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A new twist on stainless design

With a striking and innovative design evoking visions of the Singapore based Helix Bridge, stainless steel has formed an integral part in creating one of Sydney’s most exciting new structures.

Commissioned by Landcom as part of the Lachlan Line Precinct development project in North West Sydney’s Macquarie Park, the yet to be officially named cyclist bridge provides visual flair, safe accessibility, and excitement to the area. In an area with typically heavy traffic congestion, the project’s promotion of reduced car dependency creates a significant positive impact to the surrounding environment.

The design is the first of its kind in Australia, utilising a double helix arrangement with a varying diameter along its curving 178m length. While the design elements certainly lend themselves well to aesthetics, structural requirements dictated much of the overall shape. A steel truss arrangement is used, required for the long sections spanning the multiple roads below its footprint. The diameter of the spiral increases at the bridge supports and tapers along its span.  At its narrowest, it is 5.5m in diameter, and 7.8m at its widest.

Approximately 170t of 2205 grade duplex stainless steel was used, along with around 220t of structural mild steel. Due to the large quantity of material required, multiple distributors supplied material mostly on an indent basis, with some delivered ex-stock. ASSDA Members Midway Metals, Stirlings Performance Steels and Vulcan Stainless all supplied material, with the majority of plate (up to 80mm in thickness) produced by ASSDA Member Outokumpu, managed through their Melbourne office. 

A minimum 100-year service life with minimal maintenance (becoming increasingly common in the design of bridges) was a key criterion, particularly important for the hard to access structural components. From the beginning, 2205 duplex grade presented as an ideal material, thanks to its hybridised microstructural properties granting it superior mechanical properties to many forms of mild and stainless steel. 

Put simply, being stronger allows for thinner sections to be used or, alternatively, more scope for efficient design such as larger spanning or increased resistance to bending moments. Mild steel was retained  for the helical outer structure, and painted blue, which was a central design requirement. 

Arup proposed duplex stainless steel for the deck structure and wearing surface within the helix due its increased strength to weight  properties whilst maintaining high durability performance.   

Outokumpu played an instrumental role in advocating the use of the material properties of duplex grade at the early design and concept stages. Backed up by global materials experts and with a wealth of expertise in supplying stainless materials for bridges all over the world, Outokumpu aimed to provide a technical solution through the use of duplex stainless, rather than simply tender for the supply of material. “The use of duplex stainless steels in bridges around the world is becoming more and more the material of choice, so it was great to see Arup in Australia embrace it in its design”, said Con Logos, Vice President APAC at Outokumpu. “A special thanks to George Miech from my team for his tireless effort in the early stages, working closely with both Arup and RMS to have duplex stainless specified”. 

Outokumpu also assisted the fabricator and the end client, Transport for NSW, with expertise, advice, and preliminary procedures in welding the material, particularly vital with the thicker sections which require great care to ensure optimal material properties are realised in the weld and adjacent areas.

The bridge was fabricated in Sydney in four modules, which were trial assembled prior to being delivered to site, where the four segments were positioned and secured over the course of four weekends. Specially designed lifting assemblies were necessary to ensure the segments were not overstressed. 

As bridge design increasingly demands greater durability, aesthetic and creative licence and structural performance, stainless steel, of the duplex family in particular, presents a wonderful option now and into the future.

Photo credit: Landcom

This article is featured in Australian Stainless Magazine issue 71, 2021.

 

Comparisons of hot and cold formed stainless steel

When comparing hot and cold formed stainless steel, the first question you would ask yourself is: are there any chemical differences between the two? ASSDA has previously published articles on the various surface finishes including the few hot and multiple cold finished processes, however this article concentrates on the differences. 

Since the 1970s, most stainless steel is produced by melting in an Electric Arc Furnace (EAF) and then the molten stainless steel is transferred to an Argon Oxygen Decarburisation (AOD) vessel or, less commonly, a Vacuum Oxygen Decarburisation (VOD) vessel. These processes control impurities such as carbon, sulphur, nitrogen, hydrogen and other impurities which could form oxide precipitates. For critical applications such as aerospace or precipitation hardening alloys, further refining is possible, but this is a smaller market. Critically, in AOD, using the injection of inert argon as the stirring agent into the melt allows control of nitrogen additions, e.g., for duplex or high austenitic stainless steels.  

Chemistry

The basic chemistry of a specific grade of stainless steel is the same regardless of how it is subsequently shaped, i.e., as hot or cold rolled, hot forged, cold drawn/shaped or simply cast –  with the proviso that cast stainless steels typically have more chromium and (often) more silicon than their wrought counterparts. In addition, even if cast products have been stress relieved, their microstructure is dendritic so that there can be significant composition differences (localised differences in corrosion susceptibility) between the early solidifying dendrites and the final bulk solidification.

Hot formed

Producing hot formed stainless steel is deceptively simple as shown in the graphic. Currently, for about 95% of production, the molten metal is decanted from the AOD into a cooled continuous caster and emerges horizontally as a slab. The microstructure in the slab is columnar from the outsides (because of the cooling by the caster walls) with a relatively uniform equaxial microstructure in the centre. It is also covered with heavy black oxide scale with a chromium deficient layer underneath – as with weld tints. Typically, the slab is then surface ground to remove solidification features and the scale which would both otherwise be incorporated into the surface during subsequent rolling. The slab is then charged into a reheating furnace and hot rolled to homogenise the microstructure and provide either plate or coil as the product form. The grains will now be more oriented along the rolling direction. The microstructure is then further refined (and internal stresses reduced) by annealing above 1000oC.

Unless the steel is to be used where appearance and maximum corrosion resistance is not critical, e.g., in a furnace, then after hot rolling it would be shot blasted to break up the scale and then pickled. The pickling causes the dimpled appearance of a Hot Rolled Annealed and Pickled (HRAP) plate surface because the pickling acid attacks the base metal at the defects in the black oxide scale. It also gives a typical surface roughness of 5 or 6 µm Ra. There is a potentially cosmetic corrosion issue if the (typically) fast pickle does not completely remove any shallow intergranular oxide penetrations, however this is unusual. For long product such as angles or channels, another visual distinction is that the edges meet at 90o compared to the radius of curvature determined by the thickness and ductility of a cold rolled product.

Cold formed

Cold rolled flat product is quite different because it usually starts at room temperature with a dimpled surface and finishes with thinner material – and watching the increase in speed of the sheet as it gets thinner is quite startling. There is a significantly more elongated microstructure along the rolling direction, and this enhances the anisotropy in transverse to longitudinal strength compared to the relatively slight effect for hot rolled material. Long product is not cold rolled but more correctly it is cold  shaped or formed.

The increase in strength with cold work can be substantial, especially in thin materials as the cold work increase can enhance the strength of the full depth. As an example, the table from ASTM A666 data shows the substantial change in mechanical properties for 304 from annealed to half hard, i.e. half the absolute maximum possible strength – which would have negligible ductility.

Effect of cold work on strength and ductility of 304

One effect of the increase in strength with cold work is that the limit of proportionality will increase with cold work, i.e., the linear deflection occurs up to a higher stress. The reduction in break elongation is simply reflecting the proof stress closing on the tensile stress from 40% to 73% as shown below.

Variation of thickness tolerances for cold and hot rolled materials

There are also differences in the tolerance between cold and hot formed material as shown by comparisons in A480 (flat product – sheet vs. plate) and A484 (sections). However, it is not as simple as “hot formed is less precise than cold formed” as seen below. 

Surface finish

Often it is important to consider appearance and corrosion resistance to the “bright and shiny” benchmark. Hot rolled material is always going to be dimpled, even when it is electropolished and exhibiting a brilliant lustre. It will be marginally more difficult to clean than a smoother cold rolled surface but abrading the surface to give a roughness of less than 0.5 µm Ra is counterproductive. You lose the passive stainless steel and an abraded surface potentially has sulphide inclusions exposed compared to the original pickled, sulphide free HRAP surface.

The inherent roughness of a cold rolled sheet decreases steadily as the plate is rolled thinner as shown in graph. It shows the decrease of Ra from the crushing of the peaks left from the hot rolling as the sheet gets thinner. The graph is for cold rolled annealed and pickled (2B) material and is useful when someone asks for a 2B finish for a thickness not in the band. However, thickness of pickled materials is not relevant to the corrosion resistance whereas the Ra is critical to an abraded surface both for reasons of cleanability and possible crevices from torn surface flaps plus, if not passivated, exposing sulphide inclusions.

