IMPROVING LIGHTING IN THE FILAMENT INSPECTION AREA AT THE TOMSK ELECTRIC LAMP PLANT

V. D. NIKITIN, I. A. BEZLER

(Presented by the scientific seminars of the Departments of Lighting Engineering and Light Sources and of Electrical Systems and Networks)

Rational lighting is especially important in work involving increased strain on the functions of vision. Inspection of filaments (coils) in electric-lamp production is associated with an exceptionally great visual load [1]. There is a direct indication that this operation belongs to work of the highest precision [2]. At the same time, the filament is an extremely critical part of the lamp; even a minor defect in it puts the lamp out of service or shortens its service life. This imposes especially high requirements on the quality of inspection and, consequently, on the lighting conditions.

The system of a single general lighting installation in the filament inspection area of the Tomsk Electric Lamp Plant was implemented with OD-2×40 luminaires with LDTs-40 lamps; the specific power of the lighting installation was 9 W/m². The illuminance on the surface of the inspection tables did not exceed 80–100 lx. The coils were examined against an artificial light background measuring 255×215 mm. The background was produced by an LDTs-15 lamp built into the inspection table, which illuminated opal glass by transmission.

The lighting in the area was unsatisfactory for a number of reasons.

1. The illuminance from the general lighting system amounted to 20–25% of the norm (400 lx for category I 2+1, under SNiP—II V.6, by which the visual work of coil inspectors can be classified).

2. The distribution of brightness in the field of view was (item 1 in Table 1) sharply nonuniform, primarily because direct-light luminaires were used.

3. The spatial nonuniformity of the brightness distribution in the inspectors’ field of view was combined with temporal nonuniformity. The depth of luminous-flux pulsation for LDTs lamps in a two-lamp circuit with phase shift is, according to various sources, from 17 to 25% (which is equivalent to a complete interruption of the light).

4. Reflected glare from the luminaires occurred, from the glass covering the tabletop in the direction of the inspectors’ eyes.

The unsatisfactory lighting characteristics of the coil inspection area necessitated reconstruction of the lighting. It was decided to create in the area a combined lighting system with enhanced general lighting, combining the advantages of both single general and combined lighting [3]. The ratio of illuminance from these

of three lighting systems for the operation “filament inspection” is shown in Fig. 1.

Fig. 1. Ratio of illuminance for three lighting systems

General lighting (illuminance—300 lx) was calculated by the utilization-factor method. Diffuse-distribution luminaires ShOD—2×40 were selected, since they create a favorable distribution of brightness in the field of vision; as light sources, LB-40 lamps were chosen because of their high luminous efficacy and the smallest luminous-flux pulsation in comparison with other fluorescent lamps. For better spatial mixing of the luminous fluxes, the luminaires were supplied from different phases, and to prevent reflected glare they were placed above the main passage (Fig. 2).

Fig. 2. Plan of the filament inspection area

The lighting installation has been in operation since 1968 and has received favorable reviews. The installed power is 22 W/m².

For local lighting above the inspection tables, BL-2—1×40 diffuse-light luminaires were mounted, owing to which the illuminance of the table increased and the distribution of brightness in the inspectors’ field of vision became more uniform. The ratio of the brightness of the principal surfaces—

of the brightnesses to the brightness at the center of the artificial luminous background (before its rationalization) for three lighting variants are given in the table. It is obvious that, with combined lighting with reinforced general lighting, a more favorable brightness distribution is created than in the second and especially in the first case.

Table 1

In addition to improving the general lighting and creating local lighting, it was necessary to rationalize the artificial luminous background for transmitted light. This background helps increase the brightness contrast of the parts viewed against it [4] and, in essence, determines the very possibility of successful inspection of filaments (especially in the case of thin grades of tungsten). However, the errors made in creating the artificial luminous background in the area had to be corrected.

1. The brightness of the background (Fig. 3) was below the values corresponding to the optimum of contrast sensitivity (350 nt and higher).

Fig. 3. Brightness of the artificial luminous background in transmitted light

1. The distribution of brightness over the background (due to the transmitted luminous fluxes) was noticeably nonuniform. The nonuniformity index

\[ K_{\text{nonunif.}}=\frac{B_{\min}}{B_{\max}}=0.35, \]

where \(B_{\min}\) and \(B_{\max}\) are, respectively, the minimum and maximum values of the background brightness, nt.

1. The depth of the pulsations of the background brightness (due to the transmitted luminous fluxes) before improvement of the area lighting was about 50%.

As a result of the interaction of these pulsations with the pulsations of the luminous flux from the general-lighting system, a microshadow result

pulsation of the contrast and of the visible boundaries of the filaments and, as a consequence, an inevitable reduction in the visibility of defects.

Rationalization of the artificial luminous background in transmitted light was achieved by illuminating the milk glass with three parallel LDS-15 lamps (LB-15 would have been better), supplied from the three phases of the network. As a result [5]: the average brightness of the central areas of the background, where most of the inspection is performed, \(B_{\text{avg}} = 360\) nt; the distribution of brightness over the background became more uniform, \(K_{\text{uneven}} = 0.50\) (taking into account the component of the background brightness from the “overhead” fluxes); the depth of pulsations decreased to 5% (the reference value for lamps supplied from the three phases of the network).

The layout of the filament inspector’s workplace after the lighting improvement is presented in Fig. 4.

Fig. 4. Layout of the workplace after the lighting improvement.

A study of the indicators of work and of the physiological condition of the inspectors (performance of check and work tests, duration of the latent period of the visual-motor reaction and deviations when setting to zero, magnitude of missed rejects) attests to an improvement in the production and physiological indicators of the workers upon transition to the new lighting conditions.

References

1. A. N. Bessonova, V. D. Nikitin. Hygienic assessment of visual working conditions in the rejection inspection of fine grades of filaments in electric-lamp production. Hygiene of Labor and Occupational Diseases, 1970, No. 6.

2. E. Zagora. Industrial Ophthalmology. Moscow, 1961.

3. V. D. Nikitin. A combined-lighting system with enhanced general lighting as a factor in increasing labor productivity. In: Accelerating Technical Progress—the Path to Increasing Production Efficiency. Proceedings of an Intersectoral Scientific-Production Conference. Tomsk, 1970.

4. A. S. Shaikevich. The Quality of Industrial Lighting and Ways to Improve It. Moscow–Leningrad, 1962.

5. V. D. Nikitin. Information leaflet No. 37/67 of the Tomsk TsNTI. Tomsk, 1970.