White paper: Testing of HFC Fluids on Common Seal Materials in High Temperature Applications

Testing of HFC Fluids on Common Seal Materials in High Temperature Applications

In a series of white papers, Trelleborg Sealing Solutions experts provide an in-depth look at technologies related to sealing and engineered products.

Check out our latest addition to the Technical Library on the website: Testing of HFC Fluids on Common Seal Materials in High Temperature Applications.

whitepaper hfc water glycol fluids

As the oil and gas industry moves to recover more challenging reserves and enters the development of High Pressure High Temperature (HPHT) fields, the risk of fire is increasing. There is therefore a move to the use of water-based hydraulic fluids, which present significant sealing challenges. This whitepaper takes an in-depth look at sealing materials and testing in HPHT environments.

Technical Library

To take advantage of the industry-leading knowledge of Trelleborg Sealing Solutions, registered website member have access to the company’s Technical Library. This offers users a collection of technical articles, webinars and whitepapers covering various topics in the world of seals and sealing technology. Free-of-charge registration to the website also gives access to other technical resources, including an extensive range of online tools and e-Learning.

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Trelleborg’s Seal Materials Tested for Optimum Performance

Trelleborg Sealing Solutions has carried out a series of tests to show the importance of fluid type and seal material choice in “ensuring optimum seal performance and service life”.

Seal Material Testing

The world leader in engineered polymer solutions, which has been making highly developed seals for over 30 years, worked with fluid producer MacDermid to test the effect of water glycol fluids (HFC) on common seal materials.

Together the engineers for both companies tested seven seal materials which were immersed in water glycol fluids at a range of elevated temperatures up to +200°C / +392°F.

ONS Conference white paper on results
The results have been published in a white paper on the subject which will be available to collect from Trelleborg’s stand in Hall 9 at the ONS Conference in Norway from August 29 to September 01.

Each seal and fluid combination was tested for hardness change, tensile strength change, strain change and volume change. All physical changes were documented using before and after photos.

Importance of fluid and material choices
David Brown, Global Lead Group Director, Oil & Gas, Trelleborg Sealing Solutions, says: “The testing reveals the importance of fluid type and seal material choice in ensuring optimum seal performance and service life. Traditional sealing materials, such as FKM, often inert in most fluids, are exhibiting disadvantageous behaviour in HFC fluids.

“Offshore operators are free to add extra additives to suit their particular application, but these could lead to seal material incompatibilities and cause dramatic adverse effects on sealing materials.

“We recommend each application must be reviewed uniquely to optimize the seal materials with the HFC fluid to ensure seal performance and life.”

Developed in-house
The series of tests were developed by Trelleborg Sealing Solutions in 2015.

Seal Materials Testing Laboratory

The company decided to investigate the effects of high-temperature exposure of sealing materials within water-based hydraulic fluids because until now, the two materials have never been thoroughly tested together at high temperatures before.

Water-based hydraulic fluids are widely used in oil and gas, mining, hot-rolling mills, and similar applications where the potential for fire could cause catastrophic consequences.

They are also replacing traditional oil-based HLP fluids in applications where environmental regulations must be observed.

As a result, they have become more prevalent in many applications within offshore energy production as a means of protecting people, the environment and resources.

HFC fluids
The International Standards Organization (ISO) classifies fire-resistant, water-based hydraulic fluids into four categories which include HFAE, HFAS, HFB and HFC.

HFC fluids are the most common hydrous, fire-resistant hydraulic fluids because they have the best fire resistance and hydraulic properties. They are also used wherever hydraulic fluid escaping under high pressure can ignite on contact with hot materials.

The fire resistant and environmentally friendly qualities of HFC fluids make them ideal for use in offshore installations.

The fire-resistant properties mean greater fire safety, offering more time to initiate fire-fighting measures and bring people to safety in the event of an accident.

Trelleborg Identifies Sealing Materials to Extend Seal Life in High Fire Risk Oil & Gas Hydraulic Applications

Due to the different chemical makeup of HFC and HLP fluids, sealing materials proven and traditionally used with HLP fluids, though effective in HFC applications, do not necessarily provide effective performance or length of life in HFC media. In tests, Trelleborg Sealing Solutions has identified sealing materials that offer extended life in HFC applications.

HFC fluids, or water glycols, are the most commonly used fire-resistant hydraulic fluids and with their higher ignition temperature they are increasingly being used instead of HLP media or even being made mandatory in hydraulic oil & gas applications with a high fire risk. A research program by Trelleborg Sealing Solutions has resulted in identification of alternative sealing materials that give better performance and extended life in HFC fluids.

Avoiding downtime
Eric Bucci, Oil & Gas Segment Manager Americas, Trelleborg Sealing Solutions, says: “Oil & gas hydraulic applications often involve demanding dynamic movements, for instance in the case of offshore motion compensation cylinders, and due to long strokes, sealing systems can be subjected to significant wear.

Compared to oil-based HLP media the water base of HFC fluids typically increases seal wear. As oil & gas applications increasingly use HFC fluids and length of life needs to be extended to avoid costly downtime, it is imperative that we provide operators with information on the optimum sealing material for HFC fluids.”

Oil and Gas Hydraulic Applications

Testing with HFC fluids
Trelleborg undertook a series of tests on a number of sealing materials to investigate their effect on sealing systems in HFC fluids with regard to friction, wear resistance and leakage.

The materials tested included the traditional choice in hydraulic applications, polytetrafluoroethylene (PTFE) based materials with various fillers, alongside the alternatives of proprietary polyethylene Zurcon® Z80 and thermoplastic polyurethane Zurcon® Z13.

The two materials that demonstrated the least weight loss, and therefore wear, were Zurcon® Z80 and Zurcon® Z13. With these materials there was also no apparent leakage. In addition, visual inspection showed the best results were achieved with Zurcon® Z13.

While Zurcon® Z80 showed slight extrusion after one million load cycles, no abnormality is seen in Zurcon® Z13 with the same seal geometry. The filled PTFE based materials were significantly worn after 200,000 cycles.

Alternative sealing materials
Dr. Mandy Wilke, Technology Specialist Fluid Power Europe, Trelleborg Sealing Solutions, who was responsible for conducting the tests, says: “During the tests, strong influences were observed in the behavior of the seals in relation to friction and wear. Due to the significant fluctuation of the mixing ratios (water/glycol) in HFC fluids and in operation, reliable behavior of sealing systems can only be predicted to a limited extent.

“To ensure seal life and performance in hydraulic applications, it is important to know the type of hydraulic fluids in service and using test results and experience, match the correct sealing material to the hydraulic fluid. Despite the successful use of PTFE based materials with HLP fluids, alternative sealing materials, such as Zurcon® Z80 and in particular Zurcon® Z13 could offer better wear resistance and extended life in HFC fluids.”