 

This article is featured in Australian Stainless Magazine issue 71, 2021.

 

Award-winning stainless food plant

World-class processing systems demand high quality products, innovative features, and long-term yield increase, all of which have been delivered through superior workmanship, engineering, and the use of stainless steel.

ASSDA Member, INOX Australia, was engaged by a Melbourne based stock and soup manufacturer to design the integral process, fabricate, install, and commission a beef, chicken, seafood, and vegetable stock processing system. The processing system is entirely fabricated in stainless steel as it has been essential to the project design and fabrication, being the material of choice in demanding hygienic environments that involve high heat. 

Exceeding their client’s expectations, INOX supplied a processing system that provided multiple innovative features, winning the 2019 Food & Beverage Industry ‘Innovative Technology of the Year’ Award, and being nominated for ASSDA’s 2019 Fabricator Project of the Year Award. This extraordinary processing system features a single user operational interface, safe and ergonomic handling of the product during the process from start to finish and hygienic design of the process including zero wastage at end of production. It also improved the yield of raw materials by pressure processing instead of traditional atmospheric process.

The system works by depositing 1000kg of raw materials into a stainless steel basket which is lifted by an electric hoist into the automatically opened pressure vessel. The touchscreen operational interface is used to set and supply the water volume. The process is fully automatic to the set parameters and then alarms when the process is completed. Following the cooking procedure, the CIP (Clean In Place) water is circulated through the heating jacket of the vessel which serves two purposes. The first is to cool the cooking vessel to a temperature that allows the product to be discharged, and the second, to use the heat recovered from the cooking vessel to heat up the cleaning water. This reusable use of heating allows for no external heating of the cleaning water.

The liquid stock produced is then pumped through a specially designed filtration system, to a holding tank which is then ready for the product to be received by the external filling line. The stainless steel basket is then removed from the vessel and the waste product is dumped into a hopper underneath the basket, ready to be removed to a disposable waste bin. The basket is then cleaned within the vessel during the CIP process and does not exit the food processing room at any point, ensuring the equipment is cleaned and cannot be contaminated externally. 

An impressive 5000kg of 304 and 316L grade stainless steel was used to complete the project. All stainless steel material was supplied by ASSDA Members, Midway Metals, Vulcan Stainless and Tubesales Stainless. This included stainless steel tube, pipe, plate and sheet with 3mm to 12mm thickness. Several components (with thicknesses up to 75mm) required a large amount of specialised machining. The material was mechanically polished where required to achieve a better than 0.8 µm Ra surface finish. This superior material of choice meets the project’s sanitary requirements, offers structural integrity and excellent corrosion resistance in high temperature applications. 

 

This article is featured in Australian Stainless Magazine issue 71, 2021.

 

Stainless steel – a mainstay in water assets

A mainstay in the processing of sewage water in water recycling applications, stainless steel once again plays a critical part in working towards a sustainable future.

Western Water Treatment Plant (WWTP), south of Werribee in Melbourne’s Western District, is a critical asset responsible for processing around half of the city’s total sewage. The process requires a massive footprint, where a series of large lagoons use anaerobic (without oxygen) and aerobic (with oxygen) bacteria to sequentially break down and clean the feed water of solids and gases. The resultant recycled water is used for multiple non-drinking purposes, including irrigation and firefighting. 

WWTP is also largely energy self-sufficient. This energy is captured during the sewage treatment process by combusting biogas, which is captured under the covers. Biogas is used to meet much of the Plant’s electricity needs – preventing hundreds of thousands of tonnes of carbon dioxide entering the atmosphere each year. 

The site carries significant environmental importance to both the immediate and wider areas. Biogas production from the process is used to meet all the Plant’s energy needs through on-site power generation. The Plant is an enormous site – almost the same size as Phillip Island and a world-renowned wetland, declared a Ramsar site in 1983. It is home to many species of flora and fauna and a haven for birdwatchers – in summer it can host more than 100,000 birds in a month.

With current capacity concerns in the existing plant network, stretching back 120 years, and a forecasted increase in processing demands due to a growing city, the need for an additional nutrient removal plant (to complement the existing two) was established. More efficient in design and with more advanced monitoring and controls to provide class A recycled water, the new plant provides an additional 140ML of treated water per day. The plant was designed by Jacobs and built by UGL and CBP Contractors, with commissioning in 2019.

Grade 316L stainless steel was selected as a default material for the pipework, in 2B finish. Offering strong corrosion resistance even against contaminated effluent water, its ease of fabrication and ability to be installed without the need for coating and subsequent maintenance was also important.

ASSDA Member and Accredited Fabricator Roladuct Spiral Tubing was selected to manufacture and supply approximately 50t of spiral welded large diameter pipe, ranging from 300 to 1422mm in diameter. Feed material was supplied  by ASSDA Member, Midway Metals to Roladuct’s  Melbourne manufacturing site. 

Roladuct was nominated in 2019 for the ASSDA Fabricator Project of the Year Award, with judges impressed by the quantity of stainless steel used, as well as the significant environmental benefits realised by the plant upgrade.

As water assets continue to be upgraded and optimised for a growing country, stainless steel will continue to play a vital role in providing material performance and plant reliability for years to come.

 

 Photo credit: Roladuct Spiral Tubing

This article is featured in Australian Stainless Magazine issue 71, 2021.

 

Screening Melbourne’s drinking water

Stainless steel is playing a vital role in delivering effective bulk water intake screens for Melbourne’s water supply.

Designed and manufactured in Brisbane, ASSDA Member Aqseptence Group Australia has recently delivered one of the largest passive intake screens in the Southern Hemisphere. Having produced more than 4,000 screens for the last  50 years, this latest milestone achieved a nomination in the hotly contested Process Industries category of the 2019 ASSDA Fabricator Project of the Year Award. 

In mid-August 2019, Aqseptence Group was engaged by a joint venture of John Holland and KBR to provide design and construct services for a significant capital works project, covering multiple Melbourne Water assets. The screen is used as a bulk water transfer screen for the O’Shannassy Dam, located east of Melbourne. Distributing clean drinking water  to most parts of Melbourne, it is a critical asset storing  3.1 gigalitres of water among a series of reservoirs on the city’s periphery. The mammoth screen took  approximately two months to design and manufacture.

The Johnson Screens T96E passive intake measures an impressive 8.6 metres wide and stands 3.6 metres high.  It is constructed entirely in grade 316L with a mill finished  plate and No. 4 finish wedge-wire and bar. K-Tig welding  was used to join 10mm plates to achieve overall plate size  to roll into tubes. The entire fabrication was then pickled  and passivated. Grade 316L, a standard material of construction at Aqseptence Group, was specified for the grade’s ability to resist general and localised forms of corrosion, a risk even with relatively low chloride inland  water sources. Additionally, being easy to source and  fabricate, its versatility in taking many forms and profiles  is clearly on display.

The intake screen is used to provide an uninterrupted water withdrawal source while protecting assets from foreign matter and most importantly, protecting wildlife by guaranteeing uniform and low through-flow velocities. This fish-friendly screen is also a passive design as it has no moving parts, therefore simplifying maintenance and reliability. Aqseptence Group’s Vee-Wire slot system was used to ensure uniform flow through the screen at a controlled velocity, to protect surrounding marine life. Additionally, using the strength properties of 316L, the screen has sufficient mechanical rigidity to support its own weight along with hydrostatic pressures. Stainless steel was specified due to its low impact on the environment, on both the reservoir and the clean drinking water it supplies, paired with its durability, corrosion  resistance and material strength attributes.

Aqseptence Group is now focused on working with the broader network of water infrastructure authorities to help upgrade their water supply assets and continue to service  the City of Melbourne for future generations with the use of stainless steel.

This article is featured in Australian Stainless Magazine issue 70, 2020.

 

Seven ways to prevent tea staining of stainless steel

When used properly, stainless steel enjoys a strong and enduring reputation for visual appeal and structural integrity in a wide range of applications and environments. But, like all materials, stainless steel may become stained or discoloured over time, impairing the overall look. This brown discolouration - tea staining - has been identified in coastal applications in Australia and overseas.

In the late 1990s, the newly formed ASSDA Technical Committee researched the reasons for the brown discolouration. ASSDA’s work, in collaboration with the International Molybdenum Association, led to guidelines published in 2001 explaining the causes and remedial techniques. The work was later refined to ASSDA’s FAQ 6. This clarified some of the misunderstandings that have circulated about atmospheric exposure and possible corrosion of stainless steels. It does not deal with immersed exposures.

