PTFE-Lined Butterfly Valves are commonly used in piping systems to achieve flow shut-off and regulation, and they are widely applied in industries such as petroleum, chemical, metallurgy, and hydropower. In existing butterfly valve technology, the valve’s sealing primarily relies on soft sealing materials, such as rubber or polytetrafluoroethylene (PTFE).

These valves feature a seat sealing ring composed of a soft T-shaped sealing ring combined with multiple layers of stainless steel. The lining material is fixed to the inner wall of the valve body through a specialized molding process, allowing the valve to resist highly corrosive media, including strong acids and alkalis. Additionally, the valve can adopt a full-bore floating-ball (two-piece) or a fixed-ball (three-piece) structure, making it suitable for pipeline shut-off, connection, and fluid regulation and control.

In practical use, the packing of PTFE-lined butterfly valves is prone to wear, which can compromise the valve’s sealing performance. So, what causes packing wear, and how can it be addressed? Below, Dervos Valve introduces several common methods to solve this issue.

1. Conventional Packing and Its Limitations

Common packing materials for PTFE-lined butterfly valves include asbestos rope, graphite packing, and PTFE V-ring packing. These materials perform well when the valve experiences a low number of opening and closing cycles. However, as the frequency of operation increases, the packing gradually wears, and the clearance expands. When the valve reaches a certain number of cycles (typically no more than 2,000), leakage may occur at the packing. At this point, the sealing effect can be restored by re-tightening the packing gland. This method is suitable for applications with infrequent operation but is less ideal for high-frequency use.

2. Spring Washer Packing Compression Solution

For valves that operate frequently (e.g., 100,000 to 300,000 cycles per year), traditional packing maintenance is costly and frequent. To address this, a washer can be added beneath the packing, with a spring installed under the washer. The spring’s preloading force is carefully calculated to automatically compress the packing as it wears, maintaining the valve’s sealing performance. Practical experience has shown that this method can increase the valve’s operating cycles to 500,000–1,000,000 without leakage. While the packing gland still needs to be re-tightened during annual major maintenance, routine maintenance frequency is greatly reduced.

3. Hydraulic or Pneumatic Sealing Solution

A more advanced approach is the use of hydraulic or pneumatic sealing technology. This method changes the traditional valve design concept by employing a cylinder-sealed sliding ring at the packing and adding O-rings (the number of sliding rings and O-rings is determined based on friction and sealing pressure calculations). This significantly enhances the valve’s sealing lifespan and reliability.

Using the methods described above, users can select the most suitable packing solution for PTFE-lined butterfly valves according to their specific operating conditions and maintenance requirements. Choosing the correct maintenance approach not only extends valve service life but also reduces operational and maintenance costs.