chilled water piping

[Marcelobsb]

I'm about to start construction of a new building with 70 ton of chilled water capacity.
Can anyone give me ideas about the pros and cons of using cooper piping rather then steel for the chilled water lines?
I have specd ASTM A-120 seamless galvanized steel sch 40 for up to 2 1/2" and ASTM A-53 seamless black steel for larger diameters.
Customer would like to use cooper instead.

 

[HVAC68]

$$$$ would probably be a negative against using copper pipe. Any specific reason why copper is being preferred ?

HVAC68

 

[Marcelobsb]

Thanks for you reply!

Yeah, the $$$ is a big down side of going with cooper. Customer is willing to reach deeper in his pocket for that.

The cooper option is being looked at by the building owner as a more "trouble free" way to go when thinking in the long range, like 15-20 yrs. No one garantees that the chilled water will be properly chemically treated thoughout the years...

Right now the same customer has an old building with an ancient HVAC system that has been running with PLAIN WATER for the last 15 years! Not even 1% of ethylen glycol in it!!! The lines are all cooper in this building and the owner is saying that if they were galvanized he would be full of leaks and built up scale by now.

 

[friartuck]

If your client likes the idea of copper pipework and doesn't mind the extra cost, why not suggest plastic pipework. I have used various types. Generally it has a 50 year guarantee and has good insulating properties. It also is quicker to fit.

Try Durapipe or GF (George Fischer)



Friar Tuck of Sherwood

 

[KenRad]

I second the motion for plastic. Schedule 80 PVC would be a good choice for added strength, and would be MUCH cheaper than copper. As with copper, you wouldn't have to worry about internal corrosion, or external corrosion in areas where you have insulation failures that lead to condensation. The PVC also gives you some R-value, again, for condensation control.

If you want to sink some money into a quality chilled water system that will last long term, I would insulate with styrofoam (with sealed joints), and use solvent welded PVC jacketing. The result is a piping system that maintenance personnel can walk on without causing insulation damage. Fiberglass just doesn't last.

---KenRad

 

[boyceg]

We had an "infection" with our closed loop copper water cooling system. This system was not open to the atmosphere. The bug lived on copper. A biocide had to be added to kill it. Some pipes were blocked and had to be blown out with 120 PSI compressed air. The company that checks our system had to send a sample off to the head office to get an analysis done. Now, perhaps you will not be as surprised as I was.

Don't know if this problem would occur with plastic...
Boyceg

 

[TBP]

Yikes - shooting 120 PSI compressed air into chilled water piping? Unless this system was installed to a pressure piping code (and I doubt that it was), I don't know that I'd make a habit of doing that. I'd sure never EVER do anything like that with plastic pipe. Speaking of which I find it to be mechanically fragile. People try to use it for ladders, or to rig from, and it breaks. I've seen a couple of pretty impressive floods inside buildings from construction insulators stepping on plastic chilled water piping, and having it break, while they were covering the lines. These happened during retro-fit work to the upper floors in an existing courthouse. Caused a LOT of damage.

If a system is in fact, "tight", that is no make up water is being added, then corrosion should be non existant. It's the constant supply of fresh water, full of dissolved oxygen and hardness that causes the problems. Unless outdoor air intakes are in danger of freezing, glycol is not normally required. In fact, glycol systems must be checked annually to make sure that it's not breaking down into acids. If water treatment issues are being considered (as in not-much, or non-existant water treatment), then glycol absolutely assures that there MUST be some level of chemical treatment. I've also seen glycol identified as the cause for bacterial problems in closed loop systems. Glycol causes at least as many problems as it solves.

 

[boyceg]

TBP,

The air pressure was applied to the copper water passages in 50KW induction generators to dislodge the "stuff" that the bugs living on the copper had built up. Looked a lot like what would come out of a clogged sewer pipe, but smelled slightly better. Why 120 PSI? Well, 100 PSI would not do the job. The blowing out was strictly a local operation. The induction generator getting the treatment was disconnected from the system for cleaning.

And, this system was closed and pressurized to about 15 PSI. We had to have low conductivity because there were places where one end of a rubber hose would be grounded and 18 inches away at 3000 volts. We had to shut the plant down, kill the bugs and refill with deionized water until the conductivity went back down. Then replaced the additive package to keep the bugs dead.

A company by the name of Anco is responsible for our system being as reliable as it is.

Then they fired me and dumped the cooling system. They did more damage than they would have paid me in wages if I had stayed on the job for 10 more years...
Boyceg

 

[TBP]

I thought you were working with something like a chilled water piping system. Sorry about your unhappy "experience". Anyway...

Bugs that live on copper? I'm not saying it CAN'T happen, but that's odd in my experience. Copper has been used in water applications for centuries because it'll kill stuff and/or keep it from growing. Copper cladding on the hulls of wooden sailing ships was initially installed for rot/leakage prevention, but it was noticed that barnacles didn't grow very well on it. Drive a copper spike into a tree, and leave it there - you can kill a good sized tree in a year or so. There are copper based water treatment products that do an awsome job on algae in cooling ponds. I haven't been involved with them for years, so I don't know if they're still on the market. You can certainly CLOG copper water lines with debris like algae from other sources, like a cooling tower, etc. The deposits may very well trigger some kind of under-deposit corrosion.

About 75% of plant problems that are deemed "chemical" in nature, actually have a mechanical root cause. Make the mechanical side right, and a HUGE chunk of the water treatment/chemical problems either never occur, or if they are occuring, vanish.

Most mechanical/electrial people don't understand chemistry very well, and most chemical people don't really understand the mechanical & electrical side. There are notable exceptions, but I know a huge number of HVAC & mechanical people who don't understand anything at all about water treatment. And it costs them a LOT.