Dive Industry
Technician Course Literature
|
| |
This web site is hosted by the nice people below. They're great,
and tech support is absolutely top class- webmaster.
Webmasters Profile |
| |
High Pressure Breathing Air Compressor Filtration System Design
author:- Stephen E Burton BSc(hons) C.Eng, MIET -
Email to:-
scubaengineer@gmail.com
Introduction
Many homes and small workshops have single stage compressors
capable of producing 7bar/100psi pressure for powering hand tools and filling
truck tires. These simple compressors use the most basic engineering techniques
and are successfully mass produced out in the Far East as a low cost consumer
product.
It comes as quite a surprise when a dive operation comes to
purchase their first high pressure divers breathing air compressor to be met
with a price tag approaching that of a family car, and the use of which is
surrounded by a pile of legal regulations and maintenance obligations, and
competent operator requirements which if
not met, will cause several well known phenomena:-
-
The compressor may explode - blowing the operator to bits
-
The compressor will overheat and pump highly
poisonous carbon monoxide laced air
-
The compressor will pump wet air leading to the
early failure of every cylinder filled by it.
Thankfully, explosions and poisonous air (cases 1 & 2 above) are relatively
uncommon, and may
be easily prevented by routine long-term maintenance and correct positioning in a well
ventilated position away from petrol and diesel engine exhaust fumes.
However, recent Government divers breathing air testing results
(#1,7) and feedback from compressor maintenance technicians confirms that
"75% of all divers breathing air compressors are pumping air that fails to meet
the moisture content requirements of EN12021".
Since all modern divers breathing air compressors are designed
to produce clean dry divers breathing air, the non compliant air can only be
caused by one of the following faults:-
-
The condensate drains are not being vented often enough
(typically every 15 minutes)
-
The final output filter is not being changed often enough
(The change interval varies considerably dependent on the compressor pumping
rate, the filter size, and the ambient operating temperature)
-
Incorrect adjustment of the final Pressure Maintaining Valve
(PMV)
It is the operation and adjustment of the last item 'The
PMV' that causes the most puzzlement amongst compressor users, and is
the most commonly overlooked routine compressor adjustment.
High Pressure Divers Breathing Air Compressor operators...
Ignore the PMV at your peril !!! - since the
correct functioning of this simple mechanical valve removes more than 99% of all
moisture present in the final compressed air; If the PMV does not work, the high
levels of humidity still present in the air reaching the final filter tower will
trash the expensive air filter cartridge before you have even filled the first
cylinder, and condemn to early failure at annual visual inspection every
subsequent SCUBA cylinder filled by it, due to high levels of internal
corrosion.
Talking to dive center owners and compressor operators reveals a
complete misunderstanding about the basic operation of the specialist filtration system
characteristic of all high pressure divers breathing air compressors.
What this article attempts to do is to expose the commonly held
misconceptions about how compressor filtrations systems work, and to underline
the essential checks and maintenance necessary to produce clean dry divers
breathing air - and save the dive operator a pile of money long-term in unnecessary scuba tank replacement
costs.
The Multi-stage High Pressure divers breathing air compressor - an
introduction
This picture courtesy of:- Mr. Stuart Meinert, author of the Dive
Technician Training Course
Key:-
NRV = Non Return Valve - a one way valve
SV = Safety valve. The final safety valve is usually
set 10% above the cylinder maximum working pressure
PMV = Pressure maintaining valve - A crucial part of the filtration
system usually set to release pressure between 120-160 bars.
After a bit of bug filtration and three stages of compression each delivering
up to x7 multiplication in pressure, most modern high pressure divers breathing
air compressors can deliver air potentially 7x7x7= 343bars/5,000psi. Typically,
several internal safety valves limit the pressure generated to safe limits
tolerated by both the compressor mechanical parts, and the scuba tank to be filled.
Following the last compression stage, the air passes through the final Air
Filter whereupon it emerges ready to pass through the filing hose into the
divers scuba tank.
