looking for compressor advice

[pescador775]

Re Bauer portable: The valves last 7-8 years. Rings about 3000 hours, third stage piston about 2000 hours.

The RIX is a nice unit. Some of its components such as teflon piston rings and reed valves may not last as long as the poppet valves and iron rings found in oil lubricated compressors. Even so, the RIX rings are reliable for about 300 hours and changing out these components is not difficult. However, some of the claimed advantages are not real. One such claim is that chemical filters are not needed and thus, one can save money. I feel that all compressors which are used to fill steel tanks need dessicants, and if powered by an engine, or if the compressor is located in a city, a catalyst is needed. The catalyst is toxic so, at that point, a full multiplex filter is needed, including charcoal. These chemicals are normally found in filters assigned to oil lubricated compressors but should also be used with the RIX, IMO. Furthermore, although the RIX is claimed to be the best choice for pumping NITROX the manufacturer says otherwise. This may be for liability reasons. However, a certain amount of moisture is necessary to lubricate the RIX pistons and a dry gas does not provide this benefit causing slightly higher running temperatures and wear. In spite of these concerns, the RIX is considered by some divers to be a good choice for NITROX due to its oil free system and they are often used for this purpose.

Oil lubricated compressors usually last a long time without any serious work. Maintenance consists of oil changes and changing filter cartridges or repacking the filter canister and, unless one is pumping NITROX, the oil change intervals are on the order of hundreds of hours. This is cut to about 50-100 hours when pumping NITROX. Filter media (cartridge) are normallly changed at 12-15 hours for portables and longer intervals for big compressors. There are technical objections to pumping oxygen enriched air through an oil lubricated compressor. However, the objections are based on precepts promulgated by organizations with little evidence to back up their position and seems more related to a fear that the operator will accidentally shoot pure O2 into the pump. In actual fact, oil lubricated compressors are widely used for pumping NITROX. Often, a special "food grade" oil is used in the compressor although this is controversial among those who study this kind of thing. As a result of "rotary bomb" tests it has been established that some of these oils show greater resistance to oxidative breakdown compared to the usual types of oils recommended for reciprocating compressors. Consequently, food grade oils are vociferously promoted by some companies.

These facts have varying influence on maintenance costs. If a LOT of air or gas is pumped, the maintenance costs go up but the overall cost of ownership, based on dollars per tank fill, go down. Ultimately, the prospective buyer must weigh performance against their own requirements, initiative and financial resources.

 

[pescador775]

RIX are scarce right now. I've seen a dozen go in a week. They show up in all areas of the country but I wonder how many of these things the govt still have in inventory.

http://cgi.govliquidation.com/auction/view?id=780929&convertTo=USD

What is the link to the govt. auction site you found the rixx on?

Kevin

 

[dab]

RIX are scarce right now. I've seen a dozen go in a week. They show up in all areas of the country but I wonder how many of these things the govt still have in inventory.

http://cgi.govliquidation.com/auction/view?id=780929&convertTo=USD

There is also a RIX unit for sale at www.osprey-dive.com

 

[dab]

Re Bauer portable: The valves last 7-8 years. Rings about 3000 hours, third stage piston about 2000 hours.

The RIX is a nice unit. Some of its components such as teflon piston rings and reed valves may not last as long as the poppet valves and iron rings found in oil lubricated compressors. Even so, the RIX rings are reliable for about 300 hours and changing out these components is not difficult. However, some of the claimed advantages are not real. One such claim is that chemical filters are not needed and thus, one can save money. I feel that all compressors which are used to fill steel tanks need dessicants, and if powered by an engine, or if the compressor is located in a city, a catalyst is needed. The catalyst is toxic so, at that point, a full multiplex filter is needed, including charcoal. These chemicals are normally found in filters assigned to oil lubricated compressors but should also be used with the RIX, IMO. Furthermore, although the RIX is claimed to be the best choice for pumping NITROX the manufacturer says otherwise. This may be for liability reasons. However, a certain amount of moisture is necessary to lubricate the RIX pistons and a dry gas does not provide this benefit causing slightly higher running temperatures and wear. In spite of these concerns, the RIX is considered by some divers to be a good choice for NITROX due to its oil free system and they are often used for this purpose.

