Maintenance Tip

One simple task you can do to keep your system running smoothly is to periodically inspect the system tubing. In this tip we focus on the vacuum tubing - the tubing that goes from the system to the pumpbox and from the splitter (the spare lines) to the pumpbox. At most of the federated network sites this tubing (we typically use polyethylene tubing) is outside of the observatory building and thus is exposed to the elements. Solar radiation degrades the tubing causing it to crack and break. To the right is a photo of a cracked tube at Trinidad Head which caused problems with the THD leak check.

Depending where the tubing breaks you may be able to cut off the broken part and reattach the rest to the system. However, once the tubing starts to degrade it is really time to replace it. We typically order this tubing. For the swagelok fittings we try to use nylon ferrules as, to some extent, these are reusable and they also tend not to dig into the tubing as much.

We often cover the tubing with foam pipe insulation or with reflective tape to delay degradation of the tubing (you can see the foam insulation on the Trinidad Head picture above. This approach is fairly successful, although it can make it difficult to find problems with the tubing. Although the vacuum tubing is downstream of the instruments, a crack in the tubing may result in a bad system leak check. This is because the broken tubing provides a less resistant flowpath than the leak check filter, meaning particles can flow backwards through the tubing into the system.

Below are pictures of the splitter, sample and spare lines at Cape San Juan. The picture on the left shows the uncovered system during annual maintenance. The picture on the right shows the same view with all the tubes and splitter protected from UV radiation.