The air should then meet international standards for divers breathing quality
air, which basically state that the air should be clean, dry, free from odor,
and containing extremely low levels of poisonous contaminants such as oil,
carbon dioxide, and carbon monoxide.
For this article, we'll look at how a high pressure divers breathing air
compressor filtration system is designed to meet a typical modern air purity
standard such as EN12021, how this determines the compressor filter size, the
condensate purge interval times, the pressure maintaining valve setting,
Molecular sieve mass, Activated Carbon mass, and the influence of all these
parameters on predicting the filter lifetime over a range of operating
temperatures and humidity levels. First lets have a look at the air standard
we'd like to meet or exceed.
Divers Breathing Air Purity Standard EN12021
- Oxygen
20-23%
- Carbon Dioxide Less
<500ppm
- Oil
<0.5mg/m^3
- Carbon Monoxide
<15ppm
- Water Vapor <50mg/m^3 for 40-200bars
- Water Liquid
<No free water.
- Odor & Taste Freedom from both
- Particles
None(not defined)
Why use EN12021? This air purity standard was chosen so
as include essential test criteria for water vapor content and lower oil levels
associated with odorless breathing gases that were missing from older divers
breathing air test standards such as the US-Navy (#2), & even the current CGA G-7.1
Grade "E" that are known to permit the production curiously smelling (though 'not
objectionable') breathing air, and progressive internal tank corrosion through
high un-monitored moisture levels.
The compression process starts here!
The air entering the compressor has the following 'typical'
ISO 2533 parameters
-
•Nitrogen
(N2)
78.084%
-
•Oxygen
(O2)
20.946%
-
•Argon
(Ar)
0.934%
-
•Carbon Dioxide (CO2) 0.033%
The remaining
typically 0.003%(30ppm) consists of
•a mix of Neon,
•Helium, • Krypton, • Xenon, • Radon,• Hydrogen and
•Carbon Monoxide
Background Carbon Monoxide Concerns
These typical ISO 2533 air parameters listed above, would be realised in an open green
fields site, far away from any large industrial city.
However, air
tested in a city center, or near a large airport could
easily exceed these parameters especially for poisonous
trace gases such as carbon monoxide. Such a polluted location would
require the use of a hopcalite after filter to catalyze the
highly toxic carbon monoxide into the more tolerated gas
carbon dioxide, even when the cylinder is filled using a perfect compressor system.
Background Carbon Dioxide Concerns
Increasing pollution and
rising world carbon dioxide levels associated with global
warming, are expected to cause the background carbon dioxide
level to exceed the acceptable 500ppm level for divers breathing
quality air within the next 50 years, indicating a future
requirement to use carbon-dioxide scrubber pre-filters on
all divers breathing air compressors(#4)
Bauer Aeroguard Carbon dioxide removal pre-scrubber system.
This picture courtesy of Bauer Kompressoren, Munchen, Germany
http://www.bauer-kompressoren.de
But what about the air's water content?
Air at different temperatures contains widely varying
amounts of moisture content. Hot 100% humid air at the 45
degrees 'C' maximum compressor operating temperature often
quoted, contains more than 10 times as much air than cold
air near freezing point 0 degrees 'C'
100% RH air at 45 degrees 'C' contains 65.5g/m^3 water
100% RH air at 0 degrees 'C' contains 4.85g/m^3
water
Fig 1 - Humidity Content graph of air at 100% RH versus
temperature in degrees 'C'
The compressor critical final filtration system consisting
of Molecular Sieve (MS), Activated Carbon (AC) and
Hopcalite (HC) elements, can only operate in the presence of
truly tiny amounts of moisture. The bulk of the moisture
present in the air entering the compressor MUST be removed
by the high pressure compressor system design prior to the
smelly, oily, moist high pressure air hits the final air
filter cartridge for final 'trace level' filtration'.
