Very early warning, air sampling smoke detection (ASD) has traditionally been thought of as a technology only suited for clean environments. Many fire industry professionals believe that factors such as dirt, dust, moisture, vibration and other harsh conditions preclude the use of air sampling smoke detection because of nuisance alarms and detector maintenance issues. This is unfortunate because harsh industrial environments have a much greater risk of fire than the standard clean environment.
Possible fire hazards in industrial facilities include very high-voltage electrical cabinets, large motors, conveyor belts, lubricants, flammable liquids, moving parts causing friction and less-than-ideal housekeeping. Industrial facilities also tend to have ongoing maintenance activities, such as welding and metal cutting, that can set in motion smoldering and a possible fire situation well after the work has been completed. For these reasons and others, very early warning, air sampling smoke detection would provide great value to an industrial facility.
Because of a worldwide risk audit of major mobile mining equipment, an international mining company was interested in evaluating secondary smoke detection options in one of their P&H 4100 electric rope shovels. This type of equipment has very high-voltage and hydraulic/lubricant potential fire hazards. It also has all the aforementioned operational challenges for air sampling smoke detection. The electric rope shovels, being the beginning of the ore processing supply chain, mean any disruption at this point would cause problems throughout the production process. As in most industrial facilities, the cost of lost production would be much greater than the cost of the lost equipment. A recent fire at a Canadian gold mine’s processing facility caused the stock exchange-listed company to issue guidance regarding their 2012 production, and the stock price dropped 25%.
The mine’s mobile maintenance department also realized the value of the ASD data for preventative maintenance. Under normal operations, motors and other pieces of equipment used in the shovel should not produce smoke. The presence of a significant amount of smoke in these areas might not lead to a catastrophic fire, but could be a signal of an impending equipment failure.
The mobile maintenance department knows that early detection of an impending equipment failure can provide for a quick reaction that will save maintenance costs and avoid unplanned downtime. Due to the high cost of replacement parts, labor and above all, lost production, these professionals understand an early warning ASD system can easily pay for itself by detecting one potential equipment component failure.
The engineering drawings from the shovel manufacturer could not be easily obtained, thus site surveys and hand measurements had to be taken. In an industrial design, there are a number of challenges regarding system component placement. Operators and maintenance crews will have a lot more interaction with a smoke detection system in this environment than the workers in a standard office or warehouse. The system was designed with two zones. The first zone (Zone 1) was designed to protect the electrical cabinets with both in-cabinet sampling and cabinet exhaust ventilation sampling. The second zone (Zone 2) was designed to protect the lubrication/hydraulic room and the exhaust vents of the hoist and swing motors.
Blazemaster CPVC pipe was used as the main sampling air transport pipe with 3-mm sampling holes field drilled and labeled. Capillary tube and sampling bulkheads were used to sample in the electrical cabinets. The detectors, a 24-DCv power supply and battery backup were pre-wired and attached to a single mounting plate. The detectors were offset from the main mounting plate with anti-vibration spindles. The displays with annunciators were installed in the operator cab, but all indicators were turned off so not to disturb the operator with alarms during the test period. In the case of a sole operator in a production environment, constant or unexplained alarms will result in the removal of the system.
The installation was per