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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April 7th, 2010
When pipe flanges are made of a dissimilar metal to the pipes they are connecting (i.e. they are higher or lower in the galvanic series) corrosion may occur. This is especially true of flanges that are in contact with electrolytic solutions, for example sea water or acidic chemicals. Galvanic corrosion is extremely hazardous; however, there are a number of ways you can reduce this risk.
You can order flanges made from alloys that are corrosion-resistant, i.e. high in the galvanic series. However, this in itself may actually increase the risk of corrosion unless the pipes are replaced with equally corrosion-resistant materials.
This comes as a surprise for people who don’t understand how galvanic corrosion works. Simply put, the further apart two metals are in the galvanic series, the faster corrosion will occur. This is because one (the lower resistance) acts as an anode, and the more highly resistant metal acts as the cathode. In the presence of an electrolyte such as seawater, ions flow from the anode to the cathode, resulting in corrosion. If the two metals are very near each other in the galvanic table, the flow will be slow. However, if they are far apart it will increase, leading to rapid corrosion.
In an ideal world, the entire pipeline would be composed of a super-alloy such as duplex. However, this isn’t usually feasible, so you must use highly resistant pipes and pipe fittings wherever you can, and in areas where they are dissimilar, work on reducing the likelihood of the two metals coming into contact with the electrolyte.
Tags: Flanges, Pipe Fittings, Pipe Flanges, resistant pipes, super duplex alloy
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November 6th, 2009
In the industries that we at ChemiPetro supply, it’s important the products are of a very high quality, able to withstand pressure, and are chemical resistant. This is why we always recommend duplex and super duplex pipe flanges and fittings as being the most suitable.
Flanges are pipe fittings used to assemble pipes together quickly and efficiently. There are many different flange standards, depending on what the product is to be used for.
The pipe fittings we supply at Chemipetro have specific dimensions unique to the petrochemical, gas and oil industries. They are standardised to allow easy and inter-changeability between products. British pipe flanges are classified to BS standards, e.g. BS10. European pipe fittings, meanwhile, are classified to PN/DIN standards, and American to ASA/ANSI standards.
It’s important to realise you can’t match one standard with another. So you can’t put a BS flange on an ANSI pipe, for example. However, there are a growing number of pipe fittings showing a BS/ANSI configuration; this means they are compatible with both. Most of our products show ANSI standards. The US leads the world in the manufacture of high spec pipe fittings – ideal for the industries that we at ChemiPetro supply.
Super duplex stainless steel pipe fittings are made to very high specifications and are heat, pressure and chemical resistant. Although Duplex steel is corrosion and rust resistant, super duplex has higher levels of Molybdenum and Chromium, which increase its resistant properties.
Pipe flanges are potentially the weakest point in a pipe system. However, pipe flanges can be the system’s greatest strength if the right products are used.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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October 14th, 2009
Due to the high amount of corrosion in the petrochemical field, it is vital that materials are used that can combat this. Super duplex stainless steel is one of these materials. As an improvement on duplex stainless steels, it is very much the same thing with the difference being that super duplex have higher amounts of alloy and have increased resistance to pitting, crevice and stress corrosion cracking and additional increase in strength values.
Super duplex also provides more strength than normal stainless steel and duplex stainless steel because of the higher alloy content.
Super duplex will allow for high thermal conductivity, is good for welding, will resist corrosion fatigue and have low coefficient of thermal expansion. When compared to austenitic stainless steels, test results showed that super duplex had a higher heat conductivity, low thermal expansion, high energy absorption, high strength, good resistance to sulfide stress corrosion and a high resistance to pitting and crevice corrosion.
Another interesting fact is the high chromium levels found in super duplex stainless steel. The reason for this is that it gives it high pitting resistance, makes it more resistant to acid chlorides as well as caustic solutions and is suitable for more strenuous environments than other stainless steels. It is also a good replacement for nickel based steels and 300 grade stainless alloys.
At Chemipetro we have flanges, seamless steel tubing, pipe fittings and fasteners that are manufactured using super duplex stainless steel. Contact us to find out exactly what we can offer you as well as some of our other products, including socket head cap screws and stud bolts.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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September 22nd, 2009
Super Duplex stainless steel owes its existence to Duplex stainless steel, a material developed in Sweden around 70 years ago. Its composition consisted of a microstructure that contained almost equal parts of ferrite and austenite, and became one more family of grades that ranged in its corrosion performance.