 ....and here lies the big misunderstanding:-
Question: How is the 99.3% of all
water removed from the compressor air?
Answer: By the Compressor
Pressure Maintaining Valve (PMV) located after the Main MS/AC
air filter!
An adjustable Pressure Maintaining Valve PMV fitted to all
Divers breathing air compressors
This picture courtesy of Bauer Kompressoren, Munchen, Germany
http://www.bauer-kompressoren.de
The huge amounts of water removed by the compressor
condensate system become rapidly apparent to anyone who has
ever operated a correctly adjusted high pressure compressor in the
tropics.
To fill only one standard aluminum DOT-3AL3000 80cuft
(207bar/11Liter) scuba cylinder with divers breathing
quality air at 35 degrees 'C' ambient (leading to a final filter tower
of typically
45 degrees 'C') will require the compressor condensate
system to remove (11 x 207 x 65.5)/1000 = 149cc of
water, shown below
Fig 3 - Water contained in the humid 45 degrees 'C' air used
to pump just one 207bar/3,000psi scuba cylinder
To remove 99.3% of the water present in the air, the compressor MUST have a
PMV, and it must be set to at least 140bars/2,000psi.
The final filtration cartridge only removes the final
minute traces of moisture remaining
that are not removed by compression to the PMV release pressure.
Needless to
say, the compressor interstage condensate towers must be
large enough to hold all the water being collected after
each compressor stage over the full operating temperature
range, ambient humidity levels, and at the manufacturers published 'purge' times ranging from 5-30mins.
Due to the misunderstanding that exists about how divers breathing air
compressors work, it is surprising that not all of these compressors even have a
PMV, or have interstage condensate traps of sufficient volume to collect all the
water condensed. Such compressors cannot possibly produce EN12021 Divers
breathing quality air over the published life of the filter cartridge,
regardless of marketing claims!
How does the PMV remove 99.3% of the water?
This process is easy to visualize if you think of a
typical fully water saturated bathroom sponge. If you squeeze the
sponge into a shape half it's original volume, then half the
water in the sponge will be forced out. If you squeeze it
into 1 quarter of the original volume, 3/4 of all the water
will be forced out.
When compressing air to 140bars, you squeeze out (1-
139/140) of all the water present. Thus only 1/140 of the
original water will remain = 0.7% approx.
Question: After compressing to 140bars and
removal of 99.3% of all the water in the air, is the air now dry
enough to pass EN12021 humidity standards?
Answer: Sadly NOT. It isn't even anywhere
near the required dryness standard!
Consider; Air at 45 degrees 'C' has
65.5g/m^3 (66.5cc of water per cubic meter)
By compressing this air to 140 bars, we will still have
66.5/140 = 0.475g/m^3 of water remaining. Which comparing
with the EN12021 limits of 50mg = 0.050g/m^3 reveals that
unfiltered 140bar compressed air has a massive 10 times
the required EN12021 limit.
To remove this final 0.476g/m^3 of water from the already
high pressure air can now only be
using two techniques:-
- Chilling the high pressure air to close to 0 degrees 'C' so as to cause
condensation of moisture in the high pressure air. This is a very effective
technique used in industrial high pressure driers, but is rarely used in
small dive center compressor systems
- By the use of a water absorbent chemicals such as molecular
sieve, activated alumina, or silica gel.
In this instance,
lets use molecular sieve as the moisture absorbent for this
remaining 0.7% of water present in the original air.
It is important to understand that all of these absorbent
chemicals have only a small finite absorbency capacity. In
the case of molecular sieve, it is only able to absorb up to
20% of it's 'brand new' dry weight as water vapour.
So knowing the operating temperature, PMV pressure
setting, and weight of the molecular sieve used in the
compressor filter output filter, it is possible to
accurately
predict the life of the filter.
