Each type of slaker has its own method of control, for a detailed discussion on the types of slakers have a look here. In general there are three means to control a slaker, temperature, torque, and input measurement. While each slaker is controlled using one of these methods, they may also monitor some or all of the others.
Temperature is the most reliable means of control when the desired outcome is consistent highly reactive lime slurry. Slaking temperature is directly related to reactivity (see case study). Detention Slakers and Vertical Ball Mill slakers measure temperature directly in the product zone and are therefore the easiest to control. Horizontal Ball Mill slakers measure temperature at the discharge so control has some lag. Paste slakers and Batch slakers usually monitor temperature but it is not the control variable.
Paste slakers use torque either directly (via a clutch) or indirectly (via amp draw measurement) to control the consistency of the paste in the slaker. Ball mill slakers also monitor amp draw but usually with an eye to maintaining sufficient ball charge rather than controlling the reaction.
Batch slakers make no attempt to control the reaction once it has begun; instead they measure the amount of lime and water introduced into a given batch. Assuming that the lime and water properties remain stable, this will result in a consistent output. Almost all other slakers will use input measurement in some form, and may use this as the control mechanism until the unit has reached steady state.