Grab Sampling Basics

What is Grab Sampling?

Grab sampling, also known as lab sampling or spot sampling, is the collecting of a sample of liquid or gas in a pipeline, tank, or system with the intent of transporting the sample to a laboratory for analysis.

Why use a Grab Sample System?

Grab sampling can validate:

• Process conditions
• End products meet quality specifications
• Online analyzers are "fit for use"
• Product quality during custody transfer

It can also provide verification of environmental emissions. In all of these uses, capturing a representative sample is essential. However, placing a captured sample into an open bottle for transport back to the lab may not provide a representative sample.  Some chemicals will evaporate or fractionate if not maintained under pressure.

Sampling is the science of safely capturing a sample from a process or a pipeline while maintaining the chemical composition during storage or transport for later analysis. Depending on the process phase, temperature, consistency, chemical makeup and other factors, there are a variety of approaches that can be used to extract a sample. Determining the container type needed is the first decision that must be made in order to select the appropriate sampler. 

The Swagelok product selection matrix includes additional common system criteria.

Another important aspect is the temperature of the system fluid. Many processes operate at elevated temperatures and can pose a hazard from direct scalding during operator interaction or from the temperature limits of seats and seals being exceeded. Swagelok recommends consideration of a sample cooler when the supply temperature exceeds 140°F (60°C). Note that thermal safety may affect sample integrity.

Questions?

Call or email us today to discuss your grab sample needs.