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- Geng, Q., et al.
(författare)
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Temperature limit values for touching cold surfaces with the fingertip
- 2006
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 1475-3162 .- 0003-4878. ; 50:8, s. 851-862
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfaces. Methods: Data were collected in four laboratories with a total of 20 males and 20 females performing a grand total of 1655 exposures. Each touched polished blocks of aluminium, stainless steel, nylon-6 and wood using the distal phalanx of the index finger with a contact force of 1.0, 2.9 and 9.8 N, at surface temperatures from +2 to -40 degrees C for a maximum duration of 120 s. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (T-C) of the fingertip was measured over time using a T-type thermocouple. Results: A database obtained from the experiments was collated and analysed to characterize fingertip contact cooling across a range of materials and surface temperatures. The database was subsequently used to develop a predictive model to describe the contact duration required for skin contact temperature to reach the physiological criteria of onset of pain (15 degrees C), onset of numbness (7 degrees C) and onset of frostbite risk (0 degrees C). Conclusions: The data reflect the strong link between the risk of skin damage and the thermal properties of the material touched. For aluminium and steel, skin temperatures of 0 degrees C occurs within 2-6 s at surface temperatures of -15 degrees C. For non-metallic surfaces, onset of numbness occurs within 15-65 s of contact at -35 degrees C and onset of cold pain occurs within 5 s of contact at -20 degrees C. The predictive model subsequently developed was a non-linear exponential expression also reflecting the effects of material thermal properties and initial temperature. This model provides information for the protection of workers against the risk of cold injury by establishing the temperature limits of cold touchable surfaces for a broad range of materials, and it is now proposed as guidance values in a new international standard.
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| 6. |
- Rissanen, S., et al.
(författare)
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Comparison of contact cooling while touching cold surfaces with an artificial and human fingers
- 2005
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Ingår i: Elsevier Ergonomics Book Series. - 1572-347X. ; 3:C, s. 181-185
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Tidskriftsartikel (refereegranskat)abstract
- An artificial finger (AF) was developed to determine the contact cooling rate induced by different cold surfaces. The purpose of this study was to compare the contact cooling rates of the artificial and human finger when touching cold surfaces. Aluminum, steel, nylon and wood blocks (95×95×95 mm) were used as contact materials. The temperatures of the materials were -40, -30, -20, -15, -10 and -4°C. The sensor of the artificial finger, simulating a finger pad, was designed and developed to measure the heat exchange of the contact interface when touching a cold surface. In the human experiments, 30 volunteers, 15 male and 15 female subjects, participated in the study. The contact temperature of the index finger was measured with a thermocouple (T-type, diameter 0.2 mm). Individual physical hand and finger characteristics were measured. For human measurements, the metal surfaces were tested only at temperatures of -15°C or higher. Cooling curves measured by the artificial finger followed a similar pattern to those measured by the human fingers when touching metal surfaces. When touching wood or nylon, the cooling curve of the artificial finger was significantly slower than that of the human fingers. Sex and hand/finger size partly explained the great variation in skin cooling rates between individuals. In conclusion, the present type of artificial finger could be used to assess contact cooling rates of cold materials with a very high thermal penetration coefficients (over 7200 J m -2 s -1/2 K -1) and at a surface temperature of below -4°C. © 2005 Elsevier B.V. All rights reserved.
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