National Institute of Occupational Safety and Health, Japan
Measurment of the Maximam Experimental Safe Gaps for Breathing Plugs.
RR-14-1-1
N.Taguchi H.Tsurumi
By the closed explosion test vessel and the breating plug models, the writers mesured the Experimental Safe Gapes with Hydrogen/Air Mixtures for cylindrical holes.
The results of the 403 tests that were made are given in detail in the Table 7 and the Fifure 8.
First, 176 tests were made with the 38.9% — 40.0% Hydrogen/Air mixture, the Maximam Experimental Safe Gap in differnce of dasius was 0.400mm at the gap depth 25.20mm.
Next, 227 tests were made with the 49.0% — 50.0% Hydrogen/Air mixture, the Maximam Experimental Safe Gap in differnce of dasius was 0.695mm at the gap depth 25.20mm.
On the strength of canvases for protection against falling articles.
RR-14-1-2
Jiro Saito, Kinichi Kinoshita, Katsunori Ogawa
We have made research for the strength of some sorts oc canvases which are widely used outside the building under construction, so in this report we show the result of it.
As one of the methods of test we made two steel pipes - 48.6mm in diameter, 2.4mm in thickness, 5kg and 7.4kg in each pipe — fall from the experimental tower on tha canvases set in the steel frame at the some angles to the level.
From this test, we find the lowest altitude of pipes to penetrate and the angle of canvases which make most for convases being penetrated.
As the other method of test, we made in a tentative way an impact tester in which pendulum was applied, and by using of it we got the result of the test of them.
More over we analysed the motion of a thing throun out of high place and we calculated the kinetic energy of steel pipe and the angle between the direction of falling thing and the canvases in the moment when it came into collision with them.
In conclusion, as the strength of canvases it is necessary that the product breaking strength and elongation is more tham 5000kg.mm.
The Igniyion of Hydrogen - Air Mixtures By Inductive - Break Sparks In Low Voltage d.c. Circuits
RR-14-1-3
R.Tanaka
The results of these experiment, witd low-voltage d.c, circuits including air-cored inductances in which the current was interrupted be the separation of tungsten wires and a cadmium disc, are given showing the relationships of minimum igniting current to inductances and circuit voltages, together with the effect of shunt linear resistances or shunt nonlinear resistance on the minimum igniting current. Mesurements were also made of the effect of the resistance of the inductance coil which was shunted by a give value of resistor on the igniting current.
On The Safety Conditions of Safety Net
RR-14-2-1
K.Kinoshita, K.Ogawa
The number of fatal accidents by falling from high places while working occupies a large part of statistical data of fatal accidents in the construction work, until now as the method for prevention against fall safety line has been used and today a safety net is beginning to be used that purpose at the sites of dockyard and building construction yard.
So we made following test to obtain the data for safety conditions which safety net should have.
As a dummy for the test, we made a sand-bag(90kg in weight) in which a columnar iron block(10cm in diameter and 35cm in length) was set, and then we took the photographs of the motion of the falling body by a high speed camera and got the deceleration acting on it, while we measured tension working in the twines of some parts of a net by 6 load-cells in which electric wire strain gages were applied. As the result of the test safety conditions of the neto confirmed as follows:
Breaking strength of a knotted twine of the net is necessary more than 312kg (10cm in mesh), 210kg(7.5cm in mesh), and 156kg(5cm in mesh).
The breaking strength of the rope to support a net is approximately necessary to be 1.7ton.
Maximam height from which workers can leap down safety on the safety net is 5-6m in consideration of shock to human body.
Mesurement of the Ultrasonic Inspection
(Mesurements of Metal Sheet and Inspection of Weld Deposits.)
RR-14-2-2
T.Sato
Following several experiments, mesurements were made of metal sheet thickness of boilers, pressure vesels, and chemical appliance, and inspection was made of erlding defects, by recently deceloped "Ultrasonic Flow Detector and Thickness Metre".
With the metal sheet thickness, the writer inspected the butt joint and tee-joint.
With the welding this apparatus the defects of welding of tee-joint were detected readily by applying "Ultrasonic Flow Detector and Thickness Metre" to the opposite side of weld depositm contrary to the conventional side of applying the X-rays.