Corrosive chemicals in the atmosphere

In a clean atmosphere, the relative humidity is sufficient to maintain the thin self-repairing passive film which protects stainless steel. Given that chlorides are known to cause corrosion, locations within line of sight of the sea will tend to corrode, especially with onshore prevailing winds. 

Extensive research using corrosion coupons has classified corrosivity using carbon steel and zinc while measuring corrosives such as chloride and sulphur dioxide – as an indicator of industrial activity. AS 4312 presents maps with bands of corrosion rates (from extreme to low) and corrosion rates with distance from the sea or a bay.  For sheltered waters, corrosion rates drop to medium or lower within a few hundred metres, while for exposed areas like Cape Leeuwin in WA, Newcastle in NSW, or Cape Jervis in SA the rates can remain extreme to high for kilometres inland.  

The AS 2699 series of standards for ties used for brick fixing in walls uses deposited chloride measurements to arrive at similar bands of corrosivity. Those values define zones where increasing thickness of galvanizing or, 304 or 316 must be used successively depending on distance from the sea to achieve the design life in buildings. In rural or urban environments, corrosion of stainless steel is unusual although cosmetic staining can occur from vegetation, chemical spills or blown dust.  

Atmospheric conditions

Stainless steel will not corrode unless there is a sufficient concentration of aggressive ions (generally chlorides) and there is free water but not a sufficient flow to wash away contaminants. Water will condense on clean metal if the temperature falls below the dewpoint  but if there are chloride salts, then there is a lower critical relative humidity (RHcrit) which will form an aggressive salt solution by absorbing moisture from the air. This means that deposited sea salt can cause corrosion although the temperature is still below the dewpoint for a  clean surface.  

A secondary atmospheric factor is that corrosion rates roughly double for every 10oC rise in temperature; all else being equal. For instance, corrosion staining will be worse in Darwin than in Hobart.

Design, cleanability and drainage 

Open, bold exposures allow natural rainfall to wash away grime and potentially corrosive deposits. However, drying retained runoff on horizontal surfaces, surface tension at sharp edges, in crevices, or in horizontal abrasion lines on vertical surfaces, all cause increasing corrosivity and do not meet the “bright and shiny” expectations for stainless steel.

Surface roughness and standards

The widely publicised surface roughness of “no more than 0.5µm Ra” for a tea staining resistant surface is codified as 2K in EN 10088.2 which includes a requirement for a clean cut profile, i.e. no flaps or sharp edges. ASTM A240/A480 suggests that a good fabricator can achieve about 0.6µm Ra for a No. 4 finish.  ASSDA conservatively recommended finishing with 320 grit for 0.5µm. Ra is readily measured mechanically or by laser reflectance but, because multiple surface profiles can give the same Ra value, samples are frequently used for acceptance tests. Rough surfaces show significant tea staining.

Unfortunately, the 0.5µm Ra requirement is sometimes specified for HRAP plate with a typical finish of Ra ~6µm. This causes un-needed expense in removing metal. Both thick HRAP plate and thin 2B (or BA) sheet or coil were pickled as their last processing step. Even with Ra greater than 0.5µm these finishes have good resistance to tea staining. However, a rougher surface is still less cleanable and is generally not as bright. Smooth 2B or BA finished sheet has good resistance to tea staining.

There is ample evidence that smoother surfaces resist corrosion better and a mirror polish is the best possible mechanical finish. ASTM A240 and EN 10088.2 have descriptive definitions (for No. 8 or 2P respectively) which centre around high reflectivity and image clarity but do not specify Ra.

Electropolishing electrochemically cleans the surface, removes sharp edges and smooths microroughness. It provides a deep lustre but not necessarily a clear reflection. However, it only slightly reduces Ra, e.g. 0.7 to 0.5 µm for a linished strip. Electropolished surfaces have excellent resistance to tea staining.

Chemical cleanliness of the exposed surfaces

Stainless, carbon or galvanised steels may be fabricated in adjacent areas and carbon steel can contaminate the stainless steel either as floating grit or if tooling is used on stainless steel after processing carbon steel. Contamination during transport or handling is also possible. Any moisture will immediately corrode the carbon steel and cause a large brown stain compared to the contaminating particle - this is not tea staining. The illustration shows a rooster tail of carbon steel contamination on a stainless steel surface from cutting Colorbond® nearby. The contamination can be removed by pickling or, more slowly, by a passivating nitric acid application. The widespread pale spots are light tea staining.

In addition, an oxidising passivation treatment after the final metal removal substantially improves corrosion resistance, partly because the final passive film is thicker and has a higher chromium to iron ratio. However, for freshly abraded surfaces, the sulphide inclusions inherent in all steels are initiation sites for corrosion unless they are removed by a passivating acid. Bar product has more inclusions with at least 10 times the sulphur content of sheet or plate to aid machining. Nitric passivation does not change the appearance of even a mirror polished surface but does significantly increase its corrosion resistance. Further details of pickling and passivation are given in ASTM A380.

What alloy should be selected

An ASSDA/IMOA selection tool is available by searching for ‘stainless-steel-selection-system’ on www.imoa.info. It asks about environment, finish, orientation and maintenance before providing a recommended material from 304 for urban or rural exposures up to 2205 for severe marine. It does not include ferritics mainly because they are not as widely used in welded fabrications. Alloys with similar or higher corrosion resistance (as assessed by PRE) could be substituted. Super alloys are not usual for atmospheric exposures.

Maintenance – natural and/or applied

Stainless steel is low maintenance but not no maintenance. A rule of thumb is that if an adjacent window (or glass screen) needs washing, wash the stainless steel. FAQ 6 has recommendations including consideration of retained deposits and rain washing. One sub-tropical beachside council has implemented a 3 to 4-month cycle of a high pressure wash with low chloride water and detergent (and possibly a zero chloride solvent) before a fresh water rinse. Domestic cleaners, even non-abrasive ones, are not recommended as some have chloride activators and, because of their hygiene image, may have some bleach - which are both potentially detrimental.

This article is featured in Australian Stainless Magazine issue 70, 2020.

 

Stainless steel - The right choice for an environmentally sustainable upgrade

Stainless steel provides a cutting edge and environmentally friendly solution for industrial applications.

Dow Chemicals, a global chemicals manufacturer, recently completed a major upgrade of the wastewater treatment system at their Victorian Point Henry coatings plant. The plant manufactures acrylic emulsions which find use in numerous applications including house paints. ASSDA Members Stirlings Performance Steels and Barwon Valley Stainless provided supply and fabrication services for this impressive wastewater treatment facility upgrade. 

Wastewater produced in the production facility is pumped into flocculation tanks for settling and the clear supernatant is sent for further biological treatment. This treated water is recycled back to production but is also used for irrigation on site to minimise freshwater consumption.

Geelong based Barwon Valley Stainless is a preferred Dow contractor and was selected to provide the complete scope of services for the wastewater treatment plant upgrade due to their knowledge and expertise of wastewater treatments, both local and interstate. Their quality workmanship was reflected in this project as they provided civil and structural works, tank and pipe spooling fabrication, site installation and pump station commissioning. With over 25 years’ experience and competence in stainless fabrication, they were able to work successfully within Dow’s project time and location constraints. 

Stirlings Performance Steels supplied the entire portfolio of materials to Barwon Valley Stainless. This included cut-to-length large bore pipe, structural rectangular hollow section and various pipe fittings as well as laser/plasma profiled plate which were all in grade 316/L.

Reducing environmental footprint in industrial applications is important and material selection is a critical step in both maximising the lifetime of plant and equipment, while minimising the need for maintenance and servicing. This upgrade successfully satisfied both these requirements with the use of stainless steel. Grade 316 is a popular material of construction where water is processed with relatively low chlorides at ambient temperature. It provides an optimal cost benefit compared with other steel-based alternatives which require coating or lining. Additionally, the close proximity of the site to Victoria’s Corio Bay requires resistance to corrosion from airborne seawater. According to Ben Arlidge, Project Manager at Dow, “Stainless steel has provided the perfect mix of performance, workability and cost for our new wastewater treatment facility.”

The plant upgrade is a major step in providing long term certainty to the local Moolap economy, as well as in strengthening the Australian supply chain of domestic market paint products. 

 

Photo credit: Barwon Valley Stainless

This article is featured in Australian Stainless Magazine issue 70, 2020.

