Nickel-containing materials contribute towards a sustainable society

By The Nickel Institute

Nickel-containing materials are all around us: in the infrastructure, in our buildings, in our industrial installations, in our transport systems and in many of the products we take for granted in our everyday lives. Yet they are largely unrecognised.

Nickel-containing materials provide performance, durability and sustainability through a combination of corrosion resistance, strength, ductility and special physical properties, coupled with a high degree of recyclability at end of life. This enables them to provide innovative engineering approaches which help sustainability in such diverse applications as:
• building and infrastructure construction;
• chemical production;
• communications;
• desalination and water distribution;
• energy supply – including oil, gas and batteries;
• electronics;
• environmental protection;
• food preparation;
• medical equipment;
• transportation.

Case study 1: Nickel-containing materials are proven, reliable performers in the oil & gas industry
Nickel alloy heat exchanger
The unique attributes of nickel-containing materials make their use in the oil and gas sector a sound engineering and cost-effective investment.  Here are some examples where the engineering requirements are demanding and nickel-containing materials are the proven solution. They provide life-long integrity with the potential for re-use in other projects, and their high intrinsic value is such that recycling is cost-effective and well-established:
• Deep wells need tubing that is highly resistant to corrosion. For example, nickel-containing stainless steels can be cold-worked to 965 MPa yield strength and still retain high toughness and resistance to corrosion.
• Precipitation hardenable nickel alloys can be heat treated to have high strength and hardness. These properties are essential for “down-hole jewelry” (a generic term for all the special tools that are incorporated into an oil or gas well) which need exceptional strength without developing sensitivity to hydrogen embrittlement.
• Nickel alloy, and stainless steel-clad and -lined pipelines solve the problem of transporting wet corrosive oil and gas without requiring inhibitor injection to prevent corrosion.
• Vessels made of 9Ni steel (containing 9% nickel) are a cost-effective option for liquefied natural gas storage vessels with an excellent track record of safe service. That’s because 9Ni steel has high toughness at cryogenic temperatures.
• Austenitic stainless steel piping and valves in low temperature sections of plant are essential for achieving reliable toughness down to cryogenic conditions. This is necessary because liquefied natural gas is transported at minus 164°C.
• Stainless steel and nickel alloy heat exchangers provide the optimum solution to the demands for heat transfer and long-term resistance to corrosion in equipment that is virtually impossible to protect by inhibitor injection.


Case study 2: Nickel-containing alloys in desalination
Multistage flash desalination plant
Desalination is essential throughout the arid regions of the Middle East to provide potable water. Currently about half of the world’s installations are in the Middle East and more are being built.

The nickel-containing duplex, super-duplex and super-austenitic stainless steels are becoming the materials of choice because of their superior corrosion resistance and greater strength. The standard stainless steels and the cupronickel alloys, which remain workhorses for desalination (at least at lower temperatures and chloride concentrations), simply cannot always provide the reliability required under more aggressive conditions.

Although the duplex and higher-nickel stainless alloys have greater unit costs, their strength allows them to be used in thinner gauges, thereby cutting both weight and cost to the point where the alloys are competitive with existing alternatives. This becomes more important as the design life of newer, larger plants increases (it is now upwards of 40 years on average).

Case study 3: Water distribution systems in high-rise buildings are evolving toward stainless steel
The piping systems that deliver potable water and fire-fighting capabilities in tall buildings have unique requirements. They must be able to withstand not only high pressures but the motion of the building caused by seismic and wind forces. Furthermore, the increased used of grey water in sustainable construction necessitates the use of more corrosion resistant piping and storage tanks. Speed and ease of assembly are also important during the construction phase as builders grapple with tighter deadlines and a more fluid, less skilled workforce.  As buildings grow ever taller, engineers are regularly using stainless steel piping systems to meet these needs.

The Taipei Financial Centre, a 101-storey, 509-metre-high building completed in 2004 uses a stainless steel system with grooved couplings for fire protection and plumbing for both hot and cold water.

This system provides the flexibility to withstand any seismic activity. Designed especially for standard or light-wall stainless steel, it is also less costly than traditional methods of welding, flanging or threading; that’s because it can be installed quickly using less skilled labour and needs little or no maintenance.

For smaller diameter piping systems that do not require ready access, a press-fit system provides economy, reliability and fast installation. The system uses stainless steel pipe with fittings that can be permanently attached using a handheld electric tool, eliminating the risk of fire and the need for welded or threaded joints.  This type of system is being installed in Brisbane’s tallest residential tower, the Aurora. "No other pipe systems can withstand extreme changes in water temperatures and the clean-in-place routines as well as stainless steel," said Mogens Jensen, Managing Director of Blucher Australia.

Case study 4: Stainless steel reinforced bridges for long life.
Think of the time and money to be saved if a bridge spanning a saltwater estuary were to require no maintenance for, say, 120 years. No need to break into the concrete piers to replace rusted rebar, no traffic tie-ups while road crews undertake repairs.

The Dublin office of Arup Consulting Engineers designed and built such a trouble-free bridge using stainless steel rebar. The twin spans of the Broadmeadow motorway bridge in eastern Ireland opened to traffic in June 2003.

"We had an aggressive environment – salt water, wetting and drying – where future access for maintenance is very, very difficult," says Troy Burton, Arup’s associate director and the principal design engineer for the bridge. "We wanted to guarantee a 120-year design life ... and we needed to convince our client that we had a durable solution that would cost little money in the future to maintain."

