Corrosion protection for valves and pipes

Paul Boughton

Corrosion protection is a big industry, especially against that of H2S (sour gas) corrosion of steel. Brian Zielinski-Smith reports.

With the advent of oil exploration and recovery of deep natural reservoirs, CO2 has been used to enhance recovery; this introduction along with the presence of naturally forming hydrogen sulphide (H2S) produced by sulphate-reducing bacteria, and free water can cause severe corrosion problems within pipelines and valves. This type of corrosion is heavily influenced by, H2S, and CO2 content, water chemistry, flow velocity and the composition/surface condition of the steel used.

When just one of these factors change, the corrosion rate of steel changes drastically. The result of this corrosion can in most cases be a costly replacement which exceeds by many times the cost of corrosion control.[Page Break]

Wasting resources

Recognising that corrosion is a major player in the waste of precious natural resources and causes endless problems when operating in these conditions, Welding Alloys has made major investment in developing new technology to handle the hot wire TIG process of depositing base metal/overlay combinations which form protective barriers in valves and pipelines, to name a few; namely those of austenitic, 22Cr duplex and 25Cr super duplex stainless steels and nickel/cobalt based alloys, eliminating the need to produce a whole component or item of plant from an expensive corrosion resistant material.

Within the oil and gas industry, quality control and monitoring is paramount, insuring pipelines are well maintained, avoiding inclusions of cavity corrosion which lead to pipeline and valve failures.[Page Break]

Control system

As corrosion protection is an integral part of pipeline creation and maintenance, the new control system from Welding Alloys is specifically designed for this application and focuses on meeting the stringent quality requirements of valves and pipeline cladding within this industry.

The company has been able to differentiate itself by allowing online and real-time weld deposit monitoring and full data logging functionality.

Because of this it is now possible to provide a full and comprehensive 'quality trail' for every part clad; in addition, this allows the systems' controls and parameters to be completely customised and programmed, minimising production time and increasing weld deposit control by giving precise feedback and position information.

The oil and gas exploration and recovery industry has had major financial investment in recent years, especially within the research of new procedures and materials for corrosion protection. Significant outlay is made at Welding Alloys to continuously develop and review products and procedures in order to provide the best solution available.

Thorough testing and assessment has played a vital and key role in the advancement of corrosion resistance through cladding with extensive R&D being carried out by Welding Alloys on both its control systems and machines.[Page Break]

Field tests

Welding Alloys can report that through metallurgical and field tests, the valves and pipes clad utilising their specialised control technology and precision mechanics showed that after extensive use, no significant corrosion damage had occurred.

Welding Alloys reports that its control system significantly increases the accuracy of its weld deposits minimising weld defects and rework found in more traditional manual or basic hot wire TIG operations, proving to be an additional USP for their product range.[Page Break]

Welding wires

Welding Alloys Group manufactures a wide range of flux cored and metal cored welding wires - low, mid and high alloy hard-facing, mild steel fabrication, stainless steel, nickel base, cobalt base - all in diameters ranging from 0.9mm to 5mm, using our own manufacturing technology. The company also manufactures a range of aluminium welding wires and have now added a range of manual electrodes to complete their consumables offering.

Additionally, it makes custom-designed modular welding equipment, including semi-automatic wire feeders, portable automated machines for in-situ work and fully automated machines including component manipulation with robotic controls. Since 1974, Welding Alloys has manufactured and installed machines, providing operator-training to customers in more than 45 countries.

Complementary to the company's product manufacturing, its Integra division specialises in providing welding services using its own materials for the hard-facing and cladding of components worn in service.

The company's knowledge of service conditions of worn components enables it to recommend the appropriate welding method and welding materials to provide exceptional component service life, always exceeding the original performance.

Enter √

Brian Zielinski-Smith is with Welding Alloys Ltd, Fowlmere, Royston, Hertfordshire, UK.

Recent Issues