Message Board Thread - "Disconect Box image..advice"

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Disconect Box image..advice manuel-thermoimagen 10/20/2008
Well, i take this image and used Fusion's reporter 8 function to overlap it.

This disconects box is for a 150hp air cooled IR compressor, had reported twice in a 2 year time frame.

no fails or even malfuntion happens until now, what do you do with this kind of situation? how this customers has to be treated? .. any experience to share??
 
Re:Disconect Box image..advice T. R. 10/22/2008
Do you have a better image? It is hard to see if there is a problem here or not. How about posting the IR only image. The fusion picture does not give enough information. But at first glance looks like the compressor has lost a phase/single-phasing. It will fail soon if not fixed. There is more than likely nothing wrong with the disconnect, the compressor has an issue.
 
Re:Disconect Box image..advice Laland 10/23/2008
Did you take current reading per phase? I agree that it looks like the compressor is operating at single phase.
 
Re:Disconect Box image..advice Top Gun 10/23/2008
I don't think there is a single-phase problem here. The center phase thermal reading given is too high for that. Amp readings would be greatly revealing in this case. Not enough information is provided to make any good diagnoses. I see two other scenarios. One: there is a ground in one of the windings of the main compressor motor and that is elevating the current in the feeder phases of that winding, the ground is closer to the phase 3 line causing higher loading and heating there. Two: there is another single-phase circuit downstream from this main that is adding significant load on phases 1 and 3. This circuit is loaded up and causing the heating on the two outside phases. Now if we could have more information from the original thermographer that would be great!
 
Re:Disconect Box image..advice CarlM 10/23/2008
I'll take a guess. It appears that there may be signs of high resistance in the switch assemblies, particularly the A and C phases. First, eliminate the load as a factor by taking amperage readings on each phase.

Using a multimeter set for millivolts test for voltage drop across each section of the switch assemblies. For example, starting with one meter lead on the line lug test Vd (voltage drop)from the lug to the 'slot' or receiver, then moving that meter lead to the blade section, and then across the blade pivot (usually a rivet). No reading should be more than .075 volts (75mv) though the readings should be relatively close to the 'B' phase readings. Normally these assemblies are replaced rather than repaired.
Good Luck and let us know how it turns out.

CarlM
 
Re:Disconect Box image..advice CarlM 10/23/2008
Oops. Im assuming the person conducting these tests is an electrician, of course.

CarlM
 
Re:Disconect Box image..advice manuel-thermoimagen 10/30/2008
thanks for all your advice about this interesting image,

the bottom line of this image was this 'oportunity' has been reported 4 times on 4 separated inspections within 24 months period.

if this were your case, what would be your position with customer?

 
Re:Disconect Box image..advice Lady IR tech 11/2/2008
manuel-thermoimagen wrote:
for all your advice about this interesting image,

the bottom line of this image was this 'oportunity' has been reported 4 times on 4 separated inspections within 24 months period.

if this were your case, what would be your position with customer?

Monitor it.. If the changes are not moving radically up or down then there is not much that can be done with the picture as is...

it would be nice to have just the IR image and amp readings. But without them and it has not failed in 24 months it may just be it's footprint.
 
Re:Disconect Box image..advice manuel-thermoimagen 11/3/2008
Lady IR tech wrote:
Monitor it.. If the changes are not moving radically up or down then there is not much that can be done with the picture as is...

it would be nice to have just the IR image and amp readings. But without them and it has not failed in 24 months it may just be it's footprint.
here is the infrared image..
 
Re:Disconect Box image..advice Laland 11/4/2008
manuel-thermoimagen wrote:
for all your advice about this interesting image,

the bottom line of this image was this 'oportunity' has been reported 4 times on 4 separated inspections within 24 months period.

if this were your case, what would be your position with customer?

You have said that this was reported 4 times in 24 months. After every that every report, where there any corrective measures made to solve the problem. The current reading per phase shows an unbalance load.
 
Re:Disconect Box image..advice Tony Holliday (HAWK IR) 11/5/2008
manuel-thermoimagen wrote:
here is the infrared image..
I would tend to agree with Carl, did you have someone take a resistance meter reading across the switchblades? I would be interested in the readings if so.

When these knife edges are re-engaged after the disconnect has been opened and subsequently re-closed they may not have seated correctly. do you know if the disconnect has been cycled? I assume that it is door interlocked and so may have been opened and re-closed for the scan to take place and then again to re-close the door?

