Keeping Pulp Mill Agitators Running: Solving A Sealing Challenge

In every pulp and paper mill, agitators work to keep fluids in tanks that contain fibres and solids in a thoroughly mixed state. These components ensure the smooth operation of the entire production process, but they also face a constant battle against wear, abrasives, extreme pH levels and shaft misalignment. When mechanical seals fail, production grinds to a halt, downtime soars and maintenance teams have to battle costly leaks.

A Costly Problem in Pulp Mills

A major pulp mill is running at full capacity when suddenly, an agitator seal fails. The tank, holding over 200 tons of paper stock, begins leaking and production must stop. The maintenance team works against the clock, but due to the size and complexity of the equipment, replacing a traditional mechanical seal isn't a quick fix. Every hour lost costs thousands in downtime and wasted product.

This scenario is common in the pulp and paper industry. Agitators operate under high pressure — shaft sizes range from 75-150 mm turning at speeds of 200-300 rpm, but occasionally even up to 500-600 rpm and dealing with solid concentrations typically 15-20% but also as high as 60-75%. Conventional mechanical seals often struggle to cope with these extreme conditions, leading to frequent breakdowns and operational inefficiencies.

Engineering a Better Solution

To combat these challenges, John Crane developed sealing solutions specifically for the demanding environment of pulp mills. One of the most effective solutions is the Type 37FS split seal, designed for large agitators that are difficult to remove. Unlike conventional seals, the split design allows for maintenance to take place without removal, so there's no need to dismantle the agitator or empty the tank. Its elastomer bellows accommodate shaft movement, ensuring reliability even in high-wear environments.

For even greater efficiency, the Type 73 inflatable backup seal works alongside the split seal, allowing service teams to work on the mechanical seal while the tank remains full. This innovation significantly reduces downtime and prevents costly product loss.

For the harshest pulp mill conditions, the Type SB2/Type SB2A dual cartridge seals offer a double-balanced design that ensures maximum reliability. These seals are particularly suited for environmentally hazardous and abrasive fluids, commonly used in pulp mills, minerals processing, and other slurry duties with solid concentrations of up to 40% by weight and a solids hardness of 8 Mohs. Built from high-quality materials and corrosion-resistant AISI 329 and 316 or higher metal parts, these mechanical seals are designed for durability and longevity.

Optimising Performance

Mechanical seal failures don't just impact production—they waste water, energy and resources. That's why many mills are discovering John Crane's Safeunit™, a smart monitoring system that controls seal water flow and pressure. By preventing uncontrolled water leaks, mills can reduce waste, improve product quality and lower operational costs.

A Real-World Challenge

A Canadian pulp and paper mill faced frequent mechanical seal failures due to the demanding conditions of their operations. These failures resulted in unplanned downtime and increased maintenance costs, significantly impacting the mill's productivity and profitability.

To address these challenges, the mill implemented John Crane's Type 37FS, specifically designed for large, hard-to-remove agitators. Its elastomer bellows accommodate shaft movement, ensuring reliability even in high-wear environments.

Since the installation of the Type 37FS split seal, the Canadian mill has experienced over 16 years of reliable operation without a single seal-related shutdown. This long-term success underscores the Type 37FS's durability and effectiveness in demanding pulp and paper applications. You can read more by visiting our website.

Stay Efficient

In an industry where reliability is paramount, the right sealing solutions make all the difference. Whether it's reducing unplanned downtime, cutting water waste, or reducing maintenance time, John Crane's sealing technologies help pulp mills stay productive and profitable.

To see how our technologies can support your mill's success, visit our pulp and paper industry page.