From below ground to below water - Offshore pipecoating - LKAB Minerals

MagnaDense is the most used high density aggregate in the world for Concrete Weight Coating applied to offshore pipelines.

LKAB Minerals, part of the Swedish state-owned high-tech mining and mineral company LKAB, have developed a unique capacity to supply large and small projects around the world. Something they have done since the start of the company in 1989.

Negative buoyancy, stability and mechanical protection

Oil and gas pipelines need to meet several requirements for different purposes. Especially, if we focus on the Concrete Weight Coating (CWC), it is applied to ensure negative buoyancy, stability and mechanical protection.

First of all, negative buoyancy is a downward force achieved by the weight of the concrete coating to prevent the pipe from floating, or in plain terms, the weight of the pipe has to be higher than that of the water displaced as dictated by Archimedes Principle.

Secondly, stability is needed to protect from external forces causing lateral movement such as tidal, currents and ice as examples.

And finally, mechanical protection is intended to protect the pipeline and other coatings (external corrosion coating) from mechanical and physical disturbance, e.g. construction, fishing equipment and anchors.

High Density Aggregates for pipelines

Concrete Weight Coating requires a higher density of the concrete to meet the thickness restrictions and still provide the needed weight. Here is where the aggregate comes into play.

Standard concrete, using conventional aggregates, can only achieve a typical density of 2.4 t/m3. Whereas, High Density Concrete, using MagnaDense aggregate, can achieve a concrete density of up to 4.0 t/m3. Therefore, when submerged, it means that 1m3 of MagnaDense concrete will be more than 100 per cent heavier than standard concrete. The reference densities mentioned are for construction concrete, however, the density which is possible to achieve for CWC will depend on the aggregate mix used,  application method and cement mix.

A “standard” minimum requirement for density is often ~3.0 t/m3 although for impingement coating this can be in the range up to 3.4 t/m3, the latter requires higher density aggregates and can easily be achieved with MagnaDense.

Pipeline project costs

When looking at the cost for a pipeline project, this will, of course, vary for each project and circumstances. In any typical example, the majority (often around 50 per cent) of the cost will be for the steel pipe. Next, another significant portion will be the coating material and operations, excluding High Density Aggregates. Finally, the last major cost component will be the installation. In comparison, the cost for High Density Aggregates will only be a small part of the total project. However, poor quality high density material (variable density or particle sizes, impurities, etc.) can lead to insufficient negative buoyancy and costly re-work, or uncertainty and project delays.

Sensitivity in choosing the aggregate and supplier

Perhaps the essential factor for any purchaser, when choosing aggregate and supplier, is the density to achieve the required weight. But when looking at the full process and sensitivity for the project, more factors come into play. First of all, consistency is a crucial factor, as this will allow a continuous and efficient production without variations and changes. Finally, on-time delivery will also be critical. It can be an overlooked factor if you would only consider the aggregate costs because any delay caused by product deficiencies or late deliveries can cause time delays and penalties for other parts of the projects which may be very costly. In addition to this, sustainability, pricing and service are important considerations.

Partnering in a global market

“LKAB Minerals are proud to be the selected and preferred supplier in numerous projects around the world for both Concrete Weight Coating and ballasting of offshore platforms and wind farms. Indeed, we are very active and successful in the energy sector” says Michael Lindman, Business Manager Offshore at LKAB Minerals.

Although seemingly far away from many of our customers, with our mines above the arctic circle in Northern Sweden, LKAB Minerals has recently been successful in supplying Concrete Weight Coating and Offshore projects located from Australia, the Middle East and Europe to the Americas.  Downward pressure on freight rates, particularly for large shipments, means we can economically deliver the products to many parts of the world that previously may have been uneconomic.

Impressive offshore projects

Some mega-projects for which LKAB Minerals supplied MagnaDense are for example ‘Nord Stream 2’ in the Baltic Sea and the ‘Tuxpan’ gas pipeline in Mexico, in addition to other projects. 

When it comes to other types of offshore projects, the resume is equally impressive. For example, LKAB Minerals supplied Equinor’s innovative floating wind park, ‘Hywind’ Scotland, the first floating wind farm commissioned. For this particular project, LKAB Minerals provided MagnaDense as an aggregate for High Density Concrete as well as loose ballast.

Ideal aggregate properties

“Our product is the star. MagnaDense offers ideal properties. For example, it is inert and non-toxic and does not leach in any way; also, LKAB Minerals produces it in sizes for industrial use and on top of that has a high specific gravity. In addition to this, we can deliver large volumes and consistent quality. Lastly, we have a proven track record and are a reliable partner with the confidence to deliver what we promise for any project“ Lindman summarises.

