How Does the Sampling Procedure Affect the Sample Taken?
There are many factors to consider for liquid sampling. That's why we put together a five-part Ask Swagelok video series that discusses the importance of maintaining proper vapor space compression, the role of outage tubes, how vapor space is affected by sampling system design, and what you need to know to minimize the risk of cylinder rupture.
In the last video of this series, fluid sampling expert Matt Dixon discusses how the sampling procedure used affects the sample taken.
Video Transcript
LUCAS TREU:
Hi there. I'm Lucas Treu, and this is Ask Swagelok. I'm joined today at the Solon Tech Center by Matt Dixon, one of our fluid sampling experts. We're talking about liquid sampling and how to do that effectively in cylinders. So Matt, when we talk about sampling in cylinders, how does the sampling procedure actually affect the sample itself?
MATT DIXON:
The sampling procedure can definitely impact the size of the vapor space. The biggest factor is the sample supply pressure, but the procedure can amplify the effects of that pressure.
For example, the worst‑case scenario—the one that results in the smallest possible vapor space—would be closing the sample return valve while leaving the sample supply valve open. That allows the supply pressure to continue pushing liquid into the cylinder, further compressing the vapor space.
Ideally, both valves should be closed at the same time to minimize the impact of supply pressure on vapor space compression. We can address this either by adjusting the sampling procedure to instruct operators to close the valves together, or by altering the panel design—linking the valves with a mechanical linkage or geared assembly so they operate simultaneously. That prevents the supply from continuing to compress the vapor space.
LUCAS TREU:
All right. Well, thanks, Matt. And thank you all for joining us for Ask Swagelok.
