April 29th, 2010
Titanium flanges are among the most noble of pipe fittings. Which is a rather regal way of saying that they are usually more corrosion-resistant than the pipes or pipe fittings they’re connected to. We atChemipetro supply pipe flanges in a wide range of alloys. Naturally, you want the most corrosion-resistant ones possible – but you must take the existing plantmetallics into account. For example, if the pipeline is an old, solidly-built carbon steel construction that relies on sheer density and thickness to keep corrosion at bay, you could actually upset the apple-cart by installing state-of-the-art titanium flanges.
The further apart two metals are in the galvanic series, the faster galvanic corrosion will occur. Naturally, this can only take place where there’s an electrical connection in the presence of an electrolyte – but this is exactly the environment you find in a lot of petrochemical installations, especially offshore ones.
The rate and extent of corrosion will vary depending on the size of the area connecting, and the size of the two components. The rate is greatest where the cathode (i.e. the more noble element – in this case, the titanium flange) is large in comparison to the anode (the steel pipeline). If the situation is reversed, and the anode is large relative to the cathode, little corrosion will occur.
Today, compact pipe flanges are being patented that reduce the corrosion potential of dissimilar metal contact. However, these may not be compatible with existing plant systems, so the best advice is to buy standard titanium flanges – but isolate them from less noble metals.
Tags: Flanges, Pipe Fittings, Pipe Flanges, strong alloys, titanium flange
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April 27th, 2010
We at Chemipetro make flanges in a wide range of corrosion-resistant alloys for offshore use. Titanium is a popular choice for pipe fittings, owing to its high resistance to corrosive elements. However, this can cause unexpected problems if the pipeline itself isn’t of similar quality – in essence, galvanic corrosion.
Galvanic corrosion occurs when two widely dissimilar metals are coupled together in the presence of a strong electrolyte, such as seawater, and with good electrical contact. In the absence of any of these factors, galvanic corrosion will not occur. Pipe flanges and other joints represent an area of weakness, and thus corrosion-resistant alloys such as titanium and super duplex are widely used in seawater environments. However, it’s unfeasible to use these metals along the entire pipeline, and so galvanic corrosion can potentially occur.
In galvanic corrosion, the less noble (i.e. less resistant) metal acts as an anode, and the more noble alloy acts as the cathode. The two form a galvanic cell, behaving like a zinc battery. Titanium pipe fittings are highly noble, and so will behave as cathodes where there is an electrolyte and good electrical contact.
The rate of corrosion is dependent upon several factors. However, if the nobility of the connecting metal is low, and the area of exposure large, titanium flanges can cause more rapid damage to a pipeline than if a less resistant alloy was used. The answer isn’t to install lower quality flanges, but to remove any possibility of the metals coming into contact and forming a galvanic cell.
Tags: corrosion resistant alloys, Pipe Fittings, Pipe Flanges, Super Duplex, titanium pipe fittings
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April 23rd, 2010
We at Chemipetro supply a wide range of pipe fittings and flanges for the oil and gas industries. However, there are still many old, corroded flanges causing immense damage to marine and freshwater environments. Unfortunately, it’s not always possible to identify the source, and thus fine the guilty company.
An exciting new invention by Saudi Aramco scientists looks set to change that. The state-owned company, which is the world’s largest oil-producer, has an R&D team who are constantly at the forefront of oil research. Now, they have developed a laser system that can identify and catalogue an oil leakage from its unique fluorescence spectrum fingerprint, in just a few nanoseconds.
Robust enough to withstand challenging field conditions, the multipurpose laser device is safe, transportable and easy to use. The company is now working on a helicopter version that will detect and identify water seepage from leaking pipe flanges – a considerable advancement on current methods, which involves personnel having to examine pipe fittings in often treacherous conditions.
The company say their fluorescence fingerprint identification method will quickly and easily identify the exact grade and commercial origin of each type of oil, and is a major advancement in environmental safety.
Badly corroded and poorly maintained flanges are totally avoidable. Often, they are due to mismanagement and overzealous budgeting, by companies who think they are beyond detection. Hopefully, Aramco’s new system will encourage these companies to get rid of their faulty pipe fittings, and install high quality flanges like those supplied by us at Chemipetro instead.
Tags: high quality flanges, industrial pipe flanges, Pipe Fittings, Pipe Flanges, pipe replacements
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April 21st, 2010
Deep sea fields are an important source of gas and oil. However, the environment makes acute demands on pipelines, flanges and fittings. This is especially true of FPSO (floating production storage and offloading) units.
FPSOs are used to process and store gas and oil from nearby platforms or undersea projects, until such time as the processed product can be transported to shore via pipeline or tanker. They are easily installed, and may be purpose-built or adapted from tankers.
The natural environment that FPSOs operate in imposes tremendous stresses on the pipe fittings, joints and flanges, especially where they connect to the pipeline. Therefore solutions to lessen these risks are constantly sought.
The vulnerable point of any deep water FPSO system are the risers. In shallow water, these pipes attach to large, steel jacket legs of fixed platforms using high tensile pipe fittings. These ensure the riser is protected from extreme environmental conditions. Floating deep water units are not rigidly fixed; thus any motion they undergo is transmitted to the risers. The flanges are the weakest point.
