Motor swap and air dryer questions.

[ti325v]

I am setting up my compressors in a new location. I have three phase 380 volts outside my door, but they want $3000 to run the wire ! UNBELIEVEABLE....there was another dive shop here, and they moved 5 times at $3000 a pop for the three phase....
I want to swap over to 220 single, which is household current here.
My compressor has a 112M frame 5 h.p. 3 phase 380 volt motor. Manufacturer says I need 4 KW.

I have found a replacement 112M 1 phase 220 volt motor rated at 3.7 K.W.
The compressor is good for 300 bar, but I have down rated it to 220, as we only fill Al 80`s with it.
I am having a very hard time determining if they use the same motor for the 300 bar and 200 bar versions. The manufacturer is of no help.

If indeed they use the same motor.....will the 3.7 K.W. (Draws 26 Amps) be adequate to pump 220 bar ?
If not I have to make a jump up in frame size, and I will have to remachine the pulley to accept the shaft.
This unit delivers quite close to 200 l/min.
BTW this motor is costing me $190 !!!!!
1 year guarantee, TEFC, 1.15 load factor, dual ball bearing, continuous compressor rated. 45* C. 1,200 mFD capacitors....92 pounds !
Original motor was 1350 rpm, the new is 1450.



Next question...I am aware that moisture is the enemy of a filtration system.......I have available to me second hand Hitachi air dryers. I can get a 400 lit/min for about $300.
Is it worth drying the air ? I know there is massive moisture removal during compression, but how will it effect my filter life if my intake air is humidity is reduced from 90 % at 30 *C ( Dew Point about 28*C ) to an outlet dew point of 10* C ?, or about 30 % R.H at 30 *C . If I understand all that I am learning correctly.....

 

[Zodiacdiverdave]

Hi, switching over to a single phase motor may require you to change out you motor starter or contactor. You will need to check the amperage rating on your contactor and your overload protection, also your wire size to your compressor from your main breaker panel may have to be increased. Your are best to have a certified electrian or a compressor repair shop do this because if you burn your new shop down your insurance company may walk away from you leaving you with nothing but cinders.
The next thing you have to look at is the motor speed. If your new motor has a different speed then your old one then you will have to change the drive pulley so your compressor will run at the same speed or close to it. Best to start slower rather then faster. With a hand held ampmeter and when the compressor is running check the amperage draw on from the motor. Check it when the oil in it is cold and then again when it is at full pressure this is when it draws the most amps. If the motor is drawing more then 26 amps you will need to decrease your pulley diameter until the unit is drawing 26 amps or less. if you are not even close to the 26 amps then you can speed up the compressor untill it is close but not over.
Then depending on your control voltage you may have to change out the transformer or if you are lucky not use one at all. Again best to have an electrician do this so he wears the liablity.
Next, to address the purification question. I live in Canada and to sell breathing air it must meet a standard. Dew point must be -53 deg C or lower. This is to prevent equipment freeze ups and to keep moisture out of the diving or SCBA cylinders. So check the requirements for the area you are setting up in for the dew point limits but I would certainly expect you will need a purification system that has a drying element in it.
When opening a dive shop one way to quarantee failure is to sell bad air, and with a 5hp compressor, which is quite small for a dive shop, you know that little unit will be working double time to keep up with the demand. For this reason I would recommend you use a good synthetic oil like chemlub 751 or 800 depending on how warm your climate is and change it often.
Best of luck with the dive shop
ZDD

 

[ti325v]

Hi Zodiac... thanks for your answers...
I would like to address your points, line by line in the hope you can help me further, perhaps I was not as clear as I could have been.

Hi, switching over to a single phase motor may require you to change out you motor starter or contactor. You will need to check the amperage rating on your contactor and your overload protection, also your wire size to your compressor from your main breaker panel may have to be increased. Your are best to have a certified electrian or a compressor repair shop do this because if you burn your new shop down your insurance company may walk away from you leaving you with nothing but cinders.
Insurance ? here in Vietnam....hahahhahhaha....laughable...

Qualified electrician ? I am more qualified then 90% of the ELECTRICIANS here !!!
I have new controllers, not a problem...


The next thing you have to look at is the motor speed. If your new motor has a different speed then your old one then you will have to change the drive pulley so your compressor will run at the same speed or close to it. Best to start slower rather then faster.

Original motor 1350 rpm, new motor 1450. If it is an issue I can cut a new pulley for about $10 here,

With a hand held ampmeter and when the compressor is running check the amperage draw on from the motor. Check it when the oil in it is cold and then again when it is at full pressure this is when it draws the most amps. If the motor is drawing more then 26 amps you will need to decrease your pulley diameter until the unit is drawing 26 amps or less. if you are not even close to the 26 amps then you can speed up the compressor untill it is close but not over.