Even the term ‘Super Duplex’ denotes that it is a highly alloyed and super performing Duplex stainless steel material, with superior resistance to pitting and corrosion.
Benefits of Super Duplex:
Super Duplex is highly resistant to a variety of potential corrosion types, including chloride stress, suphide stress and cracking, or fatigue. This extremely strong material has a low coefficient expansion and high thermal conductivity, and its levels of resistance to corrosion make it an ideal material to use for a variety of purposes. Super Duplex provides good workability properties and weldability, and has high energy absorption.
Applications suited to Super Duplex
Super Duplex stainless steel is suited to a wide variety of applications, such as:
• On use on tubes or pipes used for the production of or handling of gas and oil
• Heat exchangers and piping used in desalination plants
• In the used of mechanical or structural components
• Piping or pipe fittings used in process industries that contain chlorides
• In industrial systems where high corrosion fatigue is needed including rotors, fans, shafts or press rolls
• On Cargo tanks, sea going vessels or welding consumables used on chemical tankers
• Any application that calls for a high strength solution.
Here at Chemipetro, a leading supplier and manufacturer of flanges and pipe fittings, we supply high quality Super Duplex stainless steel materials to suit an array of purposes.
Tags: Duplex, Pipe Fittings, Super Duplex, super duplex stainless steel
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September 3rd, 2009
Super Duplex stainless steel is designed with specific applications in mind. These applications include anything that requires high strength, plus that require above standards of excellence in terms of corrosion resistance. Super Duplex stainless steel lends itself to industries or applications such as sea water cooling plants, ocean vessels, desalination plants or heat exchanger tubes.
Machining, Forming, Welding and Hot Working
Due to Super Duplex stainless steel’s higher yield strength forming pressures, speeds – at least initially – must be higher than what is needed for 300 series stainless steel. All common methods of welding can be employed while hot working is recommended, followed by rapid cooling. Super Duplex stainless steel should also be fully annealed prior to working in order to maximize its properties.
Super Duplex Properties
Super Duplex stainless steel is NORSOK approved and has a pitting resistance equivalent number of 40. Its ability to provide high resistance to corrosion is due to the addition of chromium, molybdenum and nitrogen. Some levels of Super Duplex stainless steel such as F55 / UNS 32760 are too low in nickel and are thus capable of producing a duplex microstructure consisting of ferrite and austenite.
This level of Super Duplex stainless steel can be used in applications such as piping, pumps, chemical tanks, refineries, marine shafts, pressure vessels, flanges, pipe fittings and pipe flanges or heat exchangers where austenitic stainless steel would otherwise corrode.
NORSOK Approved
NORSOK standard is considered critical for the manufacturing or fabrication of components or materials that use induction or cold blending. It is able to establish a set of requirements that can verify a manufacturer has the required competence and experience in the fabrication of materials such as Super Duplex SS, High Alloy Austenitic SS and Nickel based alloys.
As the UK’s premier stockholder, manfucturer and supplier of pipe fittings, flanges and Super Duplex stainless steel, we at Chemipetro should be your first port of call.
Tags: Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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August 19th, 2009
So you have a huge piping project, or you company requires flanges that are strong and durable. While aluminium, cast iron, plastic and copper may be an option, steel has a number of advantages that could render your project a success.
When opting for steel, stainless steel is the ideal material to rely on. You will find that you have two popular options in stainless steel, duplex and super duplex. While duplex stainless steel is a very durable material, for higher performance, super duplex stainless steel is your ideal choice.
Duplex stainless steel is a grade of steel that ranges in corrosion performance according to the amount of alloy present. Super duplex is a high alloy, high performance stainless steel with great resistance. Here at Chemipetro we have a wide range of super duplex stainless steel products all suited to your piping needs.
Why choose super duplex stainless steel?
By choosing super duplex stainless steel parts, you are choosing to purchase very strong components, whether you buy super duplex stainless steel pipes or pipe fittings in either seamless or welded. Various flanges and pressure fittings can also be found in super duplex stainless steel. A number of super duplex stainless steel fasteners such as bolts, screws, nuts, studs, socket heads and washers are also available.
Besides being extra strong, these super duplex stainless steel components are very resistant to pitting and corrosion, whether stress corrosion or crevice corrosion. Super duplex stainless steel also has good workability and can be welded easily.
Tags: Duplex, Super Duplex, super duplex stainless steel
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