cap tube waxing
Had reach in cooler several months back with leak in evaporator. System 134. Replaced evaporator and drier. Since repair cap tube has plugged with wax 3 times. Ive thought about installing txv or is there a special drier that will stop this mess before ruining cap tube. Thanks for all replys.
Change cap tube and compressor oil if necessary.
Originally Posted by eversocold
It has been my understanding that true wax would only come from mineral oil, not POE. Back in the 12/502 days, we would use a Sporlan HH drier to remove it. This article from Sporlan mentions "wax-like" compounds with POE.
I would include the link, but I have been "spanked" for links to other sites.
Examining The Role Of Filter Driers In Today's System
Filter-driers must have the capability to remove moisture, acid, wax and other contaminants from systems using HFCs and POE oil
BY DOUG GILDEHAUS
A s more applications use alternative refrigerants such as HFCs and oils such as polyolester (POE), it becomes necessary to review their properties and how they relate to filter-drier design.
HFC refrigerants by themselves are very stable, even when heated to a high temperature. However, under some conditions, reactions can occur that may result in the formation of acids. The reaction of these refrigerants with water may cause the formation of hydrofluoric acid. In ordinary usage this reaction is negligible, but in a very wet system operating at abnormally high temperatures, hydrofluoric acid formation may occur.
HFC refrigerants require the use of synthetic POE oils. It's well documented that the properties of POE oil differ from mineral oil - POE oil is more stable at elevated temperatures than mineral oil. However, POE oil has hygroscopic (water absorbing) tendencies. Because these new oils can attract and hold moisture, using them with the new refrigerants naturally increases the amount of moisture that can be introduced into the system.
It's accepted that all refrigeration systems contain a certain concentration of moisture. Yet large amounts of moisture can interfere with component operation. If left untreated, POE oil will react with water and form organic acids. Acids from oil and/or refrigerant decomposition will attack materials within the system. Decomposition products formed from these reactions could cause symptoms such as plugged cap tubes, "sticking˛ thermostatic expansion valves and abnormal compressor wear.
POE oil has the ability to suspend and circulate debris within a system. This is an important characteristic to remember when constructing or re-piping a system. Copper oxides from the brazing operation or other debris within the system will be suspended and circulated by POE oil. These contaminants cause unnecessary wear and impede the proper operation of system components. Excellent filtration ability of a filter-drier continues to be a requirement since the removal of circulating particles will aid in maximizing system longevity.
Field reports indicate improper thermostatic expansion valve operation has been caused by minute amounts of wax-like substances. The origin of these substances is unknown. However, small amounts of wax-like substances can come from many sources within the system.
Role of Filter-Driers
Filter-driers designed for today's systems need to have the capability to remove moisture, acid, wax and other contaminants. In recent years, filter-driers have been developed with increased water removal capacities for HFC-POE oil systems.
Many filter-drier manufacturers have accomplished this by using a higher percentage of molecular sieve in the filter-drier. This material effectively removes large amounts of moisture within a system. Because POE oil can readily attract and absorb water, the use of higher water capacity filter-driers is recommended for these new systems.
Acid removal in a filter-drier is important and should not be ignored. A well-designed filter-drier needs to have ample acid capacity to handle the requirements of an HFC-POE oil system. As stated above, acid can be generated from oil and/or refrigerant decomposition.
Activated alumina is used in some filter-driers to remove these acids. Although activated alumina can remove moisture, it is the only desiccant used in refrigerant systems capable of removing organic acids from POE oil decomposition.
How components are installed or utilized in specific applications can adversely affect the operation of well-engineered systems. These variables warrant a filter-drier with the ability to remove acids if they are formed. Filter-driers with acid removal capabilities ensure generated acids do not attack system materials.
If a wax-like substance (typically seen in TXVs) impedes proper system operation, a special filter-drier containing carbon - in addition to molecular sieve and activated alumina - may be an aid in removing this type of contaminant. Carbon is a material used by many filter-drier manufacturers in special filter-drier products.
Often a filter-drier containing carbon has a lower water capacity than the manufacturer's standard filter-drier of the equivalent size. Therefore, filter-driers containing carbon are not the ideal choice for standard liquid applications on HFC-POE oil systems. However, these filter-driers are recommended for suction line service for new systems or for cleanup after compressor burn-out. Filter-driers containing carbon are ideal in these circumstances since the material blend has the capability to remove a wider range of contaminants.
Ideal filter-driers have molecular sieve, activated alumina and possibly carbon bonded together in a core, thereby eliminating the possibility of desiccant breakdown or attrition. An example of desiccant attrition is the possible creation of tiny particles - which could be released into the system - caused by desiccant beads rubbing together as refrigerant flows through loose-filled filter-driers.
A well-designed filter-drier for HFC-POE oil systems should have both molecular sieve and activated alumina for water and acid removal. A filter-drier's filtration ability continues to be important. If a system develops erratic behavior due to wax-like substances in the system, a filter-drier containing carbon - in addition to a molecular sieve and activated alumina - may be required in the liquid line. Also, this filter-drier is recommended for suction line service due to the requirements of that application.
Doug Gildehaus is product manager, contaminant control products, Sporlan Valve Co.
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