The solution was to use stainless rebar to reinforce all 16 piers that carry the 313-metre bridges across the estuary.

Burton says using stainless rebar added less than three per cent to the approximate 12-million-Euro cost of building the bridge – a negligible expense, given the savings in maintenance and repairs over its lifetime.

Stainless steel rebar is often used in highway bridges for longevity but in this case it is also used to help ensure the protection of an environmentally sensitive marine estuary.
 
Case study 5: Using a more expensive alloy allows for a low-cost design.
Liquified natural gas (LNG) is exported from the Middle East in large amounts.  Natural gas becomes a liquid when it is cooled below minus 161 °C and its volume is reduced by about 600 times.  This makes it economical to transport to distant markets in ocean-going ships, contained in nickel alloy or stainless steel tanks.

The LNG is loaded and unloaded through pipelines. Owing to the extremely low temperatures involved, the thermal expansion and contraction of the pipeline are major factors in the design and construction of the piping system. Normal LNG piping construction uses stainless steel with loops or bends to allow it to flex with the expansion or contraction of the pipe when gas flows through it.

The Osaka Gas, of Japan, design permits straight runs of piping because the coefficient of expansion/contraction of the 36% nickel-iron alloy used is low over a wide range of temperatures. The alloy contracts at a rate of 0.3 mm per meter of length between 20°C and LNG temperatures compared with 2.8 mm per meter for stainless. The total length of piping required is less, as the bends or loops needed with stainless steel are not required with the low expansion nickel-iron alloy.

Since bends or loops in the piping system are eliminated, the underwater tunnel that contains the piping can be of smaller in diameter and is therefore less expensive to construct.  Similarly, any associated pier will be cheaper.

Case study 6: Heat exchangers benefit from the corrosion resistant, long life characteristics of stainless steel
Efficient, light weight, compact plate-type stainless steel heat exchangers (Alfa Laval).

Compact plate-type heat exchangers are an excellent application for stainless steel, according to Ingegard Burling, purchasing manager for Alfa Laval in Sweden. "The material required per duty is less," she says. "You perform the same duty in a more compact type with less material, and you can afford to use a more exclusive material."

Compact heat exchangers have many advantages: they weigh less, take up less space and can cost less to install. They also have a higher level of heat recovery, and this, combined with lower volume, can mean lower pumping costs. Importantly, they use less material, which places less stress on the environment.

The main advantages of using stainless steel materials are improved corrosion-resistance and longer life, according to Burling, who adds that "in the sanitary industry, of course, there is also the benefit of cleanliness."

Compact heat exchangers are found in many different markets, including: the chemical industry; hydrocarbon processing; heating, ventilating and air-conditioning; refrigeration; food and beverages; and power generation. The market for compact heat exchangers is expanding into new areas, and there is an increasing demand for more corrosion-resistant and cost-effective material.

Case study 7: Hong Kong's new single span cable-stayed bridge has been designed to last 120 years
The Stonecutters Bridge, Hong Kong makes extensive use of stainless steel in its structure (artist’s impression).

Its deck will soar 75 metres above the entrance to Hong Kong’s Kwai Chung container port, and its two pole towers will rise 290 metres into the sky. When it is completed, in 2009, the 1,600-metre-long Stonecutters Bridge will be a key component in China’s global trade activity.
The difficulty of providing access to, and performing maintenance on, the upper part of the towers, prompted the designers at Arup Hong Kong to insist on a 120-year maintenance-free service life. To satisfy the rigorous structural and surface finish requirements, Arup Materials Consulting in London, England, chose duplex hot-rolled stainless steel plate to form the top 120 metres of the towers. About 2,000 tonnes will be used.

In seeking material for the skin, designers decided that although carbon steel had the necessary structural strength of 450 MPa, it did not offer the required zero maintenance. "The strength that was required could not be met by an austenitic stainless steel, which has a design strength of about 300 MPa," explains Graham Gedge, Arup’s specialist in project materials. "It had to be thicker and thus heavier and more expensive: with the duplex grade, we knew we could achieve a strength of 450 MPA with hot rolled plate."

There was another reason for discounting standard stainless steel: long-term performance in this polluted marine environment would have required a carefully controlled surface preparation. The duplex grade was ideal for the finish the designers specified. "It is less susceptible to pitting and staining than other candidate alloys, and allows us more flexibility in choice of final surface finishes," Gedge explains. "The control of final surface roughness becomes less critical, even if it will trap some dirt and salt."

Arup also specified stainless steel reinforcing bar in the concrete piers and main tower splash zones. The combination of duplex towers and stainless steel reinforcing bar should result in a bridge that will endure.

The Nickel Institute’s role and how we operate
The Nickel Institute exists to help people benefit from correct use of nickel-containing materials. We are a non-profit organisation which provides a common, responsible voice for the global nickel industry.  We work with other international metals associations and stainless steel development associations to develop and promote the safe use of nickel around the world.

We pursue market development through a worldwide network of highly qualified specialists, offering free technical knowledge about nickel, its properties and uses to ensure optimum performance, safe handling and use.

We actively initiate and fund scientific research programmes that examine the role of nickel in human health and the environment.

We share our knowledge about nickel freely and strive to ensure that sound science is used as the basis for regulation of the nickel industry and its user industries.

Contacting the Nickel Institute:
Dr Peter Cutler, Director, Market Support and Development
The Holloway, Alvechurch, Birmingham, B48 7QA, UK
T: +44 1527 584777, F: +44 1527 585562, Mobile: +44 7887 767 072, W: www.nickelinstitute.org