Clogged chilled water coils

[dan22]

Im on a job where the person in charge of initial installation did not properly flush the system, the last AHU unit with 6 large coils was the end of the run on the 12" chilled water mains, all the crap ended up dumping into this units coils as all the others were fed off the top of the mains, 3 of the coils are very plugged. weve been isolating and flushing the coils by filling wiht domestic water and bumping up pressure with hydro pumps and putting air into the coils and then dumping to try and help scrub it out, we get some black water out in the begining and end but after many hours not alot of progress. Has anyone used any tricks or techniques to deal with something like this?

[Brian_UK]

Depends what the debris is made of.

Some can be disolved some might need strong chemicals and some might need a good blast from a nitrogen bottle.

[lowcool]

can you remove return bends and flush this way?

[dan22]

can you remove return bends and flush this way?
possible but unlikely, this is a walk in air handler that is up and running. The debris is most likely mill scale from the steel pipe and slag from the welds, the existing system it tied into already had some problems to begin with which doesnt help. As far as the blast from the nitrogen bottle, I dont think nitrogen would help anymore than compressed air and water, would it? I think the next step will be upping the pressures, so far up to 120psi has been used.

[serviceman]

closes the valves of the uha. circulating a mixture of water with you acido.si placed clamps on the mesh connections to catch all the dirt possible, use strainer inthe ice water pumps

[lowcool]

sounds like you may have to cut the side panel,if 120 psi doesnt move it i doubt 200 psi will either.if you have no flow i cant see acids etc working either and you still have the integrity of the system to worry about.

[james10]

you could try back flushing it

[tonyhavcr]

Im on a job where the person in charge of initial installation did not properly flush the system, the last AHU unit with 6 large coils was the end of the run on the 12" chilled water mains, all the crap ended up dumping into this units coils as all the others were fed off the top of the mains, 3 of the coils are very plugged. weve been isolating and flushing the coils by filling wiht domestic water and bumping up pressure with hydro pumps and putting air into the coils and then dumping to try and help scrub it out, we get some black water out in the begining and end but after many hours not alot of progress. Has anyone used any tricks or techniques to deal with something like this?



Hi dan22 cut the pipe's any way you can install a boiler valve or 3/4' @ the bottom of the coil and a hose adapter on top in a 5 gal pal - basket mix water and liquid scale remover take a chemical pump and two washer hose's hook one to the pump and the other to bottom of coil pushing in out the top.

http://www.google.com/products?hl=en&client=firefox-a&hs=nED&rls=org.mozilla:en-US:official&q=liquid+scale+remover&um=1&ie=UTF-8&ei=PqBtTMqTFoOB8gbv0-z4Cw&sa=X&oi=product_result_group&ct=title&resnum=3&ved=0CDwQrQQwAg

http://www.amana.com/accessories/laundry/organizers/4__residential_washer_hoses___2_pack_8212546rp.pro

prim the pump use glove's and safety glasses
hook the last hose to to top into the pal - basket
run pump 5 min if there is no flow after that try pushing it in the top out the bottom if no flow then it is a solid object do no more then one coil @ a time
if you do have flow after 5 min back flush it for 5 min then you must flush well w/ clean water change the water out 5 times then test the last water in pal w/ the pH strip if after 3 flush-is of clean water you still have dirt use fresh chemical mix then re flush you must flush well this look easy to make
http://www.americanliquidwaste.com/2010/05/product-watch/zoeller-pump-company-new-product-release-scale-removal-system-srs-109/

I have done this many times
piping up to 3" to 3/4 hose it should work on larger pipes you will not need a larger hose or outlet.

put a y-strainer on the inlet of ea. coil.
keep the boiler valve there if can to flush if needed.

http://www.eaton.com/EatonCom/Markets/Filtration/Strainer-Products/Y-Strainers/index.htm

use Screen, 80 Mesh or higher it should work!

[dan22]

Well been ive been flushing, back flushing, using compressed air and water mixed trying to scrub it out, also tried blowing 250F steam and condensate to loosen it up without luck. Ran some heavy duty potassium hydroxide cleaner thru it all today and at end of day flushed and reconected to system checked with meter and no real improvement. The water in the existing system is pretty bad so Im sure as soon as the coils started to clog it acted like a dirty filter and just started catching even smaller particles.

[Magoo]

Had similar problem with a system that contractor had not installed closed circuit water treatment, did not get to stage of blocking coils though, but started cathodic corrossion reaction and chewed steel pipes out, from the inside, water leaks everywhere.
I must have flushed and drained system 20 times.
The cathodic corrossion may be your next problem.

[tonyhavcr]

I found in my area any system with a header of 1" more the main header that runs down the coil there is a plug @ the bottom of the header that can unscrew.

liquid scale is made for this type of work must use pump it is the chemical that dose the work


Scale Removers and Inhibitor
Clean and remove scale from metal equipment in nonpotable water applications.
Liquid scale removers are hydrochloric acid-based and contain antifoaming agents; not for use with galvanized or stainless steel. Season Treat is a dissolving phosphate compound to prevent scale and corrosion.

[tonyhavcr]

So what happened is it fixed and how did you fix it?

[NoNickName]

Potassium hydroxide is alkaline.
Limestone and steel are dissolved by acids, not alkali.
Try with sulfuric acid or muriatic acid (HCl 10% solution).

[casstrig]

You with find besides the solid debris grease used to coat the pipes as protection you can use a detergent one used for plates.Isolate the coil from the system use a small pump and circulate in the reverse direction for any scaling you should use a 1% solution of citric acid and circulate for one hour and flush well afterwords this will not harm any materials,but of course for the solids which are insoluble you need to open the pipework.