Hydrocarbon producers and transporters need to know the composition of the gases and liquids for accurate custody transfer and reliable, efficient operations. Gas chromatographs are often used to identify the composition of the fluids.
In a Petromin Pipeliner magazine article, Wireless Networks Solve Gas Chromatograph Communications Challenges, Emerson’s Greg Latch highlights how an Asian pipeline company successfully applied these technologies.
The project involved 30 receipt points and over 100 delivery points for hydrocarbons where gas quality is measured and/or custody transfer measurements are performed.
Greg described the two big challenges—achieving the low detection limits requirement for gas composition measurement and making the information available remotely.
For the low detection limits:
They needed to offset the risk of trace heavy hydrocarbons (that freeze in the liquefaction process) and/or unacceptable trace sulphur levels that would severely impact the downstream processes to improve overall plant efficiency and avoid penalties caused by no or low non-LNG products (NGLs, condensates).
Through the use of the Rosemount 700XA Gas Chromatograph, they:
…could measure the ppb [parts per billion] trace levels of heavier hydrocarbons and trace sulfur components flowing through the pipelines.
The 700XA GCs were chosen because they provided:
- Precise detection of gas composition with minimum field site exposure time in hazardous areas
- Easy maintenance through local and remote access via Ethernet
- Highly flexible and expandable communications network that can scale to customer growth
Gas chromatographs (GCs) provide a wealth of data-rich configuration and diagnostic information. To access this information, communication via Ethernet is required. Because of the distances involved between the GC shelters and the control rooms, various options were considered including fiber optics and wireless networks.
The costs and complexity of running fiber made the wireless approach a much better option. The team designed and installed a local Wi-Fi in-plant solution. The design included:
…a cellular-Ethernet network access point from the plant control room to offsite/remote clients and Emerson offices was created for future support if required. With the availability of remote access via wireless configuration, the user can troubleshoot the GC remotely.
The communications architecture involved connecting GCs located in sheds together on a switched network with Wi-Fi Ethernet access points to connect them to the plant network. Also on this network is a cellular-Ethernet modem to provide access for remote site support specialists and Emerson technical support centers.
For this pipeline company, it means that they can:
…now analyze and monitor the GC remotely, communicate to it remotely regardless of weather conditions, and troubleshoot certain common tasks as needed.
Read the full question and answer interview with Greg for more on the installation considerations and architecture drawing of the wireless solution. There is also an Analytic Expert blog post, Innovative Wireless Gas Chromatograph Solution from Emerson Improves Measurement and Reduces Costs for Pipelines in Asia Pacific that highlights the use of the GCs in more detail.