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History of Force Measurement in the US – Part 4

Having successfully contributed to the imposition of quality and quantity standards in the gas industry, the Bureau later took on the task, at the request of the industry, to provide standards to the electrical utilities. A variety of instruments and techniques were developed to measure current and voltage. In addition, the Bureau tested and calibrated these instruments as well as consumption meters. Later endeavors included the analysis and testing of current transformers for high-voltage power stations (under Dr. Paul Agnew), work on insulating materials, cooper wire tables (for the American Institute of Electrical Engineers and numerous other projects supporting the electrical industry.

 

The next large project to land on the Bureau’s plate was an investigation into large scales, such as railroad scales used to calculate charges on interstate shipments and grain-hoppers. Particularly in the case of railroad scales, there was little inspection or maintenance done at the state level, which lead to complaints and lawsuits when people felt the scale’s inaccuracy cost them in extra shipping fees. The railroads were left with little choice but to cooperate with the Bureau’s investigation to regain credibility. In 1913, using funds appropriated by Congress, the Bureau built a test rail car, which it then used to begin testing scales in New England and the Mid-Atlantic. Early tests resulted in the rejection 75-80% of the scales tested. A second car was built to be used in the South and Midwest. With the Bureau’s help, procedures were designed and implemented to restore accuracy in large-capacity measurement. The test cars continued their circulation into the 1930s.

 

Another railroad issue was also brought to the Bureau in 1912. An investigation had been done to determine the number of accidents (deaths, derailments and the like) occurring on the railroads each year. The primary cause of these accidents was determined to be the failure of parts like rails, wheels, flanges and axles. Samples of the failed parts were sent to the Bureau for a variety of tests to determine the source of the weakness causing the breakages. The results showed the reason for rail failure to be fissures on the interior of the rails. The Bureau worked together with the big steel companies to establish standard practices for manufacturing rails (no such standardization existed before this investigation), resulting in a two-thirds drop in the number of accidents by 1930.

 

Yet another problem involved the electrolytic corrosion caused by the trolley system, which comprised 40,000 miles of track in urban areas by 1917. The problem, first discovered in Boston in 1902, was that the current used to power the trolleys, instead of flowing through the tracks back to the generating station as conceptualized, often strayed from the tracks to better conductors, like underground pipes, cables, etc. The result was that the electricity advanced the corrosion of underground pipes, weakening them and leading to breaks, in water mains and sewers, for example. Underground telephone and telegraph wires and light and power cables were also at risk. Perhaps most alarming was the discovery of corrosion to the reinforced concrete supports of bridges, piers and buildings. Aside from the risks to safety and to possible interruption of utility service, financial losses were estimated to be in the millions of dollars due to leakage from gas and water mains and the investment for need repairs. A team assembled at the Bureau to investigate earth electrolysis and possible techniques for addressing its negative effects developed procedures to allow utility engineers to assess the situation independently and also developed an insulated feeder system to reduce corrosion. As a result of continued work on this issue, the Bureau developed an earth-current meter in 1921 which could accurately measure currents responsible for corrosion and the rate of corrosion. Another aspect of the corrosion problem had to do with the corrosive elements within soil itself, without the help of stray electrical current. To continue studying this phenomenon, the Bureau established a Corrosion Laboratory in 1922.

 

 

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

 

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