Analytical Instrumentation

  • Water in LPG and how to accurately measure it according to ASTM D7995

Water in LPG and how to accurately measure it according to ASTM D7995

Jan 19 2021

The problems of water in LPG

Water has a detrimental effect on the many uses of liquified petroleum gas causing operational problems in customer equipment and downstream processes. Water causes corrosion and creates safety hazards during the storage, distribution and use of liquified petroleum gas (LPG) and pressurised low molecular weight hydrocarbons and their mixtures.

Previously the dryness of propane has been monitored with a “functional” test such as the freeze valve test method ASTM D2713 which demonstrates that excessive water content (dissolved water) will cause freeze-up difficulties in pressure reducing systems. This method is limited to propane only.  Recent advances have been made in adapting coulometric Karl Fischer to analyse problematic samples such as LPG and LNG.  Coulometric Karl Fischer offers greater sensitivity and analyses both free and dissolved water i.e. total amount of water present.

What to expect from an LPG sample when using Karl Fischer titration 

Interfering compounds such as Mercaptans and H2S affect the accuracy of results when using coulometric Karl Fisher whilst the use of an electronic mass flow controller (for determining the gas flow) requires calibrating when changing gas types.

Both mercaptans and the use of the mass flow controller made using coulometric Karl Fischer very difficult and unable to determine low ppm levels of water.  

That was until the ECH Advantage was developed according to the new ASTM D7995 method.

Using the unique fixed sample loop principle found in the fully automated “Aquamax KF LPG Pro”.

Short analysis time, high sample throughput and removal of interferences    

The Aquamax KF pro sample loop can analyse all LPG and gas mixtures without having the problem of manually preparing a mass flow controller.  The instrument does not require additional rinsing gases, only the actual sample is passed through the measuring cell.

This allows 250 measurements within 48 hours without the need to replenish or switch any solvents which leads to considerable saving in terms of solvent and operator time.

Removal of the sulphur from the procedure means that no interference calculation is required. This eliminates any potential operation error in calculating the true result.  Aquamax KF LPG Pro are also be used for LNG, technical gas, DME, Gas mixtures and CNG.

In summary, Aquamax KF pro is the only coulometric Karl Fischer capable of 1ppm water in propane and butane whilst being ready to analyse water in all gas types without any changes or modifications

Book an online demo and let’s discuss your application.    

Aquamax KF are being used my many leading LPG producers and are perfectly supported by the ECH application teams. Book an online demo and application discussion with Tom Gallant or feel free to ask all questions.

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