As an exercise, Lets consider the following two examples of leading manufacturers compressors being used in
tropical conditions of 35degrees ambient, leading to a 45
degrees 'C' final filter tower temperature. The Industry
standard Bauer Mariner 250, and Coltrisub MCH16 divers
breathing air compressors.
It should be added that the conditions used for these calculations are
entirely representative of the ambient conditions found at most holiday dive
shop operations found in popular dive travel destinations in tropical locations,
and are by no way extreme.
Lets find out how long the MS in the filter cartridges
will last in these tropical conditions...
 Bauer Mariner 250, with P31 filter system
MS=300g,
AC=40g. Pumping rate 250L/min
35 degree ambient, 45 degree 'C' final filter
tower temperature.
From this, the MS filter bed can absorb a maximum 20% of
300g = 60g of water
Thus the MS filter bed can process 60/0.475 = 126.3 m^3 of
air
Now, since the compressor pumps 0.250m^3/min, the MS in the
filter will last 126.3/0.250 minutes = 505.2min =
8hrs
25.2mins
 Coltrisub MCH16, with standard filter
cartridge system
MS=168g,
AC=50g, Pumping rate 266L/min
35 degree ambient, 45 degree 'C' final filter
tower temperature
From this, the MS filter bed can absorb a maximum 20% of
168g = 33.6g of water
Thus the MS filter bed can process 33.6/0.475 = 70.7m^3 of
air
Now, since the compressor pumps 0.266m^3/min, the MS in the
filter will last 70.7/.266 minutes = 265.8min =
4hrs
25.8mins
- Math Notes & Calculation spreadsheets:-
Both compressors have the final output filter tower placed in the warm
airflow coming off the 100degree C cylinder heads
Empirical measurements reveal that the filter tower temperature is approx 10-14
degrees C above ambient (Ref #8)
It is the actual filter tower temperature that determines the moisture that
needs to be removed by the filter and thus determines the cartridge life (not
the ambient temperature)
- Filter Math realization spreadsheet - Used to generate these
results:-
compressor_filter_lifetime_calculator.xls
Example PMV Adjustment Instructions
Bauer PMV
150 +/- 10bars |
Coltrisub PMV
120-150bars |
But this is only half the story - What about oily
smells?
Having a good feel now for how the PMV and molecular
sieve work together to produce EN12021 'bone dry' high pressure
divers breathing air. How do we remove the oily smell?
We must use a second common chemical Activated Carbon (AC) to remove oily
smells. But the air must be perfectly dry before it gets to the AC, or it won't
remove the oily smell efficiently.
How much oil is in unfiltered compressed air? Complicated measurements involving gas spectrometers by
compressor oil manufacturers (#5) have revealed the
following oil content in compressed air measured at the
typical cylinder head temperature of 100 degrees 'C'
Fig 4. Above graph courtesy of
www.klueber.com -
Manufacturer of specialist oils for use in high pressure
compressors featuring extremely long life (8,000hrs) and
extremely low evaporation rates.
It can be seen that once 'run in', most compressors using oil
lubrication are able to achieve better than 5mg/m^3 oil level in the outlet air stream.
It is seen that mineral oils evaporate many times more than modern
synthetic types leading to smelly air, greater oil consumption, and
likely quicker saturation of the AC filter bed. From the above chart it
is easy to see why the old US Navy divers breathing air standard used
5mg/m^3 - It was since most high pressure compressors lubricated by oil could
readily achieve it!
However, 5mg/m^3 is 10 times the current EN12021 limit of
only 0.5mg/m^3. Non of the oils above will be able to achieve this level
of oil mist in the compressor output air without additional Activated
Carbon filtering, which brings us nicely to the next question:-
Question: How much Activated Carbon mass does the compressor air
filter need?
Answer: Just as for the molecular sieve, it depends on the pumping
rate, ambient temperature, and if you want to squeeze the maximum life
out the activated carbon, then from the above graph it plainly depends
on what oil you are using!
