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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. 

Water Delivery Efficiency with Stainless Steel

Stainless steel is playing an important role in delivering effective infrastructure to achieve water savings, securing a sustainable environment and future for irrigation communities in Australia.

Murray Irrigation's Private Irrigation Infrastructure Operator Program (PIIOP) Round 3 in New South Wales is a modernisation project focused on upgrading larger infrastructure within the main canals of its irrigation assets, including Mulwala and Wakool Canals.

Mulwala Canal is Australia’s largest irrigation canal, and together with Wakool Canal runs 157km long. It has the capacity to deliver more than 1,500,000ML of water per year to irrigators in the Southern Riverina, helping to generate more than $500 million of gross agriculture revenue per year for the region. 

ASSDA Member AWMA successfully delivered 91 stainless steel water control gates across the project’s irrigation system assets. This modernisation program has substantially increased water efficiencies, improved water flow, enabled ordering flexibility and significantly reduced water leakage through infrastructure upgrades.

The works included 21 Mulwala Canal Sites (65 LayFlat gates and 26 Undershot gates), Lawson Syphons (two Undershot gates), the Edward River Escape (two Bulkhead gates) and the Wakool Canal Offtake (three Undershot gates).

All gates were purpose-engineered, designed and manufactured by AWMA to meet exact site and operational requirements. The water control gates measure up to 5.5m wide and 3m high in size, fabricated from 230 tonnes of stainless steel. The stainless steel water control gates required 7.5km of weld, then pickled to improve corrosion resistance and tested in-house to international ISO 9001 quality standards. Dedicated tooling and handling equipment were also paramount in ensuring no cross contamination during all processes undertaken.

 

ASSDA Member Vulcan Stainless supplied grade 304 stainless steel plate material, whilst ASSDA member Valbruna Australia supplied grade 431 stainless steel shafts.  

 

ASSDA Member Akras Industries were also engaged in a semi-automated welding process in order to join the oversize gates back together post laser cutting and pre-pressing. Welding was carried out in line with AS1554.6 / ASME 9 /AS1210 - Class 1 classifications to ensure the highest weld integrity and compliance to quite rigid specifications as set out within the scope.

 

Another ASSDA Member Arcus Wire Group were engaged by AWMA to assist in the design and supply of 20mm, 7x19, grade 304 stainless steel wire rope cables for the purposes of raising and lowering the water control gates. 130 cables were supplied (two cables installed per LayFlat gate), with an individual Minimum Breaking Strength (MBS) of over 27,000kgf. Arcus Wire Group and AWMA collaboratively designed the bespoke cable end terminations to suit the specified MBS, and the manufacture of these products were completed in-house by Arcus Wire Group. 

Stainless steel was specified for its longevity and durability, particularly with the water control gates being submerged in irrigation water. In addition, stainless steel was chosen over aluminium in the materials specification to extend the nominated asset life from 25 years to 50 plus years. The gates have been integral to improving the efficiency and productivity of water delivery, and the use of stainless steel offers an economically maintainable and longer lasting infrastructure solution.

All new gates installed are stainless steel and telemetry-enabled for remote control, a capability that has radically changed the way Murray Irrigation manages water delivery to its customers. 

  

 

Photo banner at top of article courtesy of Ertech. 
Photo above (left) courtesy of Murray Irrigation. Photo above (right) courtesy of AWMA.

This article is featured in Australian Stainless Magazine issue 65, 2019.

Luxe Stainless

A new luxury home renovation in Cottesloe, Western Australia is leading the way in cutting-edge bathroom design with a statement stainless steel wall.

ASSDA Member and Accredited Fabricator ALLOY’s stainless steel mosaic tiles are featured in the bathroom designed by Nina Dempster of Ozbyrd Design and architect Paul Jones RBA of a recently constructed addition by builder Adrian Zorzi.

The alluring back wall of the walk-in shower is lined with ALLOY’s “SWISS CROSS” 30x30mm stainless steel mosaic tiles. The mixture of the No. 4 and No. 8 brushed and mirror finish 304-grade solid tiles offers a textured finish with a glimmering light reflection and decorative appeal.

The client wanted a brilliant surface finish to enhance the space and grandeur, particularly with no natural light feeding into the area. Stainless steel delivers the brief, with its reflective sheen and the added benefits of the material’s hygienic properties and durable nature. It also plays an important aesthetic role in the camouflage of water spots. 

The entire shape of ALLOY’s mosaic tile has a unique bevelled edge, and its manufacture from 1.6mm thick sheet ensures the tile will not dent, crack or de-laminate. No surface treatment was required on the stainless steel, being installed in an indoor environment.

The end result is a high quality, precision-engineered stainless steel product striking a balance between function and luxury style.

Photo credit: Ryan North, and are subject to copyright.

This article is featured in Australian Stainless Magazine issue 65, 2019.

 

Atlas Steels' Post Incident Safety Revamp

When Mark Ellis, a warehouse operations clerk for Atlas Steels, suffered a serious leg injury that resulted from an incident at its Ingleburn Service Centre, the business vowed it wanted to prevent this type of incident from reoccurring.

"It shook the business," says Regional Director, John Pearson. "It was a terrible thing for Mark, his family and for all of our employees. You could see and feel the devastation."

Ellis was injured when he stepped back and collided with a multi-directional sideloader forklift. Atlas’s quest to enhance safety saw the business introduce a number of measures across its operations. Other businesses working to prevent serious incidents can learn a lot from this example, particularly the important role of employees in coming up with ideas to improve workplace safety.  

“The effect of this incident on all was dreadful”, says National SEQ Manager, Maree Mihaljevic. “We are extremely focused on engaging our people and strengthening our safety system and processes.”  

A practical response

Atlas’s response to this incident included a series of practical measures. Service Centre Manager, Marc McAllister, says Atlas introduced an improved Traffic Management Plan and controls in consultation with its employees. One of the most important changes has been the introduction of a pedestrian awareness tool (PAT), a base plate that has a pole with a strobe light on top. If a pedestrian stops to work in an aisle they must place PAT in front of the aisle, or at a safe distance from them, and turn the light on. The light is at eye level with the sideloader forklift operator and provides additional visual awareness to the operator who must not enter beyond the point of PAT placement. As PAT is portable it can be used in a variety of locations.  

The business has also increased training, particularly around traffic management and sideloader forklift operation, with an online interactive training system being built from the ground up and employees being put through refresher courses.  

The way we do things around here

Consultation was conducted across the country resulting in the development of a Safety Charter that depicts a ‘Safety First’ approach and the agreed minimum safety expectations for all employees, supervisors and managers with signed ownership it is prominently displayed at each site.  

Ellis has conducted a series of presentations to his workmates and to the wider steel distribution industry that Mihaljevic, says “Demonstrated that this was real, not just an anonymous report or statistic but a worker who has a name and family. It highlighted his journey, the injury impact on others and the importance of working together in implementing and maintaining safety systems and