Aggregate competition

There are, of course, many competing products in the aggregate market. The relative strength of each aggregate is determined by several factors “We may not always provide the lowest cost product per tonne, but rather aim for the highest customer value and added service, such as reliable consistent-quality and providing customer’s the confidence of aggregate delivery.
The price of aggregates is relative to the density and quality, and with our specific gravity, the total volume need will be less than with many competing products. In addition, and more importantly, when in use, the sizing and sieve curve brings ideal compaction properties and strength of the concrete, something we have seen in tests as well as with our customers when trialling materials.” Michael Lindman explains.

Market Volatility

Over the last ten years, many in the pipe coating industry have felt the effects and frustration of volatile commodity prices, either directly with iron ore, or indirectly with base metal slags. “Many mines that supplied past projects are no longer operating, and many suppliers of by-product slag from base metal production may have production costs above the current market prices, which create uncertainty of continued sustained operation.  Our customers need the confidence that orders placed today can be delivered in the future, whether next month or next year.  This is another factor where LKAB Minerals’ competitive advantage is clear. With a mining heritage going back to the 1890s and being Swedish state-owned, we can provide the confidence customers, and project owners need. Because they know that their project will not suddenly be without promised aggregate” rest assures Lindman.

Sustainability becomes more important

In addition to product specifications and function in the customer process, other factors are gaining in importance and distinguishing suppliers. The leaching aspect and the content of the aggregate is one example. “Customers are increasingly interested in the product properties concerning leaching. In particular, as we have understood there is an industry concern with the use of by-product aggregates from base metal production as an example, which may contain contaminants,” Lindman says.

To respond to customer requirements, LKAB Minerals commissioned third-party testing even though MagnaDense is a natural iron ore product, in contrast with slag by-products from base metal production. As anticipated, the conclusion was that MagnaDense is expected to be unchanged in the composition of the ore after an exposure period to seawater of 50 years.  Furthermore, emission to seawater was tested and approved in compliance with the NEN protocol 7373:2004.

The proof is in the pudding

In fact and proving the point, the company has even repurchased material that had been in use for 22 years in Shell’s ‘Draugen’ Floating Loading Platform. This platform was commissioned at an oilfield 150 km offshore from the Norwegian coast. The reclaimed material was tested and compared with original shipping analysis that proved the material to be unchanged. With this reassurance, the material was therefore again offered to the market and sold to a customer in the construction industry.

As MagnaDense is produced from Magnetite iron ore, it is also ferri-magnetic. This means it will react to a magnet but is not itself magnetic. For practical purposes, this allows to easily separate the material with commonly used magnetic separation techniques, offering advantages for end-of-life management of installations. 

Coating application techniques

LKAB Minerals designed MagnaDense to respond to customer requirements to be easy to use in their processes, regardless if that is impingement coating, extrusion or slip-forming.

One of the reasons MagnaDense has outstanding use characteristics is the sieve curve. When talking sieve curves, quality and compaction, the industry often uses Fullers ideal curve as a reference. “Fullers curve details the ideal grading of material to achieve maximum compaction properties. Good compaction properties of the aggregate will translate to a few voids and little air, which, together with the cement/water ratio will contribute to high strength concrete. In the case of high density aggregates, this also means that you will be able to reach a high bulk density and take full advantage of the high specific gravity of the material” Michael Lindman commented on the benchmark with which LKAB Minerals compares their product.  

The opposite, using a material with similar specific gravity but low compaction properties would result in a lower total density for the concrete weight coating.

Lindman goes on to say “This is important to consider for buyers. If purely looking at the price per tonne relative to the specific gravity, without factoring in the compaction properties and bulk density, a purchaser may overpay for an inferior product.

Meeting the standard requirements

The MagnaDense sieve curve is tracking the Fuller curve almost perfectly. MagnaDense complies fully with the requirements of the European construction aggregates standard EN 12620. Even though not certified towards the other prominent standard, ASTM C33, the MagnaDense materials comply with this standard as well.

ASTM standard

Lindman explains “The ASTM standard does not require certification. It is also a bit more pragmatic concerning the grading of fine aggregate. If suppliers can demonstrate that concrete, with more fines, will retain the “relevant properties” and has been used successfully in similar concrete constructions, then strict adherence to the fine aggregate grading is not necessary.
As MagnaDense is the most used high density aggregate in the world for CWC, it is evident that MagnaDense fulfils the burden of proof and is a product under both European and ASTM standards”.  However, LKAB is continuously active in research and development to address all market needs in the main applications they serve, including CWC. “Traditionally our products have been prepared to European aggregate standards. However, some customers have expressed an interest in American ASTM standard, and we are exploring options that are right for our customers,” says Lindman.

Continuous developments of customer value

In recent projects, LKAB Minerals have more often assumed responsibility for the complete logistics to customer production sites, something that has made the process easier for customers as well as being more cost-effective. 

“Delivering a solution that takes into account confidence of supply, payment terms, logistics, technical advice as well as supplying an excellent product are key enablers for us going forward to maintain and develop our market position,” says Lindman.