Stainless at first sight

Located in the foothills of Perth, Aegis Amherst opened in July 2019 providing residential aged care in Canningvale, Western Australia. Set at the core focal point of the aged care facility presents a grand stainless steel balustrading ramp façade. 

ASSDA Member and Accredited Fabricator Balustrading WA were engaged by Absecon to fabricate and install a modern, safe, purpose-built ramp that would encompass strength and aesthetic attributes. 

The custom-designed ramp features an impressive 170 metres of grade 316 stainless steel tube. 

The handrails were manufactured from 50mm diameter stainless steel round tube. All stainless steel components were specified with a No. 7 high polish finish, supplied by several local suppliers including ASSDA Member, Stirlings Performance Steels. Mild steel flat bar was also used as the infill panels. Grade 316 stainless steel was specified primarily for its longevity, aesthetic appeal, and material strength. In addition, it is a durable and long-lasting alternative to competing materials.

Balustrading WA were heavily involved in the design brief and process, due to the extensive curvature inherent in the site. A range of advanced surveying techniques had to be used to ensure the balustrading was fabricated and installed correctly. This included using 3D image scans set into GPS grid location co-ordinates, rather than manual site measuring or templating as with more straightforward designs. As an example, the stainless steel support posts were scanned and fabricated individually to size to ensure correct fitment. In total, the project took just over 12 months to complete. 

The stainless steel ramp reflects the aged care’s cornerstone of their philosophy, by providing their residents with an environment that is comfortable and safe while delivering an aged care that helps them lead active, mobile and healthy lives.

This striking ramp facade continues to be the “hero” image for the facility, as stainless steel has once again delivered in compliance and material strength while fulfilling design and aesthetic needs.

     

Photo credit: Balustrading WA

This article is featured in Australian Stainless Magazine issue 70, 2020.

A stainless approach to protecting the environment

Safeguarding Australia’s environmental biosecurity is critical in preventing the introduction and spread of pests and diseases, and the Post Entry Quarantine (PEQ) facility in northern Melbourne is setting the benchmark in international best practice with the use of stainless steel.

The PEQ facility in Mickelham is a state-of-the-art, purpose-built operation constructed to streamline the country’s quarantine services and consolidate five pre-existing Commonwealth PEQ facilities spread across New South Wales, Victoria, South Australia and Western Australia. Managed by the Department of Agriculture and Water Resources, the 144ha site includes an administration building, modern laboratories, dog and cat receiving areas, horse facilities and separate compounds for birds, ruminants, bees, plants, horse veterinarians and dogs and cats. Today, as Australia’s flagship quarantine control centre, the integrated PEQ facility is the first point of entry for all imported animals, plant material and insects entering the country, providing secure accommodation and biological containment.

One of the more challenging aspects of the PEQ facility’s construction was the design and build of the avian compound. The complex and demanding brief included the delivery of five high-criticality biocontainment units under Quarantine Containment Level 3 (QC3) requirements, the highest level of biosecurity containment. Containment of micro-organisms and prevention of their release is of utmost importance. Mitigating and eliminating risk of exotic pathogens and disease connected to avian imports such as fertile eggs and live birds is critical.

In association with UK-based Suncombe Engineering, a worldwide leader in the field of wastewater decontamination, ASSDA Member Fineweld Stainless Steel was engaged by hydraulics contractor Geschke Plumbing to supply, manufacture, and install the wastewater decontamination plant system and connecting containment pipework for the treatment of QC3 biowaste products in the avian compound.

The wastewater decontamination plant system required a 12,500L collection vessel and 1,750 heat treatment vessel, and the collection vessel was fabricated from 316 grade and the treatment vessel from 2205 duplex stainless steel with a 2B 0.6μm finish in Fineweld Stainless Steel’s Carrum Downs workshop. Following manufacture, the treatment vessel was packaged and transported to Suncombe Engineering in the UK for final assembly into the wastewater decontamination plant and to undergo a complete Factory Acceptance Test (FAT) as a certified testing authority. The wastewater decontamination plant was then transported back to Fineweld Stainless Steel in Australia for pre-testing at their facility and then installation on site.

In addition to the two vessels, Fineweld Stainless Steel installed and welded the connecting pipework on site, manufactured from 5t of 316 grade stainless steel. All pipework welded joints – approximately 1,500 butt welds – were orbital welded and each one inspected, tested and recorded as part of the project scope to comply with the client’s strict QC3 requirements. QC3 facilities use gaseous decontaminants including vaporised hydrogen peroxide and chlorine dioxide. The use of stainless steel offers material strength, hygiene and resistance to both corrosion and the chemicals required to deactivate pathogens, whilst ensuring a gas-tight system for fumigable ductwork.

The installation took place two stories underground, therefore manufacturing and pre-spooling had no margin of error. Extensive logistical challenges were diligently managed, and in collaboration with Suncombe Engineering and Geschke Plumbing, the project was delivered on-time and on budget by the Fineweld Stainless Steel team.

In what would have been traditionally manufactured and imported from overseas suppliers, Fineweld Stainless Steel is showcasing the high quality and technical capability of Australian stainless steel manufacturing, producing high-end pressure vessels and complex works for a demanding and precise application. World-class infrastructure demands high quality products and long-term asset performance, both of which have been successfully delivered for the avian compound of Mickelham’s PEQ Facility through superior local workmanship and the use of stainless steel.

 

 

Photo credit: Geschke Plumbing

This article is featured in Australian Stainless Magazine issue 69, 2020.

 

Coloured and patterned stainless steel

Think stainless steel, and most people think ‘bright, shiny and silver’. But did you know that specifying stainless steel is not limited by its silver appearance?

Coloured and textured stainless steel is an exciting material choice for designers and architects. In addition to offering a high quality and aesthetically-pleasing finish with choice of colour, stainless steel’s superior benefits when compared with plastics or anodised aluminium include resistance to heat, light, abrasion and corrosion, and overall increased durability and performance extending the service life of the application.

This article will take a look back at the development of coloured stainless steel, detail the electrochemical colouring and PVD coating processes, and explore the various surface textures available.

History and development

Back in late 1960s, INOX developed a process for uniformly colouring smooth stainless surfaces. The colour relied on the growth of a uniform oxide-based film in a sulphuric and chromic acid mixture. The colour changed because of the interference of reflections from the top of the layer and the metal underneath it. It is like the colours in a soap bubble or an oil film, except that the INOX film had a very uniform thickness. This is because it is grown under uniform temperature and flow conditions with tightly controlled chemistry. Because the colours were subtractive rather than additive, they were not the same as a rainbow spectrum, but colours ranged through bronze, blue, black, charcoal/grey, gold, purple and green as the film grew from 20nm to 360nm. The colours also varied slightly with viewing angle because of the interference process that gives the colour.

Initially, there were two limitations and two caveats. Firstly, the coatings were easily abraded so it should not be used in heavily trafficked areas because any mechanical damage could not be repaired. Secondly, it was initially only grown on 304. And the caveats? The tight thickness limits mean that batch-to-batch colours could have slight tint variations although, this also has been exploited to provide a softer colour image.

Electrochemical colouring

Within a decade, a dual stage process was developed with an electrochemical treatment that provided greater abrasion resistance. Research in Australia showed that, for 304 base material, the film provided a slight improvement in corrosion resistance although the change is not as significant as a passivation process. Further developments showed that coloured films could also be formed on 316. The necessity for a uniform film thickness still requires factory treatment which means that it is limited to sheets or round surfaces such as tubes. Nevertheless, building facades, shopping centres and smooth surfaced art works were able to display a variety of stainless steel colours, even when the coloured stainless steel has been carefully bent into shapes.

These colours are very durable, even in Australia, as they do not fade with UV exposure and, in a graffiti-infected urban environment, solvents can be used to remove tags and other unwanted additions to coloured facades and signs. However, they are not repairable if scratched and can only be mechanically fixed as welding locally destroys the coloured film.

Surface Blackening

Do the arms of your black windscreen wipers use this colouring process? Well, no. The rich, glossy black used to be from immersion of stainless steel in molten sodium/potassium dichromate at 400oC for about 30 minutes but is now usually replaced by a 180oC cured organic coating. Shorter immersion times were used for thermal solar water heaters but they are now either painted or plastic - although black chrome has had a place in the market. 

