![]() The following are guidelines for an acceptable standing level of vacuum. The system needs to hold below the target vacuum to assure that adequate dehydration has occurred. Core tools are essential to isolate the vacuum pump and rig from the system when the ultimate vacuum level is being measured. It is not until the vacuum has been isolated that we can determine the ultimate level of vacuum. A good vacuum rig coupled to a large pump can overpower the dehydration process, pulling below 500, but not removing the moisture which simply takes time. Pulling below 500 microns and being below 500 microns are two totally different things. When is comes to the vacuum gauge reading and the actual vacuum level, and an important distinction must be made. Significant levels of dehydration are not occurring until the vacuum level is below 1,000 microns. Once you are below 5,000 microns you can be assured that dehydration is occurring and that moisture is being boiled off and removed the through evacuation process. If you cannot achieve a vacuum below 5000, it is a good indicator of a system leak, a leak in your vacuum hoses, contaminated vacuum pump oil, etc. At 5,000 microns, 99.34% of the degassing has occurred, but the moisture removal is just beginning. Using an electronic micron gauge like the BluVac+ Professional and its accompanying application will show you the characteristics of moisture allowing you to easily identify a wet vs a dry system. The use of an electronic vacuum gauge is the only way to determine when the dehydration process is complete. To properly clean (degas and dehydrate) the system, an accurate vacuum gauge is an indispensable component of the evacuation system. Keeping the system clean (contaminate free), dry and leak free during assembly will save far more time on the back end then the uncertainty it will introduce into the time required to clean the system through the evacuation process. ![]() The best advice that can be given, when it comes to evacuation, is to make sure the preparation of the copper tubing is kept the primary priority. It takes heat energy and time for the bonds to break and a deep vacuum for the pump to ultimately carry that moisture out of the system. Moisture has strong molecular bonds and does not easily free itself from the surfaces it attaches to. ![]() Removal of the air is an easy process, but the removal of moisture is much more difficult and simply takes time. More important than how long will an evacuation take is understanding when the evacuation is complete. How long an evacuation takes depends on many factors in this order, including but not limited to, the size of the system, the level of system contamination, the diameter and length of the vacuum hoses, the presence of the Schrader cores in the service valves, dryness of the vacuum pump oil, and lastly, the size of the vacuum pump. All of these can cause permanent damage to the refrigeration system. Moisture with oil forms sludge, and moisture with refrigerant forms hydrofluoric and hydrochloric acids. Modern day evacuation techniques are meant to degas and dehydrate a system, cleaning it of contaminants to a level that assures that non-condensibles – and more importantly, moisture – will cause no harm to the refrigerant or the refrigerant oil in the system. ![]() Anyone that has ever picked up a vacuum pump has asked or been asked this question, and to be truthful it is like asking “How many licks will it take to get to the center of a Tootsie Roll Tootsie Pop?” In the words of the wise old owl, “The world may never know.” Copper plating on a bearing journal due to acids formed by moisture left in the system. ![]()
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