Valmet IQ MW Moisture Measurement

Features

The moisture sensor is a dual-frequency cavity resonator excited by a low-power microwave signal. One resonance frequency varies in proportion to the total moisture in the sheet. Another frequency, insensitive to the water, is used as a reference. The frequency difference between the resonance peaks is a measure of the moisture content. Combined with an accurate basis weight measurement, the result is a reliable measurement of the moisture content.

The microwave moisture measurement is particularly suited to multiply boards since the longer wave microwave energy pe-netrates through the entire sheet measuring the moisture in all plies with equal sensitivity. It is not affected by moisture strati-fication, freeness changes, sheet composition, or contaminants from recycled furnish. Neither web fluttering nor varying air humidity affects the measurement performance. Temperature changes are automatically compensated in the moisture readings.

Benefits

• Accurate and stable measurement for precise control of moisture in machine and cross directions covering all applications from paper to pulp.
• Faster on-spec quality and therefore reduced start-up waste.
• Reduction in rejects due to moisture streaks, roll quality and related issues.
• Minimization of energy consumption by precise moisture control.
• Allows moisture to be increased to save furnish in some grades.