Physical Vapour Deposition (PVD) coating

The second major method of colouring stainless steel is PVD or Physical Deposition of a Vapour – hence PVD. The process is carried out in a high vacuum chamber with a small amount of (usually) argon gas. The gas is ionized by a high negative voltage on the target and forms a plasma of electrons and positive ions which bombard the source metal and ejects (or sputters) metal ions or atoms. These are deposited on the product to form a thin (typically 300nm) coating on the clean product. It is critical that the coated surface is free from contaminants or the coating will lack adhesion. It is routinely used to hard coat small objects like drills but, on a larger scale it produces coloured door furniture or objects whose size is only limited by the vacuum chamber. Coating larger objects and sheet material requires greater electron ionization efficiency in the plasma which typically uses magnetic fields parallel to the surface of the target. 

The source metal can also be generated by thermal evaporation but this is less common.

Unlike the electrochemical INOX process, the colour of the PVD coating is determined by the source material with a few examples shown in the table. It is also invariant with viewing angle. PVD coatings are much more abrasion resistant than the INOX system but are not indestructible. 

Patterned stainless steel: Surface texture and its effect

A range of embossed, patterned and textured stainless steel finishes are available. Hot rolled finishes are usually too dimpled for aesthetic finishes. Cold rolled mill finishes are smooth and either dull grey (2B) or very bright (BA – bright annealed) and provide differing basic appearances but the same mechanical properties. Both have significantly better corrosion resistance than as-abraded finishes. Aesthetic changes by abrasion or blasting will provide feature finishes but have only minor effects on the colour and mechanical properties although rough 

as-abraded surfaces are known to be less corrosion resistant, i.e. the 0.5 micrometre Ra criterion.

Mechanically embossed profiles on austenitic mill rolled finishes might reduce the cleanability, but they also increase the strength because of cold work strengthening - while retaining the base metal corrosion resistance. This strengthening means that thinner material can be used, such as the thin checker sheet used in toolboxes – good visuals and lower weight in the utility with security for tools. Profiled sheet for outdoor public seating is another application with thinner sheet because of the strength and a bright appearance without glare.

High wear areas such as airport baggage collection or hospital corridors often use rigidised stainless steels where a through sheet profile significantly increases strength and stiffness with a pleasing aesthetic. An added advantage for profiled finishes is that scratches only affect the peaks and are less apparent partly because they are not continuous. On a grander scale, the Petronas Towers in Kuala Lumpur, Malaysia is a more complicated Cambric profiled finish on a base 316 metal with BA stock. The profiled finish is to avoid blinding reflections while using a 316 base metal with a mill finish that has the highest corrosion resistance available.

 

Bus station seat with colourful anodised aluminium arms

Petronas Towers in Kuala Lumpur, Malaysia
Photo credit: Outokumpu

University of Florida (UF) Health Shands Children’s Hospital
Photo credit: International Stainless Steel Forum (ISSF)

Banner image - Westfield Doncaster, Victoria
Photo credit: Steel Color Australia

This article is featured in Australian Stainless Magazine issue 69, 2020.

 

Rheem Australia’s Sturdy Stainless Steel Range

Stainless steel hot water heaters offer superior design combining high thermal efficiency, corrosion resistance, durability and performance for domestic applications.

ASSDA Member Rheem Australia has been committed to delivering hot water systems for over 80 years, with its first gas water heater manufactured in 1939 in Waterloo, Sydney. Through new product development and innovation, Rheem Australia has pioneered the commercial production of Australian-made hot water systems, designed and built for Australian conditions.

Operations Manager at Rheem, Gavan Schaeche, says, “Rheem Moorabbin is leading the way with its very own Stainless Steel and Commercial Centre of Excellence. The centre performs 125km of stainless steel welds a year to keep up with the demand of the new range which has quickly become an industry favourite.”

Rheem Australia’s stainless steel hot water system range includes gas and electric storage ranging in capacities from 50L to 315L. Manufactured from a range of stainless steel grades, the hot water systems use mains pressure water delivery and do not require a sacrificial anode for corrosion protection, reducing long-term maintenance and service costs over the life of the water heater.

The electric stainless steel models in the hot water system range offer high energy efficiency, exceeding Minimum Performance Standards (MEPS) by 12-24%. In addition, stainless steel cylinders weigh significantly less than comparable vitreous enamel models, making the product easier to manoeuvre and install. It is particularly well-suited for households that have their water heater installed indoors or in elevated multi-storey locations. 

Victorian-based Plumber and Founder of The Tap Man, Chris Arms, has been providing household solutions for thirty years. Delivering reliable household appliances is paramount to maintaining a highly satisfied client base, and when Chris receives a request to replace a hot water system, he always recommends the most suitable product from the Rheem stainless steel range. 

“I like to bring my customers along on the journey to find the right solution for their home through education about what they can expect from the products and materials I’m installing.

While the stainless steel range comes at a higher price point, it’s absolutely worth the investment. In my experience, stainless steel is a robust material that’s durable, corrosion resistant and less likely to incur a leak,” Chris says.

“It’s also one of the only hot water systems where I often do a repair over a replacement, should there be an issue such as an element assembly requiring replacement. The stainless steel tank makes a repair worthwhile.”

Stainless steel can present a higher upfront cost when comparing various hot water system products, however its investment is surpassed by the material’s performance and lifespan, and cost savings in energy efficiency, service and maintenance costs.

 

This article is featured in Australian Stainless Magazine issue 69, 2020.

 

Stainless steel… Limitless

‘Limitless’ is the stainless steel sculptural creation of Gold Coast artist Ian Haggerty, whose concept was selected in a design competition by Bond University to celebrate their 30th anniversary.

The 6.5m tall sculpture takes pride of place under the university’s iconic Arch and gleams in dignity and elegance from its 316L grade stainless steel construction. Inspired by the limitless possibilities created by education, the sculpture features a world sphere at its centre with four overarching wings representing the four pillars of learning: Learning to know, learning to do, learning to live together, and learning to be.

Reflection was also a key concept in the sculpture’s design, with mirror polished stainless steel the unrivalled material choice in bringing together the alumni and future students to inspire and signify that there are no limitations to education when it comes to gender, age, race, or religion.

In a nod to celebrating local fabrication, the artist engaged Burleigh-based ASSDA Member and Accredited Fabricator Atlas Stainless Balustrade & Fabrications to fabricate and install the 1.5t sculpture. 

Stainless steel rings were laser cut in various sizes from 100kg of 5mm mirror polished plate and welded together to create the intricate bubble pattern featured in the top section of the four wings. The bottom sections were fabricated from 400kg of plasma cut plate, with 1mm sheeting used to cover the bottom eight sides to allow for the chemical etching of over 26,000 Bond University graduates in homage of their educational achievements.

The Atlas Stainless Balustrade & Fabrications team also fabricated the base structure, and sphere and wing supports from mirror polished pipe to bring together the pre-constructed world sphere and its overarching wings. The fabrication process involved the team using their in-house plasma cutter, CNC bandsaw, CNC section roller and in-house polishing equipment both by machine and hand, and specialist welding techniques.

The project took over six months to complete and the structure was installed using two cranes, joining the university’s existing landmarks as a focal point of the state-of-the-art campus landscape. Special lighting effects were also installed as part of the sculpture to highlight its key features at night and shimmer in the surrounding water of the lake fountain.

‘Limitless’ was unveiled in May 2019 to celebrate the university’s 30-year milestone and remains a legacy piece for Bond University.  

This article is featured in Australian Stainless Magazine issue 69, 2020.

 

Stainless steel makes an entrance

A collaboration between ASSDA Members using 'gold' stainless steel has delivered the epitome of opulent luxury at The Star Sydney.

The Star Sydney's multi-million-dollar transformation has seen its Pyrmont Street entrance revolutionise the guest arrival experience, with a porte-cochère facing the glittering Darling Harbour and a refurbished Grand Foyer combining innovative architecture, contemporary art and technology.

Over 4000m2 of grade 316 stainless steel with a gold finish is featured throughout the Grand Foyer and porte-cochère, enriching the luxurious look and feel of the integrated resort. ASSDA Member Steel Color Australia supplied 1mm and 1.2mm thick stainless steel sheet in various lengths from 2400mm to 3500mm and widths of 1219mm to 1500mm as the sole distributor in Australia and New Zealand for embossed, coloured, mirror finished and textured stainless steel manufactured by Steel Color S.p.a in Italy.

The stainless steel's gold colour was achieved with a titanium film using a Physical Vapour Deposition (PVD) coating process. The environmentally-friendly method vapourises titanium in a vacuum chamber to form an extremely thin layer that bonds to the steel's surface. The process also improves the performance of the steel, increasing durability and resistance to heat, light, abrasion, scratches and corrosion.

