metrification guidelines

7/31/2019 Metrification Guidelines

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METRICATION

GUIDELINES

FORASME CODES

FOR PRESSURE

PIPING B31


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1

Table of Contents

TopicPage

1. Introduction 3

2. Policy on Use of SI Units 3

3. Guidelines for Developing SI Equivalents 34 The International System of Units (SI) 4

Table 1 - SI Prefixes 4

4.1 Base SI Units 4

Table 2 - SI Base Units 5

4.2 Derived SI Units 5

Table 3 - Examples of SI Derived Units 5

4.3 Units of Temperature 5

Table 4 Temperature Reference Points 5

5. Units Conversion Factors 6

5.1 Conversion Factors for Commonly Used Units for Piping 6

Table 5 - Conversion factors - Frequently Used USCS Units to SI Units 7,8

Table 6 - Conversion Factors Mass Equivalents 9

Table 7 - Conversion Factors Length Equivalents 10

Table 8 - Conversion Factors Area Equivalents 11

Table 9 - Conversion Factors Volume Equivalents 12

Table 10 - Conversion Factors - Flow Rate Equivalents 13

Table 11 - Conversion Factors Density Equivalents 14

Table 12 - Conversion Factors Pressure Equivalents 15

Table 13 - Conversion Factors Energy Equivalents 16

6. Conversion Guidelines 17

6.1 Size Designation of Pipe, Fittings, flanges, Valves and Other Piping Components 17

Table 14- Size Designation for Pipe, Fittings, Flanges, Valves, etc. 17

6.2 Pressure-Temperature Ratings 17Table 15 -Class Ratings for Forged Fittings, Socket Welding and Threaded (B16.11) 18

6.3 Guidelines for Converting USCS Units of Length into SI Units 18

6.3.1 Toleranced versus Un-Toleranced Dimensions 18

6.3.2 Conversion of Inch Fractions 19

Table 16-Conversion of Inch Fraction to Millimeter 19

6.3.3 Guidelines for Conversion of Inch Dimensions 20

Table 17- Conversion of Most Dimensions from Inches to Millimeters 20

6.3.4 Guidelines for Conversion of Foot Dimensions 21

Table 18-Conversion of Length into SI Units 21

6.5 Guidelines for Converting USCS Units of Temperature into SI Units 21

6.5.1 Converting Limiting Temperatures 21

6.5.2 Converting Preheat and Postweld Heat Treatment Temperatures 226.5.3 Converting Lower Critical Temperatures 22

Table 19 - Conversion of Lower Critical Temperatures from Fahrenheit to Celsius 22

6.5.4 Converting Temperatures from Fahrenheit to Celsius in Allowable Stress Tables 22

Table 20- Temperatures in Celsius to be used in Stress Tables for Ferrous Materials 23

Table 21 -Temperatures in Celsius to be used in Stress Tables for Non-ferrous

Materials

24

6.6 Guidelines for Converting USCS Units of Pressure into SI Units 24


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Table 22- Conversion of Pressure from psi to kPa or MPa 24

6.7 Guidelines for Converting USCS Units of Strength or Stress into SI Units 25

6.8 Guidelines for Converting Other Units 25


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METRICATION GUIDELINES

FOR

ASME CODES FOR PRESSURE PIPING B31

1. IntroductionThese guidelines are intended to provide an understanding of systems of units used in the United

States and other countries; and establish guidance for conversion of US Customary System(USCS) of units into International System (SI) of metric units.

These guidelines are intended to be applied uniformly to convert USCS units into SI metric units

in all ASME B31, Code for Pressure Piping sections and standards.

2. Policy on Use of SI Units

A statement shall be provided in the Foreword in each book section as follows:

Either US Customary Units or SI Units shall be used with this edition, but one system of

units shall be used consistently for all Code requirements applying to an installation.

Also include the following statement in the Foreword of each book section as follows:

The equations in this code may be used with any consistent system of units. It is the

responsibility of the organization performing the calculations to ensure that a consistent set of

units is used.

3. Guidelines for Developing SI Equivalents

3.1 Either SI or USCS units may be primary.

3.2 the secondary units should be placed in parenthesis after the primary units in the text.

3.3 Separate USCS and SI tables should generally be provided if interpolation is expected. Table

designation (e.g. table number) should be the same for both the US Customary and SI tables,

with the addition of a letter in parenthesis for the secondary units Table. In the text,

references to both tables should be made. For small tables, secondary units may be placed in

parenthesis after the primary units if the result is clear and uncluttered.

