Expansion Tanks - Chilled Water

[Zoso71]

I have a bladder-type expansion tank that sits on the floor in a chilled water system. It is becoming undersized as the plant is expanding and needs to be up-sized. I am fortunate enough to have a ball valve in the expansion tank line for easy isolation.

If I have the system up and running at temperature, can I shut the expansion tank line valve and change the tank while the system is on? Since I will remain at temperature through the exchange, I don't see an expansion issue. Am I missing something hydronically?

Thanks, Steve

 

[friartuck]

What size is the pipework. If its only 2" you could do a live tap in using and explosive tee connector. These clamp around the pipe and then you install your pipe and an additional valve. Once done, the tee is hot by a hammer and a an internal cutting tool cut out a section of the main pipe. We use these where we can't shut down the mains due to loss of production etc.

Drapes

 

[micjk]

I believe the fittings that drapes mentions are called Kitz couplings. We have used them at our facility and the work very nicely.

Roy Gariepy
Maintenance and Reliability Dept.
Dorlastan Fibers LLC.
Goose Creek, South Carolina USA

 

[imok2]

Assuming all conditions remain the same; the short answer is Yes. Use the hot tap as a backup if you can't complete in one day.

 

[Zoso71]

The system is a 60-ton chilled water system. I am a contractor, and this situation is at one of my customers. Piping would have to be 3" or 4" sch 80 PVC. It is for injection mold cooling. I have an in-line rol-air-trol with a 3/4" line with ball valve dropping down to a bladder tank on the floor. I am wondering if I can just isolate the tank and replace it while the system is running? It will be down to temperature and will ramain there throughout the process.

 

[tkdhwjd]

Don't want to play a devil's advocate, but what if the process upset occurs and the system does thermally expand or contract?
You should consider all contingencies and rank them on severity and probability. Then each mitigating steps to manage those risks should be defined. If your customer is willing to take the listed risks, then it is OK. I don't believe that there is a clear answer to your question.

 

[tickle]

Is the tank really an expansion tank or is it used as a pressure source to soften the starting and stopping of the distribution pumps. Or is it there to minimise hydraulic hammer when users come on/off line?

If it is one of the above, you should be able to isolate the vessel and see if changes can be made.

Has the bladder accumulator been recently serviced, you may be able to change the bladder pressure to allow for expansion.

PS I do not know much about chilled water systems so I may be talking cr*p. If this is the case I apologise.

 

[ClydeMule]

Even if you take the tank offline and their is some kind of expansion, there should be somekind of pressure relief in the line.

Just make sure it is online, and doesn't relieve into the production managers office ( I actually saw that once).

Most plastic shops use ethlyene glycol, so keep that in mind.

We build a lot of chillers for plastics, but we use open tanks and don't have to mess with the expansion tanks much.

Good Luck!

Clyde