Digital tank gauging benefits revealed 1

PSM Instrumentation’s Mark Jones explains how the latest digital tank gauging technology can improve onboard safety and efficiency on tugs and offshore vessels

As the range of tasks carried out by offshore support vessels (OSVs) and tugs continues to increase, so do the requirements for safety and efficiency. Increasingly sophisticated design has seen the role of tugs and OSVs expand. It now includes towing, assisting offshore lifting operations, rig moves and the relocation of mobile production units, as well as inspection, maintenance and repair for the offshore energy and subsea sectors.

Designed to meet the high specification demands of modern vessels, digital tank gauging solutions are flexible and highly accurate, offering continuous measurement and a centralised display in real-time. For smaller vessel operators and owners, however, the initial cost has been a deterrent to upgrading.

Optimised for vessels with up to 30 tank measuring points, the new VPM4310 system provides a viable alternative for operators and owners looking to upgrade existing mechanical and visual monitoring systems for smaller vessels. Offering access to the same level of technology at a reduced cost compared to more complex radar-based inventory systems or transmitters connected to a programmable logic controller running custom software.

Major benefits of digital tank gauging include:

• Measuring a range of fluids
• Integrated systems with real-time measurements
• Multiple parameter measurements
• Clear display of alarms
• Reduced cabling and simple installation
• Intrinsically safe for harsh marine environments
• Minimal maintenance
• Capable of rapid upgrade
   

Integrated architecture

Modern tank gauging systems are designed to be flexible, providing measurements for a range of fluid types. Tank levels are measured electronically by hydrostatic level transmitters with submersible construction. All transmitters are inter-connected via a multi-drop serial communication network constructed with purpose designed termination modules to a display which provides real-time readings.

The display provides operators with an immediate view of all tank measurements in both bar graph and numeric format, showing level, volume and temperature. Alarm states are also clearly displayed, allowing prompt action to be taken as required.

Having all system components interconnected on a single network significantly reduces cabling needs and simplifies installation. Additional display points and connection to the vessel’s central management system can easily be added if required.

Where transmitters will be installed in hazardous areas which are subject to intrinsic safety requirements, this is accommodated by the addition of a safety barrier between the display and transmitter network.

All-weather operation and rapid installation

The rugged design of the monitors ensures reliable operation in harsh marine environments, while the termination modules which partner the hydrostatic transmitters are typically housed in aluminium for below-deck mounting or steel for above-deck mounting to ensure system protection and operating reliability.

In developing this solution, a key objective has been to simplify installation, enabling fitting to be carried out by local engineers without the need for specialist support. Systems are supplied pre-configured to suit the requirements of individual vessel applications, based on the number and size of tanks to be measured. The connection modules require just one four-wire cable to distribute power and communications.

This combination of speed and flexibility, together with the potential for customisation is an attractive option for retrofits and conversions, while enabling new vessels to be fitted out at short notice to meet changing operational demands.

The benefits of the latest digital tank gauging systems includes minimal maintenance, while the systems are upgradable to accommodate expanding needs and other instrumentation can be integrated into the measurement loop for maximum interoperability.

The low construction cost of the VPM4310 system paves the way for an uptake in digital tank gauging solutions by smaller vessels, raising the benchmark for performance while delivering improved efficiency and safety.

Iceland harbour tug upgraded

The Vestmannaeyjar Harbour Co, which provides port services for the Westman Islands off the south coast of Iceland, has upgraded tank gauges on a tug. The existing tank system on the harbour tugboat Lodsinn was proving unreliable with ever-increasing maintenance costs.

The VPM 4310 offered a replacement solution at a reduced cost. As the components were supplied already configured to suit the application, only local cabling was required by the onsite engineering team, with no need for additional specialist support. 

Mark Jones is a sales director at PSM Instrumentation