Bauer Mariner typical operational temperature in the tropics

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IyaDiver

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Gents,

I hope this may come useful to some.
I have the test data, I might as well share it.

Start at below post first, so I do not need to double post to see the test set-up :
http://www.scubaboard.com/forums/red-sea/352814-inline-co-monitors-sharm-el-sheikh-4.html

Some corrections and addition I need to make for that link :

01. The 2 channel data logging thermometer is not US$130, I think its US$170.
It is only a 16,000 points memory capacity and not 64,000.
It is the APPA 55 II
Welcome to APPA
One of this logger has a habit of registering some funny year, like 1970 or 2040...:D at least once per 10 times data loading. I never bother to check why because by downloading for the 2nd time, it usually will be OK.


02. I use two types of digital pressure gauge, one is the cheapest Eco 1 ( not Leo 1 ) and it is 0.2% accuracy, not 2%. The Leo 2 is a 0.1% accuracy, not 1%.



Some facts I learn during this compressor tinkering process :

03. Sourcing fittings for Bauer metric using Voss brand fittings and matching it to US sourced common 1/4" NPT based accesories is a nightmare. I am a real dumb dumb when it comes to fitting specification.:idk: . I need more reading time to understand various names 1 type of fitting can be called in various parts of the world, than to understand how a compressor works.:D The East/British/USA/Metric fitting standards drove me nuts. I admire the simplicity of 1/4" NPT with its must-use teflon seal tape more now, even though it does not look neat and positioning accuracy can be very difficult sometime .

04. IAN / HSM a compresor expert member of this forum is correct, Bauer fittings indeed is crappy !!! When I see Swagelok and a Voss, damn its like a Lexus compared to a Yugo . Voss single ferrule fitting is not very reliable compared to a Swagelok twin ferrule when one dismantle the fitting often.


Attached is a two days test graph.

05. I have repositioned my 14" blower and will need to do it again as I am getting 5C hotter than last week 1st time 14" blower position.

06. The graph is a combination of two days test run and since the two data loggers produced 2 different TXT files , I combined them in one Excel file. I am an Excell dummy, so bear with me. This is a 5 seconds data points. One graph has 385 data points or 32 minutes and the other is 391 data points or 33 minutes. It does not matter, the extra minutes are for the cooling down period when the compressor is already OFF.
Accuracy of all graph temperature rise is within 5 seconds between 17th and 18th December, so it is pretty accurate. Ambient temp is 30.9C for both days.

07. The 3rd stage temperature sensor is already placed at that Bauer prepared hole.


My conclusion for the test is :

- In 30-33C ambient temperature operation a Bauer Mariner standard pulley fan is not enough to have a 2+ hours non stop run without forced cooling. I do not need to test to 2+ hours, I can see from the temp rise.

- Until I repositioned the P41 filter housing to get best airflow for 2nd stage cylinder and its cooler pipe ( keep the water separator where it is now), I can not yet confirm a 100% sure why is the 2nd cylinder being the hottest one instead of the feared 3rd cylinder. I can only assume for now that the extra heat maybe because of :

AA. It is taking accumulated heat from 1st stage compression and it is not getting as much cool pressurized oil bath as 3rd stage floating piston.

BB. Maybe due to the older design of 50 BAR oil pressurized non ringed floating piston 3rd stage of Mariner's older block and temperature sensor hole traditionally been placed on that 3rd stage, no one actually worry and monitor 2nd stage cylinder head temperature like I do.:idk:

CC. The aftercooler of 3rd stage being a finned tube is surely a more superior aftercooler than the fat coiled aluminum pipe the 2nd stage uses. The finned pipe positioned is also very strategic and get best head wind from pulley fan and its round widely spaced coiling seems to do best heat removal, better than the closedly spaced coil of the 2nd stage cooler fat pipes. Looking at the fat pipe 2nd stage aftercooler placement and wind direction, the real cooling is only great for 30% or so of the pipe head-wind side.
If one were to think of a car radiator and fresh air as head wind, the 3rd stage finned aftercooler pipes is the car main radiator and the 2nd stage is like a car's air-conditioining radiator ( condensor ) placed behind engine's radiator and get second class cooling..:D . No doubt the 3rd stage aftercooler finned pipe is after the exhaust valve, it should contribute to some degree of cooling for the 3rd stage cylinder head and not only for air heading to the final water-separator.

