Flare Backpressure Study for an LNG Facility Case Study

 

The Challenge

A liquified natural gas (LNG) manufacturer had four nearly identical trains with three flare header systems. The client decided they wanted to use a new and more stringent criteria than previously performed under a different design criterion. The large scope and tedious nature of the data entry was a challenge since all calculations needed to be checked to determine the maximum pressure each flare pipe line would be exposed to.

Our Approach

ioMosaic had performed years of work at the facility under a certain design criterion, flagging any backpressure value that exceeded the PSV and piping limits in the flare system. The PSV limits were obtained from the manufacturer and the piping limits were obtained from the client-provided flange/piping ratings. The client later determined that some sections of their flare were only hydrotested to 100 psig, which is considerably less than the flange/piping ratings that were previously used as design values.

ioMosaic was requested to recreate the information in their original line designation tables (LDT) with the results of all work. The data included their respective maximum pressure, maximum flow rate, temperature, pipe design pressure, etc. ioMosaic created a spreadsheet detailing each line in the flare and their relevant pressure sources. All the individual PSV, EDP and flare SuperChem™ files were looked through to determine the maximum pressure with corresponding temperature in each pressure source’s tail pipe. This was very tedious as each file had many scenarios and calculations.

Once all the data was tabulated in the spreadsheet, a summary page was provided within the file that showed the maximum pressure in each pipeline going to flare, associated scenario, and whether it exceeded the new design criteria of 100 psig. The client used the lowest pressure rating in the flare header as a flag for further investigation. For example, a few EDPs had very high (~500 psig) pressures in their laterals to the main flare header; however, any connection was done with a “golden weld” in order to have the ability to withstand a pressure higher than 100 psig.

The Benefits

ioMosaic provided a spreadsheet robust enough where any design conditions could be entered and any pipe segment that exceeded the design value would be flagged. The file flagged all pipe segments with pressures higher than their new design values. Now the client would be able to easily update the file and in the future could avoid the large cost of manually sifting through so much data. An improvement would be in the creation of a script that pulls maximum pressures for each piping segment into a SuperChems™ file.

Learn More

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