August 12th, 2010
We at Chemipetro manufacture flanges and pipe fittings for use within the petrochemical industry. Our products such as pipe flanges are manufactured from various grades of steel, such as duplex and super duplex, specifically to meet the demanding requirements of the chemicals that are currently processed.
Oil is becoming a scarce commodity and at some time in the future it will be necessary to develop other types of energy sources which can be used as fuels. These alternatives however will provide their own technical problems and challenges which will have to be dealt with.
One such fuel could be hydrogen, which may become a major fuel in the next 50 years. If this was to happen then it would be necessary to develop large scale production, storage and transport infrastructure for this.
However when hydrogen comes into contact with steel it can have a deleterious effect. Hydrogen atoms are the smallest atomic structure and are small enough to penetrate the crystalline structure of steel. This can cause the steel to become brittle and develop fractures. Also, when exerted to high pressures, pockets of hydrogen can develop causing the steel to fracture.
To prevent this happening it is currently necessary to introduce a barrier layer to prevent the hydrogen coming into contact with the steel. Other techniques and materials will also have to be developed so that these systems can be easily manufactured on the scale which will be required.
So in the future a duplex pipe will no longer be a simple steel tube but will have to be in itself a sophisticated piece of engineering.
Tags: duplex pipe, Flanges, Pipe Fittings, Super Duplex
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July 18th, 2010
We at Chemipetro produce a wide range of pipe fittings and flanges manufactured from duplex stainless steels, But what exactly are these types of steels and why use duplex steel rather than ordinary steels?
To answer these questions it is necessary to understand what exactly stainless steel is.
Ordinary carbon steel is strong and as such has many applications. However it has one draw back, it rusts when exposed to air and moisture. Under these conditions a film of iron oxide is formed which causes the corrosion to accelerate and more iron oxide to form.
To prevent this happening, chromium is add to produce an alloy. This was first developed in 1821 by Pierre Berthier, a French metallurgist. However these first stainless steels were too brittle to be of much practical use. It was not until the early 1900’s that a process was developed for producing a practical stainless steel.
Stainless steel resists corrosion by the chromium forming a protective layer of chromium oxide. This layer is impervious to water and air and so protects the metal beneath.
Stainless steels are categorised by their crystalline structure, the most common being austenitic steels which contain nickel or manganese as well as the chromium. However these steels can be expensive especially with the higher grades which also contain molybdenum.
Duplex steels have a mixed structure of austenite and ferrite, giving them improved strength over austenitic stainless steels and improved resistance to local corrosion. This means that for a given strength, castings can have reduced thickness and weight, thus making them cheaper.
Tags: Duplex, duplex stainless steels, Pipe Fittings, Super Duplex
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May 27th, 2010
Although duplex pipe flanges are widely used in the petrochemical industry, long-distance pipelines are still mainly built from carbon steel, which has a high level of corrosion. Currently, there is great interest in the oil and gas industry to implement duplex steel as the material of choice, owing to its strength and corrosion resistance.
One of the problems with using duplex flanges in pipelines is the increased skill required by the welder to achieve an acceptable root pass. This first layer of a multi-layer weld is the most critical, because it is the one most likely to crack or become contaminated. The preferable method for depositing root passes is GTAW (gas tungsten arc welding), which uses a specialised backing shield of inert gas, such as argon. It is tricky to use this method on duplex. Besides anything else, the gas itself causes problems at the welds.
Another disadvantage with duplex flanges is that it is difficult to achieve low-temperature toughness – essential for field welds. It is felt that if a gas-free arc welding technique could be developed, that somehow also attacked this problem, then duplex could replace carbon steel on long-distance pipelines. The benefits would be a radical improvement on corrosion of pipe flanges in pipelines, with a corresponding reduction in the tonnage of metal used each year.
We at Chemipetro supply both duplex and super duplex pipe flanges and fittings, all with excellent weldability. However, their unique and complex composition means that extra care must be taken over welding, in order not to compromise strength and corrosion resistance.
Tags: duplex pipe flanges, Flanges, super duplex pipe fittings, tungsten arc welding
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April 19th, 2010
We at Chemipetro supply pipe flanges and other fittings to high industrial standards. Created in a range of superior, corrosion-resistant alloys such as titanium and super duplex stainless steel, they ensure that pumping systems run at maximum efficiency.
Of course, our pipe flanges are only as good as the systems they are connected to, which is why the new generation of progressive cavity pumps is so impressive. Deceptively simple, the system relies on two key components; an external helix rotor, inside an internal helix stator. Together, they form a tightly-bonded two-piece drive-shaft. The rotor is machined from high-tensile steel, while the stator is moulded from tough rubber or abrasion resistant polymer. The entire unit is tightly bonded inside a steel alloy tube.