In addition, the steel's surface features an anti-fingerprint (AFP) coating preventing oil and finger marks, contributing to a sleek aesthetic finish with minimal maintenance. The AFP coating provides the titanium coating with a timer colour finish, strengthening colour stability and extending the service life of the application.

Suitable for internal and external applications, coloured stainless steel can be used in many design forms and was specified for the bespoke luxurious features in The Star Sydney's Foyer and porte-cochère.

The Steel Color Australia supplied stainless steel sheeting was installed in the Grand Foyer and internal porte-cochère by ASSDA Member Karisma Joinery, across the door portals, elevator door jambs and ceiling panels, columns and wall panels. A V-Groove machine was used to form precise, sharp angles and folds, creating architectural profiles to achieve a seamless upmarket finish and meet the high-end specification.

The stainless steel clad elements for the external porte-cochère, including luxury retailer finishes for Gucci, was fabricated and installed by ASSDA Member Fabmetal Specialists. All profiles and clad elements were fabricated in their workshop in Melbourne, using an in-house V-Groove machine to achieve a crisp bend profile, prior to installation on-site by the Fabmetal team. A split batten system was used to clad the stainless steel elements across the retail facade fixtures, window mullions, headers and kickers. The Fabmetal team were also tasked to clad the revolving doors and overcame challenges with complex curved works, laminating gold stainless steel on to curved fabricated T-sections in power-coated aluminium to create a striking two-tone effect.

In a nod to architectural innovation, The Star Sydney will continue to welcome and awe its guests with its everlasting stainless steel gleam and elegance.

  

 

PHOTO CREDIT: MURRAY FREDERICKS PHOTOGRAPHY. 

This article is featured in Australian Stainless Magazine issue 68, 2020.

 

Stainless steel behind high-tech visual art

Australian designed and manufactured stainless steel wedge wire grating has been instrumental in delivering 'Aquatique', the first sculptural water installation of its design in the Southern Hemisphere.

The Star Sydney's Grand Foyer has been transformed as part of an $850 million redevelopment for the integrated resort. A unique immersive visual experience is now welcoming guests in a masterfully choreographed interplay of light, water, digital art and live performance.

The key elements of the installation include an 8K resolution, 25m wide crescent-shaped digital screen, laser light shows and 'Aquatique', a cascading sculptural water feature spanning 8m with a 2m diameter centre stage.

Central to the design and function of the sculptural water feature is the use of Australian designed and manufactured stainless steel wedge wire by ASSDA Member and Accredited Fabricator Paige Stainless.

PAIGE STAINLESS HEELGUARD® is at the cutting edge of water drainage technology, offering continuous drainage through its 5mm aperture and high-water volume intake and removal efficiency. The water feature was designed with a throughput capacity of 30,000L, with water being pumped up to 15m vertically to the water feature jets, recirculated through the PAIGE STAINLESS HEELGUARD® and reused whilst the water feature is in operation. The key was to minimise water splash during the process with PAIGE STAINLESS HEELGUARD® delivering the brief with its unique wedge design. In addition, stainless steel is an excellent material choice for water drainage technology, offering durability, aesthetics and ease-of-cleaning during maintenance inspections.

Paige Stainless' project scope also included the design, fabrication and installation of the water collection tank, substructure for the grating and centre stage area within the water feature. Over 3.5 tonnes of grade 316 stainless steel was supplied for the project by ASSDA Members Austral Wright Metals and Midway Metals, including 4mm thick plate and rectangular hollow sections.

The water feature body was manufactured at Paige Stainless' manufacturing facility in Caboolture, Queensland, and fabricated in 14 components for ease of interstate transportation logistics, efficient installation and maintenance.

Delivery and installation logistics were a focal point of the design as The Star Sydney was full operational and open to the public during installation. Provisions were made for specific delivery times and material management to make for a successful, non-disruptive transition from truck to site. Careful planning and design resulted in minimal on-site welding and passivation treatment using citric acid by the Paige Stainless installation team.

The water feature uses 100% recycled water. Its sculptural display is complemented by a theatrical light show and digital art canvas inspired by Australian artists, cinematographers and animators. As the world's largest permanent multi-sensory art experience, the Grand Foyer at The Star Sydney is a visual feast entertaining an average 30,000 guests per day.

PHOTO CREDIT: MURRAY FREDERICKS PHOTOGRAPHY. 

This article is featured in Australian Stainless Magazine issue 68, 2020.

SABRE Veto Vessel: Stainless steel plays vital role in Australian research

A scientific quest to search for dark matter has led to the opportunity for ASSDA Member and Accredited Fabricator Tasweld Engineering to fabricate a specialised stainless steel tank, known as SABRE (Sodium Iodide with Active Background Rejection) Veto Vessel to help facilitate Australian research into answering one of the universe's unsolved mysteries.

The University of Melbourne received $5 million in federal funding to build the Stawell Underground Physics Laboratory (SUPL) in an unused gold mine in Western 

Victoria. The facility will house the SABRE Veto Vessel, shielding it from astrophysical particles and enabling a range of experiments to be undertaken to determine the existence of dark matter, a form of matter that does not directly interact with light. Dark matter is by its nature, extremely hard to detect. The SUPL location is approximately 1km underground to use the earth's shield to screen out astrophysical particles, background noise and environmental factors that interfere with signals from dark matter.

The SABRE Veto Vessel was designed by the University of Melbourne in conjunction with FE Consulting Design Engineers and Tasweld Engineering. To deliver the best probability for experimental success, grade 304 stainless steel was used for the vessel's manufacture. In addition to the material's durability, gleanability and corrosion resistance, stainless steel was specified most importantly for a specific property; low radioactive content. The presence of certain radionuclides negatively affects the detection experiments, and therefore sourcing material with low radio emissivity was critical. The stainless steel plate was imported from a supplier in Germany with experience in this application and involved stringent validation testing.

The vessel took 600 man-hours and was manufactured at Tasweld Engineering's Warrnambool workshop to AS 1210 standards with rigorous equipment and welding processes applied to prevent material contamination. All welding was carried out using a TIG process, with lanthanated tungsten electrodes, and all consumables were new to avoid cross contamination. The 2.6m tall, 1800kg vessel features access ports for electrical and other connections.

The SABRE Veto Vessel was completed in October 2019 and has been temporarily installed in a laboratory at Swinburne University of Technology's Wantirna Campus for preliminary testing while the SUPL is being constructed. For the next stage of the project, Tasweld Engineering have been contracted to manufacture an additional flange assembly to allow the use of different attachments during various experiments.

Tasweld Engineering's expertise and superior workmanship, and the use of stainless steel, has delivered a positive contribution to science in a quest to unlock the mystery of dark matter and to a research facility that aims to conduct better quality experiments, including the effects of radiation in cancer cells.

 

This article is featured in Australian Stainless Magazine issue 68, 2020.

AS 1528:2019 - A new edition pitched at food safety, consistency, useability and current practice

The aim of AS 1528: Stainless steel tubes and tube fittings for food processing and hygienic applications is to standardise hygienic tube and fittings for use in dairy, food and beverage manufacturing. It has been successful in maintaining the required food safety standards in Australia and New Zealand.

AS 1528 was first issued in 2001 and developed by an ASSDA group of stakeholders in the manufacture, supply, fabrication and use of stainless steel tube and associated fittings in the food manufacturing industries.

Changing industry practice, some existing errors, internal consistencies and expansion of sizes required a revision of the standard. The drafting journey to bring AS 1528 up-to-date began in 2015 and has been a challenge, but its successful outcome is significant for the industry and a testament to everyone involved.

The new edition of AS 1528 was published in four parts by Standards Australia in October 2019:

Part 1: Tubes

Part 2: Screwed tube couplings

Part 3: Butt weld tube fittings

Part 4: Clamp tube fittings

The revision of the AS 1528 suite of standards from the 2001 edition has brought the documents' technical coverage up to current practice and recognised the target industries in which hygienic tube is used. The suite is easier to understand and use, and facilitates verification of product compliance so that it achieves the required hygienic conditions.

 

What the revision achieved

The 2019 edition achieved all of the original aims, except one (see below). The suite of four standards now presents as a consistent coverage of all the tube and fittings regularly supplied in Australia.

