Black silt in steel chilled water lines running glycol

[EricTh]

I will have to find out if there are any inhibitors in this system but it is a chilled water loop with glycol added. We get this fine black silt that clogs strainers in the sysytem. These are very small strainers in a 1/2 inch pipe that feeds a small ahu. Just trying to figure out what it could be. Thanks Eric

 

[EdStainless]

What are the materials of construction?
How was it flushed and cleaned before being put into service?
Are you running multiple filters, coarse followed by as finer one?

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P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

Iron sulphide?

I get a load of black gunk in my radiators.

Fit a magnetic filter.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

How do you chill this chilled water stream? What refrigerant is on the other side of the chiller heat exchanger: ammonia, some HCFC ?

 

[TugboatEng]

Black silt sounds like mill scale. Is this a new system? Is the system clos loop? If so, why do you have strainers?

 

[EricTh]

Thanks for the input so far. It is a chilled water system for a building and is schedule 40 steel. i assume the normal post construction flushing and cleaning. I think its about 8 years old. There are no filters only strainers. A large one at the main pump and much smaller ones at each ahu 1/2" pipe size. These are the ones that are getting clogged up. The chiller uses HCFC refrigerant 410A. It is a closed loop.

 

[EdStainless]

And is this a recent change or has it always been an issue?
If it is a change then you need to look for what caused it.
And don't let people tell you that they didn't change anything.
Even who they are buying chemicals from matters.
It sounds like more air in the system.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

Is your main filter a magnetic one?

Has the system ever been drained and refilled or topped up a lot?

If you drain a litre of and look at it in a glass jar did it look dirty? Does it settle on the bottom?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Agreed, it may be something to do with the additives / inhibitors in this ethylene glycol-water. There is a brief narrative on ethylene glycol - water refrigerant systems in Perry 7th edn which may help - see page 11-95.

 

[FacEngrPE]

Water treatment for chilled water systems is often ignored, but it is important. The black gunk may be biology eating the glycol and steel pipe. It will mess with the heat transfer.

I suggest that you find a local water treatment expert, and get his advice.

 

[LittleInch]

Silt or "gunk"

Any pictures?

Can you get it analysed?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Can we see a process sketch pls?
Is there an expansion tank/drum of sorts here? With a rubber bladder that may have disintegrated into the chilled water?