Blue M standard chamber safety features

NFPA Bulletin 86

1.Chamber. Interior seams are heli-arc welded vapor tight to prevent fume infiltration into the insulated walls. Without proper sealing, fumes will condense on insulation and could ignite.

2. Purge timer and door switch. This is provided to prevent element heat up and allow exhaust blowers to run for a preset time after every door opening. This clears excessive fumes from the chamber before energizing a possible ignition source, i.e., the heating elements or an electrical fault that may create an arc inside the chamber.

The system operates automatically any time the chamber door is opened or a power failure occurs.

3. Blowout relief panel. The panel provides one square foot area per 15 cubic feet of chamber volume. The panel will blow out and relieve internal chamber pressure if a low-level explosion occurs, minimizing possible damage.

4. Overtemperature protection. Preventing uncontrolled temperature rise is imperative. Protection device is independent of the primary control circuit with its own contractor to disconnect the main chamber power line.

5. Forced exhaust system. Maintains negative pressure inside the chamber improving the exhaust of hazardous vapors. Dampers at the chamber intake and forced exhaust intake are factory-set to meet individual chamber exhaust requirements. Airflow switch stops heaters in the event of airflow loss.

6. Airflow interlock protection devices. These shut down heating element power unless blower systems are operating.

Loss of recirculating air also allows heating element surface temperatures to surpass the auto-ignition temperature. Therefore, two interlocks are required: An electrical interlock to disconnect the heating element circuit if the motor overload protection device disconnects the blower motor, and a direct acting mechanical device that responds directly to airflow loss.

7. Direct-drive blower systems. Eliminates potential failures of belt driven systems.

8. Fire extinguishing systems. Sprinkler head, CO, or foam systems that respond to overtemperature protection control or their own direct flame or smoke sensing devices are at times specified by regulatory agencies for very hazardous applications.