mixing glycol

[mksoucy]

I am working on a job where we have an existing glycol piping network that has not been used for many years. For this job we are adding on to this glycol system and tying into 2 new chillers. We are recommending that the whole system be purged of the old glycol and refilled with new, but the owner does not want to pay the cost to do so. So we have been overruled, and they are going to 'top-off' the system with new glycol. The glycol has been tested and seems to be chemically sound however we feel that because the system has been dorment for 5+ years there is a lot of sludge in the pipe which may clog up the chillers. Does anyone have any experience with reusing glycol? Also when adding new glycol to the exisitng, I have heard that the two have to match exactly or there may be some interaction problems. Is this true, and what can happen?

 

[quark]

If the solution is chemically sound then you have every chance to reuse it but be sure to make it physically sound also. I would suggest to remove the entire solution and get it filtered atleast by a 40 micron filter and flush the entire piping before recharging.

 

[sterl]

Agree with Quark about filtering, but you do want to know something about your chemistry....

If this always a copper pipe installation, chances are you're dealing in a relatively mild sort of inhibitor package.

If its all mild steel pipe, Old Glycol likely to contain chromates and thats not of itself particularly bad but the newer "none heavy metal" inhibitor packages contain organics, which may or may not strip any chromate film and in worse case, could cause the chromates to preciptate.

To get comfortable, have somebody due a chem for at least the "type" of inhibitor and do your best then to match it if still available.