3.4 Separate secondary unit versions of graphical information should be provided where addingthe secondary units to existing graphical information would cause the result to be unclear or

cluttered.

3.5 Conversions should be made by rounding the values to the number of significant digits of

implied precision in the existing units. In each case, it will be necessary to apply a common

sense test, favoring more significant digits in the secondary units if there is any question.


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3.6 The equations in the codes for pressure piping are suitable for use only with either the SI or

US Customary units provided in this metrication guide, or with the units provided in the

nomenclature associated with that equation.

4 The International System of Units (SI)

SI units are divided into three categories of units, as follows:

Base units

Derived units

SI units also include prefixes, which are listed in Table 1. These prefixes are used to form

decimal multiples and submultiples of SI units.

Table 1 - SI Prefixes

Factor Prefix Symbol Factor Prefix Symbol1024=(103)8 yotta Y 10-1 deci d

1021=(103)7 zetta Z 10-2 centi c

1018= (103)6 exa E 10-3=(103)-1 milli m

1015=(103)5 peta P 10-6=(103)-2 micro

1012= (103)4 tera T 10-9=(103)-3 nano n

109=(103)3 giga G 10-l2=(103)-4 pico P

106= (103)2 mega M 10-15=(103)-5 femto f

103=(103)1 kilo k 10-18=(103)-6 atto a

102 hecto h 10-21=(103)-7 zepto z

101 deka da 10-24=(103)-8 yocto y

In accordance with United States and National Institute of Standards and Technology (NIST),

we shall use dot or period as the decimal marker rather than comma, used by European

countries, the spellings "meter", "liter", and "deka " rather than "metre", "litre", "deca",

and the name "metric ton" rather than "tonne". Henceforth, we will follow this approach,

although we have done otherwise up to this point.

4. 1 Base SI Units

The following provides a definition of five base SI units.

Table 2 lists the SI base units and their symbols.

Table 2 - SI Base UnitsSI Base UnitBase Quantity

Name Symbol

Length meter m

Mass kilogram k

Time second s


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Electric Current ampere A

Thermodynamic

temperature

Kelvin K

4.2 Derived SI UnitsDerived units are expressed algebraically in terms of base units, or derived units. The symbols forderived units are obtained by mathematical operations of multiplication and division. Some

commonly used derived units are listed in Table 3.

Table 3 - Examples of SI Derived UnitsDerived Quantity SI Derived Unit

Name Symbol

Force Newton N

(Kg m/s2)

Area square meter m2Volume cubic meter m3Speed, Velocity meter per second m/sAcceleration meter per second squared m/s2Mass Density kilogram per cubic meter kg/m3Specific Volume cubic meter per kilogram m3/kg

There are many more derived SI units, which are used for variety of tasks.

4.3 Units of Temperature

The most commonly used scales for measuring temperature are the Fahrenheit and Celsius

(formerly Centigrade). These thermometer scales have as their base the melting and boiling points

of water, both at atmospheric pressure. The relation of the Fahrenheit and Celsius scales is asfollows:

Table 4 Temperature Reference PointsTemperature Scale Absolute Zero Freezing Point of Water Boiling Point of Water

Fahrenheit - 459.6 degrees 32 degrees 212 degrees

Celsius - 273. 16 degrees 0 degree 100 degrees

The relationship between the two scales is:

Degree C = 5/9 (Degrees F - 32 ) and Degrees F = 9/5( Degrees C) + 32

Where, C is the reading on Celsius scale and F is the reading on Fahrenheit scale. In certain

calculations, it is necessary to express the temperature in "absolute" units. The absolute

temperature associated with Fahrenheit scale is called Rankine temperature, denoted by degree

Rankine (R ) and it has the following association:

Degree R = Degree F + 459.6


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At times 459.6 is rounded to 460 when the accuracy of the results is not of serious concern.

The absolute temperature associated with Celsius scale is termed degrees Kelvin (K) and this

relationship is expressed as follows:

Degrees K = Degrees C + 273.16

For sake of approximation, 273.16 is usually rounded off to 273.

5. Units Conversion Factors

The American Society for Testing and Materials (ASTM) standard SI 10 American National

Standard for Use of the International System of Units (SI): The Modern Metric System provides

conversion factors for converting US Customary units to SI units.

