Annunciator Panel- Purpose, Working Principle, Applications

Annunciator Panel has a grouping of annunciator lights that indicates the status of the system or equipment. It is used in process industries, buildings and other installations.

What is an Annunciator Panel?

The term annunciator panel refers to a set of warning or advisory indicators in the control room. This indicator alerts operators to one of many significant problems with operation progress-most annunciator panel layouts group warning indicators by the systems they serve. Some warning indicators require resetting when activated; others simply light up for a short time and some require a specific action before automatically resetting. New panels are equipped with digital indicators instead of traditional incandescent lamps.

The annunciator panel is also often referred to as a “light panel” and is used to draw the plant operator’s attention to a variety of process and even system problems. The low/high alarm conditions will generally be grouped into advice, caution, and warning categories each with its course of action. 

Alarm annunciators operate independently, available with 2, 4, 6, 8, 12, 16, 24, 32, and 48 inputs. In general, however, the annunciator panel is usually located in the centre of the control room, or it may be located near the location of the machinery, known as the local annunciation panel. They also often feature audible warnings to accompany the visual indicators.

Typical annunciator warnings in the process industry usually include tank high level, high line pressure, under pressures, high process temperature, and compressor trip. Also, electrical and hydraulic system alerts, provide early warning to operators of potentially hazardous system development that, require operator intervention.

annunciator panel

All indications on the announcement panel are critical including fire and system failures that require immediate action.

Purpose of Annunciator

Annunciators are discrete devices that are centralized to provide visual and audible alarms in the event of abnormal conditions or malfunctions in the process plant, machinery, or systems. Using these panels, the operator can identify which systems or equipment has malfunctioned by displaying warning lights accompanied by labels of process abnormalities.

The purpose of the blinking lights along the hooter sound is to draw the operator’s attention to the annunciator panel. It provides a reliable indication of the faulty system so that the operator can take appropriate action.

Annunciators play an important role in safety systems.

Working Principle

A change of input contacts of field instruments from Normally Open (NO) to close or from Normally Close (NC) to open causes the annunciator to change from rest to alarm mode. Hardwiring from the filed instruments to the annunciator panel provides NC/NO contact status change due to process abnormalities.

Various push buttons on the Annunciator panel

The annunciator panel must have three push buttons ACK, RESET, and TEST. Some panels include a “MUTE” push button also. The panel annunciator must be able to identify alarms as faults or emergencies.

Acknowledge-push button is used to accept the fault conditions. It silences the alarm, but the alarm condition persists till the process becomes healthy.

Reset- once the alarm condition becomes normal; upon pressing the reset button the window becomes normal.

Test– by pressing the test push button the healthy status of hardware that includes bulbs, hooters, or buzzers can be checked.

Components of an Annunciator Panel

Components of an Annunciator Panel

Annunciator window colour status

An audible tone will accompany most warnings. Warnings can be red, yellow, green, white or blue.

Colour: Red
Type: Danger
Meaning: A critical situation that requires immediate attention by the operator.

Colour: Yellow or Orange
Type: Warning
Meaning: Not critical but it should be resolved as soon as possible.

Colour: Green
Type: advisory
Meaning: Plant status is healthy and ready for operation.

Colour: Blue
Type: information
Meaning: Notice of a non-critical abnormal situation that shows not require operator intervention (e.g. blocked valve).

Colour: White
Type: Status
Meaning: Status of a particular system state, such as “Gas compressor ramp RPM”. (Sequence of operation is in progress).

Applications of Annunciator Panel

Plant Process Control

In the workplace (in chemical, plastic, pulp & paper, Oil & Gas, etc,) industrial annunciators are used to generate a warning light and sound when unsafe conditions exist.

Sensors and indicators are used in industrial annunciators to indicate various process stages. If the process deviates, the industrial annunciator generates a warning light. Using the indicators, operators can be alerted to unsafe factory operations. Industrial annunciators can be classified according to their alarm light colour, which includes amber blue, green and red.

An annunciator panel alerts operators to alarm conditions in industrial processes. An engraved name of each process alarm appears on each of the backlit windows. A hard-wired switch controls the lamps in each window, which turn “ON” when a process condition enters an abnormal state (such as high temperature, low pressure, loss of cooling water flow, or many others).

The purpose of this is to draw the operator’s attention to an alarm condition. When the process is in an alarm state, the window will remain lit until the alarm is silent. The window lamps go out when the alarm is cleared (the process returns to normal).

Fire alarm annunciator in the plant or buildings

There is usually a central fire alarm annunciator panel in large buildings where fighters can reach it quickly. Fire alarms are indicated on the annunciator panel by the zone and approximate physical location.

The alarm annunciator includes an audible hooter or a buzzers-like warning device to indicate alarm circuit failures. An annunciator for a fire alarm may also be connected to a control panel for heat ventilation and air-conditioning (HVAC) systems in large buildings.

The other applications of the annunciator panel are as follows.

  • Power generation plants
  • Electrical substations
  • Water treatment
  • Fire alarm control panels in the plant/buildings
  • Nuclear plants
  • Aviation industry
  • Marine vessels
  • Aerospace

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