That finned cooling pipe has great performance. Imagine the cylinder head of 3rd stage being at 90C. The discharged air temperature must be at least 20C hotter if not more.
Assuming it is the same temp for the cylinder head and the discharged air and temperature rise in final water separator again assumed at 40C ( exterior temp ) because we discounted the fact the thick aluminum tube it uses will slow temperature reading. Keep it simpe, that is 90C reduced to 40C or equivalent is a 50C temperature reduction.........wow !!

If it is not a financial motivation, I wonder what technical reason/s for diving compressor manufacturers not to use finned cooling pipes for 1st and 2nd stages aftercooler.


I been reading recripocating ( piston ) compressor design literature and trying to understand how to remove more heat from my Bauer. The diesel engines I tinker with is all water cooled and it is easier to remove the heat, in fact the marine diesel is even less interesting with water cooled exhaust manifolds and turbos and intercooler. This Bauer is air cooled and I never tinker with air cooled "engine".

Swampdiver said his Securus manual stated 132C as safety shut down temperature of final stage cylinder temperature. Jordair ( Bauer Canada ) user manual stated 275F as shut down temperature, that is 135C. So 130C is best to use for me.

Conservative recripocating compressor design ( as per my literature ) aims to have the discharged air no hotter than 300F ( 149C ) and in fact trying to get 275F ( 135C ) as a safer temperature for concern of carbon deposit from the oil. It seems from various design available, the piston type seems to be the hottest.

Now, in a compressor with external source as prime mover ( electric/gasoline/diesel ) and if manufacturer like a Bauer set 132C to 135C as overheat shutdown, what is their fear ? Definitely it is the compressor oil they are protecting and whatever carbon deposit that a cooked oil will produce plus the poison in the air as bonus. Exhaust gas temperature of a land based diesel generator at 90% load is hot enough to glow the exhaust manifold like an oven grilling a turkey. So fear of overheating any compressor "metal" is probably not the reason.

Marine diesel engine with pressurized water cooling sounds its overheat alarm at 108C ( I can't believe this but the Cat techie told me ) for Caterpillar 3412 and MAN D28 engine family at 97C ( 100% sure ), when these engines are rigged as land based generators, those will be safety shutdown temperature.

To think my small compressor cylinder head temperature is a whopping 130C+ without forced cooling and that is the temperature in less than 15 minutes run at ambient temp of 30-31C is indeed scarry. Maybe the compressor boys should assign Porche boys to design the air cooling system.:D Heat rejection of the air cooled 911 turbocharged engines is massive and it can survive in tropical country at 5km/h 1 hour traffic jam, is an engineering marvel. Small air vents, rear positioned in the car and not the best air-path here and there and it can survive...amazing. At idle and dead in traffic with air conditioning running, that is at least 5kw of power consumed and "X" value of heat produced and needed to be removed and Porsche did that well.

My Mariner is only 4kw for the motor, so the amount of heat produced for the compressor can't be more than 4kw worth. I do not know how many Kw goes to the fan pulley air flow works. What I know is, my 0.75kw single phase, 83,000 liter per minute cooling fan at 2,800 RPM is producing at least 3 times more air than the 1,250 RPM Bauer pulley fan, if not more.


So, compressor experts do chime in please.
Those owners of other brand of compressors, what is the shut down temperature of yours ?

How many hours run will you need and at what ambient temp when you get the auto shut down in action usually ?

Thanks
IYA
 

Attachments

  • Blower ON and OFF graph.JPG
    Blower ON and OFF graph.JPG
    116.7 KB · Views: 204
  • Water Separator 17 & 18 Dec.JPG
    Water Separator 17 & 18 Dec.JPG
    116.5 KB · Views: 162
Note :

18 Dec graph is a short compressor run.
The neon green marker labelled "ON" is when I turned on the blower. The temp dropped from 133C to 120C something as soon as the blower is turned on. The sharp temperature decline from 120C something to 50C something is the compressor being turned OFF while still being cooled by the blower.

Any sudden "drop-off" in the graph is compressor being turned OFF and blower kept running to cool it faster.

17 Dec is the compressor running from start to finish with blower ON but it is a much longer run than the 18th Dec one. This is to show the heat build up is much less with the blower ON.

If on 18th Dec test, if I ever kept running the compressor for 33 minutes instead of that 12 minutes, I wil probably hit 150C+ at 2nd cylinder.

As oil lubrication exist in every piston liners, be it 1st stage, 2nd stage and surely the oil rich 3rd stage, I set maximum temperature 130C as whichever cylinder hit that hot, compressor must be shut down.

IYA
 
Finally, I have found what I think as the answer to why Bauer would put 132 - 135 C as maximum cylinder head temperature.

