The advent of mechanisation, automation, and the use of robotics in manufacturing shows no signs of slowing down. One of the critical requirements of such systems is continuity. Any automated system only works when each segment of the process functions smoothly and without any interruption. Considering the speed at which some of these systems move the smallest glitch can often push the entire manufacturing line to shut down.

Polymer scraper blades are primarily used to remove obstructions, clear surfaces, and remove sticky materials – such as glue or residual polymers from running systems. Their purpose ensures that debris and other materials are taken out of the process so that they may not cause jamming or scratch surfaces.

There are many advantages of polymer scraper blades in such applications. While metal blades were used earlier on, there is a lot of potential damage that can be caused by these. Polymers, in contrast are hard enough to be effective scrapers, but not so hard that they will damage other elements. Further, with polymers, a designer can choose the level of hardness needed, depending on the other materials the scraper will interact with. There are numerous polymers that can be thus employed.

PTFE (Teflon)

PTFE has multiple advantages as a scraper blade. The low coefficient of friction means that it can smoothly run over a system – such as a conveyor belt or glass surface – without putting any load on the other material. PTFE is also soft – so even delicate systems can benefit from PTFE scraper blades. However, the same softness places a limit on how sharp the blade edge can be made with PTFE. Although fillings of glass, carbon, and even stainless steel (see picture) can improve the stiffness of PTFE, its use is mainly beneficial where aggressive scraping is not needed.

UHMWPE

Like PTFE, UHMWPE has a low coefficient of friction. It is also lightweight and exhibits superior wear resistance. UHMWPE is also soft, so again, its use is limited in non-aggressive applications. Unlike PTFE, UHMWPE does not perform well in high temperatures. However, it is very cost effective, highly machinable, and does exceedingly well against rough materials, that would necessarily place a lot of wear load on the scraper blades.

Nylons

Both PA6 and PA6.6 perform well as scraper blades. The addition of Molybdenum di Sulphide further improves wear resistance while the inherent hardness of the material exceeds that of PTFE and UHMWPE. Nylons are light weight, but are also prone to moisture absorption, making them better suited to dry environments.

POM

One of the most versatile polymers, POM (Polyacetal, acetal, or Delrin) is an exceptional choice for scraper blades. Unlike PTFE, UHMWPE, or Nylons, POM is a harder and can be machined to a far finer and shaper blade edge, making it excellent for fine and even aggressive scraping. The addition of PTFE fillers to POM can help reduce the coefficient of friction further. Unlike PTFE, however, POM cannot work in temperatures above 150°C.

PEEK

PEEK combines all the best characteristics of the other polymers. It is very hard, making it possible to machine to a very sharp edge. The toughness of PEEK means that it can be used in very harsh environments – mechanically, chemically, and at temperatures in excess of 250°C. The blade will not dull easily and the addition of PTFE can help to make the material more smooth. However, such a swell of properties does come at a price. PEEK is at least 6-8 times more expensive than PTFE and about 20 time more expensive than POM. Hence, it’s use is limited in applications where nothing else can be used.

At Poly Fluoro, we have the capability to design, blend, mould, and machine the scraper blade that best suits the client’s application. The use of special blends can be incorporated, if the end-use calls for it, while the dimensions of the blade itself can be fine-tuned before bulk production commences.

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Within the polymer space, PEEK (Polyetheretherketone) is considered one of the most robust materials. Not only does PEEK exhibit tensile strengths in excess of 100Mpa, but it can withstand compressive loads of over 300Mpa, making it tough enough for high-load, high-wear, and high-RPM applications where mating materials of steel can be used without fear that they will wear out the PEEK component. These properties can be further enhanced with the addition of carbon and glass, both of which give a sizeable boost to the overall strength of the material, while also making it more thermally stable.

