What is scale?
When raw water enters a boiler, it takes dissolved minerals of Calcium and Magnesium in with it in the form of carbonates and bicarbonates. These hardness salts in the water are inversely soluble – more soluble in cold than in hot water. Therefore, when they meet the high temperature and pressure of a boiler, some of the dissolved minerals come out of solution. This precipitation adheres to the heating surfaces in the form of a hard rocklike deposit called scale.
The scale deposits produce an insulating barrier to efficient heat transfer, raising fuel costs and lowering the overall efficiency of the boiler. In extreme circumstances this scale build up can cause complete boiler failure.
What problems are encountered if scaling occurs?
- Heating surfaces become coated with thick hard layers of mineral deposit which acts as an insulation to prevent the efficient transfer of heat.
- Reduced heat transfer increases the temperature of cooling solutions leading to overheating of equipment and ultimate breakdown or automatic shutdown of plant.
- Scale formation also causes blockages in system pipe work, reduction of internal pipe diameters and restriction of flow rates.
What is the solution?
To attempt to control scale formation within a boiler, scale inhibitor chemicals are dosed into the incoming feedwater to condition it. Two characteristics that are designed specifically to control scale formation are the maintenance of:
- A satisfactory alkalinity level, and
- A minimum phosphate reserve in the boiler water.
Tandex scale inhibitors have the ability to delay precipitation of hardness salts which would normally form scale in steam boiler systems. When these salts eventually precipitate in the presence of a Tandex scale inhibitor they come out of solution as fine crystallites which stay in suspension, preventing a dense compact sludge from forming. The suspended solids are thus removed during the normal blowdown, bleeding or system flushing operations. This in turn helps to keep the systems in a cleaner condition.
Here’s what you do now –
Regular tests of the boiler water will ensure that specific target ranges of scale inhibitor, alkalinity, and phosphate levels are maintained, to facilitate the most effective water treatment conditions. If target values can be maintained on a continual basis, clients will see the true benefits of a water treatment program. Conversely if the program is erratic in control, the results will not be as good, as scale is deposited much faster than it can be weathered off.
It is therefore important to conduct regular tests of the boiler water to ensure that the target ranges are maintained.
Controlled Acid descaling cleans can be carried out by Tandex personnel to remove layers of scale to improve flow, heat transfer and efficiency of the system.
For a free review of your site requirements, please contact us to discuss your particular application and system problems.