December 21st, 2010
The petrochemical industry has required the development of specialist pipe fittings and pipes and flanges over the years to meet ever more demanding requirements. This has also led to the adoption of specialist materials such as super duplex stainless steels. These materials are none the less relatively straightforward to work and can be cut and welded in the normal manor. However, we at Chemipetro also manufacture parts from specialist materials that required more demanding techniques to work them.
Once such specialist material is titanium. Known as the space age metal, Titanium is very strong but has a low density compared with iron. In fact, it has the highest strength to weight ratio of any metal. It is also extremely resistant to corrosion from sea water, chlorine and even nitro- hydrochloric acid. These all go towards making it a suitable material for those extremely tough situations.
It is, however, its very toughness that can be a problem as it takes specialist techniques to work it. To weld titanium requires careful preparation to ensure that there are no contaminants on the weld surface. This can be done with steam cleaning or an alkaline dip but gloves must be worn as even chlorine from skin can cause contamination that will ruin the weld. The weld site should then be warmed to remove all traces of moisture. Finally the weld must be carried out in an atmosphere of pure Argon, and not just on the front but on the back of the weld as well.
A well done titanium weld will have the appearance of frozen mercury and will be shiny and reflective.
Tags: Flanges, Pipe Fittings, Super Duplex, welds
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November 30th, 2010
At Chemipetro we manufacture a pipe flanges and pipe fittings which are predominantly used in the petrochemical industry. However this is not their exclusive use and there are many varied applications where the fittings we produce can be utilised, especially where they are subject to corrosive substances and therefore require to be made from corrosion resistant materials such as super duplex stainless steel.
Perhaps surprisingly one area where this specialist steel has found an application is in the water supply industry. It is surprising because although the presence of water can cause ordinary steels to rust, drinking water is not considered an aggressive medium to deal with. However in some applications, how it is produced is where the difficulty arises.
In the same way that we have become aware that fuel is a limited resource and that we have to be more selective in the way we use it, people are beginning to realise that drinking water is also an increasingly scarce resource. This is perhaps surprising when we consider that approximately 70% of the earth is covered by water. The trouble is of course that this is sea water and therefore is unsuitable for drinking and agriculture.
One of the answers to this problem is the construction of desalination plants and it is here that the special properties of super duplex stainless steel come into play. Unlike fresh water, sea water with its chemical mix of salt and minerals is very aggressive. Also it takes large amounts of energy and high temperatures and pressures to extract fresh water. All of these requirements make our products right for the water industry.
Tags: Duplex, Pipe Fittings, Pipe Flanges, Super Duplex
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October 27th, 2010
Pipelines used in the petrochemical industry can be exposed to a wide range of factors which can all have a deleterious effect on the metal of the pipeline itself.
Some of these are obvious such as exposure to sea water in marine environments. Some, such as high temperatures and pressures, are unavoidable and come from the process itself. Some come from the very nature of the liquids being handled such as bio-fuels which may seem harmless but can have an adverse effect on some metals.
Whilst the material that a pipeline and the pipe fittings are constructed from can be selected to withstand these specific individual problems, there are some situations which occur where the various factors can combine to produce a perfect storm. In these situations the effects may cause a sudden catastrophic failure to what would be an otherwise acceptable component.
This type of failure is known as Stress Corrosion Cracking (SCC) and occurs where an otherwise ductile material which can cope with various strains is subjected to a tensile stress in an environment which is corrosive and especially if subjected to high temperatures. Under these specific conditions the metal can fail unexpectedly and may appear quite normal up until the point of failure.
Duplex stainless steel is one material which has a high resistance to developing SCC and so is an ideal material to use when it is known that harsh environments may be encountered.
At Chemipetro we manufacture pipe fittingS and flanges in a range of materials including duplex and super duplex stainless steels to meet your specific requirements.
Tags: Duplex, fittings, Pipe Fittings, Super Duplex
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October 24th, 2010
From the early days of iron working it has been known that the introduction of carbon into the production process produces a much tougher material which is known as steel. It was discovered that as the carbon content was increased the metal became harder and stronger but less ductile. A high carbon content also reduces the steels weldability.
Carbon steel also has one other major flaw in that it is corrodes very easily. Therefore it is necessary to provide some sort of protecting coating if this is to be avoided. However this is not always practical and a better answer was needed in situations where the steel will oxidise. The solution was found by introducing chromium to produce an alloy that is resistant to corrosion and staining. However these early stainless steels had limited use as they were too brittle.
