Scale at Cooling Tower

Water Treatment - Cooling Towers :: Corrosion and scale inhibitors ...
to see more information on treating cooling tower scale ... - FreshAW

Awwhh. Your too quick for me......

Call a chemical water treatment representative in.

Find out if there is a cause of the scale.

The company where I work, before I started there, built a new plant in the mid 90's. The first cooling tower we put in had a galvanized basin. This raised hell, and our treatment guy had a time of it to stabilize it. The following cooling towers all have stainless basins.

It sort-of-suggests a problem with the blow-down regime. As water evaporates from the tower, dissolved solids are left behind and if the concentrations exceed their saturation solubilities, they will precipitate-out.

1. Check the settings of the blow-down equipment are correct as per the equipment manual and that the regime is working correctly.
2. Look for changes in the incoming make-up water, particularly an increase in total dissolved solids levels.
3. If there still seems to be an issue, contact the water treatment chemicals specialist by telephone, and arrange a site visit for a tower water analysis. Follow-up on all recommendations received from it.

set it and forget it ( except refilling the chemicals from time to time)

That's similar to the chemical inject we have.

Those look like two sets. (We're actually working on moving it as we speak.)

Depending on the make up and quality of the available water you can ruin a system quickly with out proper treatment. As suggested by other posters consult a chemical vendor right away. Ask for references, a bad chemical vendor can be as bad as not treating the system.

to answer your direct question...ZERO scale, scale acts as an insulator and reduces heat transfer...which is exactly what you want a cooling tower to do

How is acceptable scale limit- Refer relevant ASHRAE or CIBSE standards .

To monitor the scale at cooling tower- Consult a reputed chemical consultant or company.

Bear in mind also that if there is scale at the tower, then heat exchange surfaces in the equipment being cooled and the pipes leading to them and from them may also be furring-up.

Ring that chemical supplier and arrange a site visit. Today/this morning/within the hour is not too soon.

As usual, everyone is feeling (blindly) at all different points of the elephant, and all have a semblance of truth.

(1) If you are referring to scale AT the cooling tower, then where are you finding it? If in the fill material, 2% is a good rule of thumb as to weight gained. The question is why would there be scale on the fill material at all, if you are following the OEM guidelines (proper treatment and blow-down)? In the wet dry areas of the cooling tower (louvers, etc. at the outside air interface), there is typically some scale and some algale growth that is extremely difficult to control under the best circumstances.

(2) If the scale is not so much on the cooling tower, but is found on heat exchange surfaces, you need to recover scrapings of the material for analysis to determine the composition of the mineral(s) involved, measure the thickness of the scale, etc. If the scale is only 100 micrometers thick, the heat transfer is affected by most minerals at maximum system heat load, but might not even show up under low load conditions. If the mineral scale is quite thick then you will have to shut down and remove this (hire a professional). Option 3 (expensive) retube all heat exchangers, and correct your previous mistakes.

(3) There are treatment chemicals that can gradually remove most forms of mineral scale with stepped residual concentration (based on observation of turbidity in the water), but a word of caution about overtreatment dose: this can cause the material to slough off rapidly in larger chunks that will plug the system.

(4) There are side-stream softening treatments that will slowly remove some scale and prevent new scale, while reducing water consumption through blow-down. There is also a total softening treatment (with high efficiency softeners) of cooling tower makeup water that will produce excellent results on slowing corrosion to next to nothing on test blanks (~0.01 mils/year, 0.00025 mm/year), with no scale being formed, other than a monomolecular thick layer of silica on the metal. This latter treatment offers zero liquid discharge from the system.