March 25th, 2010
Flange shields are used to protect the faces, studs and gaskets on pipe flanges from atmospheric corrosion. Even with modern, highly resistant alloys, corrosion is still a problem – especially in refineries, gas plants and underground pipelines. To extend the life of modern pipe flanges, flange shields are therefore recommended. Designed to fit round raised face, full face and ring-joint flanges, they can cut maintenance costs considerably.
Many plant owners think it’s enough that they fit high-spec alloy flanges, such as those we supply at Chemipetro. However, environmental factors such as GICs (geomagnetically induced currents), UV radiation, dust and grime can play havoc with even the most up-to-date pipe fittings. Using shields can reduce these effects dramatically, leading to longer life and decreased chance of leakages and plant failure.
Flanges may be fitted with cloth or metal shields. The latter are available in a variety of alloys, including duplex. They are designed for high temperature, high pressure and highly corrosive environments. Shields fitted with spacing rods, which separate the shield from the flange, are especially useful where lateral and/or frontal sprayouts are a problem as they dampen the pressure.
Cloth shields are used in less extreme environments, or as extra “insurance” where high-spec flanges are already in use. They have the advantage of being cheap, and easy to fit. PTFE, polyethylene, PVC and polypropylene are the most common materials used.
Although the use of alloy shields can reduce running costs, especially on older plants, they should never be used over faulty flanges. Shields are not industry regulated the way pipe fittings are, and using them to “patch up” existing problems such as corrosion, cracking and leaking is both dangerous and illegal.
Tags: alloy flanges, Duplex, Flanges, Pipe Fittings, Pipe Flanges
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March 24th, 2010
We at Chemipetro supply flanges and pipe fittings made to rigorous, modern industrial standards. Precision manufactured from highly resistant alloys, they are guaranteed to give quality service. However, not all petrochemical plants are of recent construction, and this can bring major problems – especially when site owners incorporate new components, such as flanges, with legacy materials, i.e. those installed when the plant was built.
Mixing old with new material makes plant management an extremely complex task. Personnel and management must know exactly what goes where, and have set procedures for each component that they must memorise and adhere to. This was brought to the fore at many old planets, such as Shell’s Pulau Bukom refinery, located on a remote Singaporean island. The site was reportedly rife with leaking flanges, unreliable pipe fittings and other problems. Under or over-tightening flanges was often the cause – pipe flanges have to be tightened to specific torques. Insufficient inspection of older pipe fittings was another problem – and it was costing Shell dearly. Their answer was to implement a training program to give personnel a better understanding of tightening and inspection of flanges.
Shell’s Total Flange Assurance program was a short course aimed at the 200 existing staff and contractors, which became part of the induction procedure for new staff as well. Lasting one day, it included basic elements of inspecting pipe flanges; methods for assembly and hand-tightening; the importance of using the right lubricant following flange face inspection, and hand torque wrench usage and safety. By the end of the day, staff were proficient in the breaking out, inspection and reinstallation of a range of pipe flanges, using the right tightening technique. The scheme went live in May 2008 and has been a success for Shell and testament to their safety awareness.
Tags: Flanges, industrial pipe fittings, Pipe Fittings, Pipe Flanges
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March 23rd, 2010
If a fire breaks out at a refinery owing to poorly maintained or corroded pipe fittings, the results can be sudden and devastating. Plants are built to extremely high standards, and flanges are made to withstand both high temperatures and pressures – or they should be. Personnel are on duty 24 hours a day, and special detection equipment is installed, so faults and leaks should be targeted well before they become a dangerous problem. So why do some plants continue to have dangerous accidents?
The Valero oil refinery, in Texas City is still under investigation following a series of disastrous fires. The last was in December, 2009 – the second in a month, and started in a crude oil processing plant.
Despite the high number of people in the Valero plant on the morning of the fire, no-one was hurt, suggesting it broke out in an area where few personnel congregate and evacuation procedures were efficient. Refineries and other plants are full of areas like this – places where pipe flanges and fittings are installed, but rarely checked. These are the areas least likely to have sophisticated detection devices, too. Human error, laziness and over-tight budgeting constraints are common reasons why such accidents occur. The culprits of such incidents are, quite often, leaking or corroded pipe flanges – something that is easily preventable.
One way to minimise accidents is to install the highest quality pipe fittings in areas where checks are least likely. We at Chemipetro supply high quality pipe fittings and flanges to a wide range of clients – our main customer being the petrochemical industry.
Tags: Flanges, industrial pipe fittings, Pipe Fittings, Pipe Flanges
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March 18th, 2010
Avoiding leaky flanges is paramount to safety at any industrial plant. Traditional ANSI flanges have been used for decades, and are still the most common choice for plant components at petrochemical plants. However, they are prone to leakage – something which needs to be addressed.
A number of improvements have been made to pipe fittings in recent years. For example, the new pressure connections, such as those we supply at Chemipetro, practically guarantee a leak-free performance. However, flange designs, for all their variety, have remained resolutely traditional. Their tendency to leak has been improved by modern technology, but not eliminated.
