A large E-scrap recycling plant with a 500HP shredder needed to upgrade the explosion protection equipment on the ventilation system. In order to comply with current OSHA and NFPA regulations it is required that any industrial processing facility handling combustible dust be protected properly from explosion including the dust collection system. When processing and recycling metals and electronics, sparks are very common and could be carried through ducting and introduced to a dust collector where combustible dust is accumulated an explosion can occur. Yet an even stronger danger, and what causes the most harm to people and the facility, is the secondary explosion from aerated dust from roof rafters or on top of equipment being liberated from the first explosion pulse and igniting within the confinement of the facility. These explosions can be deadly and costly. Due to plant’s dust collectors being indoors, implementing a flameless explosion venting and passive duct isolation solutions were required.
Because of the special handling required from electronic recycling dust two approaches are frequently considered – Passive Isolation or Chemical Suppression. In order to keep maintenance down it was determined a passive isolation system would be best and meet the site’s specific downtime and budget needs.
The engineers at Converge Engineering were able to identify that existing ducting was not designed properly and the dust collection systems actually had too much capacity and was moving more CFM than needed. By completely redesigning the ducting system to increase efficiency and carrying velocity as well as upgrading the main collector’s blower motor, the Engineers at Converge Engineering were able to accomplish the removal of four small dust collectors from the system while increasing dust pick up points and particle carrying velocity. Flameless explosion vents specifically sized for the dust’s explosive characteristics were added on the top of each of the dust collectors and isolation valves were placed upstream from the collectors with emergency signal feedback upon activation by explosion. Any explosion within the dust collectors are forced through the vent and safely diffused and quenched while being isolated from travelling down the plant’s ducting system. These features were integrated into the systems shredding line’s PLC control system to provide operators feedback on dust collector status.
Redesigning this system, which was compulsory to comply with regulations, also resulted in a drastic reduction in maintenance and energy usage. Ducts no longer require frequent cleaning due to fouling and there is less motor HP moving air. The plant can now ensure their employee’s safety is well looked after and a cleaner work environment is now provided. Being safe can also save money.