Mist Elimination and High-Pressure Fabric Cleaning
Effective fabric cleaning and improved machine runnability can be achieved with an engineered mist elimination system.
Standard open-air high-pressure showers can create significant mist when impacting a fabric. And when shower pressures or fabric speed increases, the result is even more mist. This mist is laden with fiber and filler. It collects on the machine structure and cross-machine members leading to both safety and runnability issues, particularly with top formers and tissue machines. Safety issues attributed to slip hazards can be minimized when mist is eliminated. Runnability issues that mist elimination can address include:
- Drop-offs: Elimination of drop-offs that cause holes or sheet breaks
- Fabric cleanliness: Containing mist allows the mill to run the showers at higher pressure improving overall fabric cleanliness. This typically results in:
- Fewer wash-ups
- Less chemical cleaning, and
- Improved fabric life
- Contaminants: Outside and inside high-pressure showers remove surface components and interstitial contaminants
- Surface fiber: Vacuum aids in removal of loose surface fiber improving machine performance
- Poor sheet characteristics: Dewatering the fabric can result in improved sheet solids and better sheet characteristics
What is an engineered mist elimination system? The main physical components are on-machine vacuum structures with embedded high-pressure showers, off-machine separators (pre and main), and a vacuum source (exhauster). Factors to take into consideration when establishing airflow are machine speed, fabric caliper, and fabric permeability. Placement and piping design are critical to ensure the vacuum is delivered as designed for containment of the mist.
A properly designed mist elimination system allows the in-rush of air into the vacuum structures to capture the mist from the showers to prevent the mist from “escaping” with the fabric boundary layer. The result is a mist-free environment. Mist elimination systems offer a dramatic improvement to wet end hygiene, can make a significant and positive impact on runnability, and can improve sheet properties in many installations.