However, compressor output filter cartridges are currently not specified for
use only with one particular oil - and thus it is safe to assume that the
activated carbon life is based on typical maximum oil mist levels of 5mg/m^3. So we will use a
5mg/m^3 oil mist level,
as the target amount to be removed by the Activated Carbon during our generic
oil absorbency calculations. This covers all oils given in Fig 4.
Lets find out how long the AC in the filter cartridges will last...
Activated Carbon is typically quoted as being able to absorb 5-10% of a typical
oil, so for our calculation purposes,
we will assume that the activated carbon used can absorb up to a median 7.5% of
it's weight in oil.
Bauer Mariner 250, P31 filter system. MS=300g, AC=40g. Pumping rate
250L/min, 100 degree 'C' cylinder head temperature
From this, the AC filter bed can absorb a maximum 7.5% of 40g = 3g of oil
Thus the AC filter bed can process 3/0.005 = 600m^3 of air
Now, since the compressor pumps 0.250m^3/min, the AC bed in the filter will last
600/.250 minutes = 2400min = 40hours 0mins
Coltrisub MCH16, standard filter system, MS=168g, AC=50g, Pumping rate
266L/min, 100 degree 'C' cylinder head temperature
From this, the AC filter bed can absorb a maximum 7.5% of 50g = 3.75g of oil
Thus the AC filter bed can process 3.75/0.005 = 750m^3 of air
Now, since the compressor pumps 0.266m^3/min, the AC bed in the filter will last
750/.266 minutes = 2819min = 47hrs 0mins
Brilliant, we are nearly there and can comprehend the following:-
- We understand that it is the PMV alone that removes 99.3% of all water
from the divers breathing air
- Without a working PMV, the MS and AC beds in the expensive final output
filter will be likely trashed by uncondensed water before the first tank is
pumped.
- That the life of MS in the final output filter is dependent on the
ambient temperature, and specifically on the final air filter tower
temperature
- That the life of the AC in the final output filter is actually dependent
on the rate of evaporation of the compressor oil used, and that this occurs
most readily in the high temperatures achieved in the cylinder head, and that to predict
the filter life that is valid for all popular compressor oil types, an incoming oil mist
concentration of
5mg/m^3 must be used.
Which leaves only a couple of final question concerning the 'maximum gas
flow rate in L/min the filter can handle'...
Question:- How big does the filter physically need to be, and does it have
a maximum flow rate limit?
Answer:- Depends on the compressor pumping rate, the cross section
of the filter, and the required 'dwell time' for the filter media used.
As difficult as it has been to find published parameters for all other tech
data presented in this paper, I have been unable to find any published dwell time
data for either the MS or AC filter media - let alone, dwell time data given for
different temperatures and pressures
However, similar gas absorbent chemicals such as rebreather scrubber chemicals
that remove carbon dioxide, generally work on a 2 second dwell time as the minimum required
time for the gas to pass through the filter bed so as to remove 95% of the
contaminant chemical.
Activated Carbon Volume= pi x r^2 x h
r & h in [cm]
PMV pressure in bars
Dwell time in seconds ( assumed =2)
Filter max flow rate (at pressure) in liters/minute is:-
pi x r^2 x h x (60/dwell-time) x PMV / 1000
The Bauer P31 filter, r=3.5cm, h=4cm. This gives an estimated max flow
rate = 647Liter/minute
The Coltrisub MCH16 cartridge, r=2cm, h=7.5cm. This gives a max flow rate
= 394Liter/minute
Both the Bauer & the Coltrisub filter dimensions and bed sizes adequately
meeting their 250L & 266L/min pumping rates respectively.
Removing Carbon Monoxide
This is the final 'Black art' with no published information anywhere for the
design of the various catalytic converters to remove carbon Monoxide from Divers
breathing air at high pressure.
All reputable breathing divers air compressor manufacturers have filter
cartridges available that include a hopcalite catalyser for Carbon Monoxide
removal.
