JNIOSH

Abstract of RIIS Report ( SH-1962-1 )

National Institute of Occupational Safety and Health, Japan

On the Planning of Temporary Structures (1)

SH-1962-1-1
Kazuo UCHIYAMA and Kinichi KINOSHITA

: Many accidents of fracture of temporary structures have been occurred at the construction fields.
    In order to prevent these accidents, we made a plan of experimental study of temporary structures.
    This report shows the experimental results of the bearing-capacity and deformation behavior of those.
    Contents are as follows :
  1. Clamp test
  2. Test of the frames built up with the clamp
  3. Compression test of the supports for the concrete slab mold.
  4. Test of the unit scaffolding and its lateral supports.

Study on the Automatic Electrical Shock Hazard Relieving Device of a-c Arc Welder

SH-1962-1-2
M.TERAZAWA

: Better starting characteristic of a shock hazard relieving device is obtained with shorter starting time (the duration from when the welding rod gets touch with the base metal till the main contact closes). "Recommended Standard Specification of Automatic Electrical shock Hazard Relieving Device of a-c arc Welder" established by our Institute specified that this starting time shall be less than 0.08 sec.
    In the mean time, devices with considerably short starting time have been on the market.
    Of course the length of starting time depends on the starting system of the device.
    Therefore the writer investigated the correlation between the starting time and the starting system.

The Flammability of Fabrics in Compressed Air

SH-1962-1-3
K.KOMAMIYA

: The burning accident was occurred in a caisson owing to the burned working dress in 1959.
    This accident fact was considered that the burning velocity of fabrics was increased be cause the absolute oxygen content was greater (under pressure as caisson) than normal atmosphere. Than, We have studied on the effect of pressure to the burning velocity of fabrics.
    Results
  1) The burning velocity of fabrics is increased in proportion to the increase of air pressure, and under 3 kg / cm2 air pressure, the increase ratio of fabrics is equal to it under 10% oxygen enriched atmospheres, (absolute oxygen content is 29%), therefore, in this case, the fabrics become to have high flammability.
  2) It was recognized that the wearing of the nonflame working dresses was effect for prevent the burning accidents on caisson work.

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