September 8, 2003
Attn: Mr. Mitchell Gold, Standards Coordinator
Standards Development Department
333 Pfingsten Road
Northbrook, IL 60062
UL 410 TECHNICAL COMMENT
Dear Mr. Gold:
This comment is from the American Society of Safety Engineers (ASSE) addressing the proposed Underwriters Laboratories (UL.) 410 "Standard for Slip Resistance of Floor Surface Materials".
The American Society of Safety Engineers (ASSE) opposes accreditation of this project, by ANSI, recognition by ANSI of this standard, and takes the position that Underwriters Laboratories is attempting to create a standard in an inappropriate manner. From our perspective the U.L. process being used to create this standard does not meet the spirit or requirements contained in the ANSI document "ANSI Essential Requirements: Due Process for American National Standards" or its very own procedures.
It should be noted that our positions are based on the document ANSI Essential Requirements: Due Process for American National Standards, the U.L. publication Regulations Governing ANSI/UL Standards Technical Panels and the U.L. publication Now That You're a Member - A Guide to the Standards Technical Panels of Underwriter's Laboratories Inc. (UL).
To support our basic position, it is first necessary to address some of the history addressing this issue.
On 11/20/01 we wrote an extensive comment detailing our concerns with a proposed U.L. 410 Standard addressing slip resistance of floor surface materials. ASSE never received any response to this comment, nor did we receive any definitive responses to our numerous attempts to obtain a status on this project. The last we had heard of the issue was when we read an 8/30/02 U.L. Standards Newsletter that the standard had been withdrawn. Since then, a "new" U.L. 410 proposal has surfaced and is being distributed as a different draft standard.
We have brought up this issue of non-existent response to U.L. staff and the answer given to us was that on July 1, 2003 an electronic mail message was sent to Kathy Seabrook and Patrick Arkins, an ASSE staff member. Ms. Seabrook was the original signatory to the 2001 letter, and U.L. informed Ms. Seabrook that UL recently published a new bulletin. The bulletin contained a proposed new edition of the Standard for Slip Resistance of Floor Surface Materials, UL 410. This message pointed out that this bulletin was available for purchase at http://www.comm-2000.com/.
We have concerns with the actions of U.L. for these reasons:
1. There never was any response given to the original public comments, which runs contrary to Section 1.5, Consideration of Views and Objections, ANSI Essential Requirements: Due Process for American National Standards. In addition, it does not meet the requirements used by U.L. itself in its own procedures, (Section 3.4).
2. Section 1.1 of the ANSI Essential Requirements Document clearly indicates there should not be any financial barriers to participation in a developer's procedures. This concept also appears be upheld in U.L. documents itself. We find it inappropriate that Kathy Seabrook was expected to pay a fee to find out how her comments were addressed when the U.L. procedures clearly show the opposite intent. Once again, this is also backed by the ANSI Essential Requirements document and the tone and spirit of the U.L. procedures.
3. Section 2.1 of the ANSI Essential Requirements Document clearly indicates that the U.L. procedures are required to have provisions to provide standards information to all known directly and materially affected interests. Even though U.L. does have a listserve program, it was more than aware from inquiries of ASSE staff members of the Society's interest in this project. Even though numerous inquiries were made, U.L. staff did not apprise ASSE of the project when it clearly knew it (ASSE) was a directly and materially affected interest.
4. We are puzzled how U.L. can take the position that the previous comments are of no consequence since the project was withdrawn. However, the project is back with virtually the same name, scope, standard number, and text. This in our view is inappropriate and not a proper use of the standards development process.
Technical Insights Into the "New" UL 410 Proposed Standard
Although there is potential for this document in the future for evaluating various floor surface materials, there are a number of technical reasons why we believe this standard should not be considered as an ANSI standard.
To clarify the Title, we suggest changing it to "Standard for Measuring the Static Coefficient of Friction of Dry Floor Surface Materials for Product Merchantability as determined by the manually operated James Machine".