5.1 Conversion Factors for Commonly Used Units for PipingThe tables 5 through 13 provide conversion factors for various quantities associated with piping.


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Table 5 - Conversion factors - Frequently Used USCS Units to SI Units

To convert To Multiply by

Velocity

Feet per second Meters per second 0.3048

Acceleration

Feet per sq second Meters per sq second 0.3048

Area

Square feet Square meters 0.09290304

Energy

Btu Joule 1055.06

Calorie Joule 4.19002

Foot pound-force Joule 1.355818

Watt-hour Joule 3600.355818

Force

Dyne Newton 0.00001

Kilogram Newton 9.80665

Pound-force Newton 4.448222

Length

Foot Meter 0.3048

Mile (U.S. statute) Meter 1609.344

Mass

Pound Kilogram 0.4535924

Slug Kilogram 14.5939

Ton (2000 lb) Kilogram 907.1847


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Table 5 - Conversion factors - Frequently Used USCS Units to SI Units

(continued)

To convert To Multiply by

Power

Btu per second Watt 1054.35

Foot pounds per second Watt 1.355818

Horsepower Watt 746

Pressure

Atmosphere Newtons per sq meter 101325

Bar Newtons per sq meter 100000

Kilogram per sq cm. Newtons per sq meter 98066.5

Pounds per sq in. Newtons per sq meter 6894.757

Tore (mm Hg 0C) Newtons per sq meter 133.322

Viscosity

Centipoise Newton second per meter 0.001

Pounds per foot second Newton second per meter 1.488164

Volume

Cubic foot Cubic meter 0.02831685

Gallon (U.S. liquid) Cubic meter 0.003785412


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Mass Equivalents

Table 6 - Conversion Factors Mass Equivalents

TO CONVERTFROM

TO Pound

(avdp) Gram Kilogram Grains

Pound (avdp)

MULTIPLY

BY 1 453.6 0.4536 7000

Gram

MULTIPLY

BY 0.0022 1 0.001 15.4324

KilogramMULTIPLY

BY 2.2046 1000 1 1.54324E4

GrainsMULTIPLY

BY 1.4285E-4 .06479 6.4798E-5 1


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Length Equivalents

Table 7 - Conversion Factors Length Equivalents

TO CONVERT

FROM

TO

Inch Foot

Mile

(statute) Millimeter Centimeter M

InchMULTIPLY

BY 1 0.08333 25.4 2.54 0.0

FootMULTIPLY

BY 12 1 304.8 30.48 0.3

Mile (statute)MULTIPLY

BY 63360 5280 1 16

Millimeter

MULTIPLY

BY 0.03937 0.003281 1 0.1 0.0

CentimeterMULTIPLY

BY 0.3937 0.032808 10 1 0.0

MeterMULTIPLY

BY 39.3701 3.28084 1000 100 1

KilometerMULTIPLY

BY 39,370 3280.8 0.62137 100,000 10


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Area Equivalents

Table 8 - Conversion Factors Area Equivalents

TO CONVERT

FROM

TO Squareinch

Squarefoot

Squaremillimeter

Squarecentimeter

Squaremeter

Square inch

MULTIPLY

BY 1 0.006944 645.16 6.4516 0.00064516

Square foot

MULTIPLY

BY 144 1 92903.04 929.0304 0.09290

Square millimeter

MULTIPLY

BY

0.00155 1 0.01 1 E-6

Square centimeterMULTIPLY

BY 0.1550 0.001076 100 1 0.0001

Square meterMULTIPLY

BY 1550.0031 10.76391 1 E+6 10,000 1


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Volume Equivalents

Table 9 - Conversion Factors Volume Equivalents

TO CONVERT

FROM

TO U.S.

gallon

Cubic

inch

Cubic

foot Liter

U.S. gallonMULTIPLY

BY 1 231 0.13368 3.7853

Cubic inchMULTIPLY

BY 0.004329 1 0.000579 0.0164

Cubic footMULTIPLY

BY 7.4805 1728 1 28.316

Liter

MULTIPLY

BY 0.26418 61.025 0.0353 1

Cubic meter

MULTIPLY

BY 264.17 61023.74 35.3147 1000


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Volumetric Flow Rate Equivalents

