When dealing with flammable gases, it's crucial to understand the acceptable frequency rate of explosive atmospheres to ensure safety. Here's a breakdown:
Hazardous Area Classification
- Zone 0: Areas where an explosive gas atmosphere is present continuously or for long periods (>1000 hours/year).
- Zone 1: Areas where an explosive gas atmosphere is likely to occur in normal operation (10-1000 hours/year).
- Zone 2: Areas where an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time (<10 hours/year).
Gas Detection and Monitoring
- Alarm Activation: Alarms should be activated when the vapor concentration reaches 30% of the Lower Flammable Limit (LFL) in air.
- Monitoring Intervals: Gas detection equipment should monitor from each sampling head location sequentially at intervals not exceeding 30 minutes.
Ventilation Requirements
- Minimum Ventilation: 1 cfm/ft² (20 m³/h·m²) to prevent accumulation of flammable gases.
- Recommended Ventilation: 2 cfm/ft² (40 m³/h·m²) or 12 air changes per hour, with half the air supplied and exhausted near the ceiling and half near the floor.
Safety Measures
- Gas Detectors: Should be constructed to a Zone 1 standard and set to operate at 25% of the LFL of a gas or vapor.
- Protective Devices: Linked to detection systems, including alarms, warning lights, reaction quenching systems, isolation systems, fire retardant systems, plant shutdown systems, and trip devices
No comments:
Post a Comment