One way to avoid this is by developing FPSOs based on a ship design. In extreme conditions, the risers are disconnected and the ship removed to quieter waters. This method uses rapid-disconnection risers mated to special pipe flanges, which create a strong seal to prevent fluid leakage. The result is freedom from environmental stress, and fast reconnection.
We at Chemipetro have a wide range of pipe flanges, including slip-on, adapter and blind flanges – all of which are used in subsea operations.
Tags: Flanges, high tensile pipe fittings, Pipe Fittings, Pipe Flanges, pipe joints
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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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April 13th, 2010
Galvanic corrosion is an important issue in modern pipe flanges, and this includes those made from corrosion-resistant alloys, like those we supply at Chemipetro. Much research has been done on preventing corrosion in pipe fittings used in marine environments, which is where the problem mainly occurs.
Galvanic corrosion is due to an electrochemical process, and has nothing to do with inferior alloys. It occurs when two alloys with differing noble (non-corrosive) metal contents are joined in the presence of an electrolytic solution, producing a galvanic current. It’s the method by which carbon-zinc batteries produce a charge – corrosion being an unfortunate side-effect.
Galvanic corrosion is a serious problem in marine flanges. Different alloys have different properties, and it isn’t uncommon for duplex pipe fittings to be coupled to high tensile stainless pipes. When this happens, you get a galvanic coupling effect, due to the differing electrode potentials of the two metals. The part with the highest noble metal content, i.e. the flange, acts as the cathode, and the other acts as the anode. In the presence of an electrolyte (i.e. seawater) metallic ions flow from the anode to the cathode, causing corrosion at the anodic side. The result is that you get rapid corrosion that would not have occurred in either metal alone.
The problem occurs whenever two unequal alloys meet, no matter how expensive they are. Titanium and duplex are both highly resistant alloys, yet if they’re put together (titanium flanges with duplex pipes, for example) galvanic corrosion is inevitable. The development of cathodic protection systems has helped considerably in extending the life of marine pipe fittings.
Tags: Duplex, duplex pipe fittings, Flanges, Pipe Fittings, Pipe Flanges
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April 9th, 2010
We at Chemipetro supply a wide range of pipe flanges for the petrochemical industry, of both welded and non-welded design. Slip-on flanges are an example of a welded fitting. They are designed to go over the end of a pipe, which is then welded on both sides to create a leak-proof seal. Quick and easy to install, they are manufactured by us in a range of alloys including super duplex steel.
The main drawback with slip-on flanges is that they are not suitable for high temperature or high pressure applications, due to the lack of strength at the joint. While there is a certain amount of flexibility with metal contraction and expansion, they will not stand up to extreme conditions.
Weld-neck flanges are the most common type used in industry, and are especially useful in high pressure or high temperature systems. They have a long, tapered hub which gradually thickens towards the butt weld end, i.e. where the flange joins the pipe. This design reinforces the weld, thus making this type of flange superior in terms of strength and distortion resistance (dishing).
Lap-joint flanges lie somewhere between the two other types. The flange attaches to a special stub-end sleeve, which has a narrow shoulder (hub) one end and a weld bevel at the other. The rear face of the hub has an interior fillet to join it to the flange. The flange itself lacks the raised face of other pipe flanges, and slips on to the stub-end sleeve before the sleeve itself is welded into place – the flange itself in non-welded. Lap-joint pipe flanges are therefore free to spin, making them easy to align and dismantle.
Tags: Flanges, lap joint flanges, Pipe Fittings, Pipe Flanges, weld neck flanges
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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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April 5th, 2010
There are two threats to super duplex pipe flanges used in corrosive environments:
1) Galvanic corrosion caused by the presence of a lower-nobility metal, for example carbon-steel tubing or bolts. Modern super duplex pipe fittings, which are highly corrosion-resistant, are often coupled to metals much lower in the galvanic table.
2) The risk of explosion from ignition sparks; a common problem where pipelines are used to transport volatile fluids, and often a secondary effect of galvanic corrosion.
Good engineering practice involves both regular checks to pre-empt possible problems and having structures in place to prevent those problems arising in the first place. Cathodic protection is the most obvious answer. However, it only lasts as long as the “sacrificial” anode does, and should be a final seal of defence, rather than the first.
The easiest way to ensure good flange management is to isolate the fittings from their corrosive environment (in the absence of an electrolyte, corrosion won’t occur). For this reason, flange protectors are routinely used. The best type are made from high-alloy stainless steel with a closed-cell, non-metallic liner, and are packed with corrosion-inhibitor grease. Designed to protect the bolts and gaskets of raised-face and ring-joint flanges from seawater and other electrolytic fluids, they are easily fitted with no need to split the flange, and offer protection against unsightly and potentially hazardous build-up of corrosive materials.
We at Chemipetro supply precision-engineered pipe fittings in a range of corrosion-resistant, non-reactive alloys. These are guaranteed to give long life and service to any petrochemical plant, but only if a program of preventative maintenance is in place.
Tags: Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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