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A Barrier to Progress

In spite of U.S. efforts, there is still no agreement on an international standard for creating mathematical models of hydraulic pumps.

The United States, through the American National Standards (ANSI) and the National Fluid Power Association (NFPA), actively works with International Standards Organization (ISO) to create and promulgate international technical standards in fluid power technology. Nearly two years ago, engineers from all branches of hydraulics joined together to prepare a proposal to ISO that urged a new project: namely, to prepare an international standard on how to create mathematical models of hydraulic pumps. The proposal, referred to by ISO as a “New Work Item Proposal,” offered a pump modeling procedure/method.

Work on the proposal spanned at least a year in preparation for a meeting held in San Antonio last May. But in spite of U.S. support and the dedicated efforts of our national committee members, this proposal was rejected by the international fluid power community. Balloting showed five nations voting for the proposal and four voting against. However, ISO rules require a two-thirds majority before adopting a new work item. We fell one vote short.

Without the inherently powerful science that accompanies adopted models, fluid power can never be viewed as more than a blacksmith’s art. It needs the overarching science of mathematical modeling and the accompanying aura of viable technology that is conveyed with the defining science. It’s a shame when a single multinational company can block a useful and necessary advancement in the fluid power state of the art and science.

With all the support for math modeling in the United States, it would also be a shame to fail in getting international agreement on what minimal requirements are needed for math models to be used in an enlightened fluid power marketplace. Certainly, OEMs and users deserve to have transparency in their vendors’ calculations when a customer asks for verification that a certain proposed design is viable or that model data truly characterizes their pump. There is currently nothing to prevent an unscrupulous vendor from tweaking a model or a circuit to make a circuit calculation appear workable. Agreed-to models would go a long way toward discouraging such activity. A lot of useful work has been done over the past three years by the U.S. members in the quest for better mathematical models.

The next meeting of the Working Group (WG13), part of the Testing Subcommittee (SC8), will be held in London in May 2018. Tentatively, these items will be on the agenda:

  • The latest revisions for the adoption of the pump and motor test procedure (ISO 4409);
  • Pending revisions to the procedure for determining pump or motor displacement (ISO 8426);
  • Revisions to the general measurement procedures (ISO 9110); and
  • How to determine the minimum required number of data samples needed to create useful and reliable mathematical models of hydraulic pumps.

There is no project for the last item, but it is noteworthy that the international delegates to the international meeting of WG13—again, in San Antonio last year—made a special request of the United States for minimizing sample size. It has consumed many hours of our time in the U.S. delegation in a very fascinating and productive research effort. But it was done as an informal effort, and results will be shared with all international participants in London.

It’s also noteworthy that sample size is, absolutely, a math modeling requirement. However, the same members who rejected math modeling requested a special effort in the name of improving what is indisputably a math modeling need. The work of the U.S. members of WG13 and the delegates to London will be reopening the math modeling proposal and call for the development of an ISO Technical Report rather than an ISO Standard.

The content would be essentially the same from a technical point of view. However, ISO Technical Reports do not have the impetus nor mandatory compliance demands of an ISO Standard. It’s felt that having the mandatory requirements removed will make the goals more acceptable. We will have a better idea after the meetings in London.

Please feel free to e-mail me if you have any interest in joining our very capable group of researchers, academics, and industry representatives.

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