PTFE Crossflon Skidway Slide Bearings By Ian Harbottle, Divisional Manager – PTFE Slide Bearings & Skidways, Beldam Crossley
Most subsea bearing conversations do not start with material.
They often start with a concept drawing, operating parameters and a very practical question:
Will this move when it needs to — and will it still be right when nobody can get back to it?
That sounds simple enough, but in subsea work the simple questions are often the most important ones. A slide bearing, sleeper pad or sliding plate might seem like a very small part of the overall production system, but it can have a big influence on how stresses are transferred and how movement is movement is managed.
Once something is on the seabed, it is not like a bridge bearing, construction bearing or skidway plate where access is difficult but still possible. Subsea means pressure, seawater, long design life, limited inspection and, in many cases, no chance of maintenance.
That is why the most common problem I see in subsea bearing applications is not simply “what material do we use?”
The better question is:
How do we keep controlled movement in the design without introducing creep, wear or unpredictable friction over time?
The problem: low friction is not enough on its own
A few years ago, we were asked to support a subsea project where the customer needed sliding plates for offshore equipment operating at depths between roughly 400 and 780 metres.
The application involved subsea structures such as FLETs, ILTs, PLETs and PLEMs. In plain terms, these are the pipeline and flowline structures that help connect, terminate, direct or manage subsea systems. The bearings were not decorative pieces of plastic. They had a job to do.
- They had to take high vertical pressure.
- They had to allow controlled movement.
- They had to resist long-term deformation.
- They had to perform in seawater.
And they had to do that over a 25-year design life.
The customer’s first challenge was familiar: standard PTFE gives very low friction, which is why engineers like it for sliding applications, but it does not accommodate high compressive loads over long periods. It can deform. It can creep. It can lose the geometry you designed around.
Glass-filled PTFE improves load-bearing ability, but there is usually a trade-off. You gain compressive strength, but lose the low-friction behavior that made PTFE attractive in the first place.
That is the awkward corner engineers often find themselves in.
Do you design around low friction and accept lower load capability? Or do you design around load and accept higher friction?
For a lot of applications, that compromise is manageable. In subsea, it can become a serious design issue.
If friction is higher than expected, movement can happen in a less controlled way. If deformation is higher than expected, the bearing may no longer support the structure as intended. If wear is higher than expected, coatings and contact surfaces can become vulnerable. And if the part cannot be accessed for maintenance, a small assumption at design stage can become a very expensive problem later.
What we looked at first
When I work through a subsea bearing enquiry, I try not to jump straight to the material name.
The first job is to understand the movement.
- Where is the load coming from?
- Is the movement axial, lateral, rotational or a combination?
- Is the bearing surface recessed or exposed?
- What pressure is the bearing expected to accommodate?
- What is the acceptable deformation?
- What is the mating surface?
Is the bearing there to reduce wear, allow movement, or manage stress in a structure such as a PLET or FLET?
What happens if the coefficient of friction is not what the model assumed?
These are not academic questions. They decide whether the part is doing useful work or just sitting in the assembly looking like it should.
On this project, the customer needed a bearing solution that could sit in the difficult middle ground: PTFE-level friction, but with far greater load-bearing capability than standard PTFE grades would normally offer.
That became the real engineering problem.
Not “can we supply a subsea plate?”
More like:
Can we remove the trade-off between low friction and compressive strength?
The practical solution: test the compromise out of the design
The answer was Crossflon® XS, but the material only became the answer after the problem had been properly understood.
We benchmarked what we already knew. Virgin PTFE gave the kind of friction behaviour engineers expect, but not the load-bearing capacity required. A conventional glass-filled PTFE improved strength, but the friction level moved in the wrong direction for this type of application.
The customer needed both.
So, the development work focused on a reinforced PTFE formulation that could keep the low-friction behaviour while improving compressive strength, creep resistance and wear performance.
There is no magic phrase in that. It was testing, comparison, discussion and adjustment. A lot of very normal engineering work, done carefully.
We looked at the drawing details. We reviewed the loading. We considered whether the bearing should be recessed. We checked how the plates would be machined and supplied. We worked through the technical documentation the customer needed so the bearing design could be accepted into a wider subsea engineering package.
The final solution involved over fifty Crossflon® slide bearings across seven different types.
That detail matters, because subsea projects are rarely one-size-fits-all. Even within the same project, contact area, shape, location, fixings and duty can vary. A standard sheet or catalogue pad would not have answered the brief properly.
What changed for the customer?
The biggest change was confidence.
Not sales confidence. Engineering confidence.
The customer could specify a bearing material that offered a static coefficient of friction in the same range as virgin PTFE, while carrying much higher pressures when used in the correct configuration. It meant the design team did not have to overcompensate as heavily for the old compromise between friction and load.
It also gave them a more robust answer for long-term subsea service, where creep resistance and dimensional stability matter just as much as the initial friction value on a data sheet.
That is the part I think is often missed.
In subsea applications, the bearing does not just need to work on day one. It needs to keep behaving in a predictable way after installation, in seawater, and in a system that may be exposed to thermal cycles, movement, sediment interaction and structural loading over many years.
The lesson I took from the project
The lesson was not “always use the strongest material.”
It was more practical than that.
The right subsea bearing is the one that lets the structure move as the engineer intended.
Too much friction, and the structure can be subjected to unwanted stresses. Too much creep, and the geometry changes. Too little thought about the interface, and the bearing can become the weak point between two much more costly parts of the system.
That is why early conversation matters.
If we are brought in after everything is fixed, there is only so much we can influence. If we are brought in while the design is still fluid, we can help ask the right questions around operating pressure, plate geometry, tolerances, mating surfaces and long-term performance.
Subsea engineering is full of impressive structures and challenging numbers, but often the real success sits in small details that behave properly.
A slide bearing is one of those details.
Get it right, and nobody thinks about it again.
In subsea work, that is usually the best compliment you can get.
Questions worth asking when specifying subsea slide bearings
What is the real operating pressure, not just the headline load?
A large load over a large area behaves differently to the same load concentrated over a smaller interface.
Does the bearing need to be recessed?
A recessed bearing design can significantly improve load capacity and help control deformation.
What coefficient of friction has the structural model assumed?
The bearing material needs to support the model, not contradict it.
How much creep is acceptable over the design life?
Initial performance is only half the story. Long-term dimensional stability matters.
Is the bearing just facilitating movement, protecting a coating system, the structure or all three?
The answer changes the design priority.
Can the part be maintained or replaced?
If the answer is no, the bearing needs to be treated as a long-life engineered component from the start.
For me, that is the heart of subsea bearing work. It is not about selling a material. It is about understanding where movement needs to occur, where it must not happen, and how a polymer bearing can quietly do its job for years without anyone needing to replace it.
