Abstract of Special Research Report (SRR-78-1)
National Institute of Occupational Safety and Health, Japan
Special Research on Integrated Preventive Countermeasures against Natural Gas Explosion and Firre in Tunnelling Work
: The pneumatic caisson method has a history of about 50 years in Japan. As the caisson method or shield method is recently employed in many construction works, various sorts of labour accident occur as follows :
A Study on Gas Evolution from Lubricating Oil Heated in Compressed Air
|Kougaku KOMAMIYA and Takashi KOTOYORI|
: Unexpected accidents such as explosion, fire or poisoning often occur in air compressor systems. For example, on Feb. 20th in 1976, six workers were dead due to carbon monoxide poisoning in a caisson for a bridge base construction in Tochigi prefecture. The cause was carbon monoxide evolution as the result of heating and combustion of activated carbon held in an air cleaner brought about by the cooling deficiency of the air compressor. As a matter of fact the cooling deficiency of compression heat of air can cause easily the thermal decomposition and combustion of lubricating oil or carbonaceous sludges in compressed air lines, accompanied by the evolution of carbon monoxide. Furthermore the combustion of lubricating oil itself may provide an ignition source for combustion of activated carbon or other organic substances that may be present in the compressed air lines.
Combustion Hazard of Combustible Materials under Compressed Gas Atmospheres
|Kougaku KOMAMIYA and Shigeru MORISAKI|
: Danger of combustion will be increased in atmospheres at work places such as caisson work, as oxygen partial pressure is higher than air at atmospheric pressure.
Experimental Study on the Optimum Dimensions of Vertical Fixed Ladders
|Kinichi KINOSHITA, Yoshimasa KAWAJIRI and Hisao NAGATA|
: Vertical fixed ladders are commonly used at walls of buildings, chimneys, towers, etc. as a simple facility for elevation. Dimensions of vertical fixed ladders are empirically applied without any definite standards to date. This research is aimed at setting optimum dimensions of vertical fixed ladders through analyses of various experiments.
Reliability of Compressed Air Supplying System
|Yoshinobu SATO, Taiji KONDO, Noboru SUGIMOTO and Kiyoshi FUKAYA|
: On pneumatic engineering method, reliability of compressed air supplying system is closely related to the safety of work in pneumatic workrooms.
On the Strength of Bolt Joining Caisson Shafts
|Yoshio KITSUNAI, Etsuji YOSHIHISA and Masazumi TANAKA|
: Tensile and fatigue tests of bolts were performed to decide a criterion for strength of the bolts which are used to connect caisson shafts. Three groups of the bolts which had been) actually used in some caisson shafts were supplied from different sites. Strength of these bolts were compared with that of the same kinds of new bolts. The bolts were made of low carbon steels and the diameters were 3/4 and 7/8 inch. Tensile tests of the bolts were carried out using a 50 ton capacity Amsler universal testing machine. Fatigue tests of the 3/4 inch dia. bolts were conducted on a 10 ton Vibrophore machine operating at 140 Hz. The tests of the other bolts were performed on a 20 ton closed-loop servo hydraulic fatigue machine at a frequency of 10 Hz.