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Nirmalya
17-08-2006, 07:23 PM
Hi, Everybody
I am in the process of finalising couple of R134a flooded water cooled screw chillers of capacity 150 to 200 Tr. Load will range from 75 to 100 %
Kindly advice me which is more reliable Mono screw or twin screw ?
What are the specific advantages / disadvantages of mono and twin screw ?
In the present scenerio, which screw compressors are more reliable ?
Will be indebted if any body enlighten me on the subject points.
Regards
Nirmalya

US Iceman
17-08-2006, 10:16 PM
The mono-screws had some trouble when they first started in production. The gate rotors kept failing. I know those problems have been since corrected.

Twin screws are a more mature technology as they have been used for a longer time.

Both are good.

The twin screws have axial bearings for thrust loads. The bearing wear can be increased by high pressure ratio operation.

The mono-screws have only radial bearings (at least on the type I am thinking of). The main rotor is balanced by pressure differential in the axial direction, so in effect the bearing loads are all radial.

For water chilling duty where the load is always within a 75-100% load range, I would look at a fixed Vi compressor. I doubt you will need variable Vi for that operation. A capacity slide should be more than sufficient.

guapo
18-08-2006, 01:37 AM
Hi,

For me, I would recomend mono screw. I experience too much trouble in twin screw, sometimes it got welded both screw by friction.

regards,
Guapo

TXiceman
27-08-2006, 03:53 AM
I have to disagree with Guapo. After 35 plus years in industrial refrigeration, and experience with both single screws and twin rotor screws, the twin rotor machine is a much more mature and realibale design.

The single rotor designs have finally been made more reliable in low pressure differential applications such as R134A water chillers. The star gate tips tend to flex in higher pressure applicarions. Also, the star gates have a rubbing contact with the rotor where a twin rotor machine has a rolling point line contact on the rotors and are separated by an oil wedge.

Ken

US Iceman
27-08-2006, 04:25 AM
...the star gates have a rubbing contact with the rotor...


I can confirm this point. The single screw compressors I have experience with have a special process applied to the gate rotors (star gates) to help them seal with the main rotor during run-in.



The star gate tips tend to flex in higher pressure applications.


Ken, whose compressor are you describing? Do they have the gate rotor supports under the wheels? Or, is this specific to a manufacturer you are thinking of?

I'm always open to hear other peoples experience.;)

guapo
27-08-2006, 04:56 AM
Hi ken,

I agree, because during that time the mono screw is not yet well develop.

But based on my experience with mono I had no problem.
All my client now they require mono. Reliable & easy maintenance.

Best Regards,;)
Guapo

US Iceman
27-08-2006, 05:33 AM
guapo,

Which brand of mono-screws have you been using or have experience with please?

Best Regards,
US Iceman

guapo
27-08-2006, 11:39 AM
Hi US iceman,

Mostly I have J&E HALL & some vilter.

Sorry to disapoint other people here,I'm just sharing my experience.

I have also twin screw compressor but I have to overhaul that every three months bearing always damaged. The manager of the plant ask me for the permanent solution for this problem and my proposal is to change the compressor to mono screw,just the compressor. I will used same motor and oil separator. And He agree because they have also mono which will take 12 years before they open the compressor.

These 6 unit twin screw was installed by India company.

Actualy I dont believe that there is a problem in any designed of any brand or type of the compressor, it is just how you installed the compressor, commissioning, application.(just my own opinion)

Regards,
Guapo

US Iceman
27-08-2006, 05:08 PM
I have also twin screw compressor but I have to overhaul that every three months bearing always damaged.


This suggest the problem is with the repair work, a serious fault in the compressor installation, or some unknown problem with the system causing these frequent faults.

This should not be taken as a reason as to why mono-screws are better than twin screws. Something is wrong here, and not just with the bearings (unless the replacement bearings are a poor quality substitute).

TXiceman
28-08-2006, 02:52 AM
My experience is with Hall screws from the mid-80's. Most reecenetly I have seen some of the same problems with the Vilter machines.

They do seem to do OK on high temp applications where the pressure differential across the machine is not too high.

About 2 years ago, I replace a Vilter screw that was running in glycol chilling service, about -10 dF, NH3, evap condensing. The system was well designed so no problem from that. They were getting 6 to 9 months run time between failures. I put in a twin rotor Howden compressor with a new lube oil system and not a problem since and used the same vessels and exchnagers.

