Can Thermal Expansion Impact the PTFE Packaging?

by Isaac K.
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There are unique characteristics that come with PTFE fiber packing. It has a unique thermodynamic chemical system and a low friction coefficient that makes it suitable for moving equipment such as engines and compressors. On the other hand, it has undesirable qualities such as high dependence on temperature and stress relaxation, easily avoided by putting proper measures. Due to the tests performed, the temperature-driven behavior in Teflex 15-%25% Carbon Reinforced PTFE Sheet & Gasket affects its packing but can get control if the right measures can be taken. Below are vital details to get you up o speed on understanding the ins and outs related to PTFE.

The Concept of Thermal Expansion

Thermal expansion is how much a material can expand when subject to heat. The difference between this coefficient makes different materials expand by different amounts. PTFE can exhibit relatively high thermal expansion; it has a higher thermal expansion coefficient and low conductivity.

Observations show that PTFE packing works well initially, but it would overheat when the temperature increases, making the leakage control quite hard.

How To Counterbalance PTFE Thermal Expansion

These methods are meant to increase the PTFE’s thermal stability and keep the temperatures of the sealing systems stable.

a. Use of lubricants

Lubricants help to reduce friction. The addition of a lubricant during the manufacturing process helps stabilize the temperatures. That said, they come in different forms, such as emulsions and grease. Their working depends on the compatibility of the application.

b. Use of flush systems.

The use of flush systems entails the application of water to lubricate and cool down the machines. A higher intensity of pressure in the system may lead to unwanted compressions. This produces more heat due to an increase in the shape and size of the material.

The problem can be tackled by following the right installation procedures as per the instructions of the manufacturer.

c. Fillers

Fillers enhance the mechanical properties of a PTFE. A filler-added PTFE expands less compared to a virgin one. A comparison made on a virgin PTFE and that with graphite added to show that graphite expands, and that is why it is widely used as a filler material.

d. Lab Tests to Establish Findings

A laboratory test conducted to compare the PTFE packing when subjected to different temperature intensities shows a relationship between filler amounts and the torque required for shaft turning. In the end, an increase in the shaft torque tends to be lowered by a higher filler.

It is difficult to control the leak of unfilled PTFE under controlled conditions in the laboratory. Filler use is strongly recommended as it gives a good performance, and the leaking rate can be stabilized.

Final Thoughts

The performance of pump packing in PTFE is influenced by an increase in temperature due to heating. An increased temperature may increase internal stress to the stuffing box, which may scorch the pack. A lower thermal contraction is experienced when it cools down, leading to high leakage rates. Remedies such as fillers and lubricants should always be used to bring about the best results. Besides, they also offer a solution to maintaining thermal stability.

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