September 9th, 2010
A lot of products that are engineered for the petrochemical industry have much wider applications and uses. Pipe flanges and pipe fittings, for example, are not just used in pipelines for petroleum or chemical products, but can also be used for other more mundane applications such as pipelines for pumping water. It is not the type of fittings that are unique but the type of materials they are made from.
Water (unless it is sea water) is a far less corrosive medium than a lot of chemicals that are transported. Therefore for most simple applications it is possible to use cast iron or even plastic pipelines. However more corrosive elements as used in the petrochemical industry require a tougher material, and this is where the specialist stainless steels such as duplex and super duplex come into their own.
However, there are applications where even water can require a stronger material, and that is where high temperatures and pressures come into play as may be experience in boilers and heat exchangers. At Chemipetro we manufacture a special range of tubes for such applications.
Although boilers are used in heating systems heat exchangers have a much wider application. Basically, they are used where it is required to alter the temperature of one medium by transferring heating or cooling from a second medium. The two liquids (like oil and water) must never mix and are kept segregated by running in different pipelines. This process is used a lot in the chemical and food processing industry when it is necessary to heat up a medium during a manufacturing process or to chill another.
Tags: Duplex, Pipe Fittings, Pipe Flanges, Super Duplex
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August 15th, 2010
One of the most fundamental problems faced in any industry is how to join two pieces of material together. A layman asked this question would probably immediately think of glue. This is possible even with steel, where welding is effectively gluing two pieces of metal together.
There are however two fundamental problems with any sort of glued joint. The first, the joint is only as strong as the glue itself. To help overcome this with welded joints the ends of the pieces are shaped to form a V. This gives the weld a greater surface to form on and so make the bond stronger.
The second problem is that any glued joint is permanent and does not allow for anything to be dismantled should maintenance be required.
To dismantle a joint it should be connected by a removable fastening. This is where the humble nut and bolt come in. By providing flanges on the end of a pipe or a pipe fitting, and by bolting the two flanges together, a strong but removable coupling can be achieved.
But what sort of nut and bolt should be used? In concept they may all be the same but in practice they can be very different, from a simple threaded rod which is cut to length, to a 12 point ferry head unit. The choice of nuts can also be bewildering from the simple hexagonal to a bi hexagonal 12 point self locking type.
Whatever your need we at Chemipetro can provide a wide range of fastenings to meet your specific requirements even if it is a non standard and unique type.
Tags: Flanges, pipe fitting, Pipe Flanges, welded joints
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July 30th, 2010
How lengths of pipe and pipe fittings are actually connected together would seem, on the face of it, to be a relatively simple exercise but in fact it is a very complex issue.
It is possible to use pipe flanges, but this is an expensive option and is really only suitable for situations where the pipework has to be dismantled for maintenance, as all bolted flanges introduce a weakness.
It is possible to use a threaded connection where the end of one pipe is screwed into the end of another pipe. This method is commonly used for smaller pipe sizes. However the cutting of the thread reduces the thickness of the pipe material and so again introduces a weakness.
The preferred option for joining pipe lengths is a welded joint. But again there are different options depending upon the application. The most common type is the butt weld. This is a connection between two pipes of the same size. The end of each pipe is bevelled so that when the two ends are placed together a V is formed. The pipes are then welded around this V.
However in situations where there are high pressures and the flow characteristics are important, a socket weld can be used. Here one of the pipes has a larger collar which fits over the other pipe. The weld is then done on the outside. These are easy to use especially on small bore pipes.
Whatever type or pipe connection you propose to carry out, we at Chemipetro manufacture a wide range of pipe fittings and pipe flanges to meet all your requirements.
Tags: Flanges, Pipe Fittings, Pipe Flanges, socket weld
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July 15th, 2010
To the uninitiated a flange is a flange. However to the pipeline designer the use of a particular type of flange for a specific situation is critical. The use of the incorrect type of flange can lead to restrictions is flow rates, turbulence in the flow leading to cavitation and even premature failure. This can be catastrophic if it occurs in the wrong place at the wrong time. Also different types of flanges, although similar in appearance may be used for totally different applications.
A weld neck flange is probably the most common type of flange fitting for connecting two sections of pipe and is particularly used for high pressure installations; it consists of a round plate with the central bore the size of the pipe. They also have a collar which increases in thickness at the base of the plate. They are connected to the pipe by welding the collar end on to the pipe. They are recommended for installations which require a robust pipe joint especially if it is subject to temperature variations.
However there is also a long weld neck flange. Although this is similar in concept is has a considerably longer collar and is used for a completely different application. This type of flange is used where a nozzle is required for a pipe.
