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Method for testing pressurised crude oils for transport

Hydrocarbon Engineering,

The US Department of Transportation (DOT) has issued an Emergency Testing Order that requires all shippers to test crude oil from the Bakken region to ensure the proper identification of the crude oil before it is transported by rail.

The order is in response to a number of recent incidents involving the derailment of trains transporting crude oil from Canada to the US.

Crude oil vapour pressure

Shippers are required to comply with Hazardous Materials Regulations (HMR) that include testing of vapour pressure and flashpoint to ensure proper transportation and packing. To meet these regulations, vapour pressure specialist AMETEK Grabner Instruments offers specialised instrumentation to test crude oil vapour pressure.

Recently, the number of rail carriages transporting crude oil from Canada to the US has increased, as transport via rail can be simpler and more flexible than via pipeline. However, this increased use of rail transport has resulted in an increase in the number of accidents. The estimated cost of the damages from these accidents has surpassed US$ 1 billion, and caused significant environmental damage.

Classification of crude oils

Accident investigations have highlighted the need for more accurate classification of crude oils. Classification has often been based solely on safety data sheets, many of which are outdated. As a result of these investigations, US DOT issued several Emergency Testing Orders with the most recent amended version issued on March 6th 2014, which was addressed to shippers of petroleum crude. The order specifically requires the flashpoint and boiling point testing of crude oils and endorses the requirement that crude oil shipments follow volatility testing defined by HMR.

In HMR, the testing of crude oil vapour pressure is critical in determining the requirements for safe packing for transport. A boiling over of crude oils can result from a pressure build-up inside a rail carriage. This risk increases significantly if the crude oil includes gaseous components.

Testing samples

When testing crude oil samples, it is very important to handle the sample properly, in order to keep the light ends in the crude oil prior to vapour pressure testing. Crude oils may be misclassified if hazardous volatiles are allowed to evaporate prior to sampling. One solution is to ensure that the crude sample is pressurised when delivered to the vapour pressure tester.

AMETEK Grabner solution

AMETEK Grabner Instruments has developed a method for effectively testing pressurised crude oils under varying transport conditions. The company offers a package for the safe, airtight and pressurised transportation of crude oil to the vapour pressure tester. The crude oil with all of its light ends is captured inside a high-quality floating piston cylinder (FPC). Once this cylinder is connected to the MINIVAP VPXpert vapour pressure instrument, testing can begin immediately. This versatile analyser is able to test vapour pressures at temperatures ranging from 0 to 120°C, and to perform tests at vapour-to-liquid ratios (V/L) ranging from 0.02/1 to 4/1.

The Grabner method of measuring crude oil was standardised in 2003 as ASTM D6377 Standard. In 2013, the US Environmental Protection Agency approved ASTM D6377 as an alternative method of measuring the vapour pressure of crude oils.

Adapted from press release by Katie Woodward

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