What you have is a simple volumetric conversion with atmosperic pressure differential/which is available with any roots type blower literature. gravity is not your friend at altititude etc.

What you need if you do not have one already is a delaval or other brand milk house vacuum gauge kit and or a manomometer to verify the actual loading on the blower or fan regarding the manomometer you need a connection fitting plugged into the air stream(manufactured by the fan builder)-not you!!!!!!!!!

Blowers and fans will push or pull the "SAME" cubic volume as it relates to the volume design of the fan housing or blower rotor housing etc., but the actual manomometer pressure or vacuum Hg. will be less due to the altitude- in our case it was a roots blower calibration/pressure regulator-relief valve-used in vacuum service for rock dust collection as we were below sea level in the mine we were working in increasing the vacuum Hg. slightly etc.

my two cents ■

Dear Harold,

A quick calculation goes as follows:

A blower is a positive displacement gas pump. That means that the displaced volume is “always” the same, irrespective of the location.

Secondly, the performance of such a pump is determined by the intake conditions.

At sea level the atmospheric pressure is 1 bar.

At an altitude of 3850 m above sea level the atmospheric pressure is 0.64 bar (your info)

In the blower calculations you just have to replace the 1 bar by the 0.64 bar

(disregarding the influence of less oxygen in the air)

Air density at 3850 m and 0.64 bar = 1.293 * 273/(273+11) * 0.64/1 = 0.79546 kg/m3

The displaced volume = 492 m3/min

The displaced mass of air therefore is 492 * 0.79546 = 391 kg/min

With the mass flow of air and the amount of oxygen you can perform your chemical calculations and find out the air requirement for your process.

To regulate this mass flow, you can also use a variable frequency drive motor, which will be a proportional regulation.

Mind lubrication issues.

If you like me to do a more extensive table calculation, please let me know.

I will need the rpm then.

Hope to have helped a little bit

Centrifugal fans are more complicated to calculate at different pressures

success

Teus ■

I thionk you mean ambient temperature?

Air pressure at sea level is 14.28 PSI if my memory has not failed me :^)

Cold air is always more dense- that is why underground mines generally have better air in the winter as it takes less effort to push it underground.

P.S. my dear freind Teus is always a great helping hand for any one who needs it. ■

Please look at this:

http://www.comairrotron.com/highaltitudecooling.shtml

Boyle's law, Charles' law, and Gay-Lussac's Law form the combined gas law. Use these laws for calculatios. ■

Please look at this:

http://www.comairrotron.com/highaltitudecooling.shtml

Boyle's law, Charles' law, and Gay-Lussac's Law form the combined gas law. Use these laws for calculatios. ■

Dear Harold,

Every rotation of the blower rotor displaces the same amount of VOLUME.

The physical conditions of the displaced gas may be different, as the gas conditions at sea level differ from the gas conditions at a high altitude.

I calculated the density at 3850 m.a.s.l. at atemperature of 11 degrC (273/(273+11))

Approximate calculation as follows:

492 m3/min = 8.2 m3/sec = 8200 ltrs/sec

At 590 rpm, each rotation displaces 60 * 8200 / 590 = 834 ltrs/revolution

At an assumed volumetric efficiency of 0.834 the internal volume displacement = 834/0.834 = 1000 ltrs/rev

Quite a big blower and therefore I assumed a no load power requirement of 60 kW

Then I ran the blower calculation several times, iterating for the internal leakage until the results matched the data you have supplied.

Volume = 492 m3/min

Pressure rise = 29.34 kPa = approx 0.3 bar

Power = 355 kW

BLOWER CALCULATION

Pressure----Displacement----------------temp------kW

(bar(o))------m3/sec--------- m3/min---- incr

0.00-----------9.833----------590.0-------- 0--------60.0

0.10 ----------8.892--------- 533.5 -------- 9. -----158.3

0.20 ----------8.502----------510.1--------18.------256.7

0.30----------8.202-----------492.1--------28.-----355.0

0.40----------7.950----------477.0---------39.-----453.3

0.50----------7.728----------463.7---------50.-----551.7

0.60----------7.527----------451.6 --------61.-----650.0

0.70----------7.342----------440.5---------73.-----748.3

0.80----------7.170----------430.2 --------86.-----846.7

0.90--------- 7.008 ----------420.5------- 98.------945.0

1.00----------6.856----------411.3-------112. ----1043.3

ROOTSBLOWER(S)

Pump displ/rev : 1000 dm3/rev

Int.leak/.1bar : 56.5 m3/min at 0.1 bar pressure difference

Nominal rev. : 590 rpm

Actual rev. : 590 rpm

Losses at nom.rev: 60 kW

Nr of pumps <1> : 1

About the occurrence of the percentage of oxygen at high altitudes, I cannot help you.

