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Does it Matter what is Attached to Your Evacuation Rig?

Jim Bergmann ·
Watching some very good video reviews of the new TruBlu Hoses and the Fieldpiece VP85, and got into some discussion as to if attaching 1/4" hoses to the sides of the core tools can affect the evacuation. In short, yes it does and the difference is worth noting. Everything you attach to the rig makes a difference in speed, ultimate vacuum, and dehydration. The demonstration: Here is a photo of two gauges hooked to a common port showing the vacuum readings are almost identical. Within 2.3 microns, with about 5 minutes, the tank was valved off so we are just looking at the hoses and associated losses at the connections. This shows the difference is effectively "0" as both gauges are +/- 5 microns. They are located right off the side port of the core tool. In the second photo, all that was done was right gauge was attached to 1/4" of charging hose to demonstrate a remote connection with a standard hose. Several things become apparent quickly after 5 minutes, and this photo is after 10 minutes of evacuation.
  • The evacuation speed drops significantly because charging hose is outgassing and is more gas permeable then TruBlu Hose.
  • The rig loses 100 microns of ultimate vacuum because of the permeability of the hose. ( This is a single 5' charging hose.)
  • There are 112 microns of difference between the two gauges because the hose is not as gas-tight, and the conductance losses in the 1/4" hoses.
Ultimately this demonstrates two things.
  1. Attaching less capable hoses (Charging or evacuation) in parallel to TruBlu will slow the evacuation speed and decrease the ultimate dehydration. The system can only evacuate as deep as its weakest link. This is why we always recommend attaching with a brass coupler.
  2. Using a charging hose to attach the vacuum gauge will not show a reading that is reflective of what is happening in the system. The same would apply a gauge built into your manifold with charging hoses attached.
Hopefully, you found this interesting as it was something we ran across when testing the hoses and the application.  If you are going to invest in the tools, do not accidentally undermine their performance by attaching hoses and other components that are not engineered to do the job.