The UNSNWG is the United States National Working Group which works on improvements to Handbook 44 and also OIML R50. Handbook 44, is a publication from the US National Institute of Science and Technology (NIST) and the National Conference on Weights and Measures (NCWM) which regulates the trade use of measuring instruments in the USA. In this case the USNWG is working on the Belt Scale section of this document. Each year the group gets together and works on improvements to the standard, the improvments generally relate to taking out or modifying clauses which relate to outdated technology or which would bring HB44 into harmonisation with OIML R50 the world standard on the use of belt scales for trade purposes.
This year the USNWG got together as they usually do, following the annual National Weighing and Sampling Association (NWSA) technical conference which was held in Charlotte, North Carolina. The group includes reguators, users and manufacturers, there were representatives of NIST, retired inspectors, representatives from Ohio Edison, Duke Energy, Southern Company and the manufacturers were Thermo-Ramsey, Thayer, Merrick and Control Systems Technology Pty Ltd.
The photograph shows participants in the USNWG 2013 in Charlotte, back row from left Bill Ripka -Thermo Ramsey, James Alexander – Ohio Edison, Ian Burrell – CST, Jason – Thermo Ramsey, Al Page – retired inspector Montana, far right John Barton – NIST and front row, Paul Chase – consultant and retired Chief Engineer Ramsey Engineering and Lars Marmsater, retired electronics engineer and programmer, Merrick Indusries, CST’s US alliance partner. Peter Sirrico from Thayer Scale took the photograph.
One of the outstanding changes which was discussed at the meeting was the move to remove conveyor length restrictions from HB44. Previously a conveyor had to be between 40′ and 1000′ in length which meant that many existing conveyors could not be certified. The length restriction is something I had personally campaigned against for a number of years, I had argued that it was up to the manufacturers to design systems and propose technology which would work well on long conveyors. I argued that restricting the conveyor parameters for trade certified belt scales was just creating a product oriented market where belt scales all looked the same and was holding back innovation. The lifting of the length restriction is likely to take place this year.
The USNWG also works on contributing to OIML R50. Recommendation 50, as it is known, is the basis for trade certified belt weighing around the world. The USA is a member of OIML and a contributor to the current revision of R50, though paradoxically the US does not actully use the standard. Australia however bases all of its belt weigher regulations on R50. OIML R50 is reviewed approximately every 10 years and is currently under review, in fact the existing version of R50 has been in place for 15 years now. I had personally come up with a number of suggestions for R50, mainly writing in provision for new technologies to allow more advanced belt scales to be trade certified. The improvements I have championed include a new 0.1% accuracy class, the acceptance of new Belt Profiling and Totaliser Holdback technologies to permit smaller test loads which would be less than one belt revolution of material and the mixing of tests when different materials and different belt speeds are involved. Most of these have found there way into the new standard, however, there had been a setback at the last minute which sought to restrict tests to at least one belt revolution. This would have created problems in Australia as a minimum where I know that several trade certified scales are on quite long belts and it would not have been possible to certify them if we could not use a “less than one belt revolution” test load. I had been asked to give a paper on the use of “Small Test Loads” to the NWSA and in it had the opportunity to explain in detail the true affects of belt tension on trade testing using small test loads on long conveyor belts. The paper will be available for download from http://www.nwsassn.org/ as a pdf shortly.
I am pleased to report that the USNWG provided solid support for the need to test in less than one belt revolution and I am sure that their support will save the day.