Conventional ANSI flanges are fitted by bolting two faces together, compressing a gasket and creating a seal. Integrity of the joint, and loading on the bolt, largely depends on the torque applied to the bolt when it is tightened.
The torques applied to pipe flanges are very specific. Therefore the proper procedures must be followed in order to avoid under or over-tightening and gasket leakage. However, even if the flanges are tightened exactly to industrial specifications, factors such as thermal expansion, internal pressures and fluctuating loads can cause movement between the flange faces.
The design of ANSI flanges means 50% of the bolt load is needed to compress the gasket, leaving only 50% to hold the pressure. Sudden, unexpected surges in line pressure, especially, can force the flange faces apart, placing stress on the bolts and creating an inefficient seal. Essentially, then, pipe flanges are inefficient.
Recent developments include patented compact flanges and API flanges. The latter withstand much higher pressures than traditional ANSI fittings.
Tags: ANSI flanges, Flanges, Pipe Fittings, Pipe Flanges
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March 16th, 2010
We at Chemipetro supply pipe flanges for the petrochemical industry in a range of resistant alloys, for example Duplex, Super Duplex and 6% Molybdenum (6Mo, or Moly 6).
These alloys are highly resistant to pitting, chloride corrosion and stress cracking, and offer excellent weldability and impact resistance. Duplex and Moly 6 pipe fittings are often used in the same installation, as they are highly compatible.
However, marine environments create particularly corrosive conditions for pipe flanges, which can defy even the most resistant of alloys. This was proved after the installation of the Sleipner A North Sea oil platform, in 1992/93. At the time, stainless steel alloys like austenitic molybdenum and super duplex were being widely deployed on seawater piping systems. For this reason, Sleipner A was fitted with 6Mo pipe fittings and 25Cr super duplex valves on the firewater piping system.
These alloys were qualified for use in seawater systems at a temperature range of 30 – 53 degrees celsius, which at the time was thought to be more than adequate.
However, just 18 months after installation, extensive leaks were discovered in sealed areas around flanges, valve components and threaded pipe fittings. This had been observed in other platforms. It was discovered that although the flanges performed well within the established temperature range, peaks above or below this had a catalytic effect on corrosion rates.
The answer was to fit a new galvanic resistor system to the platform, to withhold corrosion at extreme temperatures. Studies 10 years later show this is a highly efficient system, minimising further corrosion of flanges and pipe fittings.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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March 11th, 2010
Alloys have progressed enormously in recent years. From basic ferritic and austenitic stainless steel, a whole plethora of exotic alloys have been formed. Super duplex, 6% moly and titanium are just three metals we at Chemipetro use to manufacture petrochemical flanges and pipe fittings.
These exotic metals are often called noble alloys. In fact, pipe fittings made from noble alloys would be prohibitively expensive, since they would need a noble metal content of 25% or higher. In metallurgy, noble metals are the rare group that includes iridium, rhodium, palladium and osmium – as well as gold, silver and platinum. These are used it is in trace amounts, alloyed to superior metals like titanium and molybdenum, so what the term means is corrosion-resistant, superior alloys like duplex, titanium and molybdenum.
A high degree of resistance is necessary in undersea pipelines and oil drilling platforms, owing to highly corrosive sea water. 6% moly and super duplex steels are commonly used in seawater piping systems, as they combine corrosion resistance with weldability and strength. However, if they are coupled to less noble metal – as is often the case – galvanic corrosion occurs. Typical examples would be partial replacement of old, cement lined carbon steel pipes with new, duplex steel ones, or coupling standard stainless steel pipes with titanium or duplex flanges.
The way forward is to use noble alloys throughout the system, but this usually isn’t feasible. Instead, various methods are used to reduce corrosion in other ways. These include isolating flanges, insulated spools and internal cathodic protection. To date, cathodic protection has been the most successful, and is the one mainly used.
Tags: Duplex, Flanges, Pipe Fittings, Pipe Flanges, Super Duplex
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March 10th, 2010
Industrial flanges and pipe fittings comply with standard dimensions – ANSI, API etc. This means companies like us at Chemipetro can easily supply flanges to companies across the world, and industrial plants can run with quiet efficiency – so long as the components are made to set standards of compatibility.
Industrial pipe flanges are used in many important areas, apart from the petrochemical industry. One in particular, the shipbuilding industry, shows the importance of installing compatible pipe fittings.
Modern shipbuilding is done in “blocks,” outsourcing different parts of the operation to different companies. Standardised systems of measurement are used, making ordering of stock quick and economical – so long as the same standards are applied across the entire outsourcing network.
This once wasn’t the case in the US Navy. A 1990 National Shipbuilding Research Program paper described how US ships installed a combination of pipe flanges – often in the same system. Commercial (ANSI) and Navy pipe flanges (Mil-Spec) were almost identical in terms of pipe sizes, pressure ratings, alloys etc. However, their physical dimensions – thickness, diameter bolt holes etc – made them totally incompatible with each other. The valves, pumps etc using those flanges were likewise unique.