Ken

NoNickName
28-08-2006, 10:27 AM
I had a number of twin screws failures, and the reason for that is 90% of the time the axial load bearings on the suction side.
Also seized rotors seems to be a common cause of failure as guapo mentioned.

guapo
28-08-2006, 12:27 PM
Well, we all had a different experiences & story, maybe bacause Industrial refrigeration is not standard like airconditioning.
It has a different system each and every job site, especially designed for every application.

US Iceman
28-08-2006, 03:30 PM
They were getting 6 to 9 months run time between failures.


What kind of failures were they having? They must have been traumatic to cause the entire compressor to be replaced.

US Iceman
28-08-2006, 03:33 PM
Also seized rotors seems to be a common cause of failure as guapo mentioned.


Were they commercial variants of twin screw compressors or industrial versions?

Seized rotors is a serious malfunction? As anyone else seen this?

nh3wizard
28-08-2006, 05:02 PM
What kind of failures were they having? They must have been traumatic to cause the entire compressor to be replaced.

Every 6 to 9 months, sounds very starnge for a twin screw:confused: , lubrication probelm or liquid coming back?:eek:

spr2003
28-08-2006, 05:47 PM
We have quite a lot of Bitzer Compact twin screw compressors running. (why they call them compact? they are big and heavvy like hell)
Prophilenic glicole chillers, R 507 medium tempereature duty for supermarket fresh food.
No failures at all, even after years.
Just one never started by new, cause of a problem with the electric motor.

refteach
28-08-2006, 07:49 PM
Over the years I have worked on Vilter, Diakin and Hall monos (also various twins, rotarys and recips ) and from what I have seen is the main cause of breaking tips on the mono screws is liquid creating an over pressure. Normally the first sign you see is the imprint of the support on the back of the blade, then if it has even more liquid, you get what looks like a delamination of the blade tips. If there is way too much liquid you will see chunking of the blade.

Also the blades on the mono screws are also sealed by oil. Oil is injected into the rotor groove and the blade acts as a piston in a cylinder with oil damming up around sealing surfaces, there is a slight amount of clearance between the rotor and the blade that is filled with an oil film so the blade is not in contact with the rotor.

Josip
06-09-2006, 11:47 PM
Hi, all :)

I am in a close contact with twin screw compressors since 1981 (Stal, Sabroe, Howden, Frick-Gram, Mycom, Grasso, Bitzer) and never ever heard or saw welded screws by friction :eek: . That is not due to bad design or bad construction it can be only due to bad maintenance, constant liquid strokes, jumpers on protection devices and so on...too many David Copperfields are out there;)

Yes it is possible to be also due to bad copy and bad material used by new (noname) manufacturers trying to catch a piece of cake on the market.

Voting for twin screw but not for every purpose, becuse there are some limits too..

Best regards, Josip :)

TXiceman
07-09-2006, 01:36 AM
Something that is paramont to all refrigeration systems is:
you can take the best compressor in the world and put it in a poorly dessigned system and the compressor will not hold up well.

You can also take a poorly designed compressor and put it in a well designed system and the compressor will not do too badly.

So we need to make sure that we are putting a compressor is awell designed system snd blaming the compressor for system problems.

With that said, I still feel that a twin rotor compressor will do better in all types of systems while a single rotor design will experience problems that would not have such drastic results on a twin rotor design. I just avoid applying single rotor machines.

Ken

NoNickName
07-09-2006, 09:03 AM
Were they commercial variants of twin screw compressors or industrial versions?



Well, the edge between the two is thinner and thinner, these times.
They were so called high temperature (Air conditioning) twin-screw compressors with built-in oil separator.

And for Josip: it's funny how they weld in seconds. The kriwan protection does not open in time. I personally witnessed two of these while seizing, and it's like listening to a turboimpeller light aircraft when climbing in vertical, until no more noise can be heard except zzzzzzzz and finally clunk of the thermal switch.
Regarding the kriwan int69 and similar, I find them to be the most useless component at all; it didn't ever save any compressor that I came across.
Also, the first version was affected by a bug: when twin screws stop, they counter rotate by high side pressure. At that time, the motor operates as a three phase generator for maybe 2 seconds. The kriwan understands the phases have been reversed and opens the alarm contact. Very annoying, but now it is solved.

US Iceman
07-09-2006, 04:16 PM
Well, the edge between the two is thinner and thinner, these times.
They were so called high temperature (Air conditioning) twin-screw compressors with built-in oil separator.