We at Chemipetro produce a wide variety of pipe fittings and flanges to ensure that you always have the correct specification of fitting for any specific application.
Tags: flange, Pipe Fittings, pipe flange, weld neck flange
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July 9th, 2010
When designing a pipe run the question is how much fluid can be pushed through a pipe at a given rate? The answer is subject to many variables, however one of the key criteria is the pressure at which the liquid is pumped.
If a high pressure is used then a higher flow rate for a given pipe size can be achieved, and smaller pipes mean less cost in materials and installation. However a pipe is only as strong as its weakest point and this is at the joints.
In continuous pipe runs, joint are usually achieved by welding. Welded joints have their own problems, but they are cost effective and produce a continuous pipe run.
However at some point it will be necessary to include a fitting such as a valve or a pump into a pipeline. Valves and pumps require maintenance and at some time will have to be taken out of line to be replaced. If they were welded into position then this would be a very difficult and time consuming process, as the joint would have to be physically cut and re-welded afterwards. This is where a flange is used.
A pipe flange is a way of terminating a pipe run with a flat face. The pump or valve will also be provided with a flange. These two flanges can then be bolted together with a gasket between to make a joint which can be easily dismantled.
We at Chemipetro produce a wide selection of pipe flanges to suit varying pressures and configurations of pipework making life easier for the pipeline designer.
Tags: Flanges, Pipe Flanges, pipes
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June 27th, 2010
Pipe fittings and flanges on today’s oil rigs and deep-water wells are routinely manufactured from high strength and corrosion-resistant alloys. We at Chemipetro supply super duplex pipe fittings across the industry.
High quality alloys means minimal risk of leaks due to flange failure. However, it also means that if a big blow-out does occur, it’s more likely to happen at the well head than the seams.
A blow-out event of any kind is a disaster. Not only can lives be lost, but billions of gallons of crude oil can contaminate the environment. Thus it’s essential that safety devices are fitted that not only give early warning of impending blow-outs, but can seal the well off at underwater flanges if such a blow-out occurs.
Brazilian and Norwegian regulators have such a device fitted as standard on their underwater rigs. Called an acoustic switch, it cuts in the moment there’s an underwater spill. US rigs are not fitted with such a device. It’s now being suggested that, had they been, the recent tragic events off the coast of Louisiana need not have happened.
The acoustic switch is, it must be said, a last-ditch device when all else has failed. Remotely triggered by crew members, it operates an underwater valve at one of the pipe flanges, shutting down the damaged well and preventing an explosion or oil leakage. If the platform has to be evacuated, it can be triggered from a life raft.
US regulators disagree that the device is necessary, raising questions about its effectiveness, and pointing out that they have their own safety devices to shut down rigs.
Tags: Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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June 5th, 2010
The pipe fittings we supply at Chemipetro are manufactured to withstand some of the earth’s most hostile environments. As mankind attempts to wring every last drop from the earth’s crust, so the wells get deeper – and the costs get higher. This was proven to tragic effect in April 2010, when the Deepwater Horizon exploded and sank, pipe flanges and all, to the bottom of the ocean, taking 11 crew members with her. The cost to marine life has been immeasurable.
Despite state-of-the-art rig technology and super duplex pipe flanges, deepwater drilling is in its infancy. The more extreme it becomes, the more dangerous it becomes too. When Deepwater blew, it was through a combination of factors, chief among which was the under-estimation of the power and speed of the earth to strike back.
Deepwater Horizon was the jewel in BP’s crown. 7 months’ previously, she had successfully sunk the deepest oil well in the world. But while a casing was being cemented – ironically, to safely shut off the well so the Deepwater could be moved –an unprecedented and abnormal pressure build-up occurred, rising and expanding in a terrifying burst of energy. Although the rig was fitted with cutting-edge blow-out preventers, or BOPs, the explosion occurred with such speed and finality that they were overridden.
It’s been suggested that back-up devices could have prevented the explosion – though this seems doubtful. What is certain is that not one factor of the blowout could be attributed to the construction of Deepwater Horizon herself. From the state-of-the-art dynamic positioning system, to the pipe flanges that proudly withstood the full force of the blowout, she was an inspirational work of art.
Tags: Pipe Fittings, Pipe Flanges, pipe joints, super duplex pipe flanges
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May 17th, 2010
Finite elemental analysis (FEA) was one of several techniques used by NACE (an international association of corrosion engineers) to investigate failure in petrochemical flanges in 2001. The study involved cracking around welded high-temperature pipe fittings. Made from high-strength austenite stainless steel alloys, these should not have failed.
