In order to monitor what’s going on chemically inside the chiller, a chemical analysis of the lithium bromide is required. This usually consists of tests for the following
Specific gravity;
Alkalinity and pH;
Copper content;
Suspended solids; and
Inhibitor concentration.
The specific gravity which is pulled at full load and measured with a hydrometer will indicate the concentration of the lithium bromide, whether it is at working strength, or too dilute to function as an absorption medium.
The pH and alkalinity can provide an indication of any air leakage into the chiller. It can also give some insight into which metals are likely to be attacked. For example, at low alkalinity and pH values, the ferrous or steel components are susceptible to corrosion. Raising the alkalinity can protect these metals while promoting an attack on the copper portions, such as the tubes.
The copper content and suspended solids will show the magnitude of the corrosive attack and also indicate how aggressively the lithium bromide charge is dissolving the machine’s components. It will likewise indicate the degree of fouling inside the chiller, and whether or not the spray headers and heat exchangers are likely to be clogged with debris.
Finally, measuring the inhibitor will show how these additional chemicals are performing inside the solution. Inhibitors are added to the lithium bromide brine to protect the various metallic surfaces and slow the rate of corrosion to acceptable levels.
Corrosion can never be totally stopped; it can only be minimized. This is the function of the inhibitor which is usually lithium molybdate.