The action relies on the rotor always having one less helix than the stator. As the rotor turns, the action forms cavities which move from the suction to the discharge end, moving the fluid along. Because there is a continuous seal between the two helices, the pump maintains a smooth and constant flow, proportional to its speed.
The latest pumps are engineered for quick and easy access to the mechanical seal during maintenance, thus avoiding the need for full disassembly. The use of highly resistant alloys such as duplex steel, plus their smooth flow function and ability to handle liquids with heavy viscosity, makes them ideal for pumping crude oil. Models are available for a variety of pipe fittings, including standard and close-coupled flanges.
Positive displacement pumps are efficient, low maintenance and built to last – the perfect complement to the duplex flanges and pipe fittings we at Chemipetro supply.
Tags: duplex steel, Pipe Fittings, Pipe Flanges, steel alloys, Super Duplex
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April 15th, 2010
As a supplier and manufacturer of high-quality pipe flanges for the petrochemical industry, we at Chemipetro understand the importance of caring for our flanges and pipe fittings once they’re installed.
All flanges need regular maintenance, or you will start to get decreased performance from other components on your site. It’s essential you eliminate problems at their source, as soon as they arise. Not only will this improve plant efficiency, it will create a safer working environment and save on running and repair costs. A large number of fires and explosions start as a result of leaking or poorly welded pipe fittings.
No matter how high the quality of the alloys, it is essential you protect flanges, gaskets and other components from their environment as much as possible. This starts by reducing corrosion to an absolute minimum. Using corrosion resistant alloys, such as super duplex, has reduced corrosion substantially – but the annular seal on the outer diameter of flanges can still be vulnerable to moisture and dirt. Once these creep in, eventually it will lead to corrosion and degradation around the gasket area.
You should also remember that welded joints are more vulnerable to corrosion than other areas of pipe fittings, even if tough stainless steel alloys are used. Excessive corrosion of flanges is dangerous, and if they have to be replaced it can lead to plant shut-down. To reduce this risk, use flange protectors to stop dirt and moisture attacking the joints.
While strong, corrosion-resistant alloys like duplex steel will ensure you get long life from the pipe flanges you buy from us atChemipetro, they will last even longer if you remember these few basic rules.
Tags: corrosion resistant alloys, Pipe Fittings, Pipe Flanges, Super Duplex, weld neck flanges, welded joints
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December 11th, 2009
The tee is among the most common of industrial pipe fittings. Depending on the application, tees are available as all-female threaded sockets, all solvent welded sockets or a combination. They are available in a variety of impact and corrosion resistant alloys, including duplex and super duplex.
Tees are 3-ended pipe fittings designed to offer a second outlet from a main, through-running pipe.
Tees are used to connect pipes of the same or differing diameters. A blocked-off tee is useful for changing the direction a pipe runs, where an elbow would not be an option (for example, to offer an observation “hatch”). The most common tees are straight tee pipe fittings, a straight-through tee with a 90-degree branch-off of the same diameter.
Tee fittings are supplied as equal or reducing tees. The above is an example of an equal tee, as all three outlets are the same size. Reducing tees have a combination of different sized outlets, and are used for branch connections from larger lines.
Standard tees are typically belled on all three ends. However, any combination of belled or plain ended tees can be produced, although they may not all be available in duplex steel unless they are custom made. Similarly, tees are available in a large range of size combinations. Unusual combinations can be accommodated by using component parts of different tees, reducing tees or reducer fittings.
We at ChemiPetro supply a wide range of tee fittings to the industry and will happily provide a quote on custom made tees, including duplex and super duplex fittings.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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October 26th, 2009
We realise that not all of our clients are exactly the same and that they might have had to create unique solutions for some unique problems. We are proud to say that we can be a helping hand when those unique problems appear by manufacturing flanges and pipe fittings specifically to your requirements.
We use a wide variety of metals including stainless steels and exotic alloys. We have also introduced new ranges made from duplex stainless steel and super duplex stainless steels. These are great for the petro-chemical industry field as duplex stainless steel and super duplex stainless steel have much better anti corrosion qualities than other stainless steels.
Duplex stainless steel and super duplex stainless steel have a much higher alloy content than normal stainless steels which makes it much stronger and less affected by corrosion and age. Basically the metal is a type of stainless steel with austenite and ferrite as an addition. It is also from there that the term duplex comes, as it is a combination of the austenite and ferrite that gives it its ‘duplex’ qualities.
