Guys,
To those who are curious to how accurate the moisture plug or humidity indicator disc is, here are some test I conducted.
First, I have to thanks SwampDiver for making the test possible. Without him, I would never knew that electronic dew point sensors are so sensitive to the pipe materials used to flow the air and 3 hours minimum waiting period to read readings is neccessary even with the best possible non-hygroscopic materials. First test I failed miserably due to copper pipe being used to flow the air and reading was at 2 ATM/BAR using a regulator. Now I read filter tower pressure, the same as the humidity plug and downstream of the PMV/Back Pressure Valve. Copper pipe is the worst of the worst, very wet metal material. SwampDiver linked me to this great 101 :
http://www.edgetech.com/docs/systems.pdf
I only got the reversible Sud-Chemie 20/40/60 and not the Texas Technology ones 10/20/30
Sud-Chemie , 1 piece purchase
Moisture Indicator Disc August Industries Inc.
Texas Technology, 1 piece purchase
Scuba Compressor
The electronic dew point sensor used is from Shaw Moisture Meters UK. It is traceable to UK National Standard.
Best accuracy at -70.5C, read as -71C , deviation 0.5C
Lowest accuracy at -42C which is read as -45.3C, deviation 3.3C
All within +- 4C accuracy limit of the sensor model choosen.
Specification of unit is -80C to 0C range
Xentaur Dew Point Calculator is used
Dew Point reading is taken when at 3000 PSI/207 BAR. Water Vapor Calculation is using Hyland and Wexler.
PMV /Back Pressure Valve is set at 2,400 PSI or 163 BAR
With GreenSpan water vapor Enchancement Factor : ( for use when water vapor is at high pressure , reduced DP will result )
Greenspan factor : http://www.rhsystems.net/papers/its90form.pdf
2O% RH at 30 Celsius at 3,000 PSI / 207 BAR = -45 Celsius ( -49 F )
** Again, it was SwampDiver who told me to use Greenspan correction.
Without Greenspan water vapor Enchancement Factor
2O% RH at 30 Celsius at 3,000 PSI / 207 BAR = -49.6 Celsius ( -57.28 F )
At -4C ( 24.8 F ) 3000 PSI ( 207 BAR ) of the Shaw Dew Point Meter , the Sud-Chemie 20% sector goes lavender color.
-4C ( 24.8 F ) at 3,000 PSI ( 207 BAR ) converted to 1 ATM equivalent WITHOUT GreenSpan correction is : -54.9C ( -66.82F )
-4C ( 24.8 F ) at 3,000 PSI ( 207 BAR ) converted to 1 ATM equivalent using GreenSpan correction is : -48.8C ( -55.98F )
So it seems the Sud-Chemie 20% sector turning to Lavender color at 3000 PSI and 30C is responding to somewhere between a Greenspan corrected and a non Greenpan values. I would say for such a cheap chemical sensor this Sud-Chemie is damn good.
EN12021 breathing standard at compressor direct output of under 300BAR ( <4410 PSI ) is 25 mg/M3 or -51.3C ( -60.34F ) Dew Point at 1 ATM at 20C production air temperature. If production air temperature is 30C, it is -51.0C ( -59.8F).
Grade E air dryness standard varies with ambient temperature use, but I use -48.8C ( -55.84F) as minimum dryness for filter cartridge life because of the Hopcalite is supposed to need air that dry to perform and activated carbon works very well drier than -45C (-49F ). .... again thanks to SwampDiver for passing me this valuable info.
I am waiting for a 10/20/30 RH version of the Sud-Chemie humidity disc to test further.
For now, I am happy to say that at 20% reading of the Sud-Chemie humidity disc as a decently accurate reference to a -48.8C dew point at 1 ATM, for concern of hopcalite function in tropical diving, without needing to spend US$3000 upwards for electronic dew point sensor. For those doing winter diving and requiring the Canadian Z180.1 standard of -63F or -52.77C , the 10/20/30 humidity disc should be more suitable to use.
