Within the oil and gas industry, hydrocarbon liquids such as crude oil, condensates, and oil and water mixtures must be sampled to yield representative samples for analysis. The resulting data is used for quality control, to determine product properties and composition, and for fiscal calculations, allocations and loss control.

In addition to complying with custody transfer standards such as API 8.2 and ASTM D 4177, the advantages of representative sampling include:

•  Higher return on investment
•  Better loss control
•  Lower operating costs

The Importance of Hydrocarbon Liquid Sampler Performance

The best hydrocarbon liquid sampling solutions provide consistent performance over a wide range of applications and conditions. Some samplers use simple linear motion with limited mechanical advantage, but the best samplers use a scotch yoke mechanism to create linear movement – similar to a car engine. This mechanism maintains consistent, complete sampler cycles, particularly at higher process pipeline pressures.

To meet the demanding and rugged environments of oil and gas production, hydrocarbon liquid samplers should be able to handle nearly any temperature or environmental conditions, offering electrical actuation choices for applications where there is no available air supply line, and pneumatic actuation choice.

Representative sampling solutions are ideal for: 

•  Custody transfer of crude oil and condensate
•  Upstream production, trading, transport, and refining of crude oil and condensate
•  Chemical and petrochemical applications

A refinery plant in Jakarta, Indonesia needed to take a representative sample during its flow process. The refinery did not have compliant sampling equipment installed in their location and was relying on manual sampling.

Optimizing Sampling Accuracy & Repeatability

The solution required was a crude oil sampling system, which consisted of a Sentry® ISOLOK® API (anvil piston instrument)–PE (in situ probe, electrically actuated) automatic sampler, a static mixer for mixing the sample, a crude oil sampler (COS) controller diverter valve, and a lab mixing skid.

The static mixer is placed into the process line close to the sample extraction point to ensure oil, water and any other products in the process line are incorporated for a representative sample. The mixer operates by incorporating the process line mixture through a series of baffles over a six-foot length of pipe. The sampler then takes a sample of 1 cc each – the industry standard – 20 times per minute and pumps it to the receiver station. The sample then is pumped to the diverter valve inside the receiver station. The diverter valve is controlled by the PLC (programmable logic controller) in the COS sampler controller, which automates the sampling and determines where the sample is deposited. The receivers are set on scales, which are wired to the COS controller. The weight of the receivers is used to calculate the amount of sample in the containers.

For this project, the diverter valve switched receivers when the sampling containers were 80 percent full. Once the receiver was full, it was taken to the lab and attached to the mixing skid. The mixing skid then circulated the sample for 5 to 10 minutes to incorporate all the liquid properties that had settled while the sampling process was occurring. The sample process time to fill a receiver by volume on this project was approximately 15 hours.

By implementing the crude oil sampling system with an automatic sampler, static mixer, COS controller diverter valve, and lab mixing skid, this refinery implemented best practices in hydrocarbon liquid sampling to ensure its samples were truly representative for analysis, so it could be confident in its data. The refinery had compliant, automated sampling equipment instead of relying on manual sampling. Their new sampling solution helped improve safety, product quality and operational efficiency.

The Sentry ISOLOK API sampling suite offers four distinct solutions to optimize sampling accuracy and repeatability for hydrocarbon liquids such as crude oil, condensates, and oil and water mixtures. All are designed for superior performance and a long life, and all provide a consistent fixed volume, employ a scotch yoke design, and feature next generation seal design in a cartridge format for longer life, easier replacement at less cost to maintain than other solutions.