Daniel Imbeau

Handling of fiberglass extension ladders in the work of telephone technicians

Abstract The purpose of this study was to obtain detailed information on the current ladder handling methods of telephone technicians. Forty-two experienced telephone technicians handled their fiberglass extension ladder on seven sites that were judged representative of actual work conditions by a joint employer–union committee. Each technician was asked to unload his ladder from the truck he uses in his daily work, to carry the ladder to the installation site, to raise it, and then to perform the reverse maneuver back to the truck. The technicians were asked to use the usual work methods. After completion of the handling activities, each technician was interviewed about various aspects of the maneuver he had just completed and on the usual work methods. In total, 49 runs were completed and videotaped. An equal number of interviews were conducted on the sites. In one of the runs, a technician caught his ladder in an overhead obstacle. The observations in this study lead to several results of practical importance. First, the ladder itself represents a risk factor for overexertion injury which cannot be eliminated form the technicians work in the short term but can be reduced through safer work methods. Second, the method currently used by telephone technicians to carry a ladder has many drawbacks which make it hazardous in the presence of several environmental conditions. Third, the method taught to and used by telephone technicians to verify the inclination of the ladder, the so-called Firemans method, appears to be a risk factor for sliding-at-the-base accidents. Relevance to industry Handling of a ladder in varied and adverse environmental conditions is typical in the work of telephone technicians. A better knowledge and understanding of the work methods used and of the conditions in which the handling tasks are performed is an important step towards reducing the related injuries and improving safety of the handling maneuvers. The results of this study apply to users of fiberglass extension ladders, that is, construction workers, electricians, various power utility workers, and cable television installers as well.

Oxygen consumption during scaffold assembling and disassembling work: Comparison between field measurements and estimation from heart rate

Abstract Four construction workers were tested on a laboratory submaximal cycle ergometer test to establish their heart rate (HR) by oxygen consumption (VO2) relationship. These workers then completed six simulations of a steel access scaffold assembling and disassembling task during which heart rate and oxygen consumption were measured simultaneously with portable monitoring equipment. Two of these subjects had little experience with this work while the others were experts. Two widely used types of scaffold frames were used in the simulation: “5-foot” closed frames and “6-foot” open frames. The mean VO2 measured during work ranged from 1.4 to 1.8 li/min. for a corresponding mean HR ranging from 131 to 155 bpm. There was a significant inverse relationship between relative intensity of HR selected by subjects and performance time. Subjects worked on average at 62% ± 9% of their maximum heart rate range. Models were developed to estimate VO2 from field HR recordings. A certain heat stress had to be taken into account for some of the subjects in the development of these models. VO2 prediction from HR is feasible and can be fairly accurate for scaffold assembling and disassembling work as long as factors which have an impact on HR such as heat stress or incomplete recovery are accounted for.

Determination of a safe slow robot motion speed based on the effect of environmental factors

The goal of this research was to determine a safe slow robot motion speed to be used for intervention tasks conducted in proximity to an industrial robot (e.g., programming and maintenance) when environmental factors were considered. The relevant factors associated with a robot station were dictated by previous research (Beauchamp and Stobbe, 1990). They were the illumination level, the luminance contrast between the robot and its background, the motion speed of the robot, and the field in which unexpected motions were initiated. The dependent variable measured was the distance the robot moved before the subject detected and responded to the unexpected robot motion. From the results, a multiple regression model was derived for predicting robot overrun distance. The model suggested that speeds in excess of 17 cm/s do not provide an adequate safety margin, and that 17 cm/s should be recommended as the maximum robot slow speed for work conducted in the vicinity of an industrial robot not equipped with dead-man switches.