	Unfilled PEEK	PEEK+30% Carbon	PEEK+30% Glass	Unit	Test
Tensile Strength	97	201	158	Mpa	ASTM D638
Young's Modulus	3650	19700	10500	Mpa	ASTM D638
Flexural Modulus	3860	17500	10400	Mpa	ASTM D790
Flexural Strength	152	317	261	Mpa	ASTM D790
Coefficient of Linear Thermal Expansion	5 x 10-5	3 x 10-5	1.7 x 10-5	cm/cm/°C	ASTM E831
Deflection Temperature Under Load	162	315	315	°C	ASTM D648
Coefficient of Friction	0.35	-	-	-	ASTM D3702

 

PEEK seals and valves are commonly used in applications where high temperatures and loads are involved. While seals are relatively simple to machine, PEEK valves can prove challenging, especially if multiple ports of entry and exit are specified. It is likely that a turn-mill centre or a vertical milling centre are needed to make valves of consistent dimension and quality.

An even bigger challenge that the valve is the PEEK manifold, which is usually machined from a solid block, with each of the six faces of the block having its own set of holes. The manifold is essential in many fluid transfer applications. It is designed and machined is a way that allows it to sit within the system, and ensure not only that the fluid conduits all align perfectly, but that no leakages take place during operation. PEEK being a very chemically resistant material, the manifolds are highly durable across a range of fluids and substances and will hold their dimensions even with large variations in temperature.

Machining the PEEK manifold is a challenging task. For one, the PEEK stock shape for machining needs to be moulded into a block form. Most commercially available PEEK stock shapes are sold as round bars. This can prove highly wasteful when the final form is rectangular, especially as PEEK is an expensive material. Even technically speaking, machining a round bar into a rectangular shape places significant internal stress on the polymer. Considering PEEK has a tendency to build up stress the more it is machined, such a route will necessarily cause the final component to crack at some point during its operation.

In contrast, Poly Fluoro uses in-house moulding to make a rectangular block that is as close to the final dimension as possible, thereby minimising the excess machining, while lower the cost. The addition of glass or carbon is also vital. Again, commercially available grades would be made using Virgin PEEK. However, the increased thermal stability of PEEK when filled with glass or carbon makes it essential in applications where high variations in temperature may be expected.

Once the moulding is done, the key step is to machine. Again, considering tolerances can be as close as 10 microns, a 4-axis or 5-axis machine is essential to minimise the number of operations needed. However, more important than the dimensions themselves is the handling of the material. Even with reduced machining as compared with a round bar, there is every chance that as the block is machined, the internal stresses will build up. Hence, care must be taken in annealing the block, not just after moulding, but between operations during machining as well. 

As you can see, the end product, if done properly, can be rather pleasing. The PEEK manifold is a very challenging part. Getting it right is not something everyone can do. Moreover, our control over the entire process – from moulding, to blending, to machining – allows us to ensure that the final properties – both for the material as well as dimensionally – are always best-in-class.

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The growth of the oil & gas industry has been one of the cornerstones of the industrial boom over the past century. While the processes of extraction, storage, refining, and distribution have all been in place for a while, the technologies in the background have continued to evolve. Further, as new and improved methods were developed, they have required the use of special materials to be incorporated.

The polymer industry has always been closely connected to oil & gas by virtue of the fact that many polymers are derived as by-products of the oil refining process. The supply and pricing of polymers such and polyethylene and polypropylene move almost in tandem with oil prices as a result. However, these base polymers are rarely the ones used in oil & gas equipment. The presence of corrosive chemicals, high-temperatures, and rough handling necessitates the use of high-performance plastics.

Polymers such as PTFE, PEEK, and PPS are especially useful because they are able to withstand multiple forces and require minimal maintenance. This means that they can be installed in equipment deep within a system and it is assured that they would not need to be constantly checked on.

Considering PTFE, PEEK, and PPS are all stable up to temperatures of 260°C, they are invaluable in oil & gas applications.

PTFE and PEEK Packing Rings

Packing rings, V-rings, V-packings or Chevron Packings are commonly used in oil extraction equipment. These components are usually made with PTFE, PEEK, or PPS and incorporate a carbon filling for added wear properties. Chevron rings are usually made to be stacked one above the other and then fitted as a single element around a metal shaft. The rings protect the shaft from wear and are themselves resistant to the gases and heat that the shaft will also experience.

