In my last two columns, I've been looking at some of the methods of obtaining the required field data to enable an effective dryer audit. I left off with the discussing simple mercury bulb thermometers, which are suitable for performing both dry and wet bulb temperature measurements, and the infrared (IR) thermometer, which measures surface temperature and can be targeted and focused.

Pressure in drying systems is fundamental. Note that vacuum is negative pressure, so when I refer to pressure, I am talking about an absolute value. Because gas is being moved around the dryer, there is a requirement for the primary and secondary movers to be able to produce sufficient pressure to overcome all of the losses as the gas moves across the system. A manometer is used to establish the static pressure across the system, and a static pressure profile can be developed to illustrate the losses across the system.