MTI Weighs in on ASTM Portable Hardness Testing Issue

If you are not aware, there is a lot of debate going on within ASTM, AMEC, and Nadcap regarding the use and viability of portable hardness testers.  MTI’s Technical Standards Committee sent the following letter to the leadership of the ASTM E28.06 Sub-Committee leadership sharing MTI’s concern on the path they are taking on this specification.

If you are in the aerospace industry and use portable hardness testers, it is imperative that you follow this issue and have a representative at ASTM’s May 21-22 meeting in San Diego to communicate the viability of portable hardness testers within the industry. The path that the committee is headed down is not good for aerospace heat treaters, given that the majority of people on this committee are not favorable to the use of portable hardness testers.

The meeting details are:

Date:  May 21 - 22
Location:  San Diego, CA
Full Details & Registration:  CLICK HERE

If you will be sending a representative to the ASTM meeting, please email Tom Morrison at MTI (tom@heattreat.net) and let him know who you will be sending, their title, and email address.

LETTER SENT TO ASTM

The Metal Treating Institute and its Technical Standards Committee have been monitoring the progress of revisions to ASTM E 10 and E 18 over the last year because of their impact on the heat treat community.  In prior meetings, we have voiced some of the concerns from our 260+ member plants across the world and we write to you now to emphasize those concerns and clarify our position on the proposed.

Our primary concern relates to the use of portable hardness testers.  One of the arguments against their use has come from industries that suspect these devices may be used in a true ‘field’ setting.  The complaint goes something like this: “The tester is thrown in the back of a pick-up truck and driven over bumpy dusty roads to the site where the test will be conducted.  How are we to know if the readings are valid or not?”

This scenario is certainly not representative of the circumstances under which heat treat and other special processors use portable testers.  Although many manufacturing/processing facilities do not represent the perfect environment for these testers, Quality Management System procedures, maintenance functions, and mitigating practices are in place to minimize the effect of these "less-than-perfect" environments.

There are additional arguments to support the use of portable testers.  Parts of odd configuration, or weighing 150 to 250 pounds are not uncommon in the aerospace industry.  Configuration may preclude the use of a stationary tester, or the weight may be far in excess of a stationary tester's design limitations, leaving no other option but portable testers.  These testers are designed to accommodate heavy, unwieldy parts, and as a result, provide much more accurate results under these circumstances than a stationary tester.  Isn't it better to use an instrument designed for this application rather than try to balance one of these parts perched on a small platform, all the while attempting to prevent any wobble?  We believe the answer is an obvious "Yes."  An alternative would be the use of coupons, but they do not represent the mass of the actual part.  Portable hardness tester results are more indicative of the actual hardness of the part than a coupon.

Risks to employees and damage to customer parts are additional important considerations.  Employee safety must be factored in to the decision to use a portable tester over a stationary one.  There is far more risk of employee injury, as well as the risk of damaging, or scrapping customer material, when using a device for a task inappropriate to its intended use.

In the world of aerospace manufacturing, control of systems and devices used for testing is paramount due to the environment to which they may be exposed.  Great effort is made to generate high calibration reliability for all testing devices, portable or otherwise, all the way down to the shop floor.  Examples include utilization of independent ISO 17025-certified labs to perform calibration of portable testers at a higher frequency than the governing specification requires; performing hardness verifications "prior to use", in addition to normal daily or "shiftly" verifications, using NIST-traceable certified test blocks; use of higher resolution calibrated Type A BHN scopes for reading indentation diameters as standard procedure to increase the accuracy of diameter measurement rather than as an "option" as allowed by the specification; regular external and internal training programs for all inspectors including supervised practical tests. 

As a result of robust Quality System requirements, coupled with good, repeatable Quality System practices, portable hardness testers are used every day, and have been for many decades, to produce accurate measurement values, from which sound decisions can be made regarding process response and outcome, acceptance to drawing or specification criteria, and continued suitability of product for its intended end use.

Our second concern is the proposed revision that would require approval by the "Cognizant Engineering Authority" for each and every use of a portable tester.  In aerospace manufacturing, the special processor is often a third-, fourth- or even fifth-tier supplier to the OEM.  Because of that distance, it is virtually impossible to follow the chain all the way up to the appropriate individual at the OEM.  And even after making that contact, the prime representative most likely has significantly less understanding of indentation hardness testing than we do, thereby increasing the decision-making process to months.  This would bring the manufacturing process for an entire industry to a virtual standstill.

A better solution would be to create a clear and obvious path from the specification or engineering drawing requirement for stationary testers per E 18 or E 10 to E 110 when parts are too large for testing to E 10 or E 18.  This should represent an "automatic" process as long as the testing certification clearly identifies the results with the "/P" format as required by E 110.

Another option would be to follow Boeing's lead and allow use of portable testers interchangeably with stationary testers as long as verifications are performed at the start and end of each lot of parts and the acceptance range is narrowed by one or two points on both ends of the range.

Limiting the use of portable hardness testers would force aerospace manufacturers who use them, employing robust, sound, and simple practices, and offering transparency and accountability for the processing we perform, to pay a very high price in time, energy, effort, and delayed production schedules.

Our third concern is the slow pace of progress on the revisions.  Specialized concerns, specific to a single industry, should not delay publication of a broad industry standard, in wide demand across many industries, due to an admitted inability to control or manage quality procedures in a field environment.  We feel the ASTM committee leadership should not stall advancement on the topic by giving merit to these objections.  Doing so contradicts ASTM's philosophy, as stated on the website, of a "consensus process."

The purported role of ASTM is to provide standardized practices that bring assurance to any user of the published standard that a test method (in this case) can provide a transparent reproducible result on which engineering decisions can be made confidently. The "pickup truck" treatment of portable hardness testers cited is an indicator of poor management, not a valid argument regarding the technical merits of the use of portable testers.

MTI requests we set the negatives aside as ‘not persuasive’ and complete the process of providing the users of portable hardness test devices with a standard that brings utility and trustworthiness to their daily use.  We further request that a vote of the E 28.06 Sub-committee and a vote of the full E 28 Committee be set for the upcoming May meeting to approve the already-proposed revisions to E 10 and E 18.

We would like to request a phone call with you and the two Co-chairs of our Technical Standards Committee once you have had a chance to digest our concerns.

We also have ideas on enhancements to E 110 to clarify that standard which we would like to share with you at the appropriate time.  In the meanwhile, we appreciate your time and look forward to hearing from you.