KR Webzine Vol.125

1. BACKGROUND

LNGC (Liquefied Natural Gas Carriers) are very dangerous because they transport reduced-volume LNG at very low temperatures. The IGC Code (The International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk) sets out the international standards for the safety of LNGC. This basically sets the filling limits of the LNGC tanks to 98%, but there may be a corresponding upward filling limit with the approval of the classification society or the relevant flag, if additional safety factors are considered.

Ship owners and shippers are increasingly applying the upward filling limit because it is possible to make a higher profit by carrying as much quantity as possible at one time. The classification society is therefore required to verify and approve the upward filling limit.

The upward filling limit verification must consider several parameters such as safety valve placement, accuracy of level and temperature measurement, and shipping temperature. Accurate verification is very difficult since it must calculate the LNG volume corresponding to a scenario when the suction port of the safety valve is submerged in LNG and to a scenario when isolated vapor pockets occur under the condition of transverse slope and longitudinal slope, as given in the IGC code.

As a result, KR has therefore developed the SeaTrust-FillingLimits S / W, which supports the filling limit calculation based on the 2018 IGC Code, helps with the process of verification and aids convenience with additional auxiliary functions.

2. KEY FEATURES

 
· Calculates the LNG filling limits and loading limits based on a 3D model
· Offers appropriate data for various shapes (including a membrane/cylinderical tank,

  parallel/tappering type, hexaheron/cylinderical dome, vertical/horizontal PRV)
· Suitable for various tank layouts (lateral and rotational layout)

· Supports calculations for transverse slope and longitudinal slope conditions, simultaneously

  calculating data for multiple tankers
· Provides Result Table (filling limits result, value of middle step, result table by height /

  volume)
· Includes 3D viewer (geometry model and dimension; full and partial result models)
· Gives filling limits volumetric contour graph viewer according to transverse slope and

  longitudinal slope range
· Generates the result report (with optional output function)

Figure 1 Support for various shapes

Figure 5 Calculation of transverse slope and longitudinal slope conditions

3. EXPECTED BENEFITS

 
· Supports calculations for filling limits of tank such as KC-1, NO96, MARK lll
· Checks loading limit according to loading temperature when loading LNG

· Analyze and approves upward filling limits verification through automatically generated result

  report
· Design modifications using preliminary prediction of filling limits can be incorporated at design

  stage
· Intuitive understanding of tanks and LNG 3D visualization shapes for each situation

· Trend analysis of LNG volumes of transverse slope and longitudinal slope range