This led to confusion for the installers, logistics and operations staff. It also meant very large ship stores, as the only answer was to provision two flange systems on each ship. The NSRP saw that non-compatibility was a serious problem, and streamlined the system by eliminating either Navy or ANSI flanges to create a standardised protocol. But until then, the costs – not to mention wasted man hours – were crippling.
Tags: ANSI flanges, Flanges, Pipe Fittings, Pipe Flanges
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March 9th, 2010
Deep into an exploration of the wreck of HMHS Britannic, one of the divers began to panic. He had lost his way – disturbed silt had left him blinded, and air was running out fast. Luckily, working by feel, he manoeuvred himself out of danger – guided by the unmistakable contours of a massive pipe flange he had marked earlier.
Corrosion-resistant pipe fittings and flanges have long been a trademark of the shipping industry. The precision engineered, high-quality alloy fittings we at Chemipetro supply to the petrochemical industry are also used in ship systems, so it’s worth taking a look at them.
Warfare has long been dependent on functioning Naval fleets, so when the arrival of submarine technology took the industry to a new level, much research went into making components capable of operating for extended periods of time underwater. Today, military scientists and industrial engineering companies work side-by-side to develop flanges worthy of the high-pressure pumping systems fitted to today’s turbo-powered behemoths – both above and below water.
In 2005, NPCA’s annual Marine and Offshore Coatings Conference coerced with the Fleet Corrosion Control Forum, NSRP and other bodies, to discuss the specific corrosion problems facing flanges and other fitments in naval submarines.
The conference added that a few subs “are used for scientific or business purposes.” This takes us full circle. That ill-fated diver got into trouble because his self-designed mini-submersible was too unwieldy to do the exploring for him. A case of bigger not always being best – which is why marine pipe fittings come in all sizes.
Tags: Flanges, marine pipe fittings, Pipe Fittings, Pipe Flanges
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March 4th, 2010
We at Chemipetro supply a wide range of precision-made pipe fittings and flanges for use in the oil, gas and petrochemical industries. Our pipe flanges, tee-joints and other fittings are widely used in offshore oil platforms; onshore oil and gas plants; submarine pipelines; chemical injection systems and fuel and lubrication systems.
Flanges and pipe fittings used in these industries must show excellent chemical and atmospheric resistance. They must have low maintenance requirements and be strong enough to withstand sudden changes in environmental temperatures and pressures. High-profile and exotic alloys, such as super duplex and titanium, are the norm. Extra precautions, such as cathodic protection, are used where necessary.
Industrial pipe fittings are not just used on drilling platforms and in refineries. They are also used in power plants. Fossil-fired, biofuel, hydroelectric and combined cycle plants all require leak-proof pipe fittings in a variety of configurations and alloys. The nuclear power industry has particularly stringent demands.
Valves, hoses and pipe fittings are used extensively in power plants to control fluid and gas flow. Hydraulic pumps, rotary actuators, accumulators, stationary compressors and gas exchangers are just some of the components reliant upon high quality pipe fittings. To minimise leakage and corrosion, as well as maximise pressure resistance, plants use pipe fittings made from titanium, duplex and other fine alloys.
Often, stainless steel alloys are used alongside softer, more flexible materials for easy bending, routing and installation of plant components. We at Chemipetro have probably the largest range of industrial pipe fittings in the UK, and can custom-design components for non-standard procedures.
Tags: Flanges, industrial pipe fittings, Pipe Fittings, Pipe Flanges
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March 2nd, 2010
Traditionally, oil rigs and workover rigs (which are used to increase production from established rigs) employ a vertical hoisting mechanism, or draw-works. This takes in or spools out a drilling line to raise or lower a travelling block – a system carrying the jointed drill-pipe assembly. The draw-works is connected to a derrick, which is connected to the ground. In this system, the weight of the tubular components is not transferred to the wellhead, and therefore stress on the flanges is minimised.
With the depletion of oil reserves new drilling methods, such as directional (non-vertical) drilling have become common. New technology allows the angle of bore to extend 90 degrees and beyond. For rigs like these, coiled tubing, rather than jointed pipe, is used.
While this offers numerous advantages compared to conventional drilling operations, there are drawbacks. The main one being that instead of a draw-works, an injector head is used. This is connected directly to the wellhead, via flanges or couplings. The wellhead is therefore subjected to considerable loads. As well as the weight of the tubing in the well, there are additional stresses generated by the twisting movements of the coil on the surface. The components affected include the Christmas tree joints, tee-joint pipe fittings, blow-out preventers, risers and casing flanges.
The method used to transmit the load back to the ground, rather than the wellhead, is a system of simple chains, which are ineffective. Now, rigid framework rigs are being tested. In the meantime, we at Chemipetro recommend rig owners buy the strongest flanges and pipe fittings they can.
Tags: 45 & 90 degree elbows, Flanges, Pipe Fittings, Pipe Flanges
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