-48.8C or -55.84F dew point with Greenspan correction is 33.7 milligrams of water per 1000 liter of air at 20C processed air temperature. In a 80CF tank of 2,180 liters of air, that is approx only 33.7 x 2.18 = 67.4 mg/M3
1 cc or 1000 milligrams is 20 drops water. So, 50 mg is 1 drop of water.
67.4 mg is near 1.5 drops of water only.
In my tropical case, -48.8C or -55.84F Dew Point is actually drier if processed air temperature is 30C because hotter air supposed to hold more moisture, very-very little difference though....it will be. 32.8 mg/m3
-52.77 C or -63F at 20C processed air temperature is 22.6 mg/M3. Only 1 drop of water for an entire air contained in a 80CF tank at 3000 PSI. However, you can never have that so dry air in your tank, because the alumminum walls will retain some moisture to begin with if a recent visual inspection was done. I think at least 2-3 uses of the tanks with such dry air, only then it can have very-very dry air inside the tank.
At 20C ambient and 50% humidity at 1 ATM, the air in that so called "EMPTY" 80CF tank after a visual inspection is already having 8,645 millligrams / 1000 liters x 11 liters ( 80CF tank is approx 11 liters ) = 95 milligrams or 2 drops free water equivalent in form of water vapor.......yikes !!
A regulator trainer from Scubapro told me at the regulator 1st stage -30C cooling can happen easy at the orifice due to the flow and pressure reduction to 2nd stage IP. Wow, ice diving sure need increased safety margin in air dryness value.
For how long you can keep that Sud-Chemie sensor disc in storage after manufacturing , you need to ask the manufacturer.
I keep my spare one in the +4C refrigerator because my ambient here is 30C and most chemical requires 25C storage temp and 2 years assumed shelf life. I am more concerned of the glue used to seal the aluminum foil of the humidity disc will fail sooner if storage at 30C and high humidity of the tropics.
Two filter towers in series using 27" all molecular sieve and 2nd tower using MS+AC+HP brand new and after 3 hours running produced a -47C (-52.6F ) at 3000 PSI, this is equivalent to -84.1C (-119.38F ) at 1 ATM without Greenspan correction or -77C (-106.6F ) with GreenSpan correction.
I have tested the compressor for non stop 5+ hours run. After more than 3 hours run, the Shaw dew point sensor will read a bit drier than a 3 hours reading due to more moisture been driven out by the 5 hours worth of air flow but very little increase. That EdgeTech installation tips for electronic dew point sensor is really good, even Shaw does not have such a moisture chart for various piping materials.
The Shaw meter dewpoint Celcius reading does fluctuates when air pressure rise between 2,400 to 3000 and down to 2,400 PSI again, which shows the sensor is adapting to different dewpoint pressure.
Previous installation was reading output of 10-ports filling manifold, it reads all 10 air-fill hoses retained moisture, regulator LP hose retained moisture and the copper tube retained moisture. I could not read lower than -55C Dew ( -67F ) Point at 1 ATM equivalent even after 5 hours of compressor running. Air flow was 2 liters per minute to the sensor.
I was hoping for Dew Point reading stability with a regulator set to 2 BAR/30 PSI, but end up all other accessories on that 10-ports filling manifold were so "wet".
The picture where it shows Dew Point display at -18.8C, it was taken at minimum 2,400 PSI filter tower pressure or -58C (-72.4F) with Greenspan calculation at 1 ATM. The filter cartridge life was approx 90 hours of 400 liters per minute flow at that time.
Two of the filter cartriges life, connected in series was estimated to last for 106.5 hours , at 400 liters/minute (14 CFM ) and at 36C processed air temperature. It turned out, I could get approx 124.5 hours of use at ending of filter life at measured final air dryness of -48.8C ( -55.98F ) at 1 ATM and Greenspan corrected. Thanks to a cooler incoming air into the two 27" filter towers at approx 33C only, even at ambient temp of 28C. Thanks to the super powerful blowers used to assist cooling of the compressors, the most well spent 1,500 watts of cooling power ever.
Hope this info will help some.
