Pratt reveals resilient seated knife gate valve for harsh environments
Diana Aoun | November 07, 2023The Pratt P77 perimeter seated bi-directional knife gate valve is engineered to efficiently handle tough slurries and abrasive materials. It meets rigorous industry standards including MSS-SP-81, AWWA C520-10 and TAPPI-TIS 405-8, making it an ideal choice for applications in mining, chemical, food/beverage and pulp and paper industries.
The P77 valve features a 360° wrap-around packing with a first-row elastomer seal and a gate reinforced by a PTFE bearing incorporated into the seat. Notable features and benefits include its ability to achieve drip-tight shut off regardless of line pressure, preventing buildup and confusion about the direction of isolation. The gate is guided through the cycle, reducing stress on the packing chamber, which in turn reduces leak paths and extends the packing's lifespan. Tightening of the packing creates hoop strength, preventing the seat from pulling out or rolling.
Source: Henry Pratt
In addition, the P77 offers flexible operability options, including conversion to hydraulic or pneumatic cylinders, bevel gears, chain wheels, electric motors or fail-safe spring cylinder operators. It features a bronze stem nut retainer to ensure secure fastening during operation and a stainless-steel stem provides resistance to corrosion. The heavy-duty cast stainless-steel yoke prevents deformation under extreme loads, ensuring reliable operation. The full-circle packing minimizes leak paths, reduces the need for adjustment and extends packing life.
The valve's rubber-seated gate provides a secure bi-directional drip-tight seal, effectively withstanding pressures up to 150 psi. It features an EPDM perimeter cartridge seat resistant to chemicals and high temperatures, preventing leakage and safeguarding downstream equipment. Additionally, the integrated PTFE gate guide reduces stress and wear on the packing, preventing blockages and flow disruptions with its non-stick properties. Multiple rows of packing enhance seal performance and provide redundancy.