When natural gas is processed, liquids are injected to remove water vapour, carbon dioxide and hydrogen sulphide.
It is vital that these liquids are completely removed from the gas stream prior to exporting the gas for sale, yet, to date, there is no effective method to determine if liquid separators are working to their stated efficiency 100 per cent of the time.
Often operators find out about a problem too late, and liquid carry-over has caused significant damage.
If hydrocarbon liquids are allowed to enter dehydration systems, foaming can occur requiring the addition of de-foaming agents.
At the exit of the de-hydration system, liquids like glycol (MEG and TEG), crawl down the walls of the pipeline causing further problems.
If the processing plant is fitted with a refrigeration (or dew pointing) system to remove as much, high value, gas condensate as possible, glycol enters the system, causing blockages, loss of efficiency, and problems with the temperature control of the system, leading to further liquids remaining in the export gas stream.
Gas analyser systems are specifically designed to avoid and filter out liquids.
Gas contracts strictly specify the gas quality, and require there to be no liquids, with good reason – if allowed into the gas network, liquids can build up in low spots and corrode the internal pipe wall.
If breaches of the contract are proved, buyers can decide to reject the supply until the process upset is resolved or re-negotiate the price.
In some cases, a large fine from the buyer or pipeline operator will also add to costs.
In gas processing plants and refineries there are often absorber beds or catalysts that are sensitive to liquids.
There have been many instances where liquids have been allowed to carry-over into the gas stream and have damaged millions of dollars’ worth of catalyst or absorbent.
AMS Instrumentation and Calibration believes process supervisors and operations teams should have the best information possible in order to make evidence-based operational decisions.
LineVu is a camera system providing a permanent video stream of pipeline activity, available to view at any time.
LineVu provides an alarm when the following contamination is detected:
Using existing tapping points, LineVu can be installed at custody transfer points, or at the entry to, or exit from, critical gas processing systems.
Under normal dry gas conditions, the system will see no movement (even though the gas may be moving at around 50 km/hour).
In the event of contamination, image processing delivers an alarm.
This offers a significant step forward in process assurance for critical applications.
LineVu is a very powerful tool to improve efficiency in gas processing and provide evidence of events where tariff agreements have been broken and justification is needed to support a decision to temporarily stop supply, or support a compensation claim from the gas supplier.
Greater process confidence is gained when operators can see events in high pressure systems.
With LineVu, a live video feed of pipeline activity is available at any time via a standard web browser.
An alarm (volt-free relay) is raised when contamination is detected, and LineVu automatically starts recording data at that point.
It continues to record until no further contamination is detected.
Time, date and location are burnt onto the video image so that, during event play-back, all relevant process data is played-back alongside the video, providing a complete picture of the event to aid fault diagnosis.
The user interface allows process data such as gas flow-rate, line pressure, position of critical valves, and other relevant details to be displayed and recorded alongside the video.
A new way of thinking
After safety considerations, ease of installation and commissioning are of great importance.
LineVu does not require sections of pipe to be removed, or pits to be dug.
It is mounted above the pipeline, using existing 2 or 3 inch (50 or 76 mm) tapping points wherever possible, behind an isolation valve.
This stand-off from the main pipeline avoids contamination of the optical windows.
With a maximum working pressure of 200 Bar, LineVu is compatible with the majority of pipeline networks and gas processing plants.
Still shots may be taken for entry into reports or sent via SMS texts to interested parties.
Time-lapse and real time video may be uploaded for remote access, and for service engineers or customers to view to improve response to an event.
Safety and benefits
Safety is a key feature and LineVu is permanently installed on a pipeline or high-pressure vessel.
Independent LOPA and FMEA studies confirm that the secondary containment system provides sufficient levels of safety for pipeline network installation.
Buyers, suppliers and asset integrity managers can all see a range of benefits from this equipment.
At custody transfer points, buyers can make better decisions, and with firm evidence they can decide the acceptability of the supply, make substantial corrections to flow meter readings for wet gas and the reduction of pipeline diameter by solid contamination.
At gas export points, suppliers can reduce downtime and with better information they can quickly determine the severity of the process failure, improve operational decisions, lower risk of financial penalties and provide proof of dry gas.
With LineVu in place, asset integrity managers can both lower the risk of hydrate blockages and decrease the requirement for pigging.
LineVu is available in Australia through AMS.
For more information visit the AMS website.
This article was featured in the May 2021 edition of The Australian Pipeliner. To view the magazine on your PC, Mac, tablet or mobile device, click here.