Oil lubricated compressors usually last a long time without any serious work. Maintenance consists of oil changes and changing filter cartridges or repacking the filter canister and, unless one is pumping NITROX, the oil change intervals are on the order of hundreds of hours. This is cut to about 50-100 hours when pumping NITROX. Filter media (cartridge) are normallly changed at 12-15 hours for portables and longer intervals for big compressors. There are technical objections to pumping oxygen enriched air through an oil lubricated compressor. However, the objections are based on precepts promulgated by organizations with little evidence to back up their position and seems more related to a fear that the operator will accidentally shoot pure O2 into the pump. In actual fact, oil lubricated compressors are widely used for pumping NITROX. Often, a special "food grade" oil is used in the compressor although this is controversial among those who study this kind of thing. As a result of "rotary bomb" tests it has been established that some of these oils show greater resistance to oxidative breakdown compared to the usual types of oils recommended for reciprocating compressors. Consequently, food grade oils are vociferously promoted by some companies.

These facts have varying influence on maintenance costs. If a LOT of air or gas is pumped, the maintenance costs go up but the overall cost of ownership, based on dollars per tank fill, go down. Ultimately, the prospective buyer must weigh performance against their own requirements, initiative and financial resources.

Thank you. Your information has been most helpful and is also consistent with other advice I have received, especially regarding the perceived advantages of the oilless system. I am still leaning towards the Bauer Oceanus for my application.

 

[Seadiver5]

If by continuous mixing you mean you are blending before the compressor with a stick or mixing chamber than the issues as I understand it would be the higher levels of oxygen can cause the valves of a bauer type compressor to heat up and that would shorten the life of the compressor.

I have had about the same luck with Bauer as I have with Mako, The Rixx seems to be far superior. by going over our compressor log books all of the compressors we use have been maintained maticulously and the Rixx has given us far less trouble than any or the other compressors we have. I feel they are also much easier to work on even for a mechanically challenged individule. by the way we keep logs that cover not only major maintinance but also minor and tank fills so we can look at total hours run vs number of tank fills vs amount of air pumped vs necessary maintinance vs environment where the compressor was run so we can get a pretty accurate comparison of how each compressor matches up

As for size of compressor the larger compressors are built out of more and better materials and they are designed to last longer than their smaller counterparts. A definite plus to me is also how fast they fill. I have spent many hours filling tanks and I can tell you I would much rather be telling hairy chested sea stories around a campfire than sitting with ear plugs in stairing at a compressor rumbling away.

BTW good maintinance would include regular inspection of all nuts and bolts and connections to insure tightness. leaky compressors have to work much harder than they should and vibration due to loose nuts and bolts can irrepairably damage a good compressor.

 

[dab]

If by continuous mixing you mean you are blending before the compressor with a stick or mixing chamber than the issues as I understand it would be the higher levels of oxygen can cause the valves of a bauer type compressor to heat up and that would shorten the life of the compressor.

I have had about the same luck with Bauer as I have with Mako, The Rixx seems to be far superior. by going over our compressor log books all of the compressors we use have been maintained maticulously and the Rixx has given us far less trouble than any or the other compressors we have. I feel they are also much easier to work on even for a mechanically challenged individule. by the way we keep logs that cover not only major maintinance but also minor and tank fills so we can look at total hours run vs number of tank fills vs amount of air pumped vs necessary maintinance vs environment where the compressor was run so we can get a pretty accurate comparison of how each compressor matches up

As for size of compressor the larger compressors are built out of more and better materials and they are designed to last longer than their smaller counterparts. A definite plus to me is also how fast they fill. I have spent many hours filling tanks and I can tell you I would much rather be telling hairy chested sea stories around a campfire than sitting with ear plugs in stairing at a compressor rumbling away.

BTW good maintinance would include regular inspection of all nuts and bolts and connections to insure tightness. leaky compressors have to work much harder than they should and vibration due to loose nuts and bolts can irrepairably damage a good compressor.

Interesting. This is the first I have heard about shorter compressor life, with a bauer type compressor, running pre-blended nitrox through it. I'm wondering if this is in theory or if actual obsevation has backed it up. Do you know why RIX does not recommend running pre-blended nitrox through thier units? What type of filter system do you use on your RIX units? It may be worth reconsidering these units for my application. Thanks.

 

[pescador775]

There is no "heating effect" on the Bauer compressor when pumping preblended NITROX. Any wear issues have to do with oil quality and intervals. With NITROX, the oil may tend to oxidize faster and more frequent changes are recommended. Oxidation of oil could lead to carbon or wax deposits. This occurs to some degree with all lubricated compressors. However, it is hardly an issue when using modern oils, eg synthetics. The problems which were sometimes encountered with mineral oils, is history. I recommend Nuvair 455 (Ultrachem, Omnilube 455).