I do not have air discharge temperature data at final stage, so I do not know how much hotter the actual discharged air is , if a cylinder head were to be at 132 - 135C.

However, looking at oil Auto Ignition Temperature aka AIT ( from a mining industry report ) which caused fire on compressor lubricant, there is some nice information on what 3000 psi of pressure effects oil Auto Ignition Temperature. The real mathematical calculation I can't find it yet, it must be bought in a form of book or studies.

Link #1 - Read page 4 :
Fig. 3 - Autoignition temperature of mineral-based fluids as a function of pressure
http://www.msha.gov/S&HINFO/TECHRPT/FANDE/OILROT.pdf


This is from Ariel Compressor, its compresors size makes Bauer looks so tiny
Link #2 - Read Page 1 :
1. Ariel compressors are designed for maximum discharge temperature of 350°F (177°C). For safe operation, lube oil auto-ignition temperature MUST exceed compressor discharge temperature at the discharge pressure. The auto-ignition temperature of oil significantly drops when pressure increases. Users must determine the lube oil auto-ignition temperature and operate the compressor at a safe temperature. Unit shutdowns MUST prevent air temperature from reaching lube oil auto-ignition temperature at operating pressure. http://www.keesofferman.nl/calculators/ariel packager guidelines CTB158.pdf


Link #3 - Read page 4 :
Tab. 2: Autoignition temperatures of several pure compounds at elevated pressures compared to the standard values
http://www.combustion.org.uk/ECM_2005/Papers/218_Hirsch.pdf


Link # 4 - Read page 23 : SulliAir Corporation, Rule of Thumbs
"For every 1 psi of compression, it reduces 1 °F of flashpoint down from the fluid’s rating. 150 psi is 150 °F less flashpoint. Also need to consider ambient rise (100 °F) and high operating temperatures (20 °F)."
NOTE : I wonder if SulliAir meant to print AutoIgnition temperature instead of Flash Point or both parameters have up to certain pressure a similiar drop ??

http://blog.ringpower.com/file.axd?file=LIT_Fluid+Reference+Guide.pdf



Link #5 - ChemLube 800 Auto Ignition Temperature : 391C or 735 F
http://www.ultracheminc.com/productimages/thumb/CMS/Files/CHEMLUBE_800.pdf


So, if Link #1 graph is applied to 735 F of CL800 auto ignition temperature, we get approx 350F at 3,000 psi or 176.67 Celcius. This is in line with Ariel Corp reccomendation of 177 Celcius as maximum allowable discharged air temperature and synthetic ester based lubricant for air service.

If Bauer uses 15% safety margin, 177C less 15% = 150.45 C as maximum discharged air temperature allowed, that may mean a 135C cylinder head temperature may equal to 150.45 C discharged air temperature........maybe. That is an estimated temperature difference of 15 Celcius cooler on the head temp over the air temp.

The only way to confirm is using a discharged air temperature probe/sensor, its not cheap at 3,500 psi working pressure and a headache to install.


All the while previous discussion on compressor oil been on Flash Point of the oil, it is not the true measure of potential of the oil being burned and create soot or carbon deposit ( if not potential fire or air contamination hazards ). Besides it is misleading to think a 250+ Celcius oil flash point is safe, now that we know it is the auto ignition temperature of the oil we must worry most and it MUST be calculated at working pressure of 3000psi or whatever pressure you guys are pumping.........dang !

The flash point of a volatile liquid is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a liquid's flash point requires an ignition source. At the flash point, the vapor may cease to burn when the source of ignition is removed.

The flash point is not to be confused with the autoignition temperature, which does not require an ignition source.

The fire point, a higher temperature, is defined as the temperature at which the vapor continues to burn after being ignited. Neither the flash point nor the fire point is related to the temperature of the ignition source or of the burning liquid, which are much higher.



So, compressor operators in high ambient temperature, best to pay attention to ALL cylinder heads temperatures and not only final stage one. 2nd stage pumping at 46 BAR ( 3 stage compressor ) is already considered high enough pressure for the auto ignition temperature of the oil to slip down by 200F.....:depressed:

Hope the information can improve the longevity of your compressor and produce consistent quality breathing air.

PS , no wonder SwamDiver hinted me on paying more attention to Auto Ignition Temperature of the oil and not its Flash Point. Holy Cow, if SwampDiver is an engineer and not a doctor, he will make one great engineer that pays attention to the finest details. I bet he is a great doctor.

IYA
 

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