pufferfish
Contributor
Does anybody know the dewpoint at which the sensor is designed to signal a colour change from green to yellow, from yellow to red?
Thanks
Thanks
Bauer Securus Monitor
- Thread starter pufferfish
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
OP
pufferfish
Contributor
Ok at risk of having a conversation with myself after a lot of digging I have found the answer to the above question.
The green to yellow light change is set at -85 C
The yellow to red light change is set at -65 C
There is no documentation out there on this unit and Bauer seems to feel the inner workings of its device are 'confidential'. Despite the fact they sell the inline hygrometer to monitor breathing air, a very demanding application, this device cannot be calibrated and there is no way to monitor when the sensor has failed or drifted off its calibration point. In other words if it drifts down and reads too dry the operator continues with the false belief the filters do not need a change when in fact the air contaminants' concentrations (H2O, CO, CO2) have started to rise in quantity due to excessive media moisture. I have seen the light remain green despite a dewpoint of -55 C. This 'false negative' situation is a very unsafe way for a unit to fail.
I suspect they have a low cost sensor in this box. These low dewpoint sensors do not remain reliable for years as Bauer seems to indicate and need to be checked and replaced if faulty. The only way this can be done with a Securus monitor is to check the unit when the light is green and at each of the change points for accuracy. Most of these low dewpoint sensors start to loose their sensitivity when exposed to excessive moisture over time.
One would be better off just recording the hours the filtration has been used or spending more on a high quality inline hygrometer where the sensor can be calibrated and its proper functioning verified. PM me if you want info on these units.
The green to yellow light change is set at -85 C
The yellow to red light change is set at -65 C
There is no documentation out there on this unit and Bauer seems to feel the inner workings of its device are 'confidential'. Despite the fact they sell the inline hygrometer to monitor breathing air, a very demanding application, this device cannot be calibrated and there is no way to monitor when the sensor has failed or drifted off its calibration point. In other words if it drifts down and reads too dry the operator continues with the false belief the filters do not need a change when in fact the air contaminants' concentrations (H2O, CO, CO2) have started to rise in quantity due to excessive media moisture. I have seen the light remain green despite a dewpoint of -55 C. This 'false negative' situation is a very unsafe way for a unit to fail.
I suspect they have a low cost sensor in this box. These low dewpoint sensors do not remain reliable for years as Bauer seems to indicate and need to be checked and replaced if faulty. The only way this can be done with a Securus monitor is to check the unit when the light is green and at each of the change points for accuracy. Most of these low dewpoint sensors start to loose their sensitivity when exposed to excessive moisture over time.
One would be better off just recording the hours the filtration has been used or spending more on a high quality inline hygrometer where the sensor can be calibrated and its proper functioning verified. PM me if you want info on these units.
Regarding your post it may be the high technical nature of the request that eludes the lack of responce in a general sports SCUBA forum. It is also common that enquiries to companies are answered by sales and marketing staff, rarley are the design engineers allowed to comment!
The dewpoint alarm settings are adjusted on the board by a number (normally 2) potentiometers, each to a relay for an alarm setting in addition to the LED display. The setting is normally to each countries air purity standard if not specified by the purchaser.
The transducer (head) resistance varies with humidity. Two palladium metal wires wound around a core of lithium chloride or bromide form a thin film over the wires, the element is protected with a sheath. This coated hydroscopic film changes in resistance in an AC current.
The accuracy is dependent on the type class A and B +/- 1% and +/- 2%.
The limits are between 160 to 200 deg F and 10,000 psig (Imperial Units)
The gas velocity can cause problems over 200MPH, OK but with a deflector.
The sensor life is limitless however calibration can be altered by certain contaminants, namley dirt or dust (normally from the molecular scieve in the filter towers) will slow down the responce time and on oil lubricated compressors the oil carry over will form an insulation film over the wire insuating the film to water vapour, rendering it inactive.
In your case with this oil lubricated comprssor unstable hydrocarbons such as ketones, halogen gas, hydrogen sulfide and sulpher dioxide will poison the sensor in a manner similar to the effect of water vapour and give a reading as water. Also ammonia, alcohols glycol and glycerols sometimes used by the home brewers in cleaning there compressor parts get carried over.
