The purpose of the drum level controller is to bring the drum up to level at boiler start-up and maintain the level at constant steam load. A dramatic decrease in this level at constant steam load. A dramatic decrease in this level may uncover boiler tubes, allowing them to become overheated and damaged. An increase in this level may interfere with the process of separating moisture from steam within the drum, thus reducing boiler efficiency and carrying moisture into the process or turbine. Boiler drum level control is critical for both plant protection and equipment safety and applies equally to high and low levels of water within the boiler drum. The functions of this control: 1. Operator adjustment of the setpoint for drum level 2. Compensation for the shrink & swell effects 3. Automatic control of drum level 4. Manual control of the feedwater valve 5. Bump-less transfer between auto and manual modes 6. Indication of drum level and steam flow 7. Indication of feedwater valve position and feedwater flow 8. Absolute/deviation alarms for drum level.

Related Terms

DEAD TIME

  1. The time interval between a change in the input signal to a process control system and the response to the signal.
  2. The time interval, after a response to one signal or event, during which a system is unable to respond to another. Also known as insensitive time.

AMPLIFICATION

  1. An increase in signal magnitude from one point to another, or the process causing this increase.
  2. Of a transducer, the scalar ratio of the signal output to the signal input

POLYFORMING

A noncatalytic, petroleum-refinery process charging C3 and C4 gases with naphtha or gas oil at high temperature to produce high-quality gasoline and fuel oil; mostly replaced by catalytic reforming; the prodTesting and Materials analysis of paraffins (P), olefins (O), naphthenes (N), and aromatics (A) in gasolines.

PNEUMATIC TEST

Pressure testing of a process vessel by the use of air pressure.

PLUGGING

1. Braking an electric motor by reversing its connections, so it tends to turn in the opposite direction; the circuit is opened automatically when the motor stops, so the motor does not actually reverse. 2. The formation of a barrier (plug) of solid material in a process flow system, such as a pipe or reactor.

PINCH-TUBE PROCESS

A plastics blowmolding process in which the extruder drops a tube between mold halves, and the tube is pinched off when the mold closes.

PHOTOELECTRIC LIQUID-LEVEL INDICATOR

A level indicator in which rising liquid interrupts the light beam of a photoelectric control system; used in a tank or process vessel.

PHOTOFABRICATION

In manufacturing circuit boards and integrated circuits, a process in which the etching pattern is placed over the circuit board or semiconductor material, the board or chip is placed in a special solution, and the assembly is exposed to light.

PHOSPHORIC ACID POLYMERIZATION

A petroleum-refinery process using phosphoric acid catalyst to convert propylene, butylene, or both, into high-octane gasoline or petrochemical polymers.

PHENOL PROCESS

A single-solvent petroleum-refining process in which phenol is the selective solvent.

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