PO Quality Control & Sampling 2 — Questions and Answers
Question 1: What is the purpose of a calibration check on a field analyzer before taking a reading?
- To reset the analyzer clock
- To confirm the analyzer is reading accurately against a known reference (Correct answer)
- To download data to the DCS
- To satisfy permit-to-work requirements
Correct answer: To confirm the analyzer is reading accurately against a known reference
Calibration checks verify that the instrument reads correctly by comparing its output against a certified reference standard.
Question 2: In statistical process control, what does a 'run of 7 points' above the mean on a control chart indicate?
- Normal random variation
- A possible process shift or assignable cause that should be investigated (Correct answer)
- The process is perfectly stable
- Instrument drift only
Correct answer: A possible process shift or assignable cause that should be investigated
Seven consecutive points on one side of the mean is a non-random pattern that signals a likely process shift requiring investigation.
Question 3: A gas chromatograph (GC) is used in a refinery primarily to:
- Measure pH of liquid streams
- Separate and identify chemical components of a gas mixture by composition (Correct answer)
- Monitor pressure drop across columns
- Detect radiation levels
Correct answer: Separate and identify chemical components of a gas mixture by composition
A GC separates gas mixture components and quantifies their concentrations, providing detailed compositional analysis for process control and product quality.
Question 4: What is the primary difference between a 'grab sample' and an 'automatic inline analyzer'?
- Grab samples are more accurate than inline analyzers
- Grab samples are taken manually at a point in time; inline analyzers provide continuous real-time data (Correct answer)
- Inline analyzers require more PPE to operate
- Grab samples measure more parameters simultaneously
Correct answer: Grab samples are taken manually at a point in time; inline analyzers provide continuous real-time data
Grab samples capture a snapshot at one moment while inline analyzers continuously monitor and provide real-time data to operators and the DCS.
Question 5: Why must sample cylinders for flammable gas be pressure-tested before use?
- To verify volume capacity is accurate
- To ensure the cylinder can safely contain the sample pressure without leaking or failing (Correct answer)
- To remove moisture from the cylinder
- To meet laboratory accreditation requirements only
Correct answer: To ensure the cylinder can safely contain the sample pressure without leaking or failing
Pressure testing confirms that sample cylinders are free of defects and can safely hold the pressurized sample, preventing hazardous leaks.
Question 6: What does 'Reid Vapor Pressure' (RVP) measure and why is it important for gasoline blending?
- The density of a fuel blend at 60°F
- The vapor pressure of a liquid fuel at 100°F, which affects evaporative emissions and volatility (Correct answer)
- The flash point of a gasoline product
- The octane rating of a blended fuel
Correct answer: The vapor pressure of a liquid fuel at 100°F, which affects evaporative emissions and volatility
RVP measures how readily a fuel evaporates; controlling it is critical for meeting seasonal EPA volatility regulations and preventing vapor lock.
PO Quality Control & Sampling 2
What is the purpose of a calibration check on a field analyzer before taking a reading?