Filling and Humidity

[100days-a-year]

Guess I died a while back and none of the compressors survived. My last 5000 or so dives have all been filled by onboard compressors , not only high humidity but salt in the air as well. Pretty sure the filters were not changed as often as recommended either. When they were changed it was rare to see anything out of the ordinary.

 

[NAM001]

I have a Bauer PE100. It has manual drains which I do every 10 minutes (the manual says every 15).

With manual drains I am having a hard time pin pointing the reason for the 75% spec. As mentioned by others 75% is not an unusual RH for fla and my location in SE texas. Most compressors I have been involved with are impossible to pump water adn cause damage. they have reed valves so you can not push water to a dead head. there fore any moisture would be pushed to the next mechanical separator. the mext thing is that 75% at 90F is no longer 95% whenthe gas igets heated to say 130F from compression. Probably the reason why there is no drain capability for he first stage output.

I was looking for documentation o the compressor and found a picture which shows only one moisture separator on the final stage. I am wondering whether the 75 spec is set to provide a life measurement of the filter. IE 40k cuft on a filter so long as the compressor does not exceed 75%. which is not a factor of the cpmpressor but the filter system used in the package. You have what looks like a 4 cuft compressor at 225-330 bar output. 75% for the system may be valid but not a concern imo.

 

[ATJ]

With manual drains I am having a hard time pin pointing the reason for the 75% spec.

This is not spec. This is just what he said. He only runs his compressor below 75% RH, too.

 

[Miyaru]

RH% at ambient pressure doesn't mean that much. Read this:
Compressor Filter System Theory - Scuba Engineer

No PMV (aka Back Pressure Valve) and you'll have humid air saturating the MS filter rapidly.....

 

[NAM001]

This is not spec. This is just what he said. He only runs his compressor below 75% RH, too.

so its his whim and not a spec based opinion.

 

[NAM001]

RH% at ambient pressure doesn't mean that much. Read this:
Compressor Filter System Theory - Scuba Engineer

No PMV (aka Back Pressure Valve) and you'll have humid air saturating the MS filter rapidly.....

absolutely correct about the BPR or PMV . it is the key to making the mechanical moisture separator function.

 

[tbone1004]

With manual drains I am having a hard time pin pointing the reason for the 75% spec. As mentioned by others 75% is not an unusual RH for fla and my location in SE texas. Most compressors I have been involved with are impossible to pump water adn cause damage. they have reed valves so you can not push water to a dead head. there fore any moisture would be pushed to the next mechanical separator. the mext thing is that 75% at 90F is no longer 95% whenthe gas igets heated to say 130F from compression. Probably the reason why there is no drain capability for he first stage output.

I was looking for documentation o the compressor and found a picture which shows only one moisture separator on the final stage. I am wondering whether the 75 spec is set to provide a life measurement of the filter. IE 40k cuft on a filter so long as the compressor does not exceed 75%. which is not a factor of the cpmpressor but the filter system used in the package. You have what looks like a 4 cuft compressor at 225-330 bar output. 75% for the system may be valid but not a concern imo.

even with auto drains, you can set the drain intervals fairly easily on most of them. Some of the newer Securus systems are a bit irritating to deal with, but it's still possible to set.

 

[rjack321]

Relative humidity is always 100% once the gas is in the 1st stage of the compressor, this "75% rule" is complete malarky

 

[NAM001]

even with auto drains, you can set the drain intervals fairly easily on most of them. Some of the newer Securus systems are a bit irritating to deal with, but it's still possible to set.

I was trying to fund a justification for the 75% thing. It made no sense to me I thought that perhaps with the factory setting the RH had a limit of 75 unless you autodumped more often.

 

[NAM001]

Relative humidity is always 100% once the gas is in the 1st stage of the compressor, this "75% rule" is complete malarky

Yes the difference in the input RH is how much condensation you generate between stage 1 and 2. 95% will produce more water than 75 will , and yes after it reaches 100 the RH stays the same only the amount of water to the first moisture seperator drain changes from little to a lot. still with check valve type valves it should never be a problem with any stage 2 operation functionality.