Hong Kong Builder
LIGHTING FOR SPECIAL INDUSTRIAL PURPOSES
By W. R. Stevens, B.Sc. and S. Anderson, B.Sc.
Illuminating Engineering Dept., The General Electric Co., Ltd.
As a result of the hostilities in the neighbourhood of Shanghai there has been during recent months a tendency on the part of firms who have hitherto operated factories in the North to move their establishments to the South and particularly to Hong Kong in order to enjoy the security and protection afforded by a British Colony.
A number of factories from Shanghai have already been transferred here and even when conditions of peace have been fully restored in Shanghai it may well be that Hong Kong will in the future be of greater industrial importance than in the past.
Consideration of industrial problems is, therefore, a matter of topical interest and the following article dealing with Lighting for Special Industrial Purposes, written by two members of the Illuminating Engineer- ing Department of the General Electric Co., Ltd. should be of particular interest to factory and workshop owners those who are proposing to establish similar establishment in this district.
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Equipment for use in
flameproof fittings are required. corrosive atmospheres, such as acids, alkalis, and sea spray, is also discussed.
Section (b) will Cover such problems as the examination of polished surfaces in connection with tin and chromium plate inspection, and the provision of artificial daylight for the colour matching of cloth and furs, and for use in industries where the critical examination of colours is involved.
(a) Installations with fittings having special mechanical features.
Situations where explosive or inflammable materials are used.
In situations of this type, ordinary lighting fittings are unsuitable owing to the danger of fire or explosion due to the surface temperature of the lamp, the risk of lamp breakage while on circuit, or the possibility of electric spark at the lamp contacts or elsewhere.
Fig. 1 A cellulose paint shop illuminated by high pressure mercury vapour lamps housed in dispersive reflectors situated outside the roof glazing.
Among the many industrial lighting problems which occur from time to time, are some which are of considerable general interest because they appear frequently. These problems are being solved gradually by the introduction of new lighting fittings and light sources and by new methods of attack on the problems involved.
In this article it is intended to discuss some of the types of installation which are passing from the problem stage into one of simple application of normal lighting technique and the development of special fittings for these applications.
It is convenient to consider two general types of
situation:-
(a) Those requiring special mechanical features in
the fittings design.
(b) Those requiring special optical arrangements
and light sources.
Section (a) includes the lighting of spraying booths and similar situations where the atmosphere is laden with explosive or inflammable materials, so that
Fig. 2 A cellulose spraying booth illuminated by means of flameproof lighting fittings.
are termed "dust-tight" or "water- Designs which tight" are but little better than the ordinary open or enclosed type of fitting, for they permit the ingress and accumulation of the dangerous vapour in explosive concentrations, and this, on ignition, may disrupt some part of the fitting or packing and thus communicate the flame to the outer atmosphere. In addition, the surface temperature of these fittings is often above that con- sidered safe with the more dangerous materials.
The type and size of the enclosure where the inflammable material exists varies from a small booth or container to a large department, but, in general, one of three alternative methods of lighting may be adopted. (a) The area may be illuminated by means of floodlights or other non-flameproof fittings situated outside and throwing light in through windows in the roof or side walls.
(b) Fittings of a non-flameproof type may be used just outside a partially enclosed dangerous
area.
(c) Fittings of special flameproof design may be
used within the area.
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