Choosing the Right Knife Gate Valve for Pulp & Paper Applications

Knife gate valves play a critical role throughout pulp and paper mills, from stock preparation and pulp processing to cleaner systems, wastewater treatment, and chemical handling. However, not all knife gate valves are designed to handle the same process conditions. Selecting the wrong valve for an application can lead to premature wear, leakage, plugging, increased maintenance, and unplanned downtime.

Understanding the operating conditions and process media is essential when evaluating valve performance.

Application Challenge: Thick Media and High Pressure Service

Many pulp and paper processes involve high consistency stock, pulp slurry, lime mud, sludge, and other challenging media that can accumulate around internal valve components. These applications often require reliable shutoff under pressure while maintaining performance in the presence of solids.

Traditional knife gate valves can struggle when media builds up in the valve body or packing area, leading to increased operating torque, seat wear, and leakage.

The ITT Fabri XS150 was designed specifically for demanding applications where pressure, temperature, and media consistency exceed the capabilities of many standard knife gate valves. With pressure ratings up to 275 PSI at 100°F and an Aflas seat capable of handling temperatures up to 400°F, the valve is well-suited for challenging process environments.

Features such as automatic clean-out and flushing capabilities help prevent media accumulation around the gate, while dead-end service capability allows maintenance to be performed without requiring downstream piping or equipment.

Application Challenge: Cleaner and Scavenger Systems

Cleaner and scavenger systems are among the most abrasive services found in a pulp mill. These applications frequently contain sand, grit, contaminants, and staple chains that can accelerate wear on valve gates, seats, and packing systems.

In many cases, valve failure is not caused by pressure but by erosion and mechanical damage resulting from the process media.

The ITT Fabri Figure C42 was developed specifically for high-density cleaner and scavenger service. Its impact-resistant overlay on the gate and seat bore helps protect critical sealing surfaces from abrasive wear. An oversized pneumatic cylinder provides additional force to cut through debris and contaminants that may become trapped in the flow stream.

The valve's open-port design minimizes material accumulation and reduces the likelihood of plugging, while replaceable seats and packing simplify maintenance and help extend overall service life.

Application Challenge: Reliable Isolation and Shutoff

Isolation valves are expected to perform one critical function: stop flow when required. In applications involving process water, stock, filtrate, or chemical systems, leakage through a closed valve can impact process efficiency, product quality, and maintenance requirements.

Achieving bubble-tight shutoff becomes increasingly challenging as valve diameters increase and operating conditions become more demanding.

The ITT Fabri C67S addresses these challenges through a patented bidirectional seat design that provides bubble-tight shutoff from either flow direction. Unlike many knife gate valves that are designed primarily for unidirectional service, the C67S delivers reliable sealing regardless of flow orientation.

The valve is rated for 150 PSI cold working pressure through 36-inch sizes and features a true full-port design through 12-inch sizes, reducing pressure loss and minimizing flow restrictions. Energized packing further enhances sealing performance while helping reduce leakage around the stem.

Selecting the Right Valve for the Application

When evaluating knife gate valves for pulp and paper service, several factors should be considered:

• Process media composition and solids content
• Operating pressure and temperature
• Required shutoff performance
• Potential for abrasive wear
• Maintenance accessibility
• Frequency of cycling
• Risk of plugging or media buildup

Selecting the right knife gate valve begins with understanding the demands of the application. From high consistency stock and abrasive cleaner systems to critical isolation points, matching valve design to operating conditions can improve performance, extend service life, and reduce maintenance requirements.

ITT Fabri, part of the ITT Engineered Valves portfolio, designs knife gate valves specifically for the rigorous conditions found in pulp and paper facilities. Combined with Crane Engineering's application expertise, these solutions help customers select the right valve for the right service, resulting in more reliable operation and lower lifecycle costs.

Whether you're evaluating an existing installation or planning a new project, Crane Engineering's valve specialists can help assess your application and recommend the ITT Fabri solution best suited to your process. Contact our team to discuss your valve challenges and discover opportunities to improve performance across your facility.