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The Fluid Systems Engineering and Management Blog

by Swagelok Northern California

Enter the Grab Sampling Matrix

by Jeff Hopkins, on 10/16/18 12:00 PM

Essential info on our grab sampling systems + a selection matrix

"Swagelok’s ability to shape and customize our closed loop sampling system to meet the exact needs of our application and meet EPA regulations is essential."

- Lab Technician at a US Refinery

Swagelok offers Grab Sample Module systems, and Grab Sample Liquid system. Check out information on each below and get the literature, including a basic selection matrix.

Grab Sampling ›

Grab Sample Module

1GSMG1NStandardGasSamplerwithoutPurgesmThe Grab Sample Module (GSM) uses cylinders for capturing either liquid or gas into a sealed, pressure-containing cylinder. Closed loop sampling provides a fresh sample that is extracted and held under the same process conditions that existed at the time of sample (with the exception of temperature). 

The GSM closed-looped sampling system pulls from a positive-pressure process and returns back to the process at a lower pressure location (such as upstream of a pump). The differential pressure drives the fluid through the sample system.

This arrangement lets you leave a GSM in the bypass or sample position indefinitely, keeping the transport lines fresh (with zero flushing time) and ready to capture a sample.

Liquid-Only Sampling System

12-GSL4-Continuous-Flow-with-PurgeThe Grab Sample Liquid (GSL) is a liquid-only sampling system for drawing fluid into a non-pressure containing bottle. The sample can be drawn and transported without the risk of spillage or evaporation because the bottle has a self-sealing septum cap. Bottles are a lower cost collection option that can be replaced easily if needed.

Fixed-volume samplers are an option that can be implemented for improved safety. This option completely separates the process pressure from the sample bottle and the user, preventing over-filling and over-pressure conditions. 

The GSL systems include Sentry Equipment's manual valve sampler to draw a sample into a bottle. It has a spring-return handle to prevent unintentional dispensing. Swagelok GSL systems are designed around the use of Boston Round or media bottles, but can accommodate other bottle geometries and materials.

Configuring a GSL

Typically, a GSL will be used with water or other low vapor-pressure liquids. A lid or septum cap can contain only a limited amount of pressure and any possibility of increasing internal pressure may cause an escapement to atmosphere. If the application is suitable for bottle sampling, the next criteria will be determining whether continuous flow and/or purging is required or if a fixed-volume option is more appropriate.

Continuous flow is useful when the sample requires constant motion or there is a long tubing run leading up to the sample point. The continuous flow at the panel will ensure the sampled fluid has not been sitting in the tubes for an extended time.



When continuous flow is not available or the sampled fluid has the potential to solidify in place, a purge option aids in cleaning the dispensing needle and internal tubing. The fixed-volume option should be considered if the sampled fluid is under high pressure or hazardous. The fixed-volume option isolates the process pressure from the user while limiting the volume of dispensed fluid, which helps prevent accidental overfilling.

Key components

On both the GSM and GSL configurations we use Swagelok tube fittings throughout the system, except for the cylinder end connections. This avoids the potential leak points of NPT connections.

A key feature of the GSM is the switching valve that directs flow. Configurations are available with either two or three Swagelok 40G series ball valves. This allows for simultaneous control of fluid routing, reducing the number of sequencing steps required to draw a sample. 

What's next: Get the latest literature (with the Grab Sampling Matrix) at our page about Swagelok Grab Sampling Systems, then get a hand with choosing. 

Grab Sample Literature ›    Help me choose › 

(Prefer to talk live? Please give us a call at 510-933-6200.)

More on this topic:

Topics:Sampling SystemsCatalogDownloadsGrab Sample Systems

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