Would be interesting to know though. (A quick search on the internet gave no results)

best regards

teus ■

I am not an expert on this but as far as my understanding goes there is little change in oxygen concentration with altitude which is due to change in partial pressures and at 3000m the Oxygen concentration in air is still 20.9% But with decreased pressure at high altitudes the same volume of air will contain less oxygen molecules figure I found is the at 12000 ft there is 40% less oxygen per breath as compared to sea level. ■

dear Harold, Mr Mantoo,

I found this link on the web:

http://www.altitude.org/calculators/airpressure.htm

It has also a pressure calculator for altitudes.

At 3850 m altitude, 63% of the oxigen at sea level is available

It also confirms the statement of Mr Mantoo that the volumetric ratio of oxigen to nitrogen stays the same at higher altutudes.

all for now ■

Dear Harold,

a)

Design for the application and the ambient and ruling conditions.

In this respect is over designing not necessary.

b)

Combustion equipment also has to be designed for the application.

Whether you are referring to burners or engines, the rule under a) always applies.

c)

The best thing to do is to consult the respective equipment supplier.

They are aware of all the design parameters.

Adapting sea level equipment to high altitude conditions might be very complicated and needs detailed knowledge and engineering.

take care

teus ■

Greetings and salutations from my corner of the slowly defrosting "Eastern Wilderness" @1140 feet above mean sea level. Harold this brings to my mind a possible very economical fix regardless of altitude etc.

Up north here we have muffler shops galore and they use cutting torches to rid themselves of bad mufflers and exhaust pipes when replacing them with new ones.

And if you have spent anytime in a welding shop they use a lot of bottled oxygen for cutting and brazing etc.

One local state wide muffler franchise with HQ in Buffalo NY decided it was spending to much money on oxygen and oxygen bottle deposits-freight cost I believe the term is demurrage I think thats right-been a long time away from the business of mining :^)

This also brings to mind a crazy story i remeber from about twenty five years ago that involved a power plant being built on Lake Erie; Seem the contructors of the plant in question were going through a huge amount of oxygen and creating a huge demmurage charges every month for oxygen bottles that went missing and they decided to find out why; so the mamagers were passing through the building under construction and they found a bunch of the fellows eating thier lunch on the lake side construction dock and they also found a launching ramp used for the oxygen bottles they were missing and of course they were taking bets on how far a cylinder would travel past the bouys during their lunch break while launching the cylinders on the ramp by breaking the valves off with a sledge hammer.

And of course you can guess end of the story as the mystery was solved and they had to find some new laborers for the construction of the power plant.

So anyway this Xorbox unit connects to the air compressor system and strips pure oxygen from the air stream of the air compressor and pressurises it to a low useable pressure for cutting and brazing torches.

The brand name is "Xorbox" if my memory serves me but googling

So anyway the Xorbox is a low voltage neat little varmint that is used in most shops with high sales volume is what is referred to as an oxygen generator which uses presure swing adsorption to strip the oxygen and store it for both continuos and later use.

AirSep purchased Xorbox in 1990 and both companies phones are listed here for you.

Xorbox 011-716-691-1255

AIRSEP Tonowanda. ny

011-716-691-0202 obviously a good way to remember :^)

This may be an easy way to solve your little predicament regarding your blower by adding a low volume oxygen source to aid combustion and avoid changing physical plant, equipment operating pressures, process flow designs, etc. in regard to your present operating conditions.

But the devil is in the details so:

I think in your case a phone call to these folks would solve your troubles.

lzaharis

Hello Teus, I hope all is well we are dealing with much cold weather here at altitude with a slow wet spring in store for us in the eastern wilderness. ■

You can try injecting oxygen in the kiln to achieve required combustion conditions. Oxygen injection in klin is routinely done in many countries to boost production in fan-limited kiln or to increase the alternative fuel substitution or to lower emissions. It will defiantly require onsite oxygen generation though and at these altitudes it will be expensive. ■

stripping nitrogen is not worth it due to the process involved etc. and it will not increase the useable oxygen and the oxygen generator will be of more benefit to you ■