Best Regards,


Tony Holliday
Hawk IR International
http://www.irwindows.com
 
Re:Disconect Box image..advice ojutter 11/5/2008
Manuel-
The reason you don't have a failure yet is that they high temperature is only a 27.6 rise above suspected ambient. It is only loaded to about 55%FLA. If it was loaded more it would be considerably hotter. A situation like this is likely going to require replacement of the disconnect since the heating is at the pivot point of the disconnect and up in the clips once this gets worse. So as has been said trending is the right approach. If your an in house guy that is a little easier than a consultant. Likely though this issue won't accelerate quickly unless they use the disconnect a lot, which probably isn't like since it is an air compressor.

 
Re:Disconect Box image..advice Pete 11/5/2008
Since the temperature decrease as you move away from the disconnect. So I tend to agree with Top Gun & CarlM about the high resistance.

I do not consider the loads to be unbalanced. Our acceptance criteria for a load this size is <10% inbalance between phases. If two phases were 80 and the third phase was 85 I might question the compressor.

Our Thermography acceptance criteria for like components:

Delta T. of >40 degf (4.4 degc)= increased inspection frequency
Delta T. of >60 degf (15.5 degc) = maintenance ASAP.

As ojutter stated the temperatures would be significantly higher if the compressor was running at a higher load.

We have had to have maintenance performed on our manual disconnects for this type of condition. In the majority of cases, cycling the disconnect, tightening connections and applying a no-ox grease to the stabs has repaired the situation. We have not had to replace a switch.... yet. First switch we did this maintenace was 15 years ago and it is still functioning fine.
 
Re:Disconect Box image..advice JKEngineer 11/5/2008
Quote:
Our Thermography acceptance criteria for like components:

Delta T. of >40 degf (4.4 degc)= increased inspection frequency
Delta T. of >60 degf (15.5 degc) = maintenance ASAP.



You have not converted delta T from F to C correctly. The conversion for a T difference is:

deltaT in F / 1.8 = deltaT in C
So 50F delta= 22C delta and 60F delta = 33C delta.
You used the conversion from temperature in F to temperature in C.

Jack

Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

Bronx, NY 10463

718-884-6644
866-884-6644 toll free
212-214-0919 fax and voice mail
Skype: JKEngineer

JKEngineer @ aol.com or JKEngineer @ KleinfeldTechnical.com
come see what we can do for you: http://www.KleinfeldTechnical.com

 
Re:Disconect Box image..advice CarlM 11/8/2008
Pete wrote:
he temperature decrease as you move away from the disconnect. So I tend to agree with Top Gun & CarlM about the high resistance.

I do not consider the loads to be unbalanced. Our acceptance criteria for a load this size is <10% inbalance between phases. If two phases were 80 and the third phase was 85 I might question the compressor.

Our Thermography acceptance criteria for like components:

Delta T. of >40 degf (4.4 degc)= increased inspection frequency
Delta T. of >60 degf (15.5 degc) = maintenance ASAP.

As ojutter stated the temperatures would be significantly higher if the compressor was running at a higher load.

We have had to have maintenance performed on our manual disconnects for this type of condition. In the majority of cases, cycling the disconnect, tightening connections and applying a no-ox grease to the stabs has repaired the situation. We have not had to replace a switch.... yet. First switch we did this maintenace was 15 years ago and it is still functioning fine.
I've had similar experiences as Pete. Small to 200 HP disconnect switches for compressors may show high resistance junctions as they age. I've been watching a few such cases over the past 6-7 years. Cleaning any contamination, using contact grease and cleaning terminations will quite often repair this sort of anomaly at this stage of degradation, especially when the disconnect is seldom used.
This reminds me of a condition I would like to share concerning compressors and fused disconnect switches and fuse sizing. I will start a new thread.

CarlM
 
Re:Disconect Box image..advice manuel-thermoimagen 11/28/2008
GREAT THREAD..

thanks to all participants: (in order of posting)
T. R.
Laland
Top Gun
Carl M
Lady IR Tech
Tony Holliday (HAWK IR)
ojutter
Pete
JKEngineer

Mayor League Posters!!

Thanks to all folks!!
roberto.cruz@thermoimagen.com

 


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