It is a good idea to check connections on your air compressor, so says Bauer. However, my experience is that the compression fittings used on the Bauer will maintain their tightness for many years without attention. Engine driven compressors produce significant vibration and Bauer has come up with a new mounting system to address this. Nevertheless, if output should ever show signs of dropping I would check all connections before trying anything else.

With RIX, when output drops it is likely time to replace the third stage. Other maintenance items include lubrication of moving parts with a special grease. There is a company in England which builds a NITROX approved RIX. The mechanicals are changed to oxygen compatible materials. The piston rings are changed to a "slip fit" to reduce heat generated by ring friction. Why RIX/USA does not do this is a mystery. The expense of the improved parts, mainly stainless steel, is very small compared to the present cost of the SA6 for example.

 

[dab]

There is no "heating effect" on the Bauer compressor when pumping preblended NITROX. Any wear issues have to do with oil quality and intervals. With NITROX, the oil may tend to oxidize faster and more frequent changes are recommended. Oxidation of oil could lead to carbon or wax deposits. This occurs to some degree with all lubricated compressors. However, it is hardly an issue when using modern oils, eg synthetics. The problems which were sometimes encountered with mineral oils, is history. I recommend Nuvair 455 (Ultrachem, Omnilube 455).

It is a good idea to check connections on your air compressor, so says Bauer. However, my experience is that the compression fittings used on the Bauer will maintain their tightness for many years without attention. Engine driven compressors produce significant vibration and Bauer has come up with a new mounting system to address this. Nevertheless, if output should ever show signs of dropping I would check all connections before trying anything else.

With RIX, when output drops it is likely time to replace the third stage. Other maintenance items include lubrication of moving parts with a special grease. There is a company in England which builds a NITROX approved RIX. The mechanicals are changed to oxygen compatible materials. The piston rings are changed to a "slip fit" to reduce heat generated by ring friction. Why RIX/USA does not do this is a mystery. The expense of the improved parts, mainly stainless steel, is very small compared to the present cost of the SA6 for example.

Is heat buildup the reason they do not recommend running pre-blended nitrox throgh the Rix unit?

 

[pescador775]

Heat buildup? The RIX may need extra cooling when pumping a dry gas regardless of whether this gas is oxygen enriched air, heliox, trimix or argon. However, RIX, the company, is probably concerned only about liability and insurance rates. Some tight azzed organizations claim that anything over 22% requires O2 certs. The safety concerns with a RIX are no more than with lubricated compressors but are different in kind. They have certainly been used to pump NITROX without problems. Other than keeping an eye on cylinder head temperature they appear fairly trouble free if the pump is in good condition to begin with. The consequences of overheating are separate from the causes. With lubricated compressors overheating is rare because the oil carries away some of the heat, but problems may occur when pumping very high pressures over long sustained periods when ambient temps are above 90F, and when a cheap, parafin oil is used. When this happens, and piston temps exceed about 400F pumping air, or perhaps less in NITROX, the oil may "diesel" causing CO to enter the air stream. As I said, this is more than theoretical but is not very common an occurrence. The RIX is not subject to dieseling but if the teflon rings are heated to >550F (less in NITROX) toxic gases may be produced and the rings damaged. This is theory inasmuch as I cannot cite any cases of this happening.

I hope this answers your questions.
Pesky

 

[Uncle Pug]

I have been blending EAN32 through a RIX SA6 for years (I also blend trimix through it as well.) The compressor will run for 2.5 hours to pump up my bank during which time the cylinder heads will reach roughly 250F 300F 350F for the 1st, 2nd, and 3rd stages, respectively (I measure and note temps more precisely with a heat gun every so often during long fills.) The current set of rings have 240 hours on them and still pump at the rate they did when new. I do use a Mako filter stack with a LF cartridge that includes dessicant as well as a carbon layer.

If I were intent on making the unit portable I could switch over to a gasoline engine but have found that not worth the trouble. To me, the noise of a gasoline engine (think lawn mower) running for several hours a day is just unappealing.

On trips we take plenty of cylinders and then get fills if need be. On a recent week long trip to the end of the road on Vancouver Island I only needed to get two tanks filled. A low SAC helps.



Note: I use an auxillary fan in front of my RIX during fills. It makes a difference.