Robert Miller, Abakan Inc., explains how a new method for the seamless cladding of pipes is enabling the development of subsea oil resources in ever-harsher conditions.
CermaClad utilises a high intensity arc amp (a ‘mini-sun’) up to 1 MW in power to rapidly fuse protective materials onto metals. The general purpose of cladding is to protect the underlying steel from the environment by applying a thin layer of expensive protective material, which represents a fraction of the cost of using a product that is made completely out of the expensive protective material. While metallurgically clad carbon steel is much cheaper than solid steel alloy, the conventional technologies used to produce it - weld overlay and laser cladding - are slow and cumbersome and have seen little to no improvement in decades. The long lead times and undesirable properties (base metal dilution, pinholes, roughness) of clad pipes produced through these technologies have forced oil and gas companies to select lower quality, mechanically lined pipe or roll-bonded, plate-to-plate options. The other option for large-diameter metallurgically clad pipes involves using a roll-bonded clad plate, which is then bent and welded to form a pipe. Although this is a higher productivity process, it involves a lot of welded area, especially in pipes with diameters larger than 14 in., which require spiral welding since the plates are not large enough to weld longitudinally. This poses a problem since failure of weld is the single most common reason for pipeline leaks. The mechanically lined (bi-metal) pipe that now makes up a significant portion of the clad pipe market costs less than metallurgically clad pipe, but provides only marginal contact between the inner and outer pipe, leading to a higher possibility of buckling, wrinkling and disbonding during application of external coatings and during subsequent installation and use. These pipes also raise concerns with respect to uniformity and reliability; and the air gap, coupled with the mixture of materials, leads to challenges in NDT (non-destructive testing) inspections that contribute to risks associated with reliability.
The industry is witnessing an increasing demand for thick-walled and large-diameter clad pipes driven by high-pressure high-temperature (HPHT) reserves that are further away from the shore and in much deeper water. The clad plate-to-pipe and the mechanically bonded pipe-in-pipe alternatives do not bode well for thicker and larger pipes due to multiple reasons highlighted above. CermaClad is a feasible alternative for thick-walled clad pipes used heavily in the Gulf of Mexico, and the large-diameter clad pipes used heavily in the Asia-Pacific region.
In addition to speed, efficiency and cost, this technology can also provide other advantages over conventional pipe cladding technologies, such as improved metallurgical properties, including a 50% higher bond strength at the interface with the base metal structure and improved structural integrity of the base material, which is achieved by limiting the penetration depth of the thermally affected zone during the cladding process, as well as lower dilution and porosity, which make it a better quality product. Another advantage is smooth, uniform and seamless surfaces that require no costly post-processing. Finally, such smooth surfaces mean decreased flow resistance, reduced friction in pipeline applications and, as mentioned, improved inspectability, thus reducing the risk that potentially catastrophic coating defects will be overlooked. In 2012, Det Norske Veritas (DNV), one of the world’s largest global risk management and testing labs, confirmed that CermaClad clad products meet the API 5LD and DNV-OS-F-101 standards for clad pipes used in extremely challenging subsea applications.
By enabling higher productivity of high performance cladding products, this system has helped change metallurgical cladding from a preferred option to the option with the highest benefit/cost ratio at the lowest risk for use in the world’s most extreme environments.
Part 1 of this article can be reached here.
Adapted by David Bizley
Read the article online at: https://www.oilfieldtechnology.com/exploration/07112013/getting_creative_with_cladding_part_2/