  1. Addition of a consistent set of pressure ratings across all parts of AS 1528. Useful for designers.
  2. The wall thickness tolerance for tube has been changed. Previously it was +nil/-0.10mm for all sizes of tube. Widening it out to ±10% brings it into line with most other tube specifications and makes it more economical to manufacture without compromising product quality. It also then matches the tolerances of the fittings in other parts.
  3. The title now includes 'hygienic applications' in addition to food processing. This recognises the wider range of applications in which these products are already used.
  4. The reference to duplex stainless steels has been removed. In practice all tube and fittings referenced by these standards are austenitic.
  5. All tube and fittings can be produced without grit polishing the internal surface. Internal surface finish is specified by measurable roughness for hygiene cleanability.
  6. Inner tube surface roughness has been set as 0.8µm Ra maximum; this is consistent across all four parts of the standard and is also consistent with US and European specifications. From a gleanability perspective this is adequate. In addition there is now a specified maximum roughness for the inner weld bead, specified as 'Rt'. This is an unusual specification but it does address directly the requirement for cleanability of the remnant weld line.
  7. For the first time there is a stated limit for inner weld surface heat tint (no more than Level 3 in AWS D18.1M, commonly referred to as 'pale straw'). Again this aligns with US and European standards and much research work promoted by ASSDA and others.
  8. Consistent working pressures and temperature ranges have been given for all tube and fittings, with the exception of clamp fittings above 152.4mm.
  9. The range of sizes has been expanded generally up to 304.8mm or 12" diameter, but lesser maximum sizes for certain fittings, depending on market availability. Smaller diameter tubes have also been included as these have some niche applications. Additional wall thickness have been added. It is not anticipated that there will be a sudden move ways from the usual 1.60mm WT and the common OD range, but there were some industry requests for the expanded size range.
  10. Part 2 covering screwed couplings has been completely restructured. The two fundamental types - RJT and IDF/Trapezoidal - are clearly separated, with all dimensional specifications included in Sections 2 and 3. Section 1 deals with the requirements common to both types.
  11. Fittings not previously recognised have now been included. This includes both RJT blank hexagonal nut and an IDF blank cap in screwed couplings (AS 1528 Part 2). Butt weld fittings (Part 3) has addition of crosses, equal radius tees and 45 degree tees. In clamp fittings (Part 4) an end cap has now been included.
  12. The branch lengths of reducing tees and crosses (Part 3) have been clarified. The previous edition have a specification for this dimension that was in some cases contradictory and in all cases confusing. The new requirement is that the branch length, measured as the extension beyond the run surface, is the same as the branch OD.
  13. Reducers, both concentric and eccentric (Part 3), now include the option of a short extension to enable orbital welding.
  14. Reducers are now standardised as 'short reducers', with the 'full flow' reducers still specified but in the absence of request the standard type is short.
  15. New appendices in Part 4 cover a very useful description of clamp conditions for correct installation (App C), specification of grooves for expanded-type clamp liners (App D) and the method for expanding (App E).
  16. Correction of a long list of typos and inconsistencies in dimensions.

 

What was not achieved

The New Zealand market is already using AS 1528 and keen to have it branded as their own, but early discussions between the committee, Standards Australia and Standards New Zealand revealed the cost imposed by Standards Australia to make the project a joint cross-Tasman effort was prohibitive. As a result, the project became simply Australia, but the committee was able to co-opt a New Zealand member, and a tube manufacturer active in both Australian and New Zealand was also included as a Drafting Leader. The project therefore included New Zealand input, even though the document is branded Australian. The committee was mindful that there is substantial cross-Tasman movement of tube and fittings, of manufactured processing equipment, of engineering expertise and of food product, so joint output was essential to maximise all-round benefits.

 

Why this revision was important

The AS 1528 suite is the only fully integrated set of standards to the Australian industry's traditional dimensions for stainless steel tube and tube fittings for hygienic applications.

The Australian food manufacturing industry is critical both because of our high standards for domestic consumption and also as a very significant export earner. Australia has a clean and green reputation that only thrives if we can guarantee freedom from contamination. 

All the commonly used and some niche tube and fitting products are covered and all are consistent.

Food manufacturing plant is getting bigger, so this edition includes provision of larger size tube and fittings. The applications are also increasingly diverse, so an expanded range of products is appropriate.

This revision presents manufacturers of tube and fittings with a clear, consistent and measurable standard for these critical products. The standard offers a pathway to economical outcomes for tube and fittings manufacturers, designers, installers and asset owners.

 

This article was written by Technical Consultant and AS 1528 Committee Chairman, Peter Moore.

This article is featured in Australian Stainless Magazine issue 68, 2020.

Stainless for  winemaking success

A growing demand for quality wines in China has seen its third-largest winemaker venture onto Australian soil with a new state-of-the-art winery incorporating over 800t of stainless steel. 

Weilong Wines’ winery in Red Cliffs, Northern Victoria is the first Australian winery development of its magnitude for many years, and the company’s investment in the Murray-Darling region is a testament to the strong reputation and quality of Australian wine. Grape crushing for the export-only wine has already commenced following the completion of the winery’s construction in March 2019 and is expected to have wine bottled before the year-end in time for the Chinese New Year celebration in January 2020.

ASSDA Member and Accredited Fabricator A&G Engineering designed, manufactured, delivered and installed all stainless steel storage and processing vessels for the new winery. The project scope was to achieve a vintage intake of over 26,000t capacity of grapes, equating to 21 million litres of wine.

Stainless steel was selected as the material of choice for the wine production equipment because of its excellent corrosion resistant properties, durability and ease-of-cleaning. Furthermore, the use of stainless steel does not impart additional flavour to the wine, preserving the original palates offered in the grape.

A total of 180 stainless steel tanks in grade 304/304L were delivered - 124 storage vessels ranging from 30kL to 1200kL, 42 fermentation vessels and 14 general processing tanks - plus associated stair towers, platforms, catwalks, support structures and connections.

Over 700t of 2mm-6mm stainless steel coil was supplied for the project by ASSDA Member, Outokumpu. In addition, the A&G Stainless Steel Sales Department was engaged to supply over 15km of primarily 304 grade tube in sizes ranging from 20mm to 300mm, plus all associated fittings.

Two 1200kL storage vessels were manufactured by A&G on site, using their own fully automated Plasma TIG welding process for tank manufacture, Site PAM (Precision Automated Manufacturing). The unique system was designed with a focus on large-capacity stainless steel vessels being constructed in the field, giving A&G the capability to custom build vessels that hold in excess of 5 million litres. 

Site PAM’s automatic planishing system compresses the weld with high pressure to ensure there are no peaks inside or outside of the tank, providing an aesthetically pleasing finish and a flat surface for the automated polishing application. All vessels were passivated for added corrosion resistance.

With safety and logistical considerations managed, 24-hour shifts were undertaken to fabricate the two 1200kL tanks to minimise downtime and maximise the efficiency of the project planners and estimators’ time on site.

The fabrication of the remaining 178 stainless steel storage vessels were spread across A&G’s three workshop premises, including Griffith in New South Wales, Mildura in Victoria and Angaston in South Australia. The extensive logistical challenges were managed with diligent project management, forward planning and transparency across the three sites and different production teams.

Transportation of the larger storage vessels required National Heavy Vehicle Regulator road permits, allowing only small pre-set time windows and significant planning to ensure loading and unloading occurred as planned to meet the scope of the permit. All vessels were delivered on A&G’s specialised tank trailers, and the larger vessels were transported on trailers specifically designed for the operation to comply with road regulations and permit requirements.

A&G was also appointed as the WH&S Principal Contractor for its portion of the works, taking responsibility and liability for all safety aspects on those parts of the site under its control. With the complexity of works being undertaken day-to-day, including the use of cranes up to 100t, heavy materials, working at heights, hot works, traffic management, job safety analysis requirements and standard operating procedures, the breadth of safety considerations were significant. Zero injuries or notifiable incidents were recorded over the duration of the ten-month project on site, a fantastic result given the magnitude of the project.

The end result is a technologically-advanced, modern winery with state-of-the-art stainless steel equipment and infrastructure built to last. With China continuing to drive growth and demand for wine imported from Australia, Weilong Wines plan to expand production each year, with the potential for future capacity to reach 168,000t per annum.

Immerse yourself in stainless luxury

Setting the benchmark in boutique luxury and innovation using stainless steel is Brisbane’s Emporium Hotel.

Developed by the Anthony John Group, The Emporium Hotel opened in July 2018. Nestled in the premier lifestyle and cultural precinct of South Bank, the 143-suite hotel is turning heads with its exquisite interior design, bespoke handcrafted features and luxurious facilities.

