Chemical dosing for cooling tower water

[u/Trigathoras69]

Hello guys, junior engineer here. I was given the task to install a control panel to inject chemicals for cooling tower water and design the suitable piping pathway and where should the chemicals be injected into the cooling tower system. I was thinking of just directly inject the chemicals into the cooling tower basin, but since the cooled water in the basin is stagnant, im afraid the chemicals will not mix well inside the basin. My supervisor suggested do the piping to that the chemicals are injected into the header at recirculation pump discharge side. The constraint with this idea is that the header is made of stainless steel, and the chemical piping is PVC. I would like to ask for any ideas or comment from you guys, especially for those who are working with cooling tower. Is there any industry standard on how to inject the chemicals into the cooling tower system?

[u/Derrickmb]

Why not spray them from the top of the tower?

[u/UnsupportiveHope → u/Derrickmb]

Many reasons.

For starters, cooling towers often have multiple cells. You’ll generally want to be able to isolate a single cell for inspections of the fan and packing. Having chemicals injected into the top will make confined space permitting more challenging.

Secondly, towers have fan forced air going up them. If you’re spraying a mist of chemicals, it’s likely that you’ll have an issue with chemicals spraying out the top of your tower.

Thirdly, it’s going to be more work and more expensive tubing the chemicals up to the top of the tower. Will also make it more difficult to resolve if you have a fitting leak.

Fourthly, it will be more difficult to see your flow. When you tube them directly into the basin, it’s easy to do a quick check on an operator round to see that you’re getting flow.

Fifthly, there’s just no point. Pumping chemicals into the basin is common practice and they mix just fine through pumping and recirculation.

[u/UnsupportiveHope → u/UnsupportiveHope]

That’s not even mentioning whether you want the chemicals going into every cell or just 1. If it’s just 1, then you won’t be able to do inspections of that cell without cutting off your chemical dosing. If it’s multiple cells then you’re just creating more issues with tubing to multiple hard to access locations.

[u/Frosty_Cloud_2888 → u/Derrickmb]

I think you might lose some with drift / evap.

[u/Derrickmb → u/Frosty_Cloud_2888]

What are the chemicals?

[u/Frosty_Cloud_2888 → u/Derrickmb]

Scale and corrosion inhibitor

[u/Trigathoras69 → u/Frosty_Cloud_2888]

yep..and biocide to prevent moss

[u/Derrickmb → u/Frosty_Cloud_2888]

What are their densities and vapor pressures and volatilities?