Cooling Tower Equalizing Line

[bullgear17]

Hi guys,

I wanted to get some help to check if connecting the cooling tower equalizing line to the supply line (cooling tower outgoing) will have significant effect on the system in terms of flow. The reason for this is that the water treatment vendor suggest that the equalizing line is stagnant of water and may be prone to corrosion and fouling and thus recommends to connect it to the supply line to have a continuous flow.

thanks

 

[cry22]

I am not sure I understand the wording correctly. If you connect an equalizing line to the supply line, it is no longer an equalizing line, you need auto isolation valves to isolate a tower.
Equalizing lines are usually made of PVC piping, no corrosion involved.
You can do tower blow-down from equalizing line, this will eliminate the concern of stagnant water. Stagnant water is more dangerous in cooling tower for legionnaire disease than for corrosion.

 

[bullgear17]

Hi cry22. Yes, that is correct. There was a recommendation from the water treatment supplier to connect the equalizing line to the supply line to promote flow and eliminate water stagnant on the equalizing line. The existing equalizing line is mild steel pipe.

 

[RobsVette]

I agree with cry22. Here are a number of reasons. I just got into this with someone the other day.

- in your particular situation it is important to note one thing. Equalization lines are very rarely stagnent and do not move. The water will always flow from one cell to another, unless you can exactly balance the water flow out the supply from one cell to another. This is because the amount of piping is different from every one cell to the pump suction to the next. Thus you will get slightly different supply water flows. Very rarely does anyone have perfectly symmetrical cooling tower supply and return piping.

To add to cry22s comment, if you connect an equalization line to the supply pipe, or try to use an oversize supply pipe you will in effect not have an equalization line because the pump will be pulling water through it. In order for an equalization line to actually equalize the water flow from cell to cell, you cannot have the pump pull water through it so that when one cell gets low vs the others, the different in heights of the water level causes water to flow. The potential for the flow rate may only be a couple of inches, but the water will start to flow. If you want to try this, find a cooling tower and close off all the equalization lines and see how long it takes for the water levels to differ significantly. It ussually doesnt take to long. If you have a good water balance and make up in each cell, you can usually get away without having one until you clog up one of the suction strainers or overflow water out the hot deck / clog up a spray nozzle.

So you really wont have a problem with water stagnant water in the equalizing line.

 

[marcoh]

You should have a side stream filtration system for cooling towers and then connect the SSF suction to the balancing line which will ensure there is always water flowing through the balancing line.

 

[nicole10g]

I am just wondering if I direct a make-up water pipe to the equalizing line instead of to the individual cooling towers, this would this minimize the stagnant water problem.

 

[bullgear17]

RobsVette,

i totally agree with you as i just wanted to get a second opinion about my justification to my team. i also think that it is not totally stagnant as water is being evaporated as well as refilled on top of the difference in piping configuration to create a flow in between. another reason i thought of in connecting this two lines was that it will be defeating the purpose of the equalizing line as it will create more unbalance flow since the pump will be pulling water as well from the equalizing line.

Marcoh,

we have side filtration system and this was the option i provided to them if they are worried about the no-flow at the equalizing line. but it is not only reliability and operations stability they are concerned with. you know corporate, the last drill will be the economics... cheers

thanks btw all for the clarifications. at least i am not alone with my assessment

 

[marcoh]

It does all come to the mighty $$$ but an effective SSF system will reduce cleaning requirements for the cooling towers and the cleaner fill will enable cooler water into the chillers, thus reducing chiller energy consumption. But to put a hard cost to these is not easy.