Braided packing manufacturers are often asked to simply […]
Braided packing manufacturers are often asked to simply provide "PTFE packaging". While this seems to be a simple requirement, it produces the questions that must be answered to ensure that the PTFE Sheet in the application is correct. Clearly understand the differences between the various forms of PTFE braided packing will be able to select a reliable seal for the pump or valve.
In all forms of PTFE woven packaging, the right choice is to take advantage of its advantages and minimize its limitations. If the selection and application is incorrect, it may result in poor performance and increased maintenance. To effectively apply PTFE, you must understand the performance of the material. Some of the unique properties of PTFE make it an excellent ingredient for woven fillers:
Excellent chemical resistance. The main reason for the use of PTFE in packaging materials is that it is not affected by various aggressive fluids, including very strong acids, bases and solvents. Perhaps the most important thing is that PTFE can withstand strong oxidizing agents such as nitric acid, chlorine dioxide, high concentrations of sulfuric acid and so on. PTFE may be the only practical choice for applications involving these media.
The low coefficient of friction is in contact with most surfaces. PTFE non-wetting, sliding, low friction performance is well known. This helps to reduce the power consumption and heat generation at the package shaft interface.
Although PTFE has its strength, some of the properties of PTFE are not desirable in many pump packaging applications. The problems encountered with PTFE fillers are usually due to their poor thermal and mechanical properties:
Cold or creep under pressure. As the temperature increases, creep also increases. When pressure is applied to a 100% PTFE packing over a period of time, the filler may become a dense solid material that needs to be adjusted frequently to maintain the seal. It will also tend to squeeze the gap at the top and bottom of the stuffing box.
The use of PTFE fiber packaging, it is particularly important to follow the manufacturer's restrictions on temperature, speed and pressure. These packages are very sensitive to adjustment when used for rotating equipment. Typically, a lower gland pressure is required and experience a higher leak rate than other packaging methods.