What Does Field Sampling Mean?
Sampling is the removal of a portion of a material for examination or analysis. Field sampling is something that can be removed from a material to monitor corrosion in the field. Many times it is easier to complete the sampling at the time of coupon removal. The weight-loss corrosion coupons, or the associated pipeline fittings, present an excellent opportunity for surface testing or fluids sampling.
Corrosion failure may require sampling and testing of corrosion products, such as in the case of microbiologically influenced corrosion (MIC), where viable cultures can provide the most meaningful results.
Corrosionpedia Explains Field Sampling
Field samples for analysis can be obtained from industrial systems by scraping accessible surfaces. In open systems or on the outside of pipelines or other underground facilities, this can be done directly. Bull plugs, coupons or inspection ports can provide surface samples in low-pressure water systems. More sophisticated devices are commercially available for use in pressurized systems. In these devices, coupons are held in an assembly which mounts on a standard pressure fitting.
Handling of field samples should be done carefully to avoid contamination with foreign matter, including biological materials. A wide range of sterile sampling tools and containers are readily available. Because many systems are anaerobic, proper sample handling and transport is essential to avoid misleading results brought about by excessive exposure to oxygen in the air. One option is to analyze samples on the spot using commercially available kits.
Where transportation to a laboratory is required, Torbal jars or similar anaerobic containers can be used. In many cases, simply placing samples directly in a large volume of the process water in a completely filled screw-cap container is adequate. Processing in the lab should also be done anaerobically, using special techniques or anaerobic chambers designed for this purpose.
Generally, the corroded components in industrial equipment are sent to the lab for more detailed investigation. In order to preserve the original form of samples and minimize sample damage, very careful sampling and sectioning practices are required. All the samples should be identified and placed in suitable packaging before being shipped to the laboratory.