Keeping it simple

Sep 02 2014

The past few decades have seen many technical advances in marine tank gauging technology aimed at delivering greater efficiency and safety.

Solutions range from single transmitters to more complex radarbased measurement systems, which can require a substantial outlay upfront. When it comes to cargo measurement - however, it is possible to take a simpler approach and still meet critical needs, claimed Mark Jones of PSM.

As marine specialists, PSM works with ship designers, owners and operators, maintenance and repair companies to deliver the best possible technical solution to specific tank level measurement needs using the latest instrumentation, software and communications technologies.

Modern tank gauging systems are designed to be flexible, capable of handling a range of fluid types from fuel oil and lubricants to hydraulic fluid and bilge, or ballast water and applications – to include both process control and inventory management.

Specialists such as PSM have been influential in moving the industry away from historical methods, such as bubbler systems that are inaccurate with low reliability and high maintenance costs.

Suppliers have developed a range of alternatives to manage individual aspects of inventory management from custody transfer to leak control and reconciliation. These modern systems use the latest instrumentation, software and communications technologies to deliver the high degree of reliability and accuracy required.

The complexity of the system required will depend on the specific process involved. Where custody transfers are involved, there may be specific legal certification requirements that need to be met and installed systems will require official approval as being fit for purpose.

Absolute accuracy is also paramount in the correct assessment of taxes, duties or royalties for fiscal billing purposes.

Many of the systems currently available for marine tank gauging focus on this higher end of the market, with specifications typically including complex combinations of radar level transmitters, temperature profiling probes and advanced calculation software.

As specialists with over 30 years’ of global marine experience, PSM became aware of a need in the marketplace for a simplified system to handle general inventory control requirements, which while capable of delivering a high degree of accuracy and reliability to enable the recording of cargo movements, was simpler to operate and cheaper to install.

Once such installation was a major shipyard in Turkey, which turned to PSM for assistance in sourcing a simplified option for its newbuild 600 dwt lubeoil barge. PSM designed and specified a system based on its TankView measurement and display software in conjunction with ICT 1000 hydrostatic level transmitters to deliver the required degree of accuracy, while reducing the initial cost of supply and installation.

The ICT 1000 is a smart liquid level transmitter, programmable for measurement range, functionality and diagnostics via RS-485 modem and supplied software configuration tool. Manufactured from 316 stainless steel to withstand the toughest operating conditions, it is fully supported and protected against overload and shock pressure conditions.

The ICT 1000 transmitters were fitted to 12 tanks. These were connected to the display and control unit using PSM RFM connection modules to form a Modbus communication loop. This digital architecture provided 0.1% measurement accuracy while at the same time reducing cable and installation complexity.

These factors were important drivers in reducing overall installation and commissioning costs, as well as ensuring build deadlines were met.

One level and one temperature transmitter were installed per tank, plus two additional level transmitters for heel and trim measurement to correct the tank level measurement for vessel orientation and draught.

A Windows PC running the PSM TankView software package provided the display and control unit. This was factory configured prior to installation to suit the specific application by defining the geometry of the tanks as well as the density/temperature characteristics of the products via API tables.

Each cargo type is available to the crew in a library of product choices, providing inventory readings in temperature corrected volume and mass units.

In additional, low and high level alarm points were designated for each tank within the system which also provides historical records of cargo level movement using its integral data logging ability.

The availability of a simplified solution that is easy to install, whether newbuild, or during retrofitting, should see a significant increase in the number of shipbuilders and operators opting to move up from more basic systems of measurement to a more technologically-driven  approach driving up the benchmark for systems performance and helping to improve profitability and visibility.

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