Research & Development on Human Equilibrium Function Measuring Device
RR-14-2-3
J.Saito, M.Ohkawa, S.kawahara
"Human Equilibrium Function Measuring Device" that was developed, consisted of balancing stage, slant distance amplifer with detector, balancing-servo mechanism and pen-recorder. Using oil-damper with bellows and cutting DC in slant distance were the main features of this device.
A null hypothesis that main factor of fuman equilibrium function were governed by physical conditions including volume, mass quantity, and center of gtavity, were tested by beasuring og equilibrium function and physical conditions.
112 Tobishoku, as high ground level worker, consisted of 5 age-group, were subjected individually.
Finding are as follows: 1) The slant distancewave(integral value or coefficient of variation) is not found to be function both human physical conditions and age. 2) It is confirmed that human equilibrium function is governed by human feed back mechanism as main factor and physical conditions as sub-factor. 3) By using integral value, human equilibrium function is discriminated. 4) DC cutting technique is effective. 5) Evaluation table of human equilibrium function is organaized.
The Ignition of Methane-Air Mixtures by Sparks with Snapping-Wire Apparatus
RR-14-3-1
R.Tanaka
Mesurements have been done of minimum igniting currents for low voltage d.c. inductive and non-inductive circuits, in methane-air mixtures, with a snapping copper wire apparatus.
It is shown that more incendive spatks are achived, for inductive circuits, than with the British Break-flash No.3 apparatus, hinting for the need for a larger safety in cases of live wire break incidents. The incendivity of appaaratus is almost equal to that of the German Schnellunterbrecker.With non-inductive circuits obvious differences of the minimum igniting currents are not indicated throughout the range of voltages investigated.
As for the effect of the wire diameter, the minimam igniting currents are nearly constant over a limited range of diameter of 0.1-0.4mm, the other conditions being eaual.
Research on Elimination of Static Charges by the Use of Radioisotopes(3rd report)
— Elimination of Static Charges of Powders —
RR-14-3-2
K.Sakanushi, R.Tanaka, S.Kouzuki
Reports on the elimination of static charges on running vinyl sheet by radioisotopes have been published in the previous papers(Vol.13, No.1, Vol.14,No.1).
This paper deals with the similar experimental results with powders and their considerations. In cases of elimination of charges in pilling charged powders are generated bu friction, during flowing in a spout(refer to the device shown in Fig.1), while in cases of falling charged powders, by falling down through silk-meshes of a shifter(refer to the device shown in Fig.16).
The elimination effeciency, in various conditions, for the powders charged by these methods are investigated, experimental data being given for the elimination effeciency of charged powders in resting situation, β-rays applied to the falling powders laterally.
From the results obtained, it is shown that the sources emitting β-particles with larger energies eliminate the static charges of the powders in a shorter time but those with smalle energies take more time(elimination efficiency of 85% for application time 1.0 sec by 90Sr with β-particles maximum energy of 0.545 Mev. 85% for the time 22 sec by 147Pm with the energy og 0.223 Mev).
As a result, it is likely to be possible to neutralize the static electricity of powders in the couse pf transportation by examining application methods of β-rays and suitable selections of β-ray sources etc.
Maximam Experimental Safe Gaps with Acerylene/Air Mixtures for Various Vessels with Flanged Joints
RR-14-3-3
H.Tsurumi, T.Hayasi, T.Matsuda
Maximam Experimental Safe Gaps with Acerylene/Air Mixtures for Various Vessels were mesured to get some informations for the design of explosion-proof electrical equipments.
From the experiments, the following facts became evident.
Maximam Experimental Safe Gap largely depends on the volume.
Maximam Experimental Safe Gap for the spherical vessel(inner volume 8,000cc, flange 25mm long) is 0.16mm; that is smaller than the Value of 0.01" obtained by Slack and Woodhead.
The concentration of the most easily ignited mixture lies from 7 to 9% by volume, when the concentration of the inner mixture is equal to that of the outer mixture.
The product of the flame velocity and Maximum Experimental Safe Gap seems to be approximately constant.
