Seleing heavy gas for instrument diplay purge

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Discussion Overview

The discussion revolves around the selection of a heavy gas for purging an outdoor display unit to prevent condensation and maintain display quality in varying temperatures. Participants explore different gases and their properties in relation to the specific environmental conditions of the application.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests using R134a for its heaviness and dryness but questions if it is overkill, considering alternatives like argon and CO2.
  • Another participant inquires about the purpose of the purge, suggesting nitrogen as a common choice to dispel oxygen and prevent oxidation.
  • A participant clarifies that the main concern is condensation in cold weather, noting that nitrogen is lighter than air and may not suit their gravity fill requirement.
  • One suggestion is made to conduct the assembly in a low humidity room to mitigate moisture issues.

Areas of Agreement / Disagreement

Participants express differing views on the most suitable gas for purging, with no consensus reached on the best option. The discussion remains unresolved regarding the optimal choice of gas and the necessity of purging.

Contextual Notes

Participants have not fully explored the implications of using each gas, such as their moisture absorption properties or the specific conditions under which they would be effective. The discussion also does not address potential safety or regulatory considerations related to the gases mentioned.

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We are working on an outdoor display unit. It will operate at a wide range of temps. There is not a requirement to purge air from the encasement but would be a smart decision I think. my thought was to use a gas that is very dry and heavy enough to simply purge the air and sit in the device like water while the sealed lens is installed.

These are being made in small qtys and volume is less than 1in3 each. Thought was to use R134a since it is a very heavy gas but wondering if that is really an overkill for this. Argon might work just as well and we have both in the shop. Not sure if either will readily absorb moisture from the air for the few minutes they would be sitting until sealed. A cheap and easy solution might be CO2.
 
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What's the purpose of the purge? If you're looking to dispell oxygen to prevent oxidation of anything inside, I've seen nitrogen most commonly used.
 
Condensation in certain cold weather conditions is our primary concern. It would not affect our circuits at all but does not project an image of quality. N is lighter than air so that would not fit our gravity fill considerations here. We are in a fairly humid climate several months out of the year so have a dry gas fill would hopefully be a quick easy step to ensure a quality display in cold temps.
 
You could always do the assembly in a low humidity room (environmentally controlled, RH & Temp, walk-in chamber).
 

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