My research has revealed only the following information:-
The Current practice is to use 1g or Hopcalite per 5Liter/min of
compressor flow rate
This hopcalite quantity has been found to guarantee the ability of the
compressor to accept an input air impurity level up to only 25ppm Carbon Monoxide and
produce compressed air of up to 330bar with less than 5ppm Carbon Monoxide content
(The old BS4275 breathing air standard)
Carbon Monoxide removal capabilities of compressor filters and
Notes on Carbon dioxide impurities caused by having too many workers in the
compressor room (Click thumbnail for HIRES image)
This filtration requirement is likely to allow the compressor to be used in a
typical polluted European or American inner city dive center, and yet still be
able to produce high pressure divers breathing air fills that meets all international air
purity standards.
Note that this quantity of hopcalite It is not enough to remove the carbon
monoxide produced by the compressor operator smoking a cigarette in the
compressor room, or enough to cope with pollution levels caused by a poorly
located air intake, or heavily polluted third world country with carbon monoxide
level above 100ppm at street level.
The compressed air flowing through the filter cartridge also needs to 'dwell'
in the hopcalite element for a reasonable amount of time (typically 0.5-2
seconds) to allow the hopcalite sufficient time to oxidize most of the Carbon
monoxide in the air stream.
Thus, a Bauer Mariner 250 compressor (250L/min delivery rate) would require a
filter cartridge with at least 250/5 = 50g of hopcalite. The existing filter cartridge
dimensions P21,31,41,61 all have sufficient 'dwell time' at the published
maximum flow rates and 140bar PMV pressure to carry out the Carbon Monoxide
oxidization process.
Other interesting info about hopcalite.
Hopcalite only removes carbon monoxide from extremely dry air, and is known
to not work with humidity levels above 50%. Thus, the hopcalite element MUST be
located after the Molecular sieve drying element, and the compressor must have a
working PMV...
The hopcalite also gets VERY hot when oxidizing the Carbon Monoxide into
Carbon Dioxide. Miner safety escape equipment is published to get so hot in high
carbon monoxide atmosphere that the canister temperature may blister the mouth
of the user!
Finally, should the hopcalite be located before or after the activated
carbon? Well, again the jury is still out on this. All manufacturers locate the
hopcalite after the molecular sieve. Then there is a school of thought that
states that you put the hopcalite before the activated carbon(AC), so the AC can
absorb the Carbon monoxide generated during the CO to CO2 oxidization process.
My personal feeling is that the hopcalite should receive as clean and as dry
a gas as possible - and thus should be located after both the molecular sieve &
activated carbon elements. Thus leaving both MS & AC elements to do their
respective jobs, before the Hopcalite does it's job. the small amounts of carbon
dioxide produced by oxidising any carbon monoxide present should not cause the
breathing gas to exceed the nominal 500ppm limit allowed by most international
divers breathing gas standards
I will carry out more research on this last topic and update the paragrap if
I hear anything that contradicts this statememt.
Just in case you are any doubt of how easy it is to cause death or serious
injury to divers through carbon monoxide poisoning, here is a recent carbon
monoxide diver death report and technical analysis for you:-
carbon_monoxide_maldives_death_accident.pdf
carbon_monoxide_maldives_death_accident2.pdf
carbon_monoxide
article.pdf
Conclusions
From the above math it is clear that both filter cartridges easily meet
their manufacturers published specifications in all areas provided that:-
- The PMV is set correctly at typically 140bars -
without a correctly functioning PMV removing 99.3% of all moisture in the
compressed air, the actions below will be ineffectual in preventing scuba
cylinder corrosion and clean dry breathing air.
- The condensate towers are purged at the manufactures recommended
intervals for your ambient temperature
- The final output filter tower is changed at the correct interval for
your actual measured ambient temperature.
- The background Carbon Monoxide level is less than 15ppm if you are
using a simple MS/AC (Molecular Sieve/Activated Carbon) filter cartridge.
