National Institute of Occupational Safety and Health, Japan
Safety Margin of Special Grinding Wheels --I. 100mm Offset Grinding Wheels, II. Abrasive Disc--
SH-1961-3-1
E.AKIYAMA and S.TONSHO
: Very few investigations have been made so far on the safety margin of special grinding units such as offset grinding wheels and abrasive discs.
Regarding the offset grinding wheels, the writers investigated the change of their strength according to the working conditions and in addition, conducted tests of the change of strength of available wheels in their service. As the result, it was found that the strength resisting to the centrifugal force was unexpectedly low. As for abrasive discs, they conducted tests of the strength of them in accordance with S. B. fibre. It was detected that the strength of an abrasive disc depended considerably on the quality of S. B. fibre, and it was keenly realized that much betterment was needed for S. B. fibre. Moreover, many abrasive discs were found to be low in the water-resistance.
Study on the Flame Transmission Limits of Hydrogen Gas and Air Mixtures
SH-1961-3-2
M.NAITO
: By the closed explosion test apparatus and the standard flame transmission testing vessel the writer studied on the flame transmission limits of Hydrogen gas and air mixtures.
The result showed that the flame transmission limits of Hydrogen and air mixture was influenced by concentration. In 23 to 39 percent, safety gap (gap length 25 mm) was less than 4 mm and in 17 to 52 percent, was less than 6 mm. Hydrogen concentration in air less than 16 percent or above 53 percent is graded by No.1.
On Results of Examination of Real State of Static Electricity in Factories
SH-1961-3-3
S.KOZUKI, S.SAKANUSHI and T.TANAKA
: The writers inquired the following items by sending questionnaire papers to factories which probably have processes generating static electricity enough to give workers electric shocks or to cause hazards of explosion or fire due to the discharge sparks. From the results of answers that were sent back to us, we examined the real state of static electricity in factories in Japan.
1) Occurrence of accidents due to static electricity since 1955.
2) Occurrence of accidents due to static electricity for late one year.
3) Processes that the generation of static electricity evident.
4) Electrified bodies on which a large quantity of static electricity is noticed.
5) Countermeasures being adopted to prevent the accidents due to static electricity.
6) Effectiveness of the countermeasures.
7) Measurement of static electricity.
