1

ASTM Committee D18 on ASTM Committee D18 on Soil and RockSoil and Rock

SI Units In D18 StandardsJanuary 27, 2014

Ron EbelharRichard Ladd

SI Units ImportanceSI Units ImportanceASTM’s Mission - Be the foremost developer and provider of voluntary consensus standards with global recognition and use

ASTM technical committees are urged to give diligent consideration to the use of rationalized SI (metric) units in their standards

Critical to the relevance of our standards on the International level

Monday 01/27/2014 2

D18 Activities to Promote ComplianceD18 Activities to Promote Compliance

Long-time commitment to use of SI UnitsOne of the first dual-units standards

(D4428/D4428M)Standards Preparation Manual guidanceSI Units – incorporated in D18.91 review

3

Unit SystemsUnit Systems There are two basic systems:

Metric and British Inch-Pound

Within these systems there are two approaches:1. Absolute where mass is the main emphasis (kgm or lbm)

2. Gravitational where force is the main emphasis (kgf of lbf)

• ASTM in the 1980s started to emphasize through Committee E43 the usage metric system as it developed into “International System of Units (SI): The Modern Metric System”

4

SI SystemSI SystemIs mute about the absolute &

gravitational approaches. Only follows the absolute approach, but

does give conversion factors for gravitational units, except for hyl mass unit & unit weight.

Frowns upon many units commonly used by various professions: such as doctors & civil engineers.

5

ASCE Civil Engineering Mag.ASCE Civil Engineering Mag.November 2013November 2013

From Article on cruse ship Costa Concordia, Pg. 28

“An Italian-American consortium”:“By noon an estimated pulling force of

6 million kgf exerted by the strand jacks operating a system of winches and

steel chains had produced a “smooth rotation movement of the hull, ____.”

6

Inch-Pound SystemInch-Pound System

ASTM is mute on both the absolute & gravitational approaches in standards.

Can a standard use both approaches within a standard; that is use lbf and lbm?

Committee D18’s solution: This work shop and the usage of D18 Standards Preparation Manual and D18.91’s Special Memorandums.

7

Justification for D18 Standards Preparation Manual Justification for D18 Standards Preparation Manual (D18 SPM)(D18 SPM)

and Subcommittee D18.91 Special Memosand Subcommittee D18.91 Special Memos

On UNITSH1.1 States “This part is intended to guide technical committee in the use of the standard formats for denoting the use of the International System of Units (SI), non-SI units (usually inch-pound), or both in ASTM standards.” D18 interprets this to mean other formats then those presented in H3 and H4 are acceptable, because the term “guide” instead of “shall or should” is used. For example, to make D18 Standards more user friendly:

a)In a combined standard, inch-pound units can be presented before SI units, especially when the apparatus was developed in inch-pound units.

b)In a SI standard, non-rationalized inch-pound units can be given for information only in parentheses.

8

On UNITS (continued)H1.2.2.1 States “For committees that have special considerations with the use of SI units in ASTM Standards, it is permissible to develop committee specific technical guidance for clarification.” D18 interprets this to mean we can give guidance on SI and inch-pounds units that are specific to the professions represented within D18’s Scope.For example, civil engineering uses “unit weight or force per volume” in many applications/standards. The units being lbf/ft3 or kN/m3. Such units are presented in D18 SPM and contained in many D18 Standards.Density units of g/cm3 are frequently used in D18 Standards, where as IEEE/ASTM SI 10 states they should be avoided.

9

On UNITS (continued) Omission Problems:

The “Blue Book”, IEEE/ASTM SI 10-2010, and NIST Guide for the Use of the International System of Units (SI) documents do not mention/present the fact that there are other components or approaches involved in metric and inch-pound (IP) system of units. That is absolute and gravitational, whereas SI 10-2010 & NIST Guide present many conversion factors for gravitational metric and IP units to SI; such as: kgf to kN and lbf to kN.Furthermore, conversion factors are given for absolute IP units to SI units, such as lb to kg (note the notation for mass is not given). It should be noted that cgs units are mentioned, “they should be avoided!” Another good one is: doctors and emergency medical services should not use blood pressure in mm Hg but Pa (can you imagine the response to “his blood pressure is 19,000 Pa”).

10

On UNITS & Omission Problems (continued):

The “Blue Book” in Part H does not mention what approach (absolute/gravitational) to inch-pound is preferred. In addition, can those two approaches be used in a given standard?To cover these omission problems, D18 is presenting this workshop and will revise the D18 SPM based on the results of the workshop and presentations to its Executive Subcommittee D18.90.

11

Highlights of D18’s Policy or Highlights of D18’s Policy or Recommendations on Units Recommendations on Units

If force is mentioned in the standard and inch-pound (IP) units are included, then the gravitational inch-pound (IP) system shall be used. That is force is represented by lbf (IP) and N (SI).

If force and mass/density are included in the standard, then only SI units are used for mass and density and the combined units is the preferred presentation (ST & [IP] or IP & [SI]).

12

Policy or Recommendations, cont.Policy or Recommendations, cont.For standards where the apparatus was

developed using the IP system of units, the D18 SPM has specialized guidance for the presentation of IP and SI units.

If the standard's "Calculation" section is complicated/extensive, only one set of units should be used; typically SI if density is involved.

13

Policy or Recommendations, cont.Policy or Recommendations, cont. The unit section within the "Scope" should define

in detail how units are being used. The D18 SPM presents five (5) typical formats, where as the "Blue Book" presents three (3).

The Civil Engineering Profession for over a century has used some units not covered or frowned upon by the SI standard; therefore it is D18's policy to continue to represent this profession by using such units as unit weight (lbf/ft3), density in g/cm3 or Mg/m3, and dimension in cm.

14

Policy or Recommendations, cont.Policy or Recommendations, cont.D18 is committed to develop standards that are

within its scope and services the “users,” both domestic and foreign.

To meet this commitment are standards should use combined rationalized units as applicable.Cover new approach of rationalized units for

apparatus

15

Rationalized Units for Apparatus Developed in Rationalized Units for Apparatus Developed in Inch-Pound Units Inch-Pound Units

The SI converted numbers should have the same/similar number of significant digits as the inch-pound units.

The apparatus description section or figure, or both contain the following type of statement/note; "The SI units presented are basically hard conversions of the inch-pound units, other rationalized SI units should be acceptable providing they meet the requirements established by the inch-pound apparatus."

16

Rationalized Units cont.Rationalized Units cont.The addition, the following note could be

beneficial: Note X—The Subcommittee (insert number) is seeking details covering apparatus specifications using rationalized SI units. Send such details to the D18 Staff Manager at ASTM International (www.astm.org or address given in every standard).

Present slides on Dispersion Cup

17

Uncorrected Version of Dispersion CupUncorrected Version of Dispersion Cup

Corrected Version of Dispersion CupCorrected Version of Dispersion Cup

Note X—The subcommittee (insert number) is seeking details covering apparatus specifications using rationalized SI units. Send such details to the D18 Staff Manager at ASTM International (www.astm.org or address given in every standard).

20

QUESTIONS ?QUESTIONS ?

ASTM web site – www.astm.org