Field services for optimized reliable stock preparation

The proper and regular maintenance of refiners, pulpers and machine screens in stock preparation and approach flow systems is essential to obtain highest possible utilization rate and reliable operation, and to minimize unplanned shutdowns.

Approach flow system study

How well is the wet end process of your production line performing? Valmet’s approach flow system study sheds light on the origins of short circulation-based problems. It helps improve the stability of the paper and boardmaking process.

Benefits

• Reveals the effects of process variability on paper or board quality
• Reduces process instabilities
• Helps improve machine runnability and product quality

The approach flow system study identifies the origins of the significant short- and long-term variations in the short circulation process and headbox which cause excessive basis weight, ash or caliper variations. These variations often occur at such a frequency that they cannot be managed by machine MD controls or printing machine tension control. They may lead to calender barring, web weaving problems at printing houses, or problems in converting, for example.

The study focuses on the factors that cause variations, such as the functionality of pumps, screens and the control of their drives, or vibrations, chest levels, poor retention aid mixing or piping design.

Paper and board analyses are included in the approach flow system study. Laboratory analyses show the real effects of the disturbance on paper or board quality, and enable benchmarking with other similar machines.

Additionally, we provide a capacity survey which studies the operational adequacy of the short circulation and its components at targeted higher production speeds by using balance calculations.

Scope of service

• Pressure level and variation measurements
• Consistency variation measurements
• Rotation speed variation measurements
• Vibration measurements
• Air content measurements
• Signals from field instruments
• Measurement analysis
• Paper or board variability analyses
• Full reporting, including prioritized recommendations

Low consistency refiner, machine screen and under-machine pulper on-site services

The correct and regular maintenance of the refining, screening and under-machine pulping systems is essential to obtain the highest possible utilization rate and reliable operation and to minimize unplanned shutdowns.

Benefits

• Increased capacity and more stable operation
• Reduced operational costs with optimized and up to date parts
• Minimized unplanned shutdowns
• Improved safety

The first step is to perform a mechanical audit which identifies maintenance and repair needs. The scope of the audit is agreed with the customer to achieve the best result. The best result is achieved when the audit is done both during the operation and shutdown. The findings for breakages, leakages and vibration are inspected and measured. (The graphics show examples of heavy wear and corrosion and mechanical failure.) The audit report, with its findings and recommendations, is delivered to the mill.

Valmet can also offer upgrade packages, mechanical seal upgrades, turbine housing, surface coatings for increased capacity and reduced operational costs.

For more information about optimizing the reliability and performance of your stock prep and approach flow systems, contact your Valmet representative.