ANTI CORROSION BARRIERR SYSTEM FOR PIPELINE / SEALINE

This service low cost anti-corrosion barrier system that can prevent hot-spot corrosion for more than 20 years and provide unbeatable protection for standby

and mothballed equipment.

	For the anti-corrosion protection of steel and other metals, especially flanges, pipework etc.; transit protection of machinery and components; long and short-term protection of stored machinery and components. Speedy stripping and re-application for inspection and maintenance on site.

SYSTEM OVERVIEW Humidity, extremes of weather and other factors, coupled with the difficulties of access, contamination and the effects of bimetallic corrosion on bolted systems, means that corrosion prevention in such systems is rarely completely successful. Electroplating and PTFE coatings are vulnerable to damage, non-corrosive bolts are expensive and still allow corrosion in the rest of the system, as do bolt caps, flange protectors and the like Until now there has been no cost-effective system that addresses all these problems, but, not only will solve many of these problems but we will do so with an estimated saving of as much as 85% over conventional techniques. World wide this means saving billions of pounds. Engineers, by adopting our system, will be able to attack corrosion within a reactive budget but at the same time will gain a pro-active, long-term solution at no extra cost. There are even more advantages to the our system - it is harmless to the environment and is completely re-usable. Unlike paint and tape wrapping systems our material is easy to remove by slicing and peeling away. The used material can then be replaced in the applicator to be re-applied once any required action has been taken. Thus no disposal problems arise, stocks can be kept to a minimum, with one material suitable for all sizes and shapes of joint, no matter how large or complex. When sprayed migrates deep within the flange and crevices. It contains a strong corrosion inhibitor which it releases wherever it is applied. The material cocoons the entire joint, sealing it completely from its environment thus preventing any deterioration. Hot salt water fog tests, equivalent to approximately thirty years exposure to a North Sea environment, have shown that, even under the most adverse conditions, the unique combination of the inhibitors and the sealing effect of the sprayed material prevents any corrosion occurring. Our protects completely, with bolts and joints emerging as fresh as they were when first treated. Our System Our system comprises the material and the specially designed applicator unit. The material, Enviropeel 170, is a thermoplastic polymer with built-in corrosion inhibitors. This means that the material, which has a hard rubber consistency when at normal ambient temperatures, becomes soft with the application of heat, becoming a sprayable liquid at its operating temperature of 170 degrees centigrade (hence the 170 in the name). The material is translucent in its standard form but is also available in five colours, red, blue, yellow, grey and white. The applicator, which also functions as a recycling unit for used material, representing a major advance in anti-corrosion application technology. The unit has two main components, the compressor, which provides the air to power the spray head, and the computer controlled heating and pumping unit. The pump has thermostatic controls throughout its delivery system, on the main tank, the air hose and the spray head - all of which are precisely monitored and controlled by a microprocessor. All components are contained within a grey and white housing which also contains the necessary tools and hoses. The unit has wheels and lifting lugs making it completely transportable for on-site use. The material is supplied as pellets, packed in tamper-proof plastic containers. On site the necessary amount is entered into the heating tank which takes only minutes to reach its operating temperature. Once at the correct temperature can readily be sprayed onto joints and pipes, building up layers to achieve the perfect seal around the components to be protected. While it is necessary, before coating to remove failed coatings and flaking rust which might trap moisture and prevent proper adhesion, this can easily be achieved with a wire brush. For optimum results blasting would be recommended, followed by a coat of primer but, since our system can be applied only 30 minutes after the primer coat, even this 'best case scenario' need not delay an ongoing corrosion prevention programme. In practice, cleaning with a wire brush followed by a coat should provide very acceptable results, with the addition of a quick primer coat before us if added security is required.

TROUBLE WITH FLANGES

Many crevices and annular spaces exist in the body of the flange and at the sealing faces. These are difficult to coat even on a new flange. When the flange is assembled, there is inevitable mechanical damage to any coating system used on the body of the flange inside the bolt holes, and of course on the fasteners. Bare steel is exposed, which is free to corrode in the atmosphere. When water is added from any source such as rain, offshore storms, wash down, drilling, the corrosion is exacerbated. The water causes corrosion products to be washed out of the flange gaps and drip onto adjacent painted surfaces.

Corrosion problems in steel assemblies such as flanges are made worse by galvanic corrosion induced by the differences between the components. This 'bi-metallic’ corrosion is a major factor in the failure of protection systems on flange joints.

The problem is enhanced on older flanges which already have corrosion inside. It is impossible to effect good surface preparation to surfaces which are inaccessible to the blast medium. Indeed, when flanges are painted, it is not uncommon to find residual blasting sand or grit lodged between the fasteners and the flange body, or up inside the bolt hole annuli. This grit acts like a sponge to retain water inside the flange and thus promotes rapid failure of any applied paint system.

The typical time to first visible leaching of corrosion products after a flange has been painted is three to six months. This figure can vary greatly depending on the location, size, and orientation of the flange. The problem of aesthetics is significant when an operator spends millions on painting platforms only to see brown corrosion products streaming from pipe flanges after only three months.

But aesthetics is not the main problem, crevice corrosion at the gasket to flange interface, usually a bi-metallic couple and progressive failure of neighbouring painted surfaces, these are the real problems.

ATTEMPTED SOLUTIONS

Before evaluating various solutions which have been tried and are being used, a list of the key attributes which the ideal system must have is given. They are, in order of importance: Must provide corrosion control for the life of the paint system

Should not use environmentally sensitive components

Must be safe and easy to apply.

