SAAB STaR High-Level & Overfill Alarm Testing

High-level and overfill alarms are critical parts of a vessel’s cargo monitoring system. However, seeing an alarm lamp illuminate does not necessarily prove that the complete protection chain is operating correctly.

Legacy SAAB TankRadar STaR installations can include several different test functions. Each test verifies a different part of the system. Understanding the distinction between automatic supervision, the SCA System Test and the TGE Gauge Test helps crews and service engineers avoid incomplete or misleading test results.

Three different levels of testing

1. Automatic system supervision

Applicable STaR high-level and overfill systems include background self-monitoring intended to identify conditions such as loss of communication or power failure.

This supervision is valuable during normal operation, but it should not be treated as a complete functional test of every alarm device and configured alarm limit. A system can remain online while an audible alarm, visual indicator or associated output still requires verification.

2. SCA System Test

The Supply and Communication Alarm panel, commonly identified as the SCA, can have a System Test function.

This test activates the panel’s visible and audible warning devices, including the relevant LEDs, buzzer, alarm horn and flashing light where fitted. Its purpose is to confirm that the alarm-annunciation equipment can operate.

The SCA System Test is therefore principally an alarm-device check. By itself, it does not demonstrate that a selected tank gauge will reach its configured alarm limit or that the complete gauge-to-alarm signal path has been tested.

3. TGE Gauge Test

Applicable high-level and overfill configurations can also provide a Gauge Test through the service interface.

During this test, the Tank Gauge Electronics simulates a changing ullage representing a rising liquid level. When the simulated value reaches the configured alarm limit, the associated alarm functions should be activated.

Depending on the installed configuration, the test may operate the SCA indication, alarm horn and alarm light. One tank and one system—high level or overfill—are selected for each test.

This provides a more complete functional demonstration than a simple lamp or horn test because it checks the response to the configured alarm limit.

What the Gauge Test verifies

When correctly prepared and performed on a compatible installation, the Gauge Test can help verify:

Selection and communication of the relevant TGE channel.
Recognition of the simulated ullage change.
Operation at the configured high-level or overfill alarm limit.
Transfer of the simulated alarm through the connected system.
Activation of the associated audible and visual alarm devices.
Alarm acknowledgement, reset and return to normal operation.

The TGE status should be checked before starting. The legacy service documentation states that the selected TGE must show an acceptable status for the test to operate.

Important operational limitations

The TGE being tested is temporarily unavailable for normal measurement during the Gauge Test. The legacy documentation also warns that simulated values may be transferred to other connected systems.

For this reason, a Gauge Test should never be started as an uncoordinated software check.

Before testing:

Obtain authorization under the vessel’s procedures.
Notify the cargo control room, bridge and other affected personnel.
Identify systems receiving data from the tested channel.
Confirm that cargo operations allow the selected gauge to be temporarily unavailable.
Review active alarms, bypasses, inhibitions and disconnected channels.
Confirm how the alarm will be acknowledged and reset.
Keep an operator ready to abort the test if the result becomes unexpected.

The installed drawings, vessel procedures and delivery-specific documentation take priority over a general legacy service manual.

A lamp test is not a complete overfill test

One of the most common mistakes is recording an SCA System Test as proof that the entire high-level or overfill function has been tested.

A successful lamp-and-horn test confirms that the annunciation devices can operate. It does not necessarily confirm the tank selection, alarm limit, gauge electronics, communication path or alarm logic.

A useful service report should state the exact test performed:

Automatic supervision reviewed.
SCA audible and visual alarm test completed.
High-level Gauge Test completed for a specified tank.
Overfill Gauge Test completed for a specified tank.
External or connected-system indication verified.
Full physical sensor or process test performed under a separate approved procedure.

This distinction makes the record clearer for the vessel, technical management and class survey attendance.

What the simulation does not prove

A successful simulated Gauge Test does not automatically verify:

The physical condition of the radar antenna or process connection.
Accuracy of the normal cargo-level measurement.
Response to an actual rising liquid surface.
Every independent sensor, switch or shutdown circuit installed on the vessel.
Mechanical condition of associated valves or cargo equipment.
Compatibility of the legacy test method with every later STaR, Emerson or Rosemount configuration.

Independent overfill protection, shutdown circuits and separate level switches must be tested according to their own approved procedures.

Recommended test record

A clear test report should include:

Vessel, tank and channel identification.
System and software version where available.
Selected high-level or overfill function.
Configured alarm limit displayed during the test.
TGE status before starting.
Start time and alarm activation time.
SCA, control-room, horn and warning-light results.
Indications received by connected systems.
Alarm acknowledgement and reset result.
Confirmation that test mode, bypasses and inhibitions were cleared.
Final channel status and normal indication.
Any exceptions requiring further troubleshooting.

Photographs of the displayed test data and alarm indications can support the report, provided vessel information and operationally sensitive data are handled correctly.

Common testing mistakes

Typical problems include:

Treating the SCA System Test as a complete gauge-chain test.
Starting a Gauge Test without notifying personnel receiving the simulated value.
Testing while the selected TGE already has an active fault.
Failing to check whether the channel is inhibited or disconnected.
Changing an alarm limit merely to make the test easier.
Leaving a bypass or service mode active after completion.
Assuming all STaR deliveries have identical hardware, software and network arrangements.
Recording “alarm tested” without identifying the tank, function and method.

Preparing for onboard support

For remote assessment or onboard attendance, provide:

Photographs of the SCA, SCC/SCD screens and gauge status.
Vessel name, port and expected cargo schedule.
List of tanks and alarm channels requiring testing.
Current alarm limits and available system drawings.
Hardware and software version information.
Details of connected alarm, monitoring or shutdown systems.
Previous test reports and outstanding defects.

Legacy-system note

This article is based partly on a sixth-edition SAAB TankRadar STaR service manual dated November 2005. The available functions and procedures can differ according to the vessel-specific delivery, installed software, system connections and later modifications.

Testing must follow the documentation applicable to the installed equipment, together with current vessel, maker, class and safety-management requirements. Reform Marine is an independent marine service company; references to manufacturers and product names identify installed equipment and do not imply OEM authorization.

SAAB TankRadar STaR High-Level and Overfill Alarm Testing