I work on very big VGT's

[Wildcard]

This is a 650 ton York R-134a Chiller that provides AC to a local hospital I take care of.. This one is spun by a 500hp motor. It's on a VSD that controls motor speed and we also vary the veins to control load. We run the surge line and monitor for a surge. The control module creates a 3d map marking where it has surged before so it won't repeat.

She blew an oil oring and I am in the process of transferring the 2600# of refrigerant into the condenser for storage. Will make the repair next week

[Wildcard]

This is the back end of a Trane CVHE450, 450 ton Centrifugal chiller at a School I take care of.
This machine had bearing spalling. It's a refrigerant cooled motor



These chillers utilize R-123 which is low pressure, the machine actually operates in a negative pressure, usually 6" on the evaporator and around 0-2psig on the condenser . You can open a drum of R-123 and the liquid will not boil off until its in the 80's

[Rawze]

Why is there a chunk of crud on that roller inside that bearing?


And WHY is that not a sealed bearing? - is there lube flowing thru the housing?. ... What RPM is it turning? ... and what viscosity oil is that bearing running on?.

I worked on, and helped design various types of industrial machinery like that for many years. that thing also looks like a permanent magnet DC? or a reluctance motor?. can be hard to tell just from a picture.

Also, is there a Tach-feedback on the motor to close-loop that VSD?.. or is it open loop and the VSD has no idea (guesses at) what rpm the thing is at? - I see that mistake a lot in industry with big DC drives like that ... Damned engineer who designs it don;t think it needs motor feed-back and then there are problems with surging, etc, later on.

-- ALSO... What type of dynamic braking system does it have on it?... and what brand/type of VSD is on it?... and how old? .. and Is that VSD protected with and a line-reactor and Amptraps (specialized solid-state fuses) on its front-end properly?

all the programming in the world will not make up for properly.. a poorly designed system.

[Wildcard]

(07-04-2021 )Rawze Wrote:  Why is there a chunk of crud on that roller inside that bearing?


And WHY is that not a sealed bearing? - is there lube flowing thru the housing?. ... What RPM is it turning? ... and what viscosity oil is that bearing running on?.

I worked on, and helped design various types of industrial machinery like that for many years. that thing also looks like a permanent magnet DC? or a reluctance motor?. can be hard to tell just from a picture.

Also, is there a Tach-feedback on the motor to close-loop that VSD?.. or is it open loop and the VSD has no idea (guesses at) what rpm the thing is at? - I see that mistake a lot in industry with big DC drives like that ... Damned engineer who designs it don;t think it needs motor feed-back and then there are problems with surging, etc, later on.

-- ALSO... What type of dynamic braking system does it have on it?... and what brand/type of VSD is on it?... and how old? .. and Is that VSD protected with and a line-reactor and Amptraps (specialized solid-state fuses) on its front-end properly?

all the programming in the world will not make up for properly.. a poorly designed system.

The chunk of crud is actually a chunk of metal missing. It's Bearing Spalling. Trane had and issue with some Timken bearings doing this due to the oiler orphis for that bearing not being big enough. It's an oiled bearing.

These compressors spin max 3600rpm but depends on design and application. Every chiller is purpose built be it for comfort cooling or a process application.

No tach feedback, it's just a WAG from programming motor parameters and motor speed at 60hz.

The York machines are fairly complicated and way over engineered for typical comfort cooling applications in my eyes, Yorks market share is Govt/Military and Ship cooling. So everything they build is to those specs. I can't really stand being near them when they are running as they have a rumble/noise that makes me feel like I need to throw up.

[Wildcard]

Here is a couple 250 ton variable speed AirCooled rotary screw compressor chillers. There was some Metallurgy issues in the condenser fins, these being in a salt environment and having epoxy coated coils. The epoxy was popping off. So I had to replace all the coils.

[Rawze]

(07-05-2021 )Wildcard Wrote:  ...
No tach feedback, it's just a WAG from programming motor parameters and motor speed at 60hz.
...

huge mistake with a system like that.. What cheap bas$tard would do such a thing is would I would be asking.

Open loop systems like that are always going to have issues... I would be looking into putting a tach on it and a better VSD instead of chasing surge, load balancing, and all sorts of other issues that can easily be avoided if it had been designed right to begin with.

I have worked with, and have designed from the ground up, drive and control systems far bigger than that in my day.

[Wildcard]

(07-05-2021 )Rawze Wrote:  

(07-05-2021 )Wildcard Wrote:  ...
No tach feedback, it's just a WAG from programming motor parameters and motor speed at 60hz.
...

huge mistake with a system like that.. What cheap bas$tard would do such a thing is would I would be asking.

Open loop systems like that are always going to have issues... I would be looking into putting a tach on it and a better VSD instead of chasing surge, load balancing, and all sorts of other issues that can easily be avoided if it had been designed right to begin with.

I have worked with, and have designed from the ground up, drive and control systems far bigger than that in my day.

Better call York, Carrier and Trane cause none of them use a tach. Not that it would be useless but in the VSD Centrifugal chiller world there are far more variables that create a surge, and we are always chasing that surge line regardless of impeller speed, as its where the machine operates the most efficient. The variables of refrigerant gas pressures, variable water flow, variable load through the chiller, maintaining oil pressure all need to be taken into the "math". If the lift gets out of whack from water flow, building load, a cooling tower issue etc, etc these chillers will surge. Unlike a turbo or a Centrifugal air compressor or water pump there are far more variables to cause a surge. Were pumping refrigerant gas and the surge line is always changing.

I have a pretty good set of training slides I could email ya if you would like to view them. I would be interested in your thoughts.