Boiler Drum Level Control Loop
This diagram represents a single-element boiler drum level loop. Feedwater enters through V-101, while steam leaves the boiler outlet. LT-101 senses level in the boiler and transmits that value to LIC-101. The controller changes the diaphragm-operated feedwater valve to restore the target level. The fail-closed valve position is shown as part of the control design and should be reviewed against the plant safety philosophy. Single-element level control suits relatively steady loads and is a useful drawing for teaching the relationship between measurement, control, and the final element. A detailed boiler P&ID would also include shutdown trips, feed pumps, blowdown, safety valves, and additional instruments.
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Scenario
A boiler operator needs a clear single-element drum level control loop.
Key decisions
- Measured variable: Sense water level in the boiler drum.
- Manipulated variable: Adjust feedwater flow with V-101.
- Safe position: Close the feedwater valve on actuator failure.
- Signal path: Send level electrically to the controller and valve output pneumatically.
When to reuse this
Use this simplified loop for a basic boiler feedwater concept; larger boilers may require three-element control.
Frequently asked questions
What is single-element drum control?
What does LIC-101 do?
When is more control needed?
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