The scope conflicts and duplicates existing ANSI standards. The scope of UL410 as revised includes "floor coatings." There is already an existing ANSI standard that covers this, ASTM D-2047. As such, UL410 would be a duplicative standard. Detergents (FTM-3), and sweeping and dusting materials (FTM-6) are neither floor coatings nor flooring materials, and thus should not fall under this standard per the title and scope. The scope should state:
"This standard provides a measurement of slip resistance of floor materials under dry conditions with leather, for quality control purposes only. This standard does not purport to represent that the tested floor material is safe for walkway surface applications. This standard is one of several standards available to evaluate slip resistance of floor materials, which may yield different results. Product application methods, usage, wear, maintenance procedures, wet conditions, contaminants, humidity, and other factors, are known to alter the in-place floor slip resistance, as compared to laboratory measurements. Physical condition, mental condition, attentiveness, footwear and other factors of pedestrians, are recognized factors affecting floor safety."
To allow use of the James Machine for wet or contaminated testing is also inconsistent with ANSI A1264.2, as well as the above-mentioned ANSI/ASTM test methods. ANSI A1264.2 appropriately allows use of the James Machine for testing under dry conditions only. This is a significant conflict with several existing ANSI standards including ASTM D 2047 and F 489, and as such, wet or contaminated testing should not be permitted under UL 410.
While the James Machine may determine SCOF, it cannot be used on contaminated or wet surfaces, and as such the James Machine does not measure "slip resistance". There should be no reference to slip resistance in the entire document, as this machine does not determine a slip resistance value. The term "slip resistance" should be deleted from Section 1.1, and be replaced with SCOF .
Section 4. Performance
Multiple James Machines: One change in this version is to permit the use of "a motorized James Machine" (Section 4.2.1). This language is vague and theoretically could permit the use of any apparatus with the name "James Machine" on it. This is of special concern as some James Machines are constructed or modified, and no data has been presented regarding the consistency of results among this variety of types. There are several manufacturers of "James Machines". One version is electro/mechanical; another has hydraulic components, whereas the original James Machine is entirely manual. There has never been a study conducted, or data provided that would indicate the various types of machines produce similar results. The standard should be limited to the original manual-propelled James Machine as specified by the original drawings, until adequate scientific studies have been performed to verify that these machines do produce similar results.
Wet/contaminated Testing: The standard appears silent on wet testing. As such, it tacitly permits such testing, though it is well known that the James Machine cannot effectively meter wet surfaces. The scope should clearly indicate that the standard addresses testing only of dry and uncontaminated surfaces.
Calibration: There is no provision for calibration of the test instrument in the standard. Considering the complexity and varieties of the device, this is a significant omission. We recommend a section on Calibration be drafted and balloted, to include reference to ASTM D6205-98 Standard Practice for Calibration of the James Static Coefficient of Friction Machine. This standard provides guidance on determining if the test instrument is mechanically calibrated and properly aligned. We recommend that, like D6205-98, the UL standard include requirements for calibration and documentation of the apparatus every 30 days.
The manually propelled James Machine requires continuous maintenance and adjustment, in part due to the required release of a heavy weight. D6205 lists several reasons why the instrument can yield faulty results, including:
· Irregular transport of the test table - Especially in the case of manually-propelled versions, the manual cranking must be done smoothly and uniformly for accurate readings;
· Improper rate of transport of test table - The rate of travel is a key factor in obtaining valid results. In the case of manually-propelled versions, this is difficult to judge subjectively;
· Wear or binding of bearings, pivots, and other components;
· Flat and levelness of test table (there is no specified method for evaluating flatness);
· Excessive movement in the strut rack gear;
· Warped or out of line back plate, chart board, strut arm, or strut rack gear, often caused by improper maintenance or storage, or by the result of the impact of the 75-80 pound weight.
Testing of Rough Surfaces
Due to the heavy weight applied, non-smooth surfaces (e.g. textured, rough) cannot be evaluated, since the roughness can result in damage to the test foot material. We recommend limiting the scope of materials that can be tested under this standard to those which are nominally smooth.
