For petroleum vapours in air, sketch and describe an explosimeter, state one cause of false reading, and explain lower and upper flammable limits?
Short answer
- Instrument: Portable explosimeter (combustible gas detector)
- Measurement: Fraction of lower flammable limit in air
- Operation: Oxidation on heated filaments changes electrical resistance
- Requirement: Normal-oxygen atmosphere for catalytic sensor
- Entry criteria: ≤1% LFL and 21% O₂
- Testing condition: Ventilation to enclosed space stopped
- False reading cause: Oxygen-deficient atmosphere
- LFL: Minimum concentration for ignition and flame propagation
- UFL: Maximum concentration for ignition and flame propagation
- ETO check: Calibrated instrument, record readings, confirm entry criteria
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the ETO section of the Marine One forum, open to members enrolled for the ETO exam.