I think the industrial manufacturers are indeed looking for ways to make their compressors less expensive. We see this right now. So as you say, the differences between the two are geting smaller.

This topic of rotors sticking together though has been a surprise to me. I'm not arguing that it has not occured, only that I have not seen it.

My exposure to the commercial type of unit is limited. However, based on some of the comments it would appear this problem of rotors "welding" would be due to failure of the check valves and excessive backwards rotation.

Are the check valves seen as a continuing problem, or is this based on a failure of something else?

Josip
07-09-2006, 05:51 PM
Hi, NoNickName :)


Well, the edge between the two is thinner and thinner, these times.
They were so called high temperature (Air conditioning) twin-screw compressors with built-in oil separator.

And for Josip: it's funny how they weld in seconds. The kriwan protection does not open in time. I personally witnessed two of these while seizing, and it's like listening to a turboimpeller light aircraft when climbing in vertical, until no more noise can be heard except zzzzzzzz and finally clunk of the thermal switch.
Regarding the kriwan int69 and similar, I find them to be the most useless component at all; it didn't ever save any compressor that I came across.
Also, the first version was affected by a bug: when twin screws stop, they counter rotate by high side pressure. At that time, the motor operates as a three phase generator for maybe 2 seconds. The kriwan understands the phases have been reversed and opens the alarm contact. Very annoying, but now it is solved.

It seems NoNickName that you give the answer for welded rotors. Now I see little more, agree about int69 it is protection only in case when there is not counter rotation.

Working with indstrial installations where we do not use int69 but different control for complete switch panel control of phases that is not possible.

Thanks for valuable info.

Best regards, Josip:)

NoNickName
07-09-2006, 05:55 PM
Oh, no. They weld when rotating the right spin.
You know what? When there's too much oil in the separator, it is flushed into the suction during any of the stops. This is no problem, because the pockets of space between male and female screw lobes increases going from discharge to suction (backwards).
Now the suction and the motor are filled with oil, and the compressor restarts.
Same story: the oil happily wants to go through the screws, but now the spaces between the lobes DECREASES as the refrigerant goes from suction to discharge (compression).
Oil is quite reluctant to be compressed. Result: the female screw (the smaller) is bent few hundredths of mm to few tenths of mm on the outside of the compression chamber. Motor still turning.
The lobes get in touch with the chamber cilindrical wall and mill it (or get milled). Still turning.
The debris, which is nothing more than iron powder, flow in the direction of the oil, and through the high side bearings. Still turning, amps increases.
Bearings are sort of nests for iron powder and they keep accumulating the powder, so much so that the thickness increases, the male and female screws are pushed to the suction because of thick deposit on the discharge, until the lobes get in touch with the suction supporting bearing plate.
End of the story. One side thick iron deposit, the other side the screws are milling the plate and more iron goes around, until there's no place for anything and the happy turning assembly stucks.
When this happens, no overhaul is possible, because the assembly is so hot and so packed, that it can't be dissasembled.
The whole compressor must be scrapped.

US Iceman
07-09-2006, 10:00 PM
Oil is quite reluctant to be compressed. Result: the female screw (the smaller) is bent few hundredths of mm to few tenths of mm on the outside of the compression chamber.


OK, the problem starts when the rotors are deflected into the rotor housing. Same thing happens on a flooded start with refrigerant.



...until the lobes get in touch with the suction supporting bearing plate.


I've seen this also. The rotors will actually mill out the end plate.



End of the story. One side thick iron deposit, the other side the screws are milling the plate and more iron goes around, until there's no place for anything and the happy turning assembly stucks.


OK, now I see what you are describing. The problem is not the rotors welding to each other. It is the rotors sticking to the end plate.

Can you provide a link to the manufacturers website so that I can see what the compressor package looks like?

Thanks.

NoNickName
07-09-2006, 10:24 PM
I'll do more. I'll post the photo of the misshap tomorrow. Only for bravehearts

NoNickName
08-09-2006, 02:42 PM
Photo 1 shows the inner ring of the bearing with clear sign of pitting in the cemented surface and deep milling
Photo 2 shows the balls, with extensive damage and pitting.
Photo 3 shows the milling by screws on the suction side of the chamber and also on the cylindrical wall of the slider (in the middle wedge)
Photo 4 shows how the floating debris damage the surface of the screw lobes. Female screw is before, and male screw is behind. The edges of the screws, especially are damaged, because of centrifugal force and contact between the two screws.

