Class II, Div. 1 Purge/Pressurization

Start-Up Conditions
Protection Method: Type "X" Pressurization System
Powering Method: Automatic Power Control Unit or Local Disconnect
Switch System Status: Protected Equipment De-energized Alarm System and Air Supply On

Operating Procedures

1. Remove hazardous substance from the protected enclosure. A vacuum device is the preferred tool for dust removal.
2. Check operation of enclosure pressure relief device (if utilized) and seal the protected enclosure.
3. Pressurize the protected enclosure to set and maintain a positive pressure of 0.50 inches (12.7 mm) of water.
4. System will apply power automatically when pressure is set and maintained at a positive pressure of 0.50 inches (12.7 mm) of water.
5. Loss of pressurization must automatically de-energize protected equipment power immediately.

   Exception: Automatic power control is not required if the enclosure is designed to prevent the entrance of dust and the pressurization system activates an audible or visual alarm in a constantly attended location.

6. Equipment that may overload or overheat, such as motors or transformers, require thermal overload cutoff switches or alarms.

Start-Up Conditions
Protection Method: Type "X" Purge/Pressurization System
Powering Method: Automatic Power Control Unit
System Status: Protected Equipment De-energized Alarm System and Air Supply On

Operating Procedures

1. Check operation of enclosure pressure relief device (if utilized) and seal the protected enclosure.
2. Pressurize the protected enclosure to set and maintain a minimum positive pressure of 0.10 inches (2.5 mm) of water.
3. Exchange the recommended volumes of purging gas.
4. System will deny power automatically until recommended volume exchange is complete and pressure is set and maintained at a minimum positive pressure of 0.10 inches (2.5 mm) of water.
5. Loss of pressurization must automatically de-energize protected equipment power immediately.

   Exception: Power may be maintained for a short period if immediate loss of power would result in a more hazardous condition and if the system activates both audible and visual alarms in a constantly attended location.

6. Equipment that may overload or overheat, such as motors or transformers, require thermal overload cutoff switches or alarms.

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Start-Up Conditions
Protection Method: Type "Z" Purge/Pressurization System
Powering Method: Local Disconnect Switch
System Status: Protected Equipment De-energized Alarm System and Air Supply On

Operating Procedures

1. Check operation of enclosure pressure relief device (if utilized) and seal the protected enclosure.
2. Pressurize the protected enclosure to set and maintain a minimum positive pressure of 0.10 inches (2.5 mm) of water.
3. Exchange the recommended volumes of purging gas.

   Exception: Power may be energized immediately if the protected enclosure atmosphere is known to be nonflammable.

4. Energize the protected equipment power manually with a disconnect switch or breaker rated for the hazardous location.
5. Loss of pressurization requires immediate attention or the manual de-energizing of protected equipment power.
6. Excessively hot equipment must be isolated in a separate protected enclosure, unless the enclosure is marked with a warning which indicates a required cool-down time period before access.

Start-Up Conditions
Protection Method: Type "Z" Pressurization System
Powering Method: Local Disconnect Switch
System Status: Protected Equipment De-energized Alarm System and Air Supply On

Operating Procedures

1. Remove hazardous substance from the protected enclosure. A vacuum device is the preferred tool for dust removal.
2. Check operation of enclosure pressure relief device (if utilized) and seal the protected enclosure.
3. Pressurize the protected enclosure to set and maintain a positive pressure of 0.50 inches (12.7 mm) of water.
4. Energize the protected equipment power manually with a disconnect switch or breaker rated for the hazardous location.
5. Loss of pressurization requires immediate attention or the manual de-energizing of protected equipment power.
6. Excessively hot equipment must be isolated in a separate protected enclosure, unless the enclosure is marked with a warning which indicates a required cool-down time period before access.

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