The petrochemical industry, with a requirement for running pipelines in sea water, raised particular problems requiring strength, workability and corrosion resistance. This led to the development of duplex stainless steel by introducing nickel and molybdenum into the mix making it particularly resistant in sea water environments. However there is always room for improvement and by increasing the chromium and nickel content to typically 25% and 7% respectively a super duplex stainless steel was produced with an increased tensile strength and resistance to pitting and corrosion.
At Chemipetro we manufacture pipe fittings and flanges in a range of materials including duplex and super duplex stainless steels to meet your specific requirements.
Tags: Duplex, fittings, Pipe Fittings, Super Duplex
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September 6th, 2010
As well as specialist stainless steels such as duplex and super duplex, we at Chemipetro manufacture pipes, flanges and pipe fittings in other specialist metals. However, none of these metals are as recognisable by name as Titanium.
This is commonly known as ‘the space age’ metal and for good reason. Its unique properties have meant that it is has been used extensively in aeronautical and military applications.
Despite its relatively recent application however it has been around for quite a while. Titanium as an element is present in all living things as well as soil and rocks. However it was not identified until 1791 when amateur geologist William Gregor noted it in some sand samples. Four year later a German chemist, Martin Heinrich Klaproth also identified the mineral and named it after the Titans in Greek mythology.
However, it was over a hundred years before a usable metal sample could be produced and not until 1932 that the first commercial samples were made outside the laboratory.
Because of difficulties machining it, it was not until the 1950’s that Titanium first became widely used when the Soviet Union used it in submarines. However its important properties of strength and lightness were quickly recognised such that the Americans declared it a strategic metal.
Titanium is as strong as steel but 45% lighter. It is also very resistant to corrosion being able to withstand acid and chlorine attack. This makes it particularly useful for the petrochemical industry.
Therefore if you have a particularly aggressive environment to cope with that also requires strength in the fittings Titanium could be your answer.
Tags: Duplex, Flanges, Pipe Fittings, Super Duplex
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September 3rd, 2010
We at Chemipetro produce a wide range of pipes, flanges and pipe fittings in a range of materials such as duplex and super duplex stainless steels. We can also manufacture parts in specialist materials such as 6% Moly super austenitic stainless steels, or if you have a specialist application which may require something a little different to solve the problem, we can help to find the answer.
But what special qualities do these types of stainless steels have and why and where would you want to utilise them?
Molybdenum minerals have been on the market for a long time. Its name is derived from the ancient Greek word Molybdos meaning lead, with which its ores were confused for a long time. It was not until 1778 that a Swedish Chemist, Carl Wilhelm Scheele finally identified the mineral.
It has some unique properties in that it has the 6th highest melting point of any element and it readily forms hard stable carbides. When used as a component in stainless steels it produces a metal alloy which is very stable at high temperatures and is resistant to corrosive elements which would degrade other types of steel.
Another useful quality of this type of steel is its good weldability and resistance to hydrogen induce cold cracking and spot weld peeling. Other types of steels are not so easily welded and require the use of specialist welding techniques.
For this reason, it is particularly useful in applications such as equipment exposed to sea water, chemical processing and handling of materials that have high halide levels.
Tags: Flanges, Pipe Fittings, stainless steels, Super Duplex
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July 6th, 2010
As well as a full range of flangesand pipe fittings, we at Chemipetro can supply a wide range of pipes and tubes to meet any need. Yet the engineering technology of pipes and pipe fittings has not always been the complex technology we know today.
From the earliest beginnings of civilisation, man has had a need to move liquids from one place to another. At first this would have been water for irrigation of crops and achieved by digging simple channels to direct the water flow. Later these water channels became more sophisticated by using stone to create water courses. Probably the most recognisable of these would be the magnificent aqueducts constructed by the Romans. These could be use to bring water for miles across difficult terrain. They were however difficult to construct. A simpler and more cost effective technique was required and also something that could be used on a smaller scale.
A solution was found with the development of wooden pipes. Initially tree logs were used that had a hole bored along the length of them. Later a method using staves and metal hoops was used, similar to the construction of a continuous barrel.
However with the development of industrial processes, the need for stronger and more durable pipes lead to the development of better materials and techniques for producing pipes and pipe fittings. With the development of the petrochemical industry came perhaps the most testing demand of pipe technology including the development of special stainless steels such as duplex and super duplex.
We have certainly moved a long way from mud ditches and tree logs.
Tags: Duplex, Flanges, Pipe Fittings, Super Duplex
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June 24th, 2010
Duplex steels have a mixed ferrite and austenite microstructure, to which various other metals such a molybdenum are added to increase mechanical strength and corrosion resistance. Duplex and super duplex pipe fittings don’t conform to one exact composition. There are several grades, which vary in corrosion resistance.