TXiceman
09-09-2006, 02:27 AM
I have seen a number of damaged by spinning backwards due to bad check valves. There is still a lot of differences between the true industrial screws and the commerical screws. Some of the lighter duty industrial machines are moving closer to the commerical machines. More machines are being built with rolling element bearings and pressure differential lube oil systems and no oil pump.

Under some operating conditions, there is insufficient oil differential to feed the oil with enough oil. A rolling element bearing can run in an oil mist and still perform, but it still has to have oil.

When a screw compressor looses the thrust bearings or balance piston, the rotors will move toward the compressor suction and can contact the suction housing.

As far as I'm concerned, the true industrial machines still have hydodynamic film sleeve bearings for the main journals and some are offered with tilting pad thrust bearings. Thes machines require a positive pressure lube oil system driven by an external pump. With the pressure lube oil system, they can operate over a much larger range of operating conditions and not cause compressor damage.

The industrial compressors have both a suction and discharge check valve. Some of the commerical machines have only one check valve ar the compressor.

I really can not tell much from the posted photos. What were the compressor operating conditions and has the compressor experienced excursisons outside of the normal operating parameters?

Ken

NoNickName
09-09-2006, 10:10 AM
I really can not tell much from the posted photos.

Can you tell: it's broken?



What were the compressor operating conditions and has the compressor experienced excursisons outside of the normal operating parameters?


How do I know? I'm not living together with that compressor, and I'm not in love with it

US Iceman
09-09-2006, 04:24 PM
When I looked at the pictures I saw some galling on the bearings and what looked like surface pitting on the rotors. The rotor tips did appear to worn off.

But that was about the extent. From this, it looks like the compressor has been operating with consistent liquid ingestion (oil or refrigerant) and certainly some metal damage.

I think the comments made by TXiceman were pointing out the differences between the two types of products and how those might contribute to the results shown.




How do I know? I'm not living together with that compressor, and I'm not in love with it


Were in the world did that comment come from? The question asked was quite reasonable.

NoNickName
09-09-2006, 04:58 PM
Well, I repeat: how am I supposed to know whether a compressor has being working out of its envelope? Can anybody here swear it did or didn't for any of the units he/she's maintaining?

TXiceman
09-09-2006, 09:06 PM
With the current microprocessor based panels and softwear for data logging equipment, it should not be too hard to connect the system into a computer to do some data logging.

Yes, it is obvious it is broken. but we are trying to find out why? Now I am on a computer with a larger monitor and can see the photos a bit better. From the damage, I suspect the thrust bearing did let the rotors shift forward intot he suction housing. The rotor tip damage appears to be pretty typical of what you see when the rotors hit the suction housing. The metal ground off the housing has to pass through the rotors and it grinds up the rotors.

The thrust bearings look like a combonation of excessive loading on the bearings, lack of lubrication and possibly refrigerant carry over. What was the condition of the roller bearings? Did they show any signs of pitting damage.

A screw compressor can take a lot of liquid refrigerant into the suction, but will reach it's limits. The excessive liquid not only dilutes the oil, but can also cause excessive bearing loads which will lead to early failure.

You need to completly flush the oil system and recharge with new oil prior to restarting the compressor. Once back into service you need to throughly check the system operation over a wide range of operating conditions. I presume this is on a smaller critically charge system with electronic EXV feed chiller. Is the system air cooled or water cooled?

Just some food for thought.

NoNickName
10-09-2006, 01:08 AM
The chiller was not supplied with any sort of data recording. So, still I don't know.
The system is air cooled with a std mechanical TXV.
Roller bearings were not pitted.
There is no oil system. The compressor has a built in oil separator. This one could not be overhauled because of the extensive damage, and was scrapped.

US Iceman
10-09-2006, 01:23 AM
When the compresor was removed did you inspect the check valves for damage?

Did this system use a economizer? And, was there a check valve in the economizer suction line?

Do you have any idea of the time in operation until failure?

I suspect finding the fault on a commerical screw compressor can be difficult. I doubt there are any recording devices as TXiceman mentioned, since these add cost.

Oil systems add cost also, so in all probability, if you see this sort of damage as a repeated failure, it may be due to just trying to save some money.

Or, something in the system design is at fault (controls, piping, installation, etc.), which is being repeated for each installation.

I can't believe this is common and accepted at the same time.

