بهداشت و ایمنی کار (Dec 2017)
An applied method to check the hoods design parameters of local exhaust ventilation system a steel making company
Abstract
Introduction: Efficiency of hoods for local exhaust ventilation system is influenced by hood geometry, its situation relative to the process and the air volume exhausted by it. The aim of this study was to present a simple and practical method based on the standards for assessment of potential problems of ventilation system in a steel making company. Material and Method: In this cross-sectional study, a checklist based on the ACGIH ventilation standards was developed for investigating potential problems related to the three types of hoods in an oxide screen process. This checklist has completed in order to feasibility study of corrective changes in evaluation of the hood hardware parameters. The differences between design and current status to the standards were considered as noncompliance. Finally, differences were analyzed statistically. Result: Based on statistical analysis, the average of current status of hoods, plans and design documents and standards were for variables of conveyors downstream enclosure (1.6, 2.38 and 2.41m), vertical distance from hoods to conveyors (0.39, 0.37 and 0.61m), conveyor longitudinal enclosing after hood (1.225, 1.288 and 0.296 m) and hood numbers (18, 17 and 31), respectively. Comparing the results between current status of hoods with plans and design documents showed no significant differences (0. P-value≤ 0.05). But, the results between current status of hoods and design documents with standards have significant difference (0. P-value≥ 0.05). A significant difference (0. P-value≥ 0.05) revealed between the average of the current status of hoods, plans and design documents and the standards for variables of hood flow (813.3, 2276.9 & 3085.9 cfm) and duct velocity leading to the hoods (2289.3, 5083.5 & 3500 fpm), respectively. Conclusion: This method can be applicable for the local ventilation systems with extensive pollution sources and hoods. One of the advantages of this method can be easily application of this system, as one of the requirements for delivering ventilation systems from contractors and the use of it for studying potential problems of the hoods that they have standards. Also, by comparing current status of hoods with the design specifications and standards, the mismatches/ unconformities in the lifetime and maintenance process of the system can be understood.
