Helium Leak Detection Chamber

• To detect small defects in manufactured PVC parts, I built and tested a leak detection chamber that was easy to assemble and quick to use.

One of the common methods to detect leaks in critically watertight systems is to use helium detection. In this case, I was tasked with building a small fixture to qualify the accuracy of this technique when used on a watertight PVC structure. I designed the frame with 8020 aluminum extrusions, and used laser-cut acrylic sheets slotted into the frames to make the walls. To make the structure relatively airtight, I used window gaskets to seal the gaps between the acrylic and the aluminum, and since the entire structure needed to hinge open and closed, I put gasket sheets around the bottom rim, so that the weight of the lid would act as the sealing force for the main body.

The test methodology was that if the PVC was punctured, and thus no longer watertight, the helium would leak into the enclosed space faster, and the detector would measure the helium concentration increasing at a faster rate than a watertight sample. However when testing, I found that the helium molecules are small enough to naturally bleed through the PVC, even when it was watertight, rendering the method useless for this application.

Helium gas was so scarce at the time that we needed to purchase our supply at a Party Goods store!

Helium was pumped into the system until it reached pressure, then it was valved off while the helium detector logged the concentration increase. After the measurement was complete, compressed air purged the system and exhasuted outside, to keep the helium concentration in the measurement room as low as possible