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25 Cards in this Set
- Front
- Back
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What are the 5 process variables?
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Pressure, Temperature, Level, Flow, and Material Composition.
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An indication of the amount of heat energy present. |
Temperature
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The force per unit of area
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Pressure
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The movement of fluid or gas from one point to another.
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Flow
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An indication of the volume of a material present at different points in a process.
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Level |
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The relative amounts of the components in a mixture.
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Composition
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What is the difference between indicators and controllers?
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Indicators provide information without changing the process. A controller has the same components as an indicator with the ability to compare the measured variable to a set point. |
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Give an example of a case when an indicator is the cause for a process upset. |
Except in cases of automatic shutdown, indicators do not cause process problems. |
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List the information that a controller provides in a troubleshooting situation. |
The measured variable indication and the controller output. |
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List the components of a flow control loop that can malfunction and be the cause for a process upset.
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The process, the sensing device, the controller (FIC 1), and the mechanical device (control valve CV 1)
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List the Troubleshooting Tools. |
Material balance Energy balance Interrelationship of Variables What is expected Time factor Process knowledge Knowledge of heat transfer principles |
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Explain: What goes in must come out, or an unstable condition must exist. |
Material balance
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Explain: Most processes require constant temperature for proper operation.
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Energy Balance
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Explain: Cause and effect. In a dynamic system, a change in a variable is normally seen in other variables. |
Interrelationship of Variables
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Explain: Usually, common sense and the laws of nature tell us what to expect next in a sequence of events.
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What is Expected
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Explain: Over what period of time has a change occurred?
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Time Factor
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Explain: The ability to solve complex process problems is very dependent on, and can be limited by, the amount that is known about the process.
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Process Knowledge
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Explain: Effective use and control of heat energy is critical in controlling a process.
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Heat Transfer
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List the six troubleshooting steps.
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Collect Data Evaluate Data Make a Judgment Develop a Possible Cause List Verify the most Probable Cause Plan and Execute Corrective Action |
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Every process variable should be considered when assessing the condition of the process.
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Data Collection
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The comparison of data to normal process conditions to determine what data is normal and what data is abnormal. Followed by the testing of these data points against others to verify or validate the data.
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Evaluation
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The evaluation should lead us to a decision. Is there a problem or not? The answer is based on the data and knowledge of the process we are dealing with.
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Judgement
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What could cause the symptoms that are present in the data?
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Develop a Possible Cause List
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Walk each possible cause through the symptoms, using the tools presented in this chapter, eliminating the causes that do not fit.
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Verify the Most Probable Cause
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When the inlet flow is stable, and level is stable, but the outlet flow is at 10% of scale, what is the most probable cause of this set of circumstances? |
A faulty outlet flow indicator. |