Table 10 - Conversion Factors - Flow Rate Equivalents

TO CONVERT FROM

TO U.S. gallons

per minute

Cubic feet

per second

Cubic meter

per hour

Liter per

second

(4

p

U.S. gallons per minute

MULTIPLY

BY 1 0.00223 0.2271 0.0631 0

Cubic feet per second

MULTIPLY

BY 448.83 1 101.9 28.32 1

Cubic meters per secondMULTIPLY

BY 15850 35.315 3600 1000 3

Cubic meters per minuteMULTIPLY

BY 264.2 0.5886 60 16.667 6

Cubic meters per hourMULTIPLY

BY 4.403 0.00982 1 0.2778 0

Liter per secondMULTIPLY

BY 15.85 0.0353 3.6 1 0

Liter per minute

MULTIPLY

BY 0.2642 0.000589 0.06 0.0167 0


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Density Equivalents

Table 11 - Conversion Factors Density Equivalents

TO CONVERT FROM

TO Grams per cubic

centimeter

Poundsper cubic

inch

Poundsper cubic

foot

Grams per cubic centimeterMULTIPLY BY

1 0.03613 62.42806

Pounds per cubic inchMULTIPLY BY

27.67991 1 1728

Pounds per cubic foot

MULTIPLY BY

0.01602 0.0005787 1

Kilograms per cubic meterMULTIPLY BY

0.001 3.6128 E-5 0.06243


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Pressure Equivalents

Table 12 - Conversion Factors Pressure EquivalentsTO CONVERTFROM

TO

Poundsper square

inch

(PSI) Atmosphere

Kilogramsper square

centimeter

Incheswater

(68F)

Millimetersmercury

(32F) Bar

Mega-Pascal

(MPa)

Kilo-Pascal

(KPa)

(PSI)

MULTIPLY

BY 1 0.068046 0.070307 27.7276 51.7149 0.068947 6.895E-3 6.8947

Atmosphere

MULTIPLY

BY 14.696 1 1.03323 407.484 760 1.01325 0.101325 101.325

Kilograms per squarecentimeter

MULTIPLYBY 14.2233 0.96784 1 394.38 735.559 0.98067 0.098067 98.0665

Inches water (68F)

MULTIPLY

BY 0.036065 0.002454 0.00253 1 1.8651 0.002491 2.4908E-4 2.4908E-1

Millimeters mercury(32F)

MULTIPLYBY 0.0193368 0.0013158 0.0013595 0.53616 1 1.333E-3 1.333E-4 0.1333224

Bar

MULTIPLYBY 14.5038 0.98692 1.01972 402.156 750.062 1 0.1 100

MPa

MULTIPLYBY 145.038 9.8692 10.1972 4021.56 7500.62 10 1 1000

KPa

MULTIPLYBY 0.145038 0.0098692 0.01019716 4.02156 7.50062 .01 .001 1

GPa

MULTIPLY

BY 1.45038E5 9.8692E3 1.01972E4 4.02156E6 7.50062E6 1E4 1E3 1E6

KSIMULTIPLY

BY 1000 68.04596 70.30696 2.7727E4 5.17149E4 68.947 6.8947 6.8947E3

MSI

MULTIPLYBY 1E6 6.80459E4 7.030696E4 2.7727E7 5.17149E7 6.8947E4 6.8947E3 6.8947E6


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Energy Equivalents

Table 13 - Conversion Factors Energy Equivalents

TO CONVERT

FROM

TO

Btu*

Calorie

(gram)**

Foot

pound

Horsepower

hour Joule

Btu*MULTIPLY

BY 1 251.8 778.169 0.000393 1055.06

Calorie (gram)**

MULTIPLY

BY 0.00397 1 3.08596 1.56 E-6 4.184

Foot poundMULTIPLY

BY 0.00129 0.32405 1 5.05 E-7 1.35582

Horsepower hourMULTIPLY

BY 2544.5 641616 1.98 E+6 1 2.68 E+6

Joule

MULTIPLY

BY 0.00095 0.239 0.73756 3.72 E-7 1

Kilowatt hour

MULTIPLY

BY 3412.97 860421 2.65 E+6 1.34102 3.6 E+6

Kilogram meter

MULTIPLY

BY 0.00929 2.344 7.233 3.65 E-6 9.807

*Based on 1 Btu = 778.169 ft-lb.**Based on 1 Cal = 4.1840 joules.


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6. Conversion Guidelines

This section provides guidance in converting USCS units into SI metric units with examples and

associated rationale for use in ASME B31, Code Pressure Piping sections and standards.