You should use a filter cartridge with a hopcalite element if your
compressor is located in either a large industrial town, if you are using
an internal combustion engine (Petrol or Diesel) to drive the compressor, or
if the compressor is located on a boat powered by an internal combustion engine. Divers have been killed from poisonous air
pumped by electrically driven compressors when the boat engine exhaust fumes
have inadvertently leaked into the compressor air intake ducting.
Further thoughts:-
- The worlds leading diver training organizations require 3 monthly
testing of a dive centers air as part of their commitment to improving dive
safety. This is poorly enforced in most tropical dive destinations.
- Inline devices exist to assist the compressor operator in monitoring the
filter end of life such as the Lawrence factor 'Eyeball' system and the
advanced Bauer Securus/B-Control system that automatically shuts the
compressor system down when the MS filter media reaches 'end of life'
   
The promising Lawrence factor 'eyeball' device to allow the compressor operator
to see if the gas contains high levels of moisture or carbon dioxide. Sadly, I
have been unable to obtain any information from Lawrence factor as to the actual
levels of moisture or carbon monoxide that this device reacts to.
Esoteric stuff and references
Deriving the intersect of MS and AC life at lower
temperatures
Bauer Mariner 250, P31 filter system.
MS=300g, AC=40g. Pumping rate 250L/min, 100 degree 'C' cylinder head temperature
The AC and MS filter beds of the P31 will last 40hrs
0mins
at an ambient temperature that causes a 1bar 100% RH of 14mg/m^3
Referring to Fig1 & 2, 14mg/m^3 will occur at a filter tower
temperature of approx 15 degrees 'C', and ambient of 5 degrees 'C'
Thus the filter MS & AC lives will simultaneously expire after
40hrs
0mins running at approx 5 degrees 'C ambient.
Closely in line with the published lower operating temperature of the Bauer Mariner
250 compressor
Coltrisub MCH16, standard filter system,
MS=168g, AC=50g, Pumping rate 266L/min, 100 degree 'C' cylinder head temperature
The AC and MS filter beds of the Coltrisub filter cartridge will last
47hrs 0mins
at an ambient temperature that causes a 1bar
100% RH of 6.27mg/m^3
Referring to Fig1 & 2, 6.27mg/m^3 will occur at a filter tower temperature
of approx 5 degrees 'C', and ambient of -5 degrees 'C'
Thus the filter MS & AC lives will simultaneously expire after
47hrs 0mins running at approx -5
degrees 'C' ambient.
Again, closely in line with the published lower operating temperature of the
Coltrisub MCH16 compressor
A small spread sheet to calculate the 1 bar ambient pressure
moisture content is given here
compressor_ambient_humidity_calculator.xls
References
- (a) hse_air_quality.pdf report
(b)hse_dive_equipment_report.pdf
- US Navy Diver compressed breathing air standard NAVSEA
TS500-AU-SPN-010, 1-3.6.4. Diving Gases – Purity Standards
- ISO 2533 'Typical Composition for air
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=7472
- Bauer Aeroguard
http://www.bauer-kompressoren.de/en/produkte/atemluft/luftaufbereitung/aero_guard/index.php
Carbon dioxide pre-scrubber to assist in the production of EN12021 divers
breathing quality air.
- Oil content in compressed air report from
www.Klueber.com at
http://www.klueber.com/Kontakt/Kontakt_Unterseiten/pdf-broschueren/Druckluftkompressoren-EN.PDF
An Archive of this report is contained here ==>
documents/oil_content_in_compressed_air_klueber.pdf
-
bauer_filter_technical_description_and_specification.pdf
-
hse_moisture_levels_in_compressed_air.pdf
- Bauer P21 Filter system
technical description .pdf (564Kb)
- Bauer Securus system
http://www.bauergroup.com/en/produkte/atemluft/optionen/securus/index.php
|