In an oil free compressor any contanination is simply "washed out" by flowing clean but humid air over the sensor. When condensation is evapourated without running off, the salt crystals could be realigned. Also in your case the condensate could have remaind electrolytic thus changing the calibration.
Never attempt to touch the sensor or you will bugger it up. If its just dust it will not be that serious however precise field-calibration of the head is extremly difficult.
Two items may be of help. A small visual moisture indicator ($60 US) (£40 UK)
can be used to pick up 20, 40, 60% relitive humidity in the gas stream prior to the indicator, the card colour (color) changes from blue to pink when wet.
Also a 2 micron stainless filter $40/ £30 can also be of use.
The problem with your system may be that it is probably fitted atop the final filter tower, hot wet and humid when the filter chemicals fail.
<Quote> "The inner workings of the device are confidential". This does not exclude you from understanding the product, its limitations and its intended operating design scope. Your supplier has a duty of care to resolve this matter, maybe remind him of his responcibilities, or change vendors.
The dewpoint alarm settings are adjusted on the board by a number (normally 2) potentiometers, each to a relay for an alarm setting in addition to the LED display. The setting is normally to each countries air purity standard if not specified by the purchaser.
The transducer (head) resistance varies with humidity. Two palladium metal wires wound around a core of lithium chloride or bromide form a thin film over the wires, the element is protected with a sheath. This coated hydroscopic film changes in resistance in an AC current.
The accuracy is dependent on the type class A and B +/- 1% and +/- 2%.
The limits are between 160 to 200 deg F and 10,000 psig (Imperial Units)
The gas velocity can cause problems over 200MPH, OK but with a deflector.
The sensor life is limitless however calibration can be altered by certain contaminants, namley dirt or dust (normally from the molecular scieve in the filter towers) will slow down the responce time and on oil lubricated compressors the oil carry over will form an insulation film over the wire insuating the film to water vapour, rendering it inactive.
In your case with this oil lubricated comprssor unstable hydrocarbons such as ketones, halogen gas, hydrogen sulfide and sulpher dioxide will poison the sensor in a manner similar to the effect of water vapour and give a reading as water. Also ammonia, alcohols glycol and glycerols sometimes used by the home brewers in cleaning there compressor parts get carried over.
In an oil free compressor any contanination is simply "washed out" by flowing clean but humid air over the sensor. When condensation is evapourated without running off, the salt crystals could be realigned. Also in your case the condensate could have remaind electrolytic thus changing the calibration.
Never attempt to touch the sensor or you will bugger it up. If its just dust it will not be that serious however precise field-calibration of the head is extremly difficult.
Two items may be of help. A small visual moisture indicator ($60 US) (£40 UK)
can be used to pick up 20, 40, 60% relitive humidity in the gas stream prior to the indicator, the card colour (color) changes from blue to pink when wet.
Also a 2 micron stainless filter $40/ £30 can also be of use.
The problem with your system may be that it is probably fitted atop the final filter tower, hot wet and humid when the filter chemicals fail.
<Quote> "The inner workings of the device are confidential". This does not exclude you from understanding the product, its limitations and its intended operating design scope. Your supplier has a duty of care to resolve this matter, maybe remind him of his responcibilities, or change vendors.
OP
pufferfish
Contributor
That is great info Iain and exactly why I posted the question on this board. It never ceases to amaze me with over 20,000 members now on SB how there is always someone with the knowledge to provide an answer to a question however technical it may be.
I don't know how common Bauer Compressor is over in the UK but here in North America they are likely the largest compressor distrubutor and the one I see the most often in dive shops. Their product the 'Securus monitor' can be seen below under Scope of Supply and this is all the technical info you will find anywhere on the unit. No documentation is provided when one purchases the unit either, and getting information from the Bauer has been difficult however I did get some info from the person in charge of air quality which has been useful. Those pre-alarm and alarm settings apparently are set in Germany and are not modified to the local environment according to Bauer. You can see that at -85 C and -60 C (compressor is shut down here) the air would be extremely dry and pass any jurisdiction's air standards. However when it fails with the green light on, one does not know where the dewpoint is and by extension the quality of the filtration media. Interestingly, I asked Bauer specifically about the contamination issues you speak of and they said no problems whatsoever, but I suspect like you have clearly pointed out that the use of such a probe in an enviroment with so many potential contaminants is likely a poor design. For them to say 'don't worry, be happy' is not only bad marketing but a health and safety liability as well.
