PTFE Seals

Polytetrafluoroethylene (PTFE) is a thermoplastic polymer that can be used in a variety of sealing applications; it is particularly suitable where the application conditions exceed the parameters of elastomeric seal use, but are not as highly demanding as applications that require the use of metal seals.

What is PTFE?

Discovered accidentally in the DuPont™ laboratory in Jackson, New Jersey, USA in in 1938. The molecular structure of PTFE is based on a linear chain of carbon atoms which are completely surrounded by fluorine atoms. The carbon-fluorine bonds are among the strongest occurring in organic compounds. As a result PTFE has thermal stability across a wide temperature range.

It’s high melting point (342 °C) and morphological characteristics allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C, and with the addition of fillers – up to 300°C. It has the unique ability to resist material degradation, heat-aging and alteration in its physical properties during temperature cycling. Alongside this rare combination of material characteristics PTFE also has unlimited shelf life.

Why use PTFE seals?

Notably PTFE demonstrates extraordinary chemical resistance: the intrapolymer chain bond strengths preclude reactions with most chemicals, thereby making it chemically inert at elevated temperatures and pressures with virtually all industrial chemicals and solvents. Only a few media (some molten alkalis) are known to react with PTFE seals making them the perfect sealing solution for highly aggressive chemical applications.

PTFE also has the lowest friction coefficient of any known solid; it has self-lubricating capabilities which offers continuous dry running ability in dynamic sealing applications and has superb stick/slip capabilities.

Focus on dry coatings

The advantages of using PTFE in sealing applications are; functionality at high and low temperatures, dynamic sealing with high wear capabilities, high pressure sealing (using combinations of PEEK back-up rings) and compatibility with highly aggressive chemical combinations.

Our range of PTFE seal products include back-up rings, rod and piston seals, slipper seals and spring energised seals in a wide variety of sizes. Materials depend on application requirements but we offer a wide range from Virgin PTFE or including filler combinations of MoS2, glass, carbon, carbon fibre, graphite, and bronze.

These characteristics make PTFE seals perfect for the demanding applications involved in Oil & Gas, Aerospace, Automotive and Chemical Process markets (to name but a few) and Ceetak’s engineering team are experienced in the design of PTFE sealing solutions to meet the complex specifications these types of application demand.

Read our overview and more detail about PTFE seals HERE

Our customer designs and manufactures a leading range of unique downhole technology and drilling solutions that contribute to a net zero energy industry.

The Application

A seal was required for the rod of a downhole drilling tool – a hydraulic dynamic (rotary) application. Our solution is a PTFE rotary seal. Read on to find out about more.

The application has a normal operating pressure of 500 PSI at 60 RPM, but maximum pressure can reach 6,500 PSI in static operation. Reverse pressure was unlikely in this application but the engineers wanted to ensure some level of resistance.

Two single acting seals were considered, but groove space is limited. Keeping the grooves closed is preferable for bearing strength.

The maximum operating temperature reaches 200°C and the application media drills mud and completion fluids (with wiper arrangement already installed).

Our Sealing Solution

Due to the pressure, temperature and chemical media parameters of this application, an elastomer seal selection was not suitable.

Our engineers selected our standard FTOR profile PTFE seal This is a double acting slipper seal ideally suited to hydraulic applications and capable of sealing under alternating pressure directions.

It’s ideal for sealing high pressure loads with slow to moderate rotational speeds. The PTFE rotary seal has side wall notches equally spaced, so the part can be fitted symmetrically either way.

The initial sealing force is provided by the elastomer O-ring. This is seated within a machined saddle and activated by system pressure to perform under high pressure demands. The central lubricating channel design ensures low friction and wear.

Additionally, the sealing set has been designed with a scarf cut PEEK back-up ring. This is to ensure stability and seal performance at maximum working pressure of 6,500 PSI.

Customer Satisfaction

Our customer tested the sealing arrangement at higher pressure (up to 10,000 PSI). Consequently, our customer is pleased it seals successfully over and above the application requirements. They have adopted this seal design for other sizes of parts in similar equipment.

Read more about our rotary seals HERE