HVAC Pipes flushing

[Manu68]

Dear Experts,

After the chilled water pipes are commissioned, what is the water flushing procedure to be followed.
How many times the flushing is to be done for the pipes. What are the chemicals to be used in this cleaning process.

Highly appreciate if any standards or procedure can be shared.

Thanks,
Manu

 

[EnergyProfessional]

Typically your flush with clear water, with a detergent, and with clear water again to get the detergent out. Your piping needs to allow to flush through branches, you may want to take out certain devices (like pressure independent cartridges, or flow meter wheels). the flush flowrates through each branch also need to be high enough to flush dirt out. So if your 10"pipe gets flushed with 1 gpm, all dirt will stay in there.

 

[urgross]

Normally, the chilled water lines are flushed as part of commissioning. Alkaline phosphate detergent would be typical for treatment. As part of the procedure, include bypasses at clean equipment such as control valves and coils. Make sure to clean any strainers that were not bypassed. Surprising things can come out of the pipe; I almost always encounter plastic wrap, which really screws up a valve or strainer.

 

[ChasBean1]

Commissioning has become such a buzzword that it’s no longer a third party inspection and verification process but rather the be-all and end-all of quality control. I don’t like that pressure as a third party commissioning agent and I have yet (after 19 years) to “commission a chilled water pipe” as you mention.

But as part of the Cx process I’d expect to see that pipes have been thoroughly flushed after filling, chemicals (either acid or caustic) have been applied for 2-3 days to develop a passive oxide layer in the piping, pipes have been thoroughly flushed again, then pump start-up strainers have been removed and all system y-strainers have been flushed.

The final piece of the verification process would be that the right concentration of chemicals had been added, expansion tanks are correctly charged and online, make-up water is aligned to the system and that glycol mix tanks work and have the right pressure switch settings.

 

[Drazen]

i am not native english speaker, so i may stick to some terms more strictly than most, but that rarely if ever created problems.

i consider flushing a mechanical cleaning. chemical treatment is separate process. in flushing, you use mechanically filtered water to remove whatever you can from interior of piping.

flushing can last for long depending on system layout. if you have one-circle system, sludge from bottom of boiler can reach the most distant radiator and rest there. so you have to open flushing valves on all branch ends, and flushing is complete only when there is clear water at all flushing points.

 

[cry22]

Look at your masterspec on water treatment, it is all in there.
I think you mean desinfection, followed by flushing.