Given that the rings are machined with v-grooves and that they need to fit into one another perfectly, not all manufacturers are able to make such components. Care needs to be given to tolerances, which can be as low as 2 microns, to ensure a fit. Further, special attention needs to be given on the blending of carbon, as this needs to be uniform if the part is to have a life of 10-15 years, as required.

Sealing Rings and Gaskets

Sealing rings and gaskets are especially useful in high-pressure environments. Not only does the oil & gas process involve corrosive chemicals at high temperatures, but the pressures at which these push their way through the system can be highly erratic.

Sealing rings and gaskets – usually made with PTFE or a PTFE+PPS blend – need to be soft enough to create an adequate seal, but hardy enough to take high pressures without deforming.

Sealing rings are normally used in metal-to-metal joints and should be able to take pressures in excess of 100 Bar. They are integral in ensuring that the system does not leak and/or lose pressure – both of which can have highly adverse effects.

Valves, seats, and conduits

Polymer valves – such as butterfly valves, ball-valves, or even specialized valves and conduits – are vital to managing flow within a system. The liquids or gases within these systems can corrode even robust materials like stainless steel. PTFE and PEEK are often used as ball-valve-seats, while PTFE and PPS can also be machined to make special valves and t-joints to ensure that the system is not eaten away over time by the chemicals present.

PTFE Pipe Lining

PTFE pipe lining is a common process to ensure that large pipes – usually made using mild steel – are kept protected from corrosion. The PTFE is first extruded as a pipe with a wall thickness of 2.5-4mm and this is then drawn into the mild-steel pipe using a hydraulic press to create a uniform layer inside the steel pipe. The layer of PTFE within the mild steel ensures that the metal is totally protected. Such lined pipes are essential to create a piping system that can survive years, or even decades without getting corroded or developing leaks.

PTFE Sliding bearings

While the primary purpose of polymers is to protect and create efficiencies within fluid systems, PTFE also finds application in the bearings that allow oil & gas pipelines to stretch across vast distances. The sliding bearing is made using a layer of PTFE and sits under the pipe support. The purpose of the bearing is two-fold. First, it allows for compressive loads to act upon it. The high compressive strength of the PTFE is needed for this. More importantly, PTFE’s low coefficient of friction allows for a sliding movement. This movement is crucial since a metal pipeline will experience tremendous thermal expansion and contraction during the course of a single day. The sliding movement of the bearing allows for this and ensures that no stress develops under the pipe supports that may lead to pipes being damaged or the supports collapsing.

PTFE Tubes

No fluid system is complete without the incorporation of PTFE tubes. Like lined pipes, the tubes allow for the passage of fluids without succumbing to corrosion or fracturing under high pressure. PTFE tube is expensive, so its use is mainly restricted to areas where it is absolutely necessary.

Certain applications – such a labs and research set ups – will use PTFE umbilical cords to transport gases from the refining process and to the labs for testing. The composition of these gases tells us whether the refining process is producing the right results. Since the gases cannot react with anything else before they reach the lab, PTFE is used. Typically, there will be 12-15 different separate gases to collect, so the cord is composed of a bundle of tubes, each at least 200-500 meters long.

Sealing materials

Beyond sealing rings, various polymer sealing materials are also incorporated into oil & gas systems. A key product is ePTFE (expanded PTFE) gasket tape. This is a soft, highly compressible tape made using pure PTFE. As such, it has all of PTFE’s properties, with the added benefit of being up to 65% compressible.

ePTFE tape can be made from anywhere as low as 0.2mm to as high as 15mm thick. In effect, the tape can be laid between two metal components and the system tightened to ensure that the gap between the two metals is completely sealed. A typical flange-to-flange connection can be installed using expanded PTFE and will stay perfectly sealed for years on end.

Again, like PTFE, the tape can withstand high temperatures and pressures of up to 100 Bar, making it a vital product in any fluid system.

Specialized components

Over the years, Poly Fluoro has had the opportunity to develop multiple specialized systems and components for the oil and gas industry. From special molding frames using PTFE+Glass, measuring and analysis chambers using a combination of PTFE, PVC, and acrylic, and even heat exchanger assemblies for chemical baths. Our expertise in machining, forming, extruding, and molding high-performance polymers allows us to understand the problems from first principles and identify the right polymer needed for the application.

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