The study was carried out on 24” diameter pipes leading from charge heater units. These pipes carried i-butane at an operating temperature of 650oC, under high pressure, to reactor vessels. The pipe was welded to 24″ flanges made of the same steel alloy. This was the site at which cracking occurred, despite the steel being selected for its ability to withstand temperatures in excess of 650oC.
Tests were carried out on a piece of failed pipe welded to a flange. The pipe, which had three distinct cracks of 5 – 20 cm long, was first subjected to a dye penetration test. The mechanism of damage, changes in microstructure and alterations in grain boundary chemistry were then analysed using a variety of metallurgical techniques. These included optical microscopy; scanning electron microscopy; X-Ray fluorescence, tensile tests and FEA.
Although the flanges and pipe fittings were made of the same alloy, there were marked differences between the grains of the flange and pipe metal. Cracks near the weld went deep into the flange, and carbide precipitation, grain sliding, and brittle granular precipitation could be seen.
Most telling were the FEA results. These confirmed that pipe flanges undergo severe thermal, internal pressure and bolt-loading stresses which, when combined, can lead to catastrophic failure. We at Chemipetro supply super duplex flanges, which are heat, pressure and chemical resistant. However, the importance of correct fitting must never be underestimated.
Tags: Flanges, Pipe Fittings, steel alloys, Super Duplex
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May 11th, 2010
We at Chemipetro supply pipe flanges and fittings in a wide range of corrosion-resistant alloys, which will resist most extreme conditions. However, you should still check their condition regularly, especially in highly acidic or hydrogen-rich environments.
High concentrations of hydrogen are widely found in the petrochemical industry, either through the pipe fittings of corrosive chemicals or as a side-effect of galvanic corrosion. Under these conditions, hydrogen ions can enter the metal by active or passive diffusion, causing it to become brittle. Eventually, it will crack.
In the 1970s, various experiments were carried out on the permeation rates of hydrogen into different types of steel. It was found that the cracking rate was consistent with the rate of permeation, and that hydrogen could be deposited in trap sites or at grain boundaries and other internal discontinuities.
Hydrogen traps can be reversible or irreversible. Reversible traps allow the hydrogen to diffuse back out. Irreversible traps don’t do this, and are therefore the most damaging. Fractures occur because the hydrogen lowers the surface energy of the metal.
Hydrogen embrittlement is related to the degree of strength that is already present in the alloy matrix. Metals that are in a state of higher strength, i.e. age hardened or cold-worked, are actually at a higher risk of cracking than those of a lower strength. Hydrogen diffusion coefficients are another factor. Titanium pipe fittings, for example, generally have higher diffusion rates than those with high aluminium content.
Modern alloys are constantly being refined. Buying your pipe flanges from us at Chemipetro will minimise the likelihood of hydrogen-induced cracking. It can be minimised further by good plant practice.
Tags: corrosion resistant alloys, Pipe Fittings, Pipe Flanges, titanium pipe fittings
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May 7th, 2010
Although modern flanges are made from highly corrosion-resistant alloys, such as duplex, they are quite often fitted to pipelines made of lower nobility metals such as carbon steel. This means there is a risk of corrosion at flange joints and other vulnerable areas.
If galvanic corrosion is allowed to take hold, it can weaken flanges, even those made from corrosion-resistant alloys. This is because, in a galvanic reaction, the higher nobility steel acts as a cathode. Although corrosion occurs on the anodic side, part of the galvanic effect is the evolution of hydrogen on the cathode side. This can result in hydrogen embrittlement of the metal.
Hydrogen embrittlement occurs when hydrogen ions enter the metal, weakening its structure. It has been reported in petrochemical components such as K500 drill collars and duplex flanges – in other words, alloys which are normally known for their strength. Therefore it’s important that pipelines are monitored efficiently, especially where corrosion-resistant pipe fittings are in contact with lower nobility metals, such as carbon steel.
Pipeline corrosion monitoring starts at the point of installation, and should then be ongoing. Pipe flanges create air-tight or liquid-tight seals. Once corrosion begins, that seal is broken. It then becomes a point of weakness, with the potential for catastrophic failure. This is especially true of buried pipelines – soil is a very corrosive environment.
Where pipe fittings are buried, a soil corrosion rate monitor should be used. Modern regulations demand that pipeline operators have measures in force to maintain integrity of pipelines, flanges and pipe fittings. A corrosion rate monitor will enable this to be done at relatively little cost.
We at Chemipetro would also recommend you use our super duplex flanges in corrosive environments.
Tags: corrosion resistant alloys, duplex flanges, Pipe Fittings, super duplex flanges
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