ) for thread identifica-
not subsequently heat treated and all pipe with wall thickness
tion are required to have access to properly certified API
reference master pipe gages.
1.10 Pipe Processor Markings
Pipe heat treated by a processor other than the original pipe
manufacturer shall be marked as stipulated in 1.1 - 1.7. The
processor shall remove any identification that is not indicative
of a new condition of the product as a result of heat treating
(such as, prior grade and original pipe manufacturer's name
or logo).
APPENDIX J- SUMMARY OF DIFFERENCES BETWEEN PSL 1 AND PSL 2 (INFORMATIVE)
Parameter PSL I PSL2 Reference
Grade range A25 through X70 B through X80 Table I
Size range 0.405 through 80 4112 through 80 Table I
Type of Pipe Ends Plain-end, threaded-end; Plain-end Table I
belled-end; special coupling pipe
Seam welding All methods; continuous welding All methods except continuous Table I
limited to Grade A25 and laser welding
Electric welds: welder frequency No minimum 100 kHz minimum 5.1.3.3.2
Heat treatment of electric welds Required for grades> X42 Required for all grades 5.1.3.3.1; 5.1.3.3.2; 6.2.6
(B through X80)
Chemistry: max C for seamless 0.28% for grades;;, B 0.24% Tables 2A, 2B
pipe
Chemistry: max C for welded 0.26% for grades;;, B 0.22% Tables 2A, 2B
pipe
Chemistry: max P 0.030% for grades eo A 0.025% Tables 2A, 28
Chemistry: max S 0.030% 0.015% Tables 2A, 28
Carbon Equivalent: Only when purchaser specifies Maximum required for each grade 4.2; 4.3; 6.1.3; SR I 5.1
SRI8
Yield Strength, Maximum None Maximum for each grade Tables 3A, 38
UTS, Maximum None Maximum for each grade Tables 3A, 38
Fracture Toughness None required Required for all grades 6.2.5; 9.3.5; 9.10.4; 9.12.6;
Table 14
Repair by welding of pipe body, Permitted Prohibited 5.3.2; 9.9; B.I; B.2
plate, and skelp
Repair by welding of weld seams Permitted by agreement Prohibited 4.3; 9.8.5.6; 9.9; B.I.2; B.4
without filler metal
Certification Certificates when specified per Certificates (SRI 5.1) mandatory 12.1 04
SRI5
Traceability Traceable only until all tests are Traceable after completion of 5.6
passed, unless SR IS is specified tests (SRI5.2) mandatory
149
APPENDIX K-END LOAD COMPENSATION FOR HYDROSTATIC TEST PRESSURES IN
EXCESS OF 90% OF SPECIFIED MINIMUM YIELD STRENGTH (NORMATIVE)
(By agreement between the purchaser and the manufac- SI Unit Equation:
turer, the following method may be used to determine the
hydrostatic test pressure.) SF- PRA R
1000' Ap
K.1 As a measure to prevent distortion when testing at pres-
sures equivalent to stresses in excess of90% of specified min- D AI
imum yield strength, the manufacturer may apply a
calculation to compensate for the forces applied to the pipe 2t A/i
end that produce a compressive longitudinal stress. The cal-
culation in this appendix is based on Barlow's equation (see where
9.4.3) modified by a factor based on the Maximum Shear
Theory (see note). The calculation may be applied only when A I internal cross-sectional area of pipe,
testing in excess of 90% of the specified minimum yield
strength. In no case may the gage pressure for testing be less Ap cross-sectional area of pipe wall,
than that calculated using Barlow's equation at 90% of speci-
fied minimum yield strength. AR cross-sectional area of ram, in.2 (mm2),
Note: The calculation is an approximation of the effective hoop PI hydrostatic test pressure in psi (kPa),
stress (SE), which is practical for application under mill pipe testing
conditions. Other calculations provide closer approximations of internal pressure on end-sealing ram, psi (kPa),
effective hoop stress but are complex and therefore impractical for
application. effective hoop stress in psi (MPa) equal to a
percentage of the specified minimum yield
K.2 The test pressure calculated shall be rounded to the strength,
nearest 10 psi (100 kPa).
D specified outside diameter, in. (mm),
K.3 The hydrostatic test pressure compensated for pipe end
loading shall be calculated according to the following equa- specified wall thickness, in. (mm).
tion:
K.4 The above equation may be manipulated algebraically
U.S. Customary Unit Equation: to provide calculation in other terms appropriate to the manu-
facturer's testing facility.
SF_ PRAR
" AI' K.S Appropriate techniques for the control of effective
hoop stress based on measurements of intemal pipe and ram
D AI pressures vary according to hydrotester system design. The
manufacturer shall provide a control technique appropriate to
2t AI' his installation.
151
APPENDIX M-CONVERSION PROCEDURES
The following procedures were used to make the soft met- where
ric conversions of U.S. Customary units to SI units in the SI wall thickness, mm,
metric conversion of API Spec 5L. wall thickness, in.
M.1 Fractions The Sf wall thicknesses were rounded to the nearest 0.1 mm.
Fractions and numbers with fractions in U.S. Customary M.4 Inside Diameter
units were converted to the full decimal equivalent in U.S.
