Diesel Generator Over Heat Problem 1

[aliccan]

We are currently testing five diesel generators at the field .

all of the systems are identical (As we know)

The systems are operating Air Condition Compressor @ 21 Bar 310 cc and 24V 300 Amp alternators

Air condition compressor catalog power is 8 kW
Alternator is consuming 1 kW due to low need
According to this calculation we need 9 kW
Engine is 21 kW @ 1500 rpm Perkins

As one of our systems is working at 90C the all the other system is going to overheat at 112 C, and two of the ac compressors are seized(Nearly all of the compressor pressures were identical)

We checked ,hoses, coolant levels, bearings , radiator, fan but we couldnt find what could be the reason for overheat,

I am very suspicious about the AC compressor load, It shall consume more than double to go for overheat but the pressures were all the same ?

Do you have any comments ?

 

[wayne440]

Given your previous reference to burning belts and now seized compressors, it seems as if the designer(s)of your project should seek serious on site assistance.

Here are a few quick thoughts,

(1)Just because you have a radiator and fan does not mean they are properly sized for the application.

(2)You checked the coolant level, but what about the mix of same? Too much antifreeze can be as bad as too little.

(3)Was adequate oil put in the AC system when it was charged?

 

[aliccan]

According to the oven tests and field tests none of the systems were over heating , now 4 systems are overheating and 1 system is working according to the tests.

The mix is %50 and we have fully charged the oil according to the catalog data and oil sump stick.

I am suspicious that at 50 Degrees Celcius the Air Condition Compressor is using much more power than the catalog , and the calculated engine derate is around %40 so the systems looks like on its limits. But i dont get why one of them is not overheating .

 

[LionelHutz]

What's different between the working system and the bad systems? There must be something. Keep searching if you haven't found it. Obviously, the A/C compressors seizing shows there is a problem in the A/C system.

 

[HowDidYouBreakThat]

Get an optical tachometer and check the speed of the pulley on the AC compressor. Check with the manufacturer for the recommended speed. Overdriving the compressor will do everything you described. Also, check to see if the pulley sizes on the working unit match the failed units.

 

[dicer]

So what is the amp draw of the various AC units? Are they different? What you need is a proper load bank and use the same
system on each of the different gen sets. Maybe the current draw is different for each separate AC/ Alternator unit.
Or are you saying that these AC/alternator units are mounted on the engine? I don't understand the actual setup that you have.
Either way a true test is to load bank it, and get rid of all the other parasitic losses of accessories.

 

[aliccan]

Thanks all obviously it was a design error coming from the Air Condition Company, compressors were seizing the systems and when the a/c system turned back to normal the coollant temperature level decreased 6-7 C and didnt elevated after regime temperature level. Thanks all for the comments.

 

[rmw]

If I understand your posts, I'm curious why in a 50C environment you are using a 50% mix of antifreeze. How cold does your winter get if any?

rmw

 

[waross]

Antifreeze has a higher specific heat than water and cools the engine more efficiently. Some marginally sized radiators will not cool effectively with water. There was a Ford model years ago that was noted for overheating if the anti-freeze was replaced with water.
Another issue is the corrosion inhibitors that are part of the formulation of a good quality anti-freeze.
During my years in Honduras I twice heard severe weather alerts on the radio warning that temperatures would drop to 70 deg. F (21 deg. C) overnight. Not much winter but I always used a proper anti-freeze (coolant) mix when installing or servicing a diesel generator. 50:50 or close to it.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

Antifreeze does not have a higher specific heat than water. It increases the boiling point of water (reduces vapor pressure, thus allowing a higher operating temperature and delta T to improve heat rejection rate), and it contains corrosion inhibitors.

 

[waross]

Thank you for the correction, Compositepro.
I believe that my observations were valid even though the reason was not.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

I need more practice at diplomacy. I highly respect your contributions, Bill, and have learned a lot from your posts. I simply wanted to correct a misstatement, and I did state why your answer was essentially correct with regard to heat transfer. I only replied because I feel it is important on a forum like this to not let erroneous information to spread.

 

[ScottyUK]

If you find a good course in diplomacy please enrol me and a few others who frequent this patch...

 

[waross]

I meant to say;
"Thank you!"
No sarcasm or putdown intended.
I gained some knowledge. That's what this site is for.
Thanks again.
Yours
Bill
Ps Have one on me in the Pub.
BR

Bill
--------------------
"Why not the best?"
Jimmy Carter