6.2 Size Designation of Pipe, Fittings, flanges, Valves and Other PipingComponents

In both the USCS and SI units systems, Nominal Pipe Size (NPS) followed by a dimensionless

number, such as NPS 1 , 2, 24, 30, etc., is used to designate the size of a pipe, fitting, flange,

valve, and other piping components, including connecting nozzles of pumps, vessels, tanks, etc.

In some areas of the world, Diameter Nominal (DN) followed by a dimensionless number, such

as DN 25, 50, 600, 750, etc. is used to designate the size of a pipe, fitting, flange, valve, and other

piping components, including connecting nozzles of pumps, vessels, tanks, etc.

Table 14shows NPS and DN equivalents. B31 codes and standards should always show NPS.

DN equivalents should generally be shown as well, but it is acceptable to just show the NPS

values as long as a table similar to Table 14is also provided in the code or standard.

Table 14- Size Designation for Pipe, Fittings, Flanges, Valves, etc.Nominal Pipe Size (NPS) Diameter Nominal (DN)

1/8 6

1/4 8

3/8 10

1/2 15

3/4 20

1 25

1 1/4 32

1 1/2 402 50

2 1/2 65

3 80

4 100

For even sizes greater than NPS 4, DN size is obtained by multiplying NPS size designator by 25.

For example NPS 6 = DN 6 X 25 = DN 150.

6.3 Pressure-Temperature Ratings

In USCS units, the pressure-temperature ratings of pipe, fittings, flanges, valves, and other

components are expressed in Class followed by a dimensionless designator. Examples are:

Class 25

Class 75

Class 125

Class 150

Class 250

Class 300

Class 400


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Class 600

Class 800

Class 900

Class 1500

Class 2500

Class 4500

Intermediate, limited, and Special Class ratings are also used to designate pressure-temperature

ratings of components. Refer to relevant piping component standards, such as ASME B16.1,

B16.5, B16.11, B16.34, etc.

For pressure-temperature ratings of NPS 4 and smaller forged fittings, socket welding and

threaded, see Table 15.

Table 15 -Class Ratings for Forged Fittings, Socket Welding and

Threaded (ASMEB16.11)

Forged ThreadedFittings

Forged Socket WeldingFittings

Class 2000 Class 3000



The pressure-temperature ratings are designated by Pression Nominal (PN). In some European

and Asian codes and standards. Because Class ratings are not equivalent to PN ratings, it is

not possible to establish a equivalency relationship between the two rating systems. ASME

B16 Standards Committee has decided to use Class rating system only in all ASME B16

standards, so Class ratings should be used whenever referring to ASME and most other US based

standards. When referring to standards that use PN ratings, PN ratings should be used.

6.4 Guidelines for Converting USCS Units of Length into SI Units

Dimension length may be used in many different forms to designate size, length, diameter, radius,

thickness, or other parameter. Sometimes a number is used to designate size without utilization of

units of length in either USCS or SI metric system of units. At times, dimension length may be

subjected to established tolerances while in other cases no tolerance is applicable. Guidelines for

converting dimension length take into consideration whether tolerances are applicable or not.

Use of term "nominal" indicates that the stated size or dimension is only for designation, not for

measurement. The actual dimension may or may not be the nominal size and may or may not be

subject to established tolerances.

6.4.1 Toleranced versus Un-Toleranced Dimensions

Dimensions that have tolerances are those that are considered important for adequate fit-up and

for the pressure and structural integrity of the piping components. These dimensions must be

converted such that the metric dimensions are essentially the same as the USCS dimensions, and

the converted tolerances ought to permit deviations from the specified dimensions that are


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functionally identical to those permitted by the USCS tolerances. Examples of toleranced

dimensions include the pipe wall thickness, pipe outside diameter, etc.

Dimensions that have no tolerances are those that need not have precision for fit-up and some

deviations in them do not significantly affect the structural and pressure integrity of piping

components. Examples of such dimensions are the flange outside diameter and the height of the

flange raised face.

6.4.2 Conversion of Inch Fractions

Initially, smaller dimensions were expressed in inch fractions, such as 1/16 in., 1/8 in., etc. Later,

these inch fractions were converted into decimal inches. 1/16 in. was converted to 0.0625 in. or

0.06 in. Similarly, 1/8 in. was expressed as 0.125 in. or 0.12 in.

