Shutdowns stations, manual

The recirculating air stream is considered an integral portion of the life safety system therefore, in a hazardous occupancy cleanroom (such as a semiconductor wafer fab), the system should not be automatically shut down by the smoke detection system. In lieu of automatic shutdown, a manually operated remote switch is to be provided at an approved location outside the fabrication area (UBC 1202.2.5). Since such a detection could happen at any time, our recommendation for the location of the switch is in a continually occupied but relatively secure spot, such as the nearest Emergency Control Station (ECS). UBC 1202.2.5 also dictates that the return air system of one hazardous cleanroom area shall not be connected to another eleamoom oeeupancy. 

Manual shutdown stations should use a two-stage operation to avoid inadvertent operation. For example, a push button could be covered with a flap guard thus requiring that the operator take two actions (open the flap then press the button) before the shutdown takes place. 

Isolation or emergency shutdown (ESD) valves should be installed to stop fuel flow and the process feed flow into the heater in the event of heater tube rupture. These valves can be automatically actuated by controls or safety interlocks or can be manually operated remotely. Remote actuation can be from a control room console or in the field field actuation stations should be located at least 50 ft (15 m) from the heater. It is also common to provide a manual block valve, located at least 50 ft (15 m) from the heater, on each of the fuel and process feed lines. These should be accessible to operators in the event of an incident involving the heater. 

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