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by Thomas Webster on Fri, Dec 17, 2021 @ 07:12 AM
Grab sampling is a diagnostic tool used to snapshot a system process or environmental product. Being able to analyze a process at any point in the greater system lends insight into how the system is developing and allows for the diagnosis of issues where process design went awry. In SAGD, the biggest challenges revolve around the temperature and viscosity of the fluid. The temporal nature of these snapshots can be deceiving, however: samples can rapidly volatize, meaning long-term storage or extended transit for study could have misleading findings, at best. Even with this drawback, some diagnostic information is better than none. Despite notable constraints on measurement and analysis, grab sampling advantages and disadvantages merit discussion for industry best practices.
Grab sampling is a collection of a product in-process, and it is of high importance that the sample be representative of the mixture it is being collected from. Two factors play an outsized role in determining whether the sample is representative: the collection, and the volatility and susceptibility of the sample to outside conditions once removed from the mixture.
Grab Sampling Advantages and Disadvantages at a Glance
While grab sampling is a valuable diagnostic tool for obtaining an informative peek into system processes, there are many considerations that should be heeded to ensure the proper course of action (if any) is taken following sample analysis. Any changes to a system based on the false assumptions of a non-representative sample or a sample that has changed drastically from the initial mixture could potentially lead to further issues when calibration and adjustments are applied. The goal for grab sampling must therefore be a sample that is representative and at the very least has any differences that arise due to a change in environment accounted for.
To better evaluate options, here’s a closer look at grab sampling advantages and disadvantages:
| Pros | Cons |
| Invaluable diagnostic tool | Results possibly misleading if not properly accounted for |
| Allows systematic review of individual processes of larger SAGD operations | Review can only be as good as sampling; certain samples may be more susceptible to the environment once removed from the original mixture |
| Gas and liquid mixtures can be analyzed | Pressurized mixtures must be held in cylinders (non-pressurized liquids can be collected in glass or polyethylene bottles) |
| Sampling technology allows for continuous motion, for instance in the case of liquids that would otherwise freeze without continuous flow | Sampling of mixtures in excess of 60°C should be cooled to prevent injury to operators; samples at lower temperatures will tend to solidify; cooling sample may reduce the representativeness |
Properly collected and analyzed, grab sampling allows operators to peer directly into their system processes and fine-tune to the specific needs of their environment. Care should be taken in sample collection, both for sample integrity and operator safety when handling certain samples (extreme temperatures, high pressure, corrosive, etc.).
Choosing the Right Panel for Sampling
Due to the wide range of samples available for collection in SAGD industries, there exist numerous panels designed and calibrated for particular needs. One big distinguishing factor is the style of grab sampling systems, separated on the basis of pressurized and non-pressurized samples: grab sample modules (GSM) and liquid-only sampling systems (GSL). GSM panels can be designed for either pressurized gas or liquid retention, while GSL covers all other liquids. In addition to pressurization, there may be additional concerns for sample collection, such as continuous flow to prevent freezing, purging for toxic or corrosive elements, and fixed-volume containers to prevent overfilling. Pictured below are two infographics to help choose the correct grab sampling panel as determined by sample needs.
The manner of sample collection may come into play beyond the container itself. GSM panels contain a closed-loop system that allows for the sample to flow into the collection and out to a lower pressure location in the system. For some samples, this can eliminate the need for purging of the grab sampling system entirely. Meanwhile, GSL panels will have slightly different applications depending on gas or liquid sampling: gases should fill the container top-down to push out any liquid or condensate and liquids bottom-up to push out any vapour.
Weighing Options for Grab Sampling Advantages and Disadvantages
The ability to evaluate SAGD processes step-by-step allows for an unmatched level of diagnostic feedback; Field Advisors can support your system at any stage from assessment to assembly. Edmonton Valve & Fitting can customize panels that are specifically designed for the unique requirements of SAGD, especially for temperature and viscosity. We are committed to the long-term operation of your grab sampling system with training for your employees on proper usage and maintenance.