TXiceman
10-09-2006, 03:13 AM
We just had a Carrier 23XL screw (compressor is built by Ingersoll Rand) come in for repairs. It was having problems with the slide valve sticking and erratic control. Once we got the compressor open there was severe wear on the slide vlave and the slide valve piston rod. When we finally got the customer to look at the operating hours, this machine had over 50,000 hours of operation with minimal manitenance.

Screw compressors are tough and what we usually see killing one is lube system failure or liquid slugging. We have run across some failures due to a mechanical design flaw, but this will effect a specific machine size or series and the failure mode is pretty consistant.

A lot of the commerical machines have a communication port that is either BAC Net, Modbus or other network protocol. If the machine has a communication port such as a RS232 or RS485 port, you can use a terminal emulation program such as PC Anywhere to access the port and set it up to log the data on a preset time.



Ken

NoNickName
10-09-2006, 10:40 AM
When the compresor was removed did you inspect the check valves for damage?

Yes, no damage. It was perfectly operational.



Did this system use a economizer? And, was there a check valve in the economizer suction line?

No economiser



Do you have any idea of the time in operation until failure?

Less than 8000 hours



I can't believe this is common and accepted at the same time.

I'm not a supporter of screw compressors.



A lot of the commerical machines have a communication port that is either BAC Net, Modbus or other network protocol. If the machine has a communication port such as a RS232 or RS485 port, you can use a terminal emulation program such as PC Anywhere to access the port and set it up to log the data on a preset time.
Ken

We build chillers, thanks. I know how to set a network up. If anybody is paying for it, nonetheless.

US Iceman
10-09-2006, 04:29 PM
Screw compressors are tough and what we usually see killing one is lube system failure or liquid slugging. We have run across some failures due to a mechanical design flaw, but this will effect a specific machine size or series and the failure mode is pretty consistant.


I would concure with the above. The highlighted comment above is the item I'm interested in. As NoNickName stated, the problem seems to be related to the continuous oil flooding during shutdown.

Now, if this is the recurring issue... Is there anything that can be done or modified to correct that or is it due to the assumption or design criteria used by the compressor manufacturer?



When there's too much oil in the separator, it is flushed into the suction during any of the stops. This is no problem, because the pockets of space between male and female screw lobes increases going from discharge to suction (backwards).
Now the suction and the motor are filled with oil, and the compressor restarts.


Just to ask some basic questions at this point...

Can the oil that floods the compressor during shutdown, gravity drain back to the oil separator? From your description, it sounds like the oil must be "compressed" to be removed from the compressor.

Or, is this due to the oil level being too high in the separator, so that as oil seeks it's own level between the compressor and separator the oil level is too high in the compressor for drainage to occur?

Less than 8000 hours of operation is terrible. If this is consistent, then there is a major fault in either:

the service being provided for the compressors is allowing too much oil to be charged into the separators or,
the design assumptions used by the compressor manufacturer, i.e., single compressor per circuit (no oil equalizing?), hot starts per hour (insufficient time to allow oil to gravity drain to separator), or perhaps the suction check valve (allowing the oil to stack up on top of the suction check. When the compressor re-starts, all of the oil is flowing through the compressor each time)

A lot of the commerical machines have a communication port that is either BAC Net, Modbus or other network protocol. If the machine has a communication port such as a RS232 or RS485 port, you can use a terminal emulation program such as PC Anywhere to access the port and set it up to log the data on a preset time.


Thanks Ken, my experience on the small screw packages is somewhat limited so this is a good thought to know.

NoNickName
10-09-2006, 05:24 PM
NO, the oil cannot be removed from the suction, unless disconnecting the compressor, and it has no other way to get into the separator than through the screws.
This shows the relative superiority of screw compressor having external oil reservoir and separator.

The fact is: unexperienced service company are told to top the oil up when it looks low in the sight glass. As a direct result, liters and liters of oil are added.
The situation worsen in case refrigerant with high relative oil dilution are used, like R404a.

US Iceman
11-09-2006, 01:36 AM
The fact is: unexperienced service company are told to top the oil up when it looks low in the sight glass. As a direct result, liters and liters of oil are added.
The situation worsen in case refrigerant with high relative oil dilution are used, like R404a.


Which is what I was suspecting. The faults are caused by improper service work or other problems, not necassarily something by the compressor maufacturer.

Granted the use of an external oil reservoir/separator does offer some benefits. Unfortunately, this benefit costs some extra money, which the commercial market tends to shy away from.