Stainless steel was the material of choice for the five-star hotel and selected for its quality, opulent aesthetic and luxury appeal. Over 5.5 tonnes of grade 304 stainless steel sheet, 1.2mm thick in a No. 8 mirror finish was used throughout the five-star hotel and supplied by ASSDA Member Fagersta Steels

ASSDA Member and Accredited Fabricator, Langford Metal Industries, was engaged to laser cut the mirror finish material to bring the developer’s trademark design to life, which was installed by Thump Architectural.

The frangipani inspired pattern represents the Queensland theme and character, and the laser cut stainless steel prevails throughout the hotel on mullions, sliding doors, external panels, columns, cabana suites surrounding the 23m infinity edge pool – almost anywhere and everywhere, serving both a functional and decorative purpose.

A remarkable feature of the hotel is its rooftop bar on the 21st floor, The Terrace. Presenting panoramic views of South Bank Parklands, the Brisbane River and the city skyline, The Terrace maximises the warm Queensland weather with two retractable roofs offering full, partial or no exposure.

Measuring 7.5m long, 2.1m wide and 50mm thick, the ceiling of the first retractable roof features the impressive frangipani stainless steel design. The sliding panel is a composite structure incorporating insulation and structural members which are clad top and bottom with mirror polished stainless sheet. For structural purposes, the panel was shaped into a shallow moon profile to form the roof’s arch. When retracted, a second roof made of glass is revealed, which is also retractable for a complete outdoor rooftop experience.

The stainless steel ceiling and surrounding elements complement the rooftop bar’s sub-tropical luxe vibe with ceiling-to-floor glass doors, lush greenery, and white backlit onyx floor tiles and bar.

 

Photo Credit: Emporium Hotel

Coastal living

Stainless Steel Pool Fencing

Safety is the number one consideration when building a pool fence, and stainless steel delivers in compliance and material strength while fulfilling design and aesthetic needs.

A stunning canal-front home on the Gold Coast features a streamlined stainless steel vertical balustrade system as supplied by ASSDA Member Miami Stainless.

The custom-designed stainless steel pool fence features 50mm square mirror-polished posts and upper and lower rails. Complying with Queensland pool fencing and safety barrier regulations, the vertical stainless steel wire balustrades were spaced 80mm apart and installed using Miami Stainless’ Nutsert Swage Stud System on the base with a ProRig Flip Toggle into the handrail.

Grade 316 stainless steel was specified for its aesthetic appeal, material strength and corrosion resistance, particularly with the home’s waterfront location and close proximity to the coastline.

In addition, stainless steel is a durable and long-lasting alternative to aluminium balustrades and offers reduced household maintenance when compared with glass. Glass fencing often requires frequent cleaning to remove chlorine or saltwater splashes and finger marks. 

The stainless steel pool fence ticks all the boxes in combining safety, unobstructed views, durability, minimal maintenance and luxury style.

 

Photo credit: Miami Stainless

 

Shielding gases for welding and their effects on stainless steel properties

Shielding gases form an integral part of all conventional welding processes. 

They serve multiple functions but are primarily there to shield the weld pool from the atmosphere and to provide a medium which can allow the flow of electricity from an electrode to a workpiece. Even processes that do not have an external gas supply such as Manual Metal Arc Welding (MMAW or MMA or SMAW) and Gasless Flux-cored Arc Welding (FCAW) all have a shielding gas which is generated by the decomposition of the flux in the presence of the welding arc.

The shielding gas can also have an effect on arc stability, weld shape and depth of penetration as well as the mechanical properties and metallurgy of stainless steel weldments.

The gas shielded processes such as Gas Tungsten Arc Welding (GTAW or TIG) and Gas Metal Arc Welding (GMAW or MIG) use shielding gases of a variety of compositions depending on the application. As the electrode in GTAW is made of tungsten, the shielding gas is typically argon or helium to prevent oxidation of the electrode. This restriction does not apply to GMAW and therefore the gas composition may include active gases such as carbon dioxide and oxygen. Small quantities of other gases such as nitrogen and hydrogen can be utilised with both of these processes as they are particularly advantageous for the welding of stainless steel. While neither gas is inert by definition, they can be used with GTAW as neither react with tungsten.

There are three key properties of the shielding gas which control the way the weld pool behaves; the ionisation potential (how easily an atom will give up an electron), the thermal conductivity of the gas, and finally the surface tension between the weld pool and the shielding gas.

Ionisation potential

The shielding gas allows transfer of electrons between the electrode and the workpiece. Upon arc initiation, electrons are emitted from either the workpiece or the electrode depending on which is positively charged. These electrons collide with gaseous atoms which results in these atoms liberating one of their electrons which results in a chain reaction that sustains the arc. The ionisation potential of the gas is the ease with which they will give up an electron. ‘Hotter’ gases are those which require more energy to ionise or release an electron. Helium has a higher ionisation potential than argon, so has a higher arc voltage and hence a higher heat input for the same current and arc length. 

A similar principle applies to molecular gases (H2, N2, O2, CO2) which dissociate in the arc into individual atoms and then recombine upon cooling, releasing energy in the process. Argon is often mixed with small amounts of other gases to improve weld penetration.

Thermal conductivity

The thermal conductivity of a shielding gas affects its ability to transfer heat across the arc. It influences the radial heat loss from the centre to the periphery of the arc column as well as heat transfer from the arc to the molten weld pool. Gases with low thermal conductivity such as argon will tend to have a narrow hot core in the centre of the arc and a considerably cooler outer zone. The result is a weld with a narrow ‘finger’ at the root of the weld and a wider top. On the other hand, helium has a high thermal conductivity, so heat is more evenly distributed across the arc, but as a result the depth of penetration is lower. Mixing gases allows combination of the advantageous properties of each gas while limiting the drawbacks.

 

 Surface tension

Surface tension affects the bead profile of a weld. Picture how water beads up on a newly polished car. This is undesirable in welding as it creates a steep angle between the weld and the parent which could lead to defects such as undercut, lack of sidewall fusion and decreased fatigue performance. This is another reason why pure argon is not used as a shielding gas for the GMAW process. 

Gas components

Oxygen

Though seemingly counterintuitive as it is well known that hot metals oxidise, small amounts of oxygen are often added to shielding gasses for the GMAW process. Small amounts of oxygen reduce the surface tension between the molten weld pool and the surrounding atmosphere. Lower surface energy results in a flatter and smoother weld bead with less tendency to undercut the parent metal. To minimise alloy losses by oxidation, oxygen content is typically limited to 2%. The heat tint will be more severe than for a weld without oxygen additions to the shielding gas.

Carbon Dioxide

GMAW also utilises CO2 as a constituent of the shielding gas. A common concern with stainless steels is embrittlement and corrosion through sensitisation due to chromium carbide formation, but the carbon pickup from CO2 has been demonstrated to be low enough that the resultant weld metal still achieves the required (≤0.03%) carbon content for L grade designation. The chosen CO2 content is therefore more about penetration and wetting than it is about carbon pick-up. Carbon dioxide contents in GMAW are typically 2-5% while flux-cored wires utilise 20% mixtures with argon or even 100% CO2

Hydrogen

Unique to austenitic stainless steels is its immunity to hydrogen cracking – except possibly in very heavily cold-worked material. This allows the addition of hydrogen to the shielding gas in quantities from 2–15% providing more heat in the arc and better penetration. Hydrogen quantity for manual welding is usually restricted to 5%, with the higher concentrations limited to automated process such as orbital GTAW. Hydrogen cannot be used as a component of the shielding gas for ferritic, martensitic or duplex stainless steels due to a risk of cracking. 

Nitrogen

Nitrogen is a useful shielding gas additive for duplex stainless steels which contain dissolved nitrogen. It is added to increase pitting resistance and in acting as an austenite stabiliser to create a balanced ‘duplex’ microstructure in the weld, especially for thin materials which cool too rapidly to allow sufficient austenite to form. Nitrogen can be added to both the welding gas and the purge gas to prevent the loss of nitrogen during welding.


This article has dealt with gases for the active side of a weld. When welding tube or pipe, it is normal to feed an inert gas such as argon or nitrogen into the tube or pipe to maintain low oxygen levels and minimise heat tint formation to no more than pale straw. This usually requires a sensitive oxygen meter or possibly previously proven purging practices. In thick sections, purging must continue for all passes. Nitrogen purging of duplex root passes will improve the corrosion resistance but may also upset the phase balance. Hydrogen additions have been used in purge gases for both austenitic and duplex welds to minimise heat tints.