Customary units without rounding, and the full decimal The Sl inside diameters of pipe were calculated (not con-
equivalents in U.S. Customary units were then converted to verted) using the following formula:
Sl values using the following formula:
where
Nm = 25.4· N SI inside diameter, mm,
Sl outside diameter, mm,
where SI wall thickness, mm.
the SI equivalent of dimensions with fractions The SI inside diameters were rounded to the nearest 0.1 mm.
in U.S. Customary units, mm,
M.S Plain-end Mass Per Unit Length
N the full decimal equivalent of dimensions with
fractions without rounding, in. The S[ plain-end mass per unit length were calculated (not
converted) using the following formula:
The SI equivalents of dimensions with fractions in U.S.
Customary units were then rounded to the appropriate num- Wl'em = 0.024 66(Dm - tm)l",
ber of places in mm.
where
M.2 Outside Diameter SI plain-end mass per unit length, kg/m,
SI outside diameter, mm,
The U.S. Customary values for outside diameters of pipe SI wall thickness, mm.
and couplings were converted to SI values using the follow-
ing formula: The SI plain-end mass per unit length were rounded to the
nearest 0.0 I kg/m.
Dm = 25.4· D
M.6 Yield Strength and Tensile
where Strength
SI outside diameter, mm, The U.S. Customary values for yield strength and tensile
strength were converted to SI values using the following for-
D outside diameter, in. mula:
The SI outside diameters of pipe and couplings smaller ys", = 0.006 894 76 • ys
than size 18 were rounded to the nearest 0.1 mm. The SI out- Is", = 0.006 894 76 • Is
side diameters of pipe and couplings size 18 and larger were
rounded to the nearest 1.0 mm.
M.3 Wall Thickness
The U.S. Customary values for wall thickness were con-
verted to S[ values using the following formula:
tm = 25.4· t
153
154 API SPECIFICATION 5L
where f Factor
SI yield strength, MPa, Standard Alternative
Test Pressure Test Pressure
Grade Size
0.60 0.75
Ys yield strength, psi, A25 59/ 16 0.60 0.75
1.1'/1/ SI tensile strength, MPa, A&B 2: 23/ 8 0.60 0.75
X42 & higher :559/16 0.75 0.85
0.85 0.90
t l· tensile strength, psi. > 59! 16 and:5 85/ 8 0.90
> 85/ 8 and < 20
The converted SI strengths were rounded to the nearest 1
MPa. 2: 20
M.7 Hydrostatic Test Pressure M.B Temperature
The U.S. Customary values for hydrostatic test pressures The U.S. Customary values for temperatures were con-
for all sizes of threaded pipe, all Grade A25 plain-end pipe verted to SI values using the following formula:
smaller than size 59/16, and all Grade A and Grade B plain-
end pipe smaller than size 23/8 were converted to SI values where
using the following formula: °C SI temperature, degrees Celsius,
temperature, degrees Fahrenheit.
Pili = 0.006 894 76 - P
The SI temperatures were rounded to the nearest 1°C.
The converted hydrostatic test pressures were rounded to
the nearest 100 kPa. M.9 Charpy Impact Energy
The SI hydrostatic test pressures for plain-end size 59/16, The U.S. Customary values for impact energy were con-
Grade A25 and for sizes 23/8 and larger Grades A and higher verted to SI values using the following formula:
were calculated (not converted) using the following formula: EIII = 1.355 82 - E
P'" = 2 000 -I- YSIII - tn/ Dill where
E/II energy, J,
where E energy, ft-Ib.
SI hydrostatic test pressure, kPa, The SI energy values were rounded to the nearest I J.
P hydrostatic test pressure, psi, M.10 Minimum Length of Couplings
f = stress factor, see table below, The U.S. Customary values for the minimum lengths of
couplings in inches and fractions were converted to full deci-
yS/II SI yield strength, MPa, mal equivalents in U.S. Customary units without rounding,
and then the full decimal equivalents were converted to Sl
1/11 SI wall thickness, mm, values using the following formula:
Dill SI outside diameter, mm. where SI minimum length of couplings, mm,
NLm
The calculated hydrostatic test pressure were rounded to NL the full decimal equivalent, without rounding,
the nearest 100 kPa, not to exceed 17 200 kPa for sizes 3 1/2 of the minimum lengths of couplings, in.
and smaller or 19 300 kPa for sizes larger than 3 1/2.
The calculated standard hydrostatic test pressures for
Grades X42 and higher were rounded to the nearest 100 kPa,
not to exceed 20 700 kPa. The calculated altemative hydro-
static test pressure for Grades X42 and higher were rounded
to the nearest 100 kPa, not to exceed 50 000 kPa for pipes
smaller than size 16, or 25 000 kPa for pipes sizes 16 and
larger.
SPECIFICATION FOR LINE PIPE 155
The Sf minimum lengths of coupling were rounded to the where
nearest 0.0 I mm. SI width of the coupling bearing face, mm,
M.11 Diameter of Coupling Recess b width of the coupling bearing face, in.
The SI width of the coupling bearing face were rounded to
The U.S. Customary values for diameters of the coupling the nearest 0.1 mm.
recess's were converted to Sl values using the following for-
mula: M.13 Coupling Weights
QIII = 25.4· Q The u.s. Customary values for calculated coupling weights
were converted to SI values using the following formula:
where Will = 0.453 5924 • w
Sf diameter of the coupling recess, mm, where
Q diameter of the coupling recess, in. SI calculated coupling weight, kg,
The Sl diameter of the couplings recesses were rounded to
the nearest 0.0 I mm.
w calculated coupling weight, lb.
M.12 Width of the Coupling Bearing The SI calculated coupling weights were rounded to the
Face nearest 0.0 I kg.
The U.S. Customary values for widths of the bearing face
of couplings were converted to SI values using the following
formula:
bill = 25.4· b