Question of Frick TDSH163L compressor

[Tung]

Dear Sirs,
I recently tore down a Frick TDSH 163L screw compressor,
and found there is a serious damage on female rotor' shoulder on discharge casing(as showed in attached pictures),
then I was just confused by this phenomenon, the roller bearing that supports female rotor on discharge casing seems Ok, it only has some light scratches on the roller surface, and it sits firmly on the bearing seat,
also you may check the attached pics, the wall of discharge casing doesn't has any sign of hit, and on the other side, the suction casing bores and the roller bearings are both Ok, my question is if the four roller bearings on both casing are not damaged, then what will cause the damage on female rotor and the bore on discharge casing?

the customer told me that this compressor has never torn down since the day it was installed on the site,
can anybody here kindly provide your opinion to this?

your help will be appreciated!

[Magoo]

The compressor is history, sell them a replacement.

[Tung]

This compressor has been repaired and run for two weeks, so far so good,
I had the wornout part welded and grinded, we treat a worn part in that way all the time, and it works,
the customer intends to use this compressor for their gas processing for another 10 years(as what they said).

[Tung]

OK, here is another question for this compressor,
before it came to my work shop, the compressor had vibration and noise problem,
now it seems the wear on rotor and the bore on wall of discharge casing are the cause for the abnormal condition,
can anybody help on explaining why the worn parts would get the compressor vibrating and making noise? one explanation came to my mind is the lubricant that is suppose to lubricate the bearings bypassed to discharge port and thus make compressor vibrating, am I right on the statement?

[josef]

Hi Tung, Figure 2 why the circle on the female side?, You had a problem on the rotor?

[RANGER1]

As josef says, alsoI can only come up with lack of oil for whatever reason. The heat generated around this localized area could then cause galling in the labrynth area!
The vibration can't say, as no pictures or rotors or bearing inner races.

Does this machine have liquid injection oil cooling?

[Tung]

Hi Josef,
I believe the circle is the evidence that female rotor hit the wall of discharge casing,
it happens quite frequently to TDSH compressors, but in this case, it is not so serious, I think.

Hi RANGER1,
Thanks for the comment, I attach a doc file that has some more pictures to illustrate this matter more clearly.

[Tung]

Can not upload the file as the size exceeds8990 the allowance.???????????

[Tung]

In the bore, the rotor rubbed against the surface and caused serious wear,



Notice there is an oil feeding hole on the groove, the groove is covered by rust, so I guess it is the sign of lack of oil.

[josef]

Tung, we need to see the area where the bearing travels.
I am also interested in female rotor, close the lid at the place of damage.

[Tung]

sorry, this is the only picture I can provide,
8994
on the shaft surface that locates on discharge casing blocking diameter, it also wears,
this compressor serves as high stage compressor on a two stage CO2 compression system, it doesn't have liquid injection.
I recalled this compressor used to have high discharge and oil temp problem, we solved the problem by enlarge the oil injection orifice, the modification was instructed by Frick, Waynesboro.

[RANGER1]

If the female rotor continued to rub againdt discharge end housing, would it not also stop oil supply in that direction as well!
This could start a chain reaction of events.

[Lodiev]

This is definitely the work of a liquid flood back from the suction side accumulator/ liquid condensing in suction piping. I have seen this on all Frick screws after a liquid entered either the suction side or through the oil sep after it stood still for a while and gas condensed in the oil sep.

[Tung]

Hi Lodiev,
Thanks for your advice,
At first I also suspected the liquid flood back would be the cause for the damage,
but I did not see the sign on the surface of both rotors,
besides, the roller bearings and ball bearings are OK just with some light scratches,
then my conclusion to this event is some unexpected particles go into the area between the female rotor and the wall of discharge casing then into the blocking dia and cause the damage, because I did have found some particles inside the compressor.

[RANGER1]

Hi Josef,
I believe the circle is the evidence that female rotor hit the wall of discharge casing,
it happens quite frequently to TDSH compressors, but in this case, it is not so serious, I think.

Hi RANGER1,
Thanks for the comment, I attach a doc file that has some more pictures to illustrate this matter more clearly.


Tung,
Why do you think rotors touch discharge end frequently in your statement?
I've only worked on a couple og TDSH283 compressors, not the 163.

I find the frick oil filter housing on the larger Fricks a bit weird as oil pases through inner diameter of filter into housing, then bearings.
If you do not keep housing spotless you are already looking for trouble.
Also if you do not use genuine Frick oil filters.

[mrfreezeit]

We rebuild lots of screws about 100 per year and 50-60 of them are Frick. Not for their frequency of failure, but for the quantity of the compressor brand in the states. Our opinion (3 of us with 20 years experience average) is the bearing wear allowed the rotor to get into the gas seal. Best way to fix is to bore it and sleeve it. Do not weld to cast steel, it will not last. We have rebuilt much worse conditions on a compressor. We do it all the time and offer 2 year warranty on the rebuilds so we are very confident in fix. 3 weeks ago we repaired one with a warped rotor shaft.

The discharge housing looks like it just needed to be buffed out. Liquid would have caused deeper grooves in the rotor, these are very light probably particles from failing bearings and failing thrust bearings.

I did not see any signs of oil loss, which generally shows up from heat discoloration of the metal. You do have a very wet charge. You have a lot of water in your system from running vacuum, poor oil maintenance, or bad charge. This caused the rust discoloration and unless treated will result in premature failure. The compressors we get off of gas wells are usually this bad, but not closed loop systems or gas compression duty.

Rotors only touch the discharge end when thrust bearings fail or liquid slugs occur, neither of which are frequent unless you are doing something wrong or something breaks.

The bearings are bad! You see light wear, I see a failed bearing and the cause of most of these issues. The vibration was probably from the bearings compounded with the loss of seal on the gas seal. If your clearance on the gas seal is off, you may be getting abnormal gas pulsation into the bearing cavity.

The RETA conference in San Antonio, TX will be having compressor tear down sessions of many of the common industrial refrigeration compressors by the manufacturers. November 6-9th, 2012 San Antonio Texas.