TXiceman
11-09-2006, 04:21 AM
What brand of screw are we dealing with here? I have applied a number of Copeland/Bitzer screws on 404a, 134 and 507 and no problems as long as the chiller is designed right and is not allowed to collect oil during low load conditions. Is the chiller multicircuited so that one circuit can be shut down at 50% load. TXV's are not good for controlling much below 50% flow with any degree of realibility. Is the suction line designed correctly with the proper risers for oil return? I generally used double suciton risers on screw compressors to aid in oil return at low load conditions.

If you are logging the chiller with oil at off load conditions, and the operators are adding oil due to adjust an oil level in the separator, when the system load returns, the compressor will load up andd pull the oil oit of the chiller. This oil is rich in refrigerant and will damage the compressor in sufficient quantities.

During initial start up, it is normal to add oil a time or two until the oil starts returing to the compressor. Once past this point, you should not have to add oil unless you can trace it to an oil loss. The oil is not gone in a closed loop system. It has just moved.

One reason to see an oil loss on a short term basis is the compressor taking liquid. The excess refrigerant will dilute the oil and also increases the velocity in the oil separator to the point that the coalescing elements are overloaded and allow oil to leave the separator. This can lead to blowing out the elements and oil loss will become a continuning issue. I would check the oil separator elements.

While you may not be a proponent of screw compressors, I am. Like I noted earlier, these are tough compressors and will run in conditions that would kill a recip much faster. The more I hear on this case, the more I feel it is a system related problem or a maintenance problem.

Ken

NoNickName
11-09-2006, 07:18 AM
TX, your attitude is getting me nervous. I'm not telling you what brand of compressor it is, because it is unfair.
And thanks for explaining to a manufacturer like us how chillers should be built.

US Iceman
11-09-2006, 05:34 PM
The more I hear on this case, the more I feel it is a system related problem or a maintenance problem.


That's what I'm thinking also.



TX, your attitude is getting me nervous.


What is there to be nervous about? His comments are exactly right. Both of us "iceman's" have worked for manufacturers also, so we do have some insight in the difference between component problems and systems issues.

I'm not sure why you have to get defensive:confused:

Josip
11-09-2006, 07:33 PM
Hi,


NO, the oil cannot be removed from the suction, unless disconnecting the compressor, and it has no other way to get into the separator than through the screws.
This shows the relative superiority of screw compressor having external oil reservoir and separator.

The fact is: unexperienced service company are told to top the oil up when it looks low in the sight glass. As a direct result, liters and liters of oil are added.
The situation worsen in case refrigerant with high relative oil dilution are used, like R404a.

So, this compressor was a pump, and that is the end of this story. NoNickName, you should tell us this at begining :D Everything is very clear now.

Construction of that compressor and built-in oil separator maybe is not so bad (even good) but there is no security against stupidity.

Many times I had a situation where the oil in sight glass (on oil separator) was at very low level (actually enough) with compressor running. When compressor stops all oil return and level is ok. Having no expirience, unfortunately they did just the worst.

Sh't happens :(

Best regards, Josip :)

TXiceman
12-09-2006, 02:28 AM
NoNickName, all I am doing is thinking out loud. This is the way problems are solved. You have to ask questions and hopefully get truthful answers. I have no idea if you work for a manufacturer of compressors or systems.

No reason to get defensive. I have worked with Kobelco, Howden, Mycom, Grasso/GEA, Frick, Vilter, Copeland/Bitzer, Carrier, Hiatachi and a little with Refcom screw compressors.They have all had some problems over the years and managed to get them straightened out.

90% of the time, we can trace a problem directly back to either poor operation/maintenance proceedures or a improperly designed system. I generally look at the operation and design first thing.

I have over 35 years of experience in designing and building refrigeration systems of all types and a lot of field experience trouble shooting problem jobs.

I have no idea of your background or experience. Unless you are willing to open you mind and accept suggestions and comments from others in the field, you will hinder your ability to learn in this field.

I wish you luck and I will comment no farther on this issue.

ken

winfred.dela
12-09-2006, 03:19 AM
Hi Txiceman,

Please do not stop commenting.

I've been lurking in this thread since i found RE forum this month.
Been learning and enjoying the bantering and ideas that flow. . .

I just read all the post in this thread without posting coz i have no experience with screw.
Have seen a lot but have not repaired one.

If you stop, that would be sad.
I will miss your post in this thread and also the smile i have during the bantering.

hope you keep your COOL iceman. . .
and keep all the ideas flowing . . .
so we Lurkers wil learn a thing or two.