Start up amperage on the motor is about 50 running is about 24, at full load.

Then depending on your control voltage you may have to change out the transformer or if you are lucky not use one at all. Again best to have an electrician do this so he wears the liablity.

Thats me !

Next, to address the purification question. I live in Canada and to sell breathing air it must meet a standard. Dew point must be -53 deg C or lower. This is to prevent equipment freeze ups and to keep moisture out of the diving or SCBA cylinders. So check the requirements for the area you are setting up in for the dew point limits but I would certainly expect you will need a purification system that has a drying element in it.

Please note, I was asking about pre drying the air, as I have access to cheap hitachi air dryers used in medical applications. Will there be any real benefit in removing 80% of the moisture from the air BEFORE it goes into the compressor ?

Of course the compressors have water traps, and proper filtration. Hopcalite, molecular sieve and activated carbon.
I know the air is compressed to 100% R.H. No matter what, but....if i reduce the amount of water going in, I will reduce the amount of water coming out and (the point of the question,) saturating my molecular sieve. So my filtration will last longer.....and hope fully less water blown back into the oil, as there is less water coming in, less dilution of the oil....longer compressor life.
I have two of these units, they provide grade e and EN1201.
I only fill 30 or so tanks a day, so I do not think I am over working them... They run about 2.5 hours a day.
I am working with Jim Sheldon and he feels for my needs these compressors are not undersized, but the business will grow to 80 -90 tanks a day, at that point he is putting together a proposal for 2 new compressors and a huge air bank...

Currently I am using coltri synthetic. Change at 50 hours.

I do have a scale accurate to .01 gram and am sorting out now how many tanks I can fill before the sieve is full, as I understand it, it can adsorb 22% by weight of water before it has to be changed.
I am in the tropics, and not really that worried about a reg freeze up...lowest water temp here is 24* and in the summer it is 32*

Thanks

Larry



When opening a dive shop one way to quarantee failure is to sell bad air, and with a 5hp compressor, which is quite small for a dive shop, you know that little unit will be working double time to keep up with the demand. For this reason I would recommend you use a good synthetic oil like chemlub 751 or 800 depending on how warm your climate is and change it often.
Best of luck with the dive shop
ZDD

 

[h90]

I am setting up my compressors in a new location. I have three phase 380 volts outside my door, but they want $3000 to run the wire ! UNBELIEVEABLE....there was another dive shop here, and they moved 5 times at $3000 a pop for the three phase....
I want to swap over to 220 single, which is household current here.
My compressor has a 112M frame 5 h.p. 3 phase 380 volt motor. Manufacturer says I need 4 KW.

I have found a replacement 112M 1 phase 220 volt motor rated at 3.7 K.W.
The compressor is good for 300 bar, but I have down rated it to 220, as we only fill Al 80`s with it.
I am having a very hard time determining if they use the same motor for the 300 bar and 200 bar versions. The manufacturer is of no help.

If indeed they use the same motor.....will the 3.7 K.W. (Draws 26 Amps) be adequate to pump 220 bar ?
If not I have to make a jump up in frame size, and I will have to remachine the pulley to accept the shaft.
This unit delivers quite close to 200 l/min.
BTW this motor is costing me $190 !!!!!
1 year guarantee, TEFC, 1.15 load factor, dual ball bearing, continuous compressor rated. 45* C. 1,200 mFD capacitors....92 pounds !
Original motor was 1350 rpm, the new is 1450.



Next question...I am aware that moisture is the enemy of a filtration system.......I have available to me second hand Hitachi air dryers. I can get a 400 lit/min for about $300.
Is it worth drying the air ? I know there is massive moisture removal during compression, but how will it effect my filter life if my intake air is humidity is reduced from 90 % at 30 *C ( Dew Point about 28*C ) to an outlet dew point of 10* C ?, or about 30 % R.H at 30 *C . If I understand all that I am learning correctly.....