Millimeter dimensions should be converted from the initial inch fractions rather than the decimal

inch dimensions. For example, 1/16 in., when converted from fraction, converts to 1 .6 mm. The

decimal "equivalent" (0.06 in.) converts to 1.5 mm.

1/16 in., at times, has been converted to nearest 0.1 mm, sometimes converted to the nearest 0.5

mm, and at other times converted to the nearest 1 mm. The conversion depends on the needed

precision of the measured dimension. Therefore, the millimeter equivalent for 0.06 in, is

sometimes 1.6 mm, sometimes 1.5 mm, and other times 2 mm. This approach applies to

conversion of other inch fractions as well.

Table 16 provides the recommended conversions for inch fractions:

Table 16-Conversion of Inch Fraction to MillimeterInch Fraction Proposed SI

Conversion

1/64 in. 0.4mm1/32 in. 0.8mm

3/64 in. 1.2mm

1/16 in. 1.5 mm

3/32 in. 2.5 mm

1/8 in. 3 mm

5/32 in. 4mm

3/1 6 in. 5 mm

7/32 in. 5.5 mm

1/4 in. 6 mm

5/16 in. 8 mm

3/8 in. 10mm

7/16 in. 11 mm

1/2 in. 13 mm

9/1 6 in. 14 mm

5/8 in. 16mm

11/16 in. 17 mm

3/4in. 19mm

7/8 in. 22mm

1 in. 25 mm


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6.4.3 Guidelines for Conversion of Inch DimensionsIn case of nominal size or dimension, simply use even multiples of 25, and interpolate for intermediate

values rather than converting and rounding to the nearest millimeter. Examples are shown in Table 26below. This approach does not apply to nominal size of pipe or piping components designated by

nominal pipe size (NPS).

Tablet 17- Conversion of Most Dimensions from Inches to MillimetersDimension, inches Dimension, mm

1 25

1 1/8 29

1 1/4 32

1 1/2 38

2 50

2 1/4 57

2 1/2 64

3 75

3 1/2 894 100

4 1/2 114

5 125

6 150

8 200

10 250

12 300

14 350

16 400

18 450

20 500

24 600

28 700

30 750

36 900

40 1000

54 1350

60 1500

72 1800


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6.4.4 Guidelines for Conversion of Foot Dimensions

Use Table 18 to convert size or length expressed in foot to meters. Rationale of rounding involves

rounding to the whole number or the numbers on the right hand side of the decimal to a multiple

of 0.25.

Table 18-Conversion of Length into SI UnitsSize or Length,

ft.

Actual Converted

Size or Length, m

Rounded Size or

Length, m

1 0.3048 0.3

2 0.6096 0.6

3 0.9144 0.9

4 1.219 1.2

5 1.524 1.5

6 1.829 1.8

7 2.1336 2.0

8 2.438 2.5

9 2.7432 2.7510 3.038 3.0

15 4.57 4.5

20 6.096 6.0

50 15.24 15.0

100 30.48 30.0

200 60.96 60.0

6.5 Guidelines for Converting USCS Units of Temperature into SI Units

In USCS of units, temperature is expressed in degrees Fahrenheit (F) while degrees Celsius are

used in metric SI units. The following formula can be used to convert Fahrenheit into Celsius.Degrees Celsius = 5/9 (Degrees Fahrenheit - 32)

6.5.1 Converting Limiting Temperatures

The minimum and/or maximum temperature limits in Fahrenheit degrees for materials shall be

converted to the nearest one degree Celsius.

For example, Note 2 of Table A-l of ASME B31. 1-2004 Edition containing temperature of 775

F, will read "Upon prolonged exposure to temperatures above 413 C, the carbide phase of

carbon steel may be converted to graphite."

Note 12 of Table A-l of ASME B 31.1 -2004 Edition currently reads:

"This is a product specification., Allowable stresses are not necessary. Limitations on metal

temperature for materials covered by this specification for use under B31.1 are:

Grade 1 and 2 -20 F to 600 F

Grade 2H -20 F to 800 F

After converting the temperature limits and rounding to the nearest degree Celsius in Note 12

reproduced above will read as follows:


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"This is a product specification., Allowable stresses are not necessary. Limitations on metal

temperature for materials covered by this specification for use under B31.1 are:

Grade I and 2 -29 C to 316 C

Grade 2H -29 C to 427 C

6.5.2 Converting Preheat and Postweld Heat Treatment Temperatures

Preheat and postweld heat treatment (PWHT) temperatures or range of temperatures in Fahrenheit

degrees shall be converted to the nearest five (5) degree Celsius.