Must be cost effective and require minimal maintenance.

Should be inspect able.

There have been a number of attempted solutions on offshore facilities, the list below represents the most common. A short description and analysis is provided for each approach.

FLANGE PROTECTORS

This system was originally designed to protect personnel and adjacent equipment from product leaking from the flange gap. It was modified into a corrosion control system later. There are a number of problems with this approach: 1. The crevice which is formed when the band is attached to the flange, actually accelerates coating failure on the outside of the flange. Ultimately, the corrosion products under the band will swell and cause deformation and even possible breakage of the band.

2. To be effective the system needs periodic maintenance to check and refill the inhibiting grease which is injected into the annular confines. This is completely impractical on an offshore facility and for most other land-based facilities.

3. Inspect ability is poor, corrosion could be ongoing under a de-formed protector, and there is no way to see it.

4. It is the most expensive of all the options.

CAULKING

The use of caulking type compounds of various types have been used. They are unsuccessful for the following reasons:

1. The caulk does not bond to the steel. It forms a tight crevice which retains water through capillary action.

2. Once the initial sea1 has been violated, the remaining caulk actually retains any water present by preventing natural evaporation, and thus exacerbates the problem.

3. The system provides no inspect ability.

FILLING AND TAPING

If the correct materials are used, this system can do a passable job of providing long-term corrosion control. However, it does have some drawbacks:

1. Very difficult to remove with no inspect ability or access to work on the flange if needed.

2. Highly labour intensive increases cost and installation time.

3. Often the sealing material does not displace all the water and does not dry the steel. This causes anaerobic conditions with associated microbial induced corrosion risk.

4. Many tape wrapping systems use components which are harmful to the environment.

TAPING ONLY

This is not a good idea. The tape invariably has a limited life, and when it fails, the problem is free to continue. This simply does not work.

WAX FLOODING

Temporarily sealing the flange and filling with a wax material is a valid approach. However, the system has some disadvantages:

1. Can be expensive.

2. No inspect ability

PAINT FLOODING

Seal the flange and flood with a conventional paint. This method will not work long term because the paints cannot establish a bond to corroded steel.

BOLT AND NUT CAPS

These involve the application of plastic caps over bolts and nuts, usually with some form of rust inhibitor applied before application. Effective but limited, they suffer the following disadvantages:

1. They only protect the fixings, not the flange itself

2. Different sizes are required to accommodate different bolts, requiring large stocks

3. Some situations do not allow sufficient space for their use

4. They are expensive

CONCLUSION

Clearly, while offering some reduction in the amount of damage caused by corrosion, solutions currently available to industry leave a lot to be desired. None fulfill the list of criteria with which we started. This is why Alocit developed Enviropeel which fulfills all the requirements set out above - and more - see the Q&A page for details

ASTM TESTING

As part of the ongoing testing programme has undergone various trials, including the very severe ASTM B117 hot salt fog test. Results after 3000 hours (the equivalent of 30 years in a hostile marine environment) show that pipework protected by us was unaffected by corrosion whereas the portions exposed to the corrosive elements were severely corroded.

The photographs show the contrast between the exposed and protected portions of one the test pieces. The corrosion on the unprotected pipe was such that the flange would have been completely unserviceable.

The flanges on the test pieces, however were in pristine condition, without any rust, even the nuts and bolts were in their original condition.

APPLICATIONS

Wellheads

Wellhead/Christmas Tree assemblies are found at the top of conductors (a series of steel casings) which form the drilled aperture to the underground, or under seabed, reservoir. They are found in the harshest of conditions, especially on offshore platforms, where they are subject to a highly accelerated corrosive environment. As they form a safety barrier between the reservoir formation and the environment, should any component fail there cou1d be considerable environmental damage. Because of this vulnerability to extremes of environmental conditions, the wellhead assembly has to be completely protected against corrosion.
First the substrate is cleaned, removing old coatings and rust and then the wellhead is primed with Alocit 28.15 because of the damp and oily residues. Following this the Enviropeel is applied, providing perfect protection from all corrosive forces.

Gas Production Plant

This gas production plant in Malaysia needed a fresh look at the corrosion problems it suffered, requiring constant maintenance.

The rust products streaming from the flange illustrated left show how difficult it is to prevent corrosion in such situations. The pipes are well maintained yet, despite repainting, rust reappears within weeks. By coating the flanges with our service the problem is completely prevented.

The valve above shows how problems become more than just aesthetics - this valve will soon be completely unserviceable..

Ground Penetrations

When pipelines go underground, the interface between soil and air is the area which suffers most from corrosion. Traditional cures involving bituminous coatings and tape wraps can be effective in the short term but are often hazardous to the environment and can ‘unwrap’, trapping moisture and making the situation worse. We can eliminates these problems and provides long-term effective protection.

Long term, effective protection
Full encapsulation of vulnerable soil/air interface
Greater integrity (will not unwrap)
Easy to inspect, remove and re-apply
High dielectric strength
No environmental problems

SOLID, ONE-PIECE ENCAPSULATION OF VULNERABLE AREA - NO UNWRAPPING/TAPE FAILURE PROBLEMS

VAPOUR CORROSION INHIBITORS

The use of Vapour Corrosion Inhibitor impregnated foam adds a whole range of possibilities. Large voids can be easily protected by the insertion of foam strips which release corrosion inhibitors into the area enclosed by us. The pictures show the foam inserted into a void before spraying plus some examples of finished flanges and fixings