CTX_MATE The CTX Loading, Salvage and Spill Reduction Program

CTX_MATE Specifications

It is not well known even by experienced tanker operators that it is often possible to reduce spillage by a factor of three or more, by simply listing and trimming the ship properly, provided the crew react promptly and correctly to the specific loading and damage situation they face, For both operation and design purposes, the tanker industry (and the CTX) requires a software package that has the following capabilities.
  1. A program that does all standard tanker loading and longitudinal strength calculations based on shear force and bending moment allowables but whose accuracy is not limited to small trim and heel situations. It must work directly from hull and tank offsets (direct integration) rather than relying on pre-computed tank tables. It must be able to handle arbitrary hull forms and tank shapes.
  2. It must automatically fill out standard tanker cargo survey reports.
  3. A program that checks intact stability for any loading pattern, computing both port and starboard righting arm curves and checks compliance with the IMO Code on Intact Stability A749. It should also display flooding limits. It should calculate the roll radius of gyration. Double hull tankers roll like pigs, especially in ballast. The main cause of this is the high roll radius of gyration. The program should gives the crew the information they need to minimize this quantity. The program should also compute the pitch radius of gyration which can be useful input to vessel motions studies, SBM mooring analyses and the like.
  4. The program should check compliance with IMO Regulation 25 on subdivision and stability. It should also check stability and flooding for the raking damage mandated by IMO Reg 13F.
  5. The program must also serve as a salvage program. Given the location and extent of damage, it should compute changes in the location (and amount for damaged tanks) of liquid in the tanks and damaged compartments. Free surface effects should be computed by direct integration, not from estimates of waterplane inertia. These estimates can be grossly wrong in many tanker damage situations. In the case of the unusually shaped ballast tanks in double hull tankers, they can be grossly wrong without any damage.
  6. Damage and spill analysis must be an extension of the normal use of the program. so there is no need to change to an unfamiliar, at best incompletely tested program in the middle of a crisis. There can be no delay prone, error prone communication and data translation problems associated with using a totally different data format on a computer thousands of miles from the scene. There can be no real difference between intact and damaged calculations. The crew merely indicates which tanks are damaged and where and program then computes strength, righting arms, etc accounting for any flooding and/or run off.

    And the crew will be familiar with it. Turning to a program the crew doesn't know and have rarely if ever used in the middle of a crisis simply won't work. Since CTX_MATE is an everyday tool, its use in a damaged situation is merely an extension rather than a whole new ball game at a time when the ship cannot afford to fight thru all sorts of learning and teething problems.

    Hydrostatic balance must be integrated into the code and, for any given loading pattern and damage pattern, the program must compute the equilibrium oil outflow from each damaged tanks based on the vertical extent of the damage. The results must be automatically reflected in draft, trim and list, damaged stability, and strength calculations. Ullage space over/under-pressure must be accounted for. The program must compute and display both hydrostatic loss and exchange loss. This capability can serve as a ship specific, hydrostatic balance trainer through which crews adn others can study a variety of potential damage scenarios and the outflow which result from alternative response strategies. Without such training, effective use of hydrostatic balance in a real spill is unlikely. With such training, the amount of spillage can often be reduced by a factor of three or more, and in some cases eliminated, by simply trimming and heeling the ship properly.

  7. In a stranding, the program must be able to compute at least the grounding reaction force and centers. All other calculations, including oil outflows, must be available when stranded. The relationship between stranding and spillage can be crucial. For a given damage, oil spillage will generally be much larger in grounded situations than in ungrounded, especially if the tide is dropping.
  8. The program must work from the tank offsets directly rather than from Tank Tables, so that it can be used as a tanker design tool testing the impact of different tank arrangements, and different bulkhead locations on strength, stability, and spillage in a given damage scenario.
  9. The program must understand the difference between tank gauging systems that work in ship coordinates (radar, floats, etc) and systems that work in earth coordinates(surveyor tapes, UTI, pressure, etc). In the latter category, it must understand the difference between systems that operate from a fixed point near the deck (surveyor tapes) and systems that operate from a fixed point near the bottom (most pressure sensing). It must also correctly handles arbitrarily (within reason) shaped sounding pipes.
  10. The program must be able to operate both in an easily used graphical mode and in batch mode. The former will be used on board in actual tanker operation and for training and visualization purposes. The latter will allow the program to be embedded in a larger analysis to study a wide range of designs, tank arrangements, and the like.
  11. The program will actually be a library which will include a hydrostatics capability, oil outflow capability, a computerized tank table capability, hull section modulus capability, etc. This library will form the core of the CTX tanker software on which a number of CTX projects will be based, including spill visualization.

Such a program exists. It is called CTX_Mate CTX_Mate is based on MLOAD, a proprietary program which has the above capabilities. MLOAD has been approved as a Loading Instrument by both Lloyds Register and the American Bureau of Shipping. MLOAD has over 100 ship-years use on at least 13 different ships including single hulls and double hulls. MLOAD has also received extensive use in the non-interactive mode by MKIT, the Martingale Tanker Design Package. This code base has been donated to the Center for Tankship Excellence (CTX). The CTX has cleaned up the code, improved the visualization capabilities and renamed the program CTX Mate. The CTX has distibuted this package under the Gnu Public Licence, that is, open source, freely available to any one to use as they wish; but, if a recipient makes any modification or extensions to the software, he must make the resulting code available on the same terms. The most recent version can be downloaded from here.

At least as important as the free availability is the fact that the CTX_MATE source code is open to scrutiny and improvement by all. Except for Mate, all tanker loading and salvage programs are closed source, which means nobody other than their authors really know how they work. All these programs have bugs but we are completely dependent on the owners of the program to discover and tell us about them. In some cases, the owning entity no longer even exists. This is not a good system.

Email about this project should be sent to mate@c4tx.org.