While it may seem odd to select a duplex steel with higher corrodibility, it must be remembered that selecting alloys for pipe flanges is often a juggling act. Slightly higher corrodibility may be offset by superior mechanical strength, so a steel of this grade may be the choice if you are working at high pressures, but in a fairly neutral environment.
Duplex steels are graded according to their alloy content. Super Duplex steels have the highest level of alloy, and therefore the lowest resistance to crevice corrosion and pitting. Pitting resistance of steel is measured by its PRE (pitting resistance equivalent).
Ordinary austenite and ferrite stainless has a PRE of 17 – 18%. s1803 duplex has a PRE of 34% – the same as N08904 austenite steel, although the latter has poorer resistance to acids, and is more sensitive to stress-corrosion cracking. The highest PRE is achieved with S32750 and S32760 super duplex – both of which we supply at Chemipetro. They differ in that S32750 has added tungsten to increase pitting resistance, but both have a PRE of at least 43%.
The high chromium content of super duplex steels makes them the ideal choice for acidic and caustic environments. Duplex and super duplex pipe flanges are widely used in chemical, petrochemical, pulp and paper and marine environments, often replacing high nickel super-austenitic steels such as S31254.
Tags: Duplex, duplex steel, Pipe Flanges, Super Duplex
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June 21st, 2010
Duplex and super duplex steels are widely used in the petrochemical industry, as well as oil and gas refineries and marine rigs. They are prized for their superior corrosion-resistance, strength and durability.
We at Chemipetro are increasingly supplying duplex flanges and pipe fittings to demanding 21st century environments, such as deep-water oil wells and petrochemical plants. However, duplex steels were actually developed more than 70 years ago, for the Swedish paper industry.
The first generation duplex steels were specifically designed to be resistant to the chemical process fluids used in the paper pulp industry, such as chloride-enriched cooling waters. The second generation alloys now in use have improved upon this, having superior stress and pressure-resistant qualities, and enhanced resistance to pitting. The chemicals used in the modern petrochemical industry are far more pressurised and corrosive than the Swedish pulp mills were.
Duplex is so-called because it has a mixed microstructure of roughly equal proportions of austenite and ferrite. To this, chromium, nickel and molybdenum are added in varying amounts to improve resistance to pitting and weldability. Super duplex steels were developed in the 1980s in response to the increased use of highly corrosive and high-pressure industrial environments.
The phrase, “the whole is better than the sum of the parts” could have been written for duplex. Its resistance to stress-cracking through corrosion is superior to type 316 steel alloys, and its mechanical strength is roughly double that of singular austenitic steel. The one criticism of duplex pipe flanges has been embrittlement at extreme temperatures. However, this is being addressed by development of cool-welding techniques, and alloys that withstand sub-zero and arctic conditions.
Tags: Duplex, duplex pipe flanges, Pipe Fittings, super duplex steels
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May 13th, 2010
We at Chemipetro supply flanges and pipe fittings made of extremely resistant alloys, such as super duplex, to the process industries. The development of these alloys is the result of many hundreds of hours of research. This research is on-going, because even today cracking in petrochemical pipelines, flanges and pumps is a problem – and it isn’t restricted to low-nobility alloys like carbon steel.
When selecting pipe flanges for the petrochemical industry, corrosion resistance is the thing that is usually given highest consideration. However, not all of the accidents that occur in plants today are attributable to corroded pipe fittings alone. Petrochemical pipelines operate under extremes of pressure and temperature. The volatile and corrosive chemicals they contain can leak out in a number of ways, often suddenly and with great force.
NACE (the National Association of Corrosion Engineers) is an internationally recognised organisation that actively researches corrosion control. As recently as 2001, a NACE white paper reported problems of early cracking in pipes and pipe fittings fabricated from alloys selected for their corrosion resistant properties. Failure was observed in the welded areas of stabilised austenitic stainless steel charge heater pipes, in a petrochemical plant where working temperatures in excess of 650 degrees were recorded.
Using detailed FEA (finite elemental analysis) and other techniques, the study showed that a combination of thermal pipe movement, internal pressure and bolt movement at the flanges all contributed to cracking. When choosing pipe flanges, therefore, operators should never depend on the corrosion factor alone. How the flanges are supported to minimise vibrational, thermal and pressure stresses is just as important.
Tags: corrosion resistant alloys, Pipe Fittings, Pipe Flanges, Super Duplex
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