Accurate tank measurement is fundamental to safe and efficient vessel operation. At Scanjet PSM, we understand that a tank gauging system is not simply an instrument package, it is a critical safety, compliance and operational control system.
The Primary Tank Gauging System
A typical tank gauging system utilises hydrostatic level transmitters at each measurement point or tank. These sensors provide continuous, real-time level data to a central display interface.
Live tank data can be presented in both textual and graphical formats at key vessel locations such as:
- Bridge
- Engine Room (ER)
- Cargo Control Room (CCR)
Where required, the system also provides draught indication and consolidated outputs to the vessel’s Alarm & Monitoring System (AMS), ensuring consistent and reliable data across all operational platforms.
Why Two Independent Systems May Be Required
Using Fuel Oil Service Tanks as an example, these tanks supply fuel directly to engines and generators and are therefore vital to vessel propulsion and safety. In such cases, regulations and best practice often require a secondary, fully independent method of level measurement.
Common secondary arrangements of tank gauging include:
- A local level gauge or sight glass for visual verification
- Independent high- and low-level switches for alarm activation
- Manual sounding arrangements
- A self-powered contents gauge
- A second independent level transmitter
On vessels without manual sounding pipes, two transmitters per tank may be installed. Modern systems can incorporate a redundancy feature so that if one transmitter fails, the system continues to operate and display live data without interruption. This layered approach ensures operational continuity and safeguards against single-point failure.
Ensuring Accurate Tank Monitoring Across All Operations
Reliable tank measurements are critical not just for operational control, but for safety, environmental protection, stability management and regulatory compliance. Implementing robust primary and independent secondary systems ensures vessels can operate with confidence, even in challenging conditions.
Safety & Redundancy
A properly designed dual-system approach:
- Prevents reliance on a single system for critical tanks
- Ensures accurate readings even if one system fails
- Supports safe cargo transfer and bunkering operations
Pollution Prevention
Accurate tank monitoring plays a direct role in environmental compliance. Robust gauging systems:
- Reduce the risk of overfilling
- Support MARPOL compliance
- Provide early detection of abnormal tank levels
Stability & Trim Control
Reliable tank level data is essential for:
- GM (metacentric height) calculations
- Trim and list control
- Effective ballast management
Regulatory Compliance
International Rules, including SOLAS, MARPOL, the IBC Code and the IGC Code, require:
- A primary gauging system
- An independent secondary method (manual or electronic)
- Independent high-level alarms for overfill protection
Understanding Primary and Secondary Tank Gauging Systems
Effective tank management relies on a clear distinction between primary systems, which provide continuous operational monitoring, and secondary systems, which offer independent verification and safety assurance. Together, they form a comprehensive measurement strategy that safeguards operations, supports compliance, and ensures reliability even in critical situations.
| System | Purpose | Common Types | Key Characteristics |
| Primary Gauging System | Continuous operational monitoring and control | – Pressure sensors
– Radar level measurement – Float gauges |
– Automated
– Integrated with vessel monitoring displays – Provides real-time data and trend analysis |
| Secondary Gauging System (Independent) | Verification, backup, and safety assurance | – Manual sounding tape
– Ullage tape – Independent electronic sensor – Self-powered contents gauge – Dedicated high-level alarm system |
– Separate wiring, logic, and power
– Fully independent from the primary system – Confirms accuracy and detects faults |
With over 50 years’ experience across all vessel types, Scanjet PSM delivers reliable, compliant and fully supported tank gauging solutions. For tailored guidance on selecting, installing or maintaining tank gauging systems for your vessel, contact us today and ensure your operations remain safe, efficient and fully compliant.