Duplex stainless steel and super duplex stainless steel are much cheaper to manufacture, which in turn means that it is much more cost effective for you to use. The fact that it is also a stronger material that withstands corrosion better also means that less is needed in the manufacturing process. The pipes, flanges or fittings can be thinner and smaller than before as these will provide the same effect as the thicker and bigger ones, such as blind flanges and weld neck flanges.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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October 12th, 2009
In the early 1990s, duplex stainless steel was introduced to the electric power industry by metallurgists who had been doing research on combining metals for welding purposes.
They used austenite and ferrite in the same material, which worked beautifully, and was also a very cost effective new material that did not corrode easily. The name duplex comes from the fact that thay made a two phase micro-structure that consists mainly of ferritic and austenitic stainless steel.
Today we have both duplex and super duplex stainless steel and the use of these has revolutionised the industrial and production industries.
Duplex quickly proved to be much cheaper to use in more than one way. The materials are much less costly, but manufacturers could also use less of it for their end product. Duplex does not corrode easily, which means when talking about a pipe for instance, that the pipe can be much thinner as the duplex will last for much longer.
We have a full range of duplex flanges in many materials, such as ASTM a182 f51, and pipe fittings available but can also manufacture these to specification for you. Please contact us for our full range and quotations, and remember that we have a 24-hour emergency break down call out service as well as offering other products such as stud bolts and tie rods.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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September 23rd, 2009
Duplex stainless steel was first created in order to address corrosion problems stemming from chloride bearing cooling waters or other chemical process fluids.
Duplex stainless steel is a family of grades which are ranged in accordance to their corrosion performance, as well as their content of alloy; Duplex’s alloy content being almost equal proportions of ferrite and austenite.
Super Duplex was a term phrased in order to indicate its highly alloyed composition of which provides a pitting resistance of >40. The chemical composition is based on Cr% + 3.3Mo% + 16N%.
Super Duplex contains very high levels of chromium which provides above average resistance to acids, caustic solutions and acid chlorides. It also provides high levels of corrosion resistance to any environment which uses chemicals or petrochemical solutions. It is fast replacing 300 series stainless steel or high nickel super-austenitic steels.
Based on a chemical composition which has high contents of nickel, chromium and molybdenum, Super Duplex improves intergranular and pitting corrosion resistance. With the addition of nitrogen to promote structural hardening it not only raises yield strength but also strength values without impairing its toughness.
The Various Alloys
Super Duplex stainless steel resides in the group of Duplex stainless steel. It is graded for its corrosion performance and for its content of alloy. Duplex can be divided into four groups:
1. Super Duplex, which contains 25-26Cr and increased Mo and N. This grade is comparable to 25 Cr and 2507
2. Lean Duplex stainless steel such a 2304 which contains no added Mo
3. 2205, which is a grade considered the work horse as it accounts for over 80% duplex use
4. 25 Cr duplex.
All of these materials are available from us here at Chemipetro.
Tags: Duplex, duplex alloys, duplex stainless steel, Super Duplex
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September 17th, 2009
The two phase microstructure led to the name Duplex. The microstructure consists of grains of ferritic and austenitic stainless steels. When Duplex stainless steel melts it hardens from this liquid phase into a completely ferritic structure. As it cools to room temperature approximately half of these ferritic grains change into austenitic grains. The result is that Duplex stainless steel contains about half of each material, ferrite and austenite.
This Duplex structure gives this particular family of stainless steel its much applauded properties. For one it provides about twice the strength of regular ferritic or austenitic stainless steels. Duplex stainless steels also provide much higher levels of toughness and ductility over ferritic grades. They don’t, however, match these superior properties provided in austenitic grades of stainless steel.
Superior Qualities
While all stainless steels offer resistance to corrosion, the levels depend on their individual compositions. If chloride pitting or crevice resistance is required then they must contain in their composition a mixture of chromium, molybdenum and nitrogen. Duplex stainless steel has corrosion resistance levels that are similar to austenitic stainless steels. For instance from types 304 or 316 grades to 6% molybdenum stainless steels.
Duplex grades have excellent resistance to stress corrosion cracking. This is a property that has been inherited from their ferritic makeup. While austenitic stainless steels provide superior corrosion resistance, ferritic stainless steel provides superior stress cracking resistance.
Due to the lower nickel and molybdenum composition, Duplex stainless steels can be lower in cost. Apart from this and due to their yield strength, it is often possible to reduce the thickness. The combination of these two factors offers not only cost savings, but also savings in relation to weight – especially when compared to austenitic stainless steels.
Duplex stainless steel can be found here at Chemipetro, one of the UK’s leading manufacturers of pipe fittings and flanges, for reasonable prices.
Tags: austenitic stainless steels, Duplex, duplex alloys, duplex stainless steel, ferritic stainless steel
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