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High Pressure Pipeline Solids & Liquid Sampling - Thursday, January 15, 2009
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High Pressure Sample Technique Improves Understanding of Pipeline Contamination
Rapid Energy Services is one of the first pipeline service providers to use high pressure sample containers to withdraw line liquids and contaminating solids from natural gas pipelines. The traditional approach used by pipeline service providers is to withdraw a sample from the gas pipeline in a glass bottle. The glass bottle is capped and mailed or delivered to a laboratory for analysis. The goal in the analysis is to determine the nature of the contamination in the gas pipeline.
The drawback to using this traditional approach is the exposure of the pipeline sample to the atmosphere for an extended period of time before analysis. The oxygen in the air will transform iron sulfide into a different species than is present in the pipeline. This transformation can mislead the interpretation of the analysis leading to an incorrect conclusion as to the best approach to clean the pipeline. The pipeline sample will also lose any volatile solvent characteristics, changing the solvent nature of the sample.
By using the traditional approach field technicians are exposed to a potentially hazardous environment of high pressure gas being released from the pipeline.
Isolating the line in a high pressure cylinder allows field technicians to safely capture a representative sample over an extended period of time. Normal collection periods range from 30 to 90 days. Over this time the sample cylinder remains in place collecting material from within the pipeline. The amount of contamination recovered is always greater than what is possible in the traditional sampling method. The greater volume of pipeline contamination recovered allows lab technicians to conduct more comprehensive testing, greatly improving the accuracy of results.
The high pressure cylinders are de-pressurized at the laboratory in a specially designed system that allows safe release of pressure and capture of liquids and solids. Samples are immediately prepared and testing conducted. The time between removing samples and completing analysis is normally less than 4 hours.
In lines that are operated in dry condition (less than 7 pounds of water per million cubic feet of gas) extended periods of 90 days allow for capture of condensate water in sample containers mounted at the 6 o'clock position on the line.
Additionally, corrosion coupons can be mounted within the sample container to record the corrosion rate of a submerged coupon. The coupon in this situation can simulate low spots in the pipeline such as road and river crossings. This corrosion rate information is very valuable in assessing the overall integrity of the gas pipeline.
Rapid's high pressure sample method is advancing the understanding of natural gas pipeline contamination testing.
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