Design and Validation
We point out that Dr. Robert Brungraber, a well-known slip resistance authority, while still with Bucknell University, had the following observation regarding other unresolved concerns with this test apparatus:
...the tangent of the angle of inclination of the articulated strut is equal to the static coefficient of friction only if both the shoe and the articulated strut are weightless It is my opinion that either James never analyzed his device or else he assumed that his use of an 85-pound superimposed weight made the weights of his shoe and strut negligible. I have never analyzed the James Machine but the ones that I have seen use rather heavy steel struts and shoes that may very well not be negligible. James also appears to have ignored any friction losses in his device, which I also believe to be unwarranted.
In addition, meaningful precision and bias testing to validate repeatability and reproducibility have yet to be conducted as of this writing. We recommend:
· Ruggedness testing be conducted similar to ASTM specifications to establish the impact of pertinent variables in the test method;
· The standard be revised to incorporate the results of the ruggedness testing;
· An interlaboratory study using the revised protocol is conducted to serve as a basis for a precision statement.
While the proponents of this test method cite extensive support for the correlation between a James Machine reading of 0.5 and the human perception of a slip resistant surface, it is important to remember that the James Machine can only test flooring materials in a controlled laboratory environment, not actual floors.
The laboratory James test procedure does not simulate field [in-place] conditions. Field-testing of the floor under evaluation should be checked with a portable tester to determine slip resistance considering environmental conditions, maintained conditions, and usage. Controlled laboratory conditions are different than in place conditions. Any such correlations between the material in pristine condition and those subject to a variety of other unaccounted variables are at best questionable.
This standard should be restricted only to quality control testing, to determine dry or static coefficient of friction rather than slip resistance. Passing properly conducted D2047 or UL410 dry tests may, at best, be a measure of an acceptable manufactured product, but is not the complete measure of floor safety in the field.
While there has been discussion regarding the validation of this number, no studies, research, or other scientific documentation have been produced to support the 0.5 threshold as they directly relate to the James Machine for the prescribed combination of materials, contaminants, and test feet. Despite repeated requests over many years, Sidney James research data has never been produced to support the 0.5 COF and it's correlation with pedestrian safety. We do not object to the use of this number as it relates to merchantability, but it should clearly be stated as such with no implication that it relates to a safe or unsafe walking surface.
Test Foot Material
Section 4.2.4 specifies leather. There are many concerns with using leather as a constant in such testing:
· No matter how 'standardized' it is, leather is not a homogenous material. As an organic substance, each piece of leather could be considered a unique material.
· Leather has different properties at different levels of thickness.
· Sanding of leather often results in a material with frictional properties different from the pre-sanded surface;
· Leather is highly absorbent and highly sensitive to humidity. Once used for wet testing, its properties are permanently altered. This means that once leather material has been used in a wet test, it is no longer useful for testing;
· Leather can react differently depending on how worn the material has become. The standard does not provide important details regarding the use of such test pad materials, such as when the material should be disposed of and wear considerations.
We recommend studies be conducted to identify a more consistent, representative, and suitable footwear surrogate material for use with this test method.
Test Method Details
Section 4.16.1, the test method calls for the test shoe, once sanded, to be 'wiped free of dust.' This is vague, providing insufficient detail for consistent usage. More specifics should be provided, including the material to use for wiping, to perform this task away from the test area to avoid contamination, and the frequency of replacing the wiping material with fresh material.
Section 4.16.7 specifies that the operator is to rotate the large handwheel slowly and uniformly at 10 to 12 rotations per minute. Since this is manually done it is dependent upon the operator to correctly determine this rate of rotation. The rate of rotation directly affects the rate of table movement. This is an obvious source of variability that can substantially affect the SCOF readings of the device. In light of this fact, ruggedness testing and an interlaboratory study should be conducted and the results analyzed to allow for quantification of all main effect variables including handwheel rotation speed effects. If there are significant effects and/or indications of significant interactions then statistical designs can be run not only to define the operational effects, but also optimize them for the most repeatable and reproducible results.
The report should be more detailed and include information such as:
· Name of product tested,
· Date of manufacture,
· Method and date of equipment calibration
· Complete set of readings plus average.
Clearly this standard is duplicative in nature, technically faulty, and being created through a poor process not meeting the tenets of ANSI. We urge ANSI to withhold accreditation of this project and recognizing it as an American National Standard until the issues detailed above are resolved and corrected.
Thank you for your attention to this matter.
James "Skipper" Kendrick