mjpetrag
Mechanical
- Oct 16, 2007
- 224
All,
There is a project at our site to inject sulfuric acid into one of our cooling towers to help descale or prevent scaling of our HX tubes. The cooling tower is a 3-cell design, with each cell's water level equalized. Circulation rate is about 20000 GPM total for the tower. Construction of the tower is FRP, converted from previous construction of wood. The basin is constructed of carbon steel. The proposal is to inject acid into the water level of each basin cell, with a pH probe on the water circulation loop. This will be managed by our chemical treatment vendor, Nalco. I have some concerns
How will this impact the corrosion rate of the carbon steel basin? Is there a chance of localized corrosion at the basin where the acid is added? While the pH of the bulk fluid might be within range, at the points where the injection occurs, there could be a very low pH localized there.
When a cell is shut down say for fan maintenance, we shut down/lock out the fan, return water, and make up water to that cell. If the acid isn’t turned off, the pH will get extremely low in that cell’s basin. This is a risk. Obviously this should be controlled by LOTO, but if it’s missed this will be a big problem
When the tower is shut down for maintenance and basin is drained, any drips coming out of the acid addition tubing after the basin is empty will hole-through the basin. The tubing has to be free draining to prevent this from occurring. I could see this happening if we just block in the acid without clearing the line afterward.
These were just the main things I could come up with. I plan on speaking with Nalco to see if other customers with this setup have any issues, but also wanted to poll the forum here for their experiences.
Thanks!
-Mike
There is a project at our site to inject sulfuric acid into one of our cooling towers to help descale or prevent scaling of our HX tubes. The cooling tower is a 3-cell design, with each cell's water level equalized. Circulation rate is about 20000 GPM total for the tower. Construction of the tower is FRP, converted from previous construction of wood. The basin is constructed of carbon steel. The proposal is to inject acid into the water level of each basin cell, with a pH probe on the water circulation loop. This will be managed by our chemical treatment vendor, Nalco. I have some concerns
How will this impact the corrosion rate of the carbon steel basin? Is there a chance of localized corrosion at the basin where the acid is added? While the pH of the bulk fluid might be within range, at the points where the injection occurs, there could be a very low pH localized there.
When a cell is shut down say for fan maintenance, we shut down/lock out the fan, return water, and make up water to that cell. If the acid isn’t turned off, the pH will get extremely low in that cell’s basin. This is a risk. Obviously this should be controlled by LOTO, but if it’s missed this will be a big problem
When the tower is shut down for maintenance and basin is drained, any drips coming out of the acid addition tubing after the basin is empty will hole-through the basin. The tubing has to be free draining to prevent this from occurring. I could see this happening if we just block in the acid without clearing the line afterward.
These were just the main things I could come up with. I plan on speaking with Nalco to see if other customers with this setup have any issues, but also wanted to poll the forum here for their experiences.
Thanks!
-Mike