6.5.3 Converting Lower Critical Temperatures

Lower critical temperatures in Fahrenheit degrees shall be converted to the nearest five (5) degree

Celsius. Table 19 lists some examples.

Table 19 - Conversion of Lower Critical Temperatures from Fahrenheit

to CelsiusLower Critical Temperature F Lower Critical Temperature C1,340 7251,350 7301,375 7451,430 7751,480 8051,490 8101,505 820

6.5.4 Converting Temperatures from Fahrenheit to Celsius in Allowable

Stress Tables

Conversion of Fahrenheit temperatures in for allowable stresses or design stress intensity tables

shall not be done by using formula to convert Fahrenheit to Celsius degrees and rounding to the

nearest one or five degrees. Table 20 provides listing of temperatures in Celsius that will be used

in Appendix A for ferrous materials. There is no direct relationship between the Fahrenheit and

Celsius temperatures listed in the two columns of the table hereunder; however, the approach is

same as that followed by ASME Section II, Part D.


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Tables 20 and 21 show the temperatures for listing the allowable stresses for

ferrous and non-ferrous materials respectively. Please note that there is not a

temperature for temperature conversion from Fahrenheit to Celsius.

Table 20- Listing of Temperatures in Celsius to be used in Stress Tables

for Ferrous Materials

Temperatures in Celsius (C)

-30 to 40

65

100

125

150

200

250

300

325

350

375

400

425

450

475

500

525

550

575

600625

650


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Table 21 - Listing of Temperatures in Celsius to be used in Stress Tables

for Non-ferrous MaterialsTemperatures in Celsius (C)

-30 to 40

65

100125

150

175

200

225

250

275

300

325

350

375

400

425

450

475

500

525

550

575

600

625

650

675700

725

750

775

800

825

850

875

6.6 Guidelines for Converting USCS Units of Pressure into SI Units

In SI metric units, pressure may either be expressed in mega Pascals (MPa) or kilo Pascals (kPa)

depending upon the magnitude of the pressure. In USCS units, pressure is expressed in pounds

per square inch (psi).

Table-22 provides values of pressure converted from psi to MPa and kPa. Pressure equal to and

above 100 kPa has been rounded to the nearest multiple of 25.


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25

In cases of jurisdictional boundaries the temperature or pressure needs to be more accurate, such

as the jurisdictional boundary of 15 psi. Here the metric equivalent would be kPa rounded to one

decimal place (103.4 kPa).

Table 22- Conversion of Pressure from psi to kPa or MPaPressure, psi Pressure, kPa Pressure, kPa

Rounded

Pressure, MPa

Rounded

1 6.8947 7

2 13.789 15 ---

3 20.684 20 ---

5 34.473 35 ---

10 68.947 70 ---

15 103.42 100 ---

25 172.367 175 ---

50 344.735 350 ---

75 517.102 525 ---

100 689.470 700 ---

125 861.837 850 ---150 1034.2 1025 1

175 1206.572 1200 1.2

200 1378.94 1375 1.4

250 1723.675 1725 1.7

300 2068.41 2075 2.0

350 2413.145 2425 2.4

400 2757.88 2750 2.75

450 3102.615 3100 3.1

500 3447.35 3450 3.4

600 4136.82 4150 4.1

1,200 8273.64 8275 8.31,500 10342.05 10350 10.3

6.7 Guidelines for Converting USCS Units of Strength or Stress into SI

UnitsTensile and yield strengths of materials in SI metric units shall be those listed in the ASTM or

ASME material specifications. Units for strength shall be expressed in MPa.

In SI metric units, stress shall be expressed in MPa in allowable stress tables as applicable to each

ASME B31 Code section.

6.8 Guidelines for Converting Other UnitsSince the unit of time in USCS and SI metric systems of units is seconds, therefore, there is noneed to convert it. Use seconds as currently being used.

For force, Newtons (N) will replace pounds-force (lbf).

For moment, Newton-meters (N-m) will replace inch-pound-force (in-lbf).

For energy, Joules (J) will be used in place of foot-pound-force (ft-lbf).


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SI metric unit system has no equivalent of Brinell and Rockwell C hardness scale.

Surface finish shall be expressed in micro meters in lieu of micro inch currently used in USCS

system of units.

metrification guidelines

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