5 HP is 3.75 kW. Should be almost the same, or?

 

[Zodiacdiverdave]

Sounds like you have the electrical taken care of and the motor swap isn't a problem. I am not sure of the type of air driers these are. most people use an air conditioner or a dehumidifer to deal with high humidity at the intake but if these are PSA driers with an out put pressure greater then 2 psi then a 2-3 PSI releif valve and 0-5 psi gauge on the intake line to the compressor would be required. This is so the pressure on the first stage piston is not too great. If it ecxeeds 2 psi at the intake then you could damage the compressor.
ZDD

 

[ti325v]

Hi zodiac...
thanks for the advice...
The motor worked out perfectly, I finally heard back from the manufacturer, and they use the same motor on the 200 and 300 bar models, so it may not pump to 300 bar, with the very slightly smaller motor. For all I know it may, but I will not be banking from these compressors, I will use units from Sheldon...(BTW it is a bauer block)
Regarding the air dryers.....
These are used in medical applications, of course they are installed prior to the air being compressed....I believe they basically function as a dehumidifier...I have seen three of these machines from Hitachi in the dental clinics where I maintained the computer networks, I have searched all over the web for a picture, and as the guy who sells them has no English and I have limited Vietnamese, there is little or no information forthcoming...I get the impression from your post that this is actually done (dehumidifying the air)....now I am a little confused about pressure at the intake of the compressor, I have to research what a PSA dryer is..
a couple of psi above atmospheric will damage the compressor ???
I can understand any resistance or constriction in the intake of the compressor causing serious problems, can you tell me how a slight over pressure on the intake could damage it ?
I know a couple of psi is a large percentage of atmospheric pressure...Do you mean I would effectively be supercharging the compressor...more air in them first stage then it was designed to handle ? I guess that would chain react to all the stages....Is this the case ???? higher bearing loads would not be an issue as the pump is designed to run at 300 bar, so maybe damage the valves? Possibly the rings????
Is there actually any benefit to reducing the incoming humidity ???? As I understand it, unless the environmental humidity is VERY low, after first stage compression we are at 100% humidity...
I just had the idea to do it the other day when I brought the motor and saw the air dryers in his shop....as I said I though the real benefits would be increased compressor life, less water in the oil....instead of (but hoping for) reduced saturation of the molecular sieve...
Thanks

 

[Zodiacdiverdave]

Hi again TI325V, if you can dry the air entring the compressor intake which is usually done by have the intake located in an air conditioned room or a room that has dehumidifiers to dry the air.
This will certainly have benifits but I am not sure if they would be cost effective considering the cost of the units and electricity but who knows until you try it.
If you introduce pressureized air at over 2 psi the load on the compressor during start up may break your crankshaft off at the pulley. The first stage piston has a large surface area and if the piston is at bottom dead center, which it would be due to the air pressure driving it to the bottom of the stroke and the motor has to over come this initial load during start up, the weak link in the drive train is the crank and I have seen cranks break there befor when starting even with no load so care must be taken when doing this. I have built up and sold Nitrox Membrane systems that do a similar thing by introducing pressurized nitrox to the compressor we install relief valves and gages to prevent damage to the compressor.
Good to hear your motor swap went good, I think that if you measure your amprage draw when it is at 300 bar you will find it is below or at the FLA rating that is posted on the motor data plate.
You also mentioned earlier about monitoring your dew point, I use an digital dew point meter to monitor the output air, it is rated to 5000 psi but there are also units that are rated to 7000 psi. These are more expensive then using scales but much more acurate and easier to use.
ZDD

 

[ti325v]

Hi Zodiac..
Thanks again for your help....
Can you give me a link to the dew point meter ?
Also Re; air conditioning, dehumidifying....
I can buy 200 lit/ min for $210. 400 l/min just slightly more...Electric costs are not horrible...I feel that chilling an uninsulated room to draw the air from is problematic as there are no insuation materials available here, along with the no room issue. I am not going to even try to cool my compressor room. I run the compressor out doors in the evenings anyway..
Is there actually any benefit to reducing the incoming humidity ???? As I understand it, unless the environmental humidity is VERY low, after first stage compression we are at 100% humidity...
I just had the idea to do it the other day when I brought the motor and saw the air dryers in his shop....as I said I though the real benefits would be increased compressor life, less water in the oil....instead of (but hoping for) reduced saturation of the molecular sieve...
Thanks

 

[Zodiacdiverdave]

I use a Dew point meter model LPDT-65 by Cosa Instruments their web site is URL="http://www.cosa-instrument.com"]http://www.cosa-instrument.com[/URL] There are other manufactures but I found for the price you can't beat it. It is good to 5000 psi(340 Bar) and they can sell you a fitting to mount it in for continous sampleing.
Another good unit is made by donaldson but is a hand held meter good for 6000 psi and is ment for periodic sampling.
I got my meter 5 years ago, I believe it cost $1500 then. Other units can cost up to $5000.00 and don't do anything my little meter wont do.
ZDD