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Needs some info about internal coating of Chilled water (MS pipes) 1

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fcu45

Structural
Jul 10, 2012
87
Hi

For the project I'm working on, there is chiller cooling system. I need to increase my knowledge about any requirements/ specifications needs to be met for the internal coating of the MS pipes used for the chilled water pipes, (Black carbon steel pipes).

I saw a piece of that MS pipe and found it to be having rusted surface and I was told that there will be some flushing that will apply a protective coat in the internal surface, but I need more details.

Thanks
 
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Flushing serves to remove excess rust/sludge, but there is no coating effect that I know about. What such coating would mean for control valve seats and cams?!

Engineer should specify water treatment for your system. In general, basic element of such a treatment would be removal of oxygen dissolved in water, and, depending on water hardness some other measures may be needed. It's important whether the system is used for heating as well, and, in general, pH of water in working conditions should be assessed.

If you have much rust, your water treatment system is likely inadequate or even non-existent. There are micro-filtration equipment that can improve condition of existing system, but careful specifying is needed. Mistakes are very costly. I have seen systems that become inoperative few years after start-up.
 
Thanks dear Drazen for these great info

So why not to shorten the issue by using either non corrosive pipes such as PVC similar to ones used for water supply?

There may be an issue regarding pressure of the chilled water but I believe there are strong non corrosive pipes in the market.

Or at least to have the MS pipe painted with proper anti rust coat from inside, wouldn't that be much easier than removal of oxygen from the water?

I feel those pipes will be "Unnecessarly" the weakest point of this expensive system? and affects the system life time?
 
In theory, chilled water pipes do not have oxygen in the water supply as everyone goes to great lengths to prevent it with vents, air separators and water treatment. Chilled water systems are closed to atmosphere.

Plastic piping is prone to mechanical damage

 
PVC makes a nice insulation jacket and an affordable drain pipe and... nope that's it.

Water treatment is your road to follow.
 
fcu45,

steel pipes are there for a reason, and things are not too simply when looked through life cycle of system.
though there are many variations of plastic materials these days, pvc is not used for pressure pipes, as kiwi pointed.

pe-x is used, and can mostly stand pressure and tempeature, but is not rigid enough, and hanging such pipe is major issue. now on the market there are three-layer pipes, like pe-x/aluminum/pe-x, and they are already offered in range up to 4". middle aluminum layer serves to improve rigidity, somewhat reduce thermal expansion, and prevent oxygen intrusion (bare pe-x is "porous" for oxygen).

there is also issue of how to compensate for thermal expansion, which becomes relevant even for chilled water when you have very long lines. i am still concerned about any plastic layout where self-compensation is not possible. as soon as you have axial compensators, piping needs to handle forces in multiple directions and not only that steel piping can withstand much more, but also there is large experience and much of elaboration as regards to steel pipes.

in general, you can easily use plastics in small systems, need careful comparison for middle-sized system, and plastic is often not useful for large systems.

you don't have something like simple solution, if such solution exists, everyone would be using it.

currently there are companies like german geberit that offer several alternatives of non-corrosive metal pipes for use in such systems, but first they are much more expensive than ordinary black pipes, and second, for each of such systems you cannot avoid care for water treatment, each and every of such pipe types has precise specs for system water. oversimplification for sake of reliability is not an option, with proper water care your system can last for decades.
 
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