IYA
To those who are curious to how accurate the moisture plug or humidity indicator disc is, here are some test I conducted.
First, I have to thanks SwampDiver for making the test possible. Without him, I would never knew that electronic dew point sensors are so sensitive to the pipe materials used to flow the air and 3 hours minimum waiting period to read readings is neccessary even with the best possible non-hygroscopic materials. First test I failed miserably due to copper pipe being used to flow the air and reading was at 2 ATM/BAR using a regulator. Now I read filter tower pressure, the same as the humidity plug and downstream of the PMV/Back Pressure Valve. Copper pipe is the worst of the worst, very wet metal material. SwampDiver linked me to this great 101 :
http://www.edgetech.com/docs/systems.pdf
I only got the reversible Sud-Chemie 20/40/60 and not the Texas Technology ones 10/20/30
Sud-Chemie , 1 piece purchase
Moisture Indicator Disc August Industries Inc.
Texas Technology, 1 piece purchase
Scuba Compressor
The electronic dew point sensor used is from Shaw Moisture Meters UK. It is traceable to UK National Standard.
Best accuracy at -70.5C, read as -71C , deviation 0.5C
Lowest accuracy at -42C which is read as -45.3C, deviation 3.3C
All within +- 4C accuracy limit of the sensor model choosen.
Specification of unit is -80C to 0C range
Xentaur Dew Point Calculator is used
Dew Point reading is taken when at 3000 PSI/207 BAR. Water Vapor Calculation is using Hyland and Wexler.
PMV /Back Pressure Valve is set at 2,400 PSI or 163 BAR
With GreenSpan water vapor Enchancement Factor : ( for use when water vapor is at high pressure , reduced DP will result )
Greenspan factor : http://www.rhsystems.net/papers/its90form.pdf
2O% RH at 30 Celsius at 3,000 PSI / 207 BAR = -45 Celsius ( -49 F )
** Again, it was SwampDiver who told me to use Greenspan correction.
Without Greenspan water vapor Enchancement Factor
2O% RH at 30 Celsius at 3,000 PSI / 207 BAR = -49.6 Celsius ( -57.28 F )
At -4C ( 24.8 F ) 3000 PSI ( 207 BAR ) of the Shaw Dew Point Meter , the Sud-Chemie 20% sector goes lavender color.
-4C ( 24.8 F ) at 3,000 PSI ( 207 BAR ) converted to 1 ATM equivalent WITHOUT GreenSpan correction is : -54.9C ( -66.82F )
-4C ( 24.8 F ) at 3,000 PSI ( 207 BAR ) converted to 1 ATM equivalent using GreenSpan correction is : -48.8C ( -55.98F )
So it seems the Sud-Chemie 20% sector turning to Lavender color at 3000 PSI and 30C is responding to somewhere between a Greenspan corrected and a non Greenpan values. I would say for such a cheap chemical sensor this Sud-Chemie is damn good.
EN12021 breathing standard at compressor direct output of under 300BAR ( <4410 PSI ) is 25 mg/M3 or -51.3C ( -60.34F ) Dew Point at 1 ATM at 20C production air temperature. If production air temperature is 30C, it is -51.0C ( -59.8F).
Grade E air dryness standard varies with ambient temperature use, but I use -48.8C ( -55.84F) as minimum dryness for filter cartridge life because of the Hopcalite is supposed to need air that dry to perform and activated carbon works very well drier than -45C (-49F ). .... again thanks to SwampDiver for passing me this valuable info.
I am waiting for a 10/20/30 RH version of the Sud-Chemie humidity disc to test further.
For now, I am happy to say that at 20% reading of the Sud-Chemie humidity disc as a decently accurate reference to a -48.8C dew point at 1 ATM, for concern of hopcalite function in tropical diving, without needing to spend US$3000 upwards for electronic dew point sensor. For those doing winter diving and requiring the Canadian Z180.1 standard of -63F or -52.77C , the 10/20/30 humidity disc should be more suitable to use.
-48.8C or -55.84F dew point with Greenspan correction is 33.7 milligrams of water per 1000 liter of air at 20C processed air temperature. In a 80CF tank of 2,180 liters of air, that is approx only 33.7 x 2.18 = 67.4 mg/M3
1 cc or 1000 milligrams is 20 drops water. So, 50 mg is 1 drop of water.
67.4 mg is near 1.5 drops of water only.
In my tropical case, -48.8C or -55.84F Dew Point is actually drier if processed air temperature is 30C because hotter air supposed to hold more moisture, very-very little difference though....it will be. 32.8 mg/m3
-52.77 C or -63F at 20C processed air temperature is 22.6 mg/M3. Only 1 drop of water for an entire air contained in a 80CF tank at 3000 PSI. However, you can never have that so dry air in your tank, because the alumminum walls will retain some moisture to begin with if a recent visual inspection was done. I think at least 2-3 uses of the tanks with such dry air, only then it can have very-very dry air inside the tank.
At 20C ambient and 50% humidity at 1 ATM, the air in that so called "EMPTY" 80CF tank after a visual inspection is already having 8,645 millligrams / 1000 liters x 11 liters ( 80CF tank is approx 11 liters ) = 95 milligrams or 2 drops free water equivalent in form of water vapor.......yikes !!
A regulator trainer from Scubapro told me at the regulator 1st stage -30C cooling can happen easy at the orifice due to the flow and pressure reduction to 2nd stage IP. Wow, ice diving sure need increased safety margin in air dryness value.
For how long you can keep that Sud-Chemie sensor disc in storage after manufacturing , you need to ask the manufacturer.
I keep my spare one in the +4C refrigerator because my ambient here is 30C and most chemical requires 25C storage temp and 2 years assumed shelf life. I am more concerned of the glue used to seal the aluminum foil of the humidity disc will fail sooner if storage at 30C and high humidity of the tropics.
Two filter towers in series using 27" all molecular sieve and 2nd tower using MS+AC+HP brand new and after 3 hours running produced a -47C (-52.6F ) at 3000 PSI, this is equivalent to -84.1C (-119.38F ) at 1 ATM without Greenspan correction or -77C (-106.6F ) with GreenSpan correction.
I have tested the compressor for non stop 5+ hours run. After more than 3 hours run, the Shaw dew point sensor will read a bit drier than a 3 hours reading due to more moisture been driven out by the 5 hours worth of air flow but very little increase. That EdgeTech installation tips for electronic dew point sensor is really good, even Shaw does not have such a moisture chart for various piping materials.
The Shaw meter dewpoint Celcius reading does fluctuates when air pressure rise between 2,400 to 3000 and down to 2,400 PSI again, which shows the sensor is adapting to different dewpoint pressure.
Previous installation was reading output of 10-ports filling manifold, it reads all 10 air-fill hoses retained moisture, regulator LP hose retained moisture and the copper tube retained moisture. I could not read lower than -55C Dew ( -67F ) Point at 1 ATM equivalent even after 5 hours of compressor running. Air flow was 2 liters per minute to the sensor.
I was hoping for Dew Point reading stability with a regulator set to 2 BAR/30 PSI, but end up all other accessories on that 10-ports filling manifold were so "wet".
The picture where it shows Dew Point display at -18.8C, it was taken at minimum 2,400 PSI filter tower pressure or -58C (-72.4F) with Greenspan calculation at 1 ATM. The filter cartridge life was approx 90 hours of 400 liters per minute flow at that time.
Two of the filter cartriges life, connected in series was estimated to last for 106.5 hours , at 400 liters/minute (14 CFM ) and at 36C processed air temperature. It turned out, I could get approx 124.5 hours of use at ending of filter life at measured final air dryness of -48.8C ( -55.98F ) at 1 ATM and Greenspan corrected. Thanks to a cooler incoming air into the two 27" filter towers at approx 33C only, even at ambient temp of 28C. Thanks to the super powerful blowers used to assist cooling of the compressors, the most well spent 1,500 watts of cooling power ever.
Hope this info will help some.
IYA