Bauer inline Securus monitor
Do you know which way the probe might drift should it become contaminated with excessive water, oil, S02, or otherwise? This one seems to have drifted down or it is reading the air drier than it actually is. One other design engineer from a high-end low pressure hygrometer manufacturer said there are no probes on the market that require no maintenance and which will work forever. They were very surprised at the demanding application this so called calibration-free probe was being used for.
The problem is though these units are very common throughout the diving air industry and they are sold as 'maintenance and calibration' free for the explicit use of monitoring moisture in breathing air, a very demanding application. When they fail in the false negative mode the risk of injury does exist as not only does the humidity start to rise and present a risk for divers in a cold water environment, but the hopcalite's function becomes compromised with increasing humidity which may lead to increasing CO levels. The activated charcoal also demands a dry environment to function properly.
Thanks for the suggestions regarding work arounds for the problem. Clearly the unit needs replacement but one is hesitant now knowing the design limitations to re-install the same technology which likely will fail again after a few years. My personal opinion is that Bauer should not be selling a unit for monitoring breathing air quality where one cannot calibrate the unit or verify its proper functioning as this is inherently unsafe. They should either sell a proper unit that one can calibrate or not offer this product at all.
I couldn't agree more with your statement, "this does not exclude you from understanding the product, its limitations and its intended operating design scope. Your supplier has a duty of care to resolve this matter, maybe remind him of his responcibilities, or change vendors." Especially the responsibility aspect and I am working on what to do about the rest.
I don't know how common Bauer Compressor is over in the UK but here in North America they are likely the largest compressor distrubutor and the one I see the most often in dive shops. Their product the 'Securus monitor' can be seen below under Scope of Supply and this is all the technical info you will find anywhere on the unit. No documentation is provided when one purchases the unit either, and getting information from the Bauer has been difficult however I did get some info from the person in charge of air quality which has been useful. Those pre-alarm and alarm settings apparently are set in Germany and are not modified to the local environment according to Bauer. You can see that at -85 C and -60 C (compressor is shut down here) the air would be extremely dry and pass any jurisdiction's air standards. However when it fails with the green light on, one does not know where the dewpoint is and by extension the quality of the filtration media. Interestingly, I asked Bauer specifically about the contamination issues you speak of and they said no problems whatsoever, but I suspect like you have clearly pointed out that the use of such a probe in an enviroment with so many potential contaminants is likely a poor design. For them to say 'don't worry, be happy' is not only bad marketing but a health and safety liability as well.
Bauer inline Securus monitor
Do you know which way the probe might drift should it become contaminated with excessive water, oil, S02, or otherwise? This one seems to have drifted down or it is reading the air drier than it actually is. One other design engineer from a high-end low pressure hygrometer manufacturer said there are no probes on the market that require no maintenance and which will work forever. They were very surprised at the demanding application this so called calibration-free probe was being used for.
The problem is though these units are very common throughout the diving air industry and they are sold as 'maintenance and calibration' free for the explicit use of monitoring moisture in breathing air, a very demanding application. When they fail in the false negative mode the risk of injury does exist as not only does the humidity start to rise and present a risk for divers in a cold water environment, but the hopcalite's function becomes compromised with increasing humidity which may lead to increasing CO levels. The activated charcoal also demands a dry environment to function properly.
Thanks for the suggestions regarding work arounds for the problem. Clearly the unit needs replacement but one is hesitant now knowing the design limitations to re-install the same technology which likely will fail again after a few years. My personal opinion is that Bauer should not be selling a unit for monitoring breathing air quality where one cannot calibrate the unit or verify its proper functioning as this is inherently unsafe. They should either sell a proper unit that one can calibrate or not offer this product at all.
I couldn't agree more with your statement, "this does not exclude you from understanding the product, its limitations and its intended operating design scope. Your supplier has a duty of care to resolve this matter, maybe remind him of his responcibilities, or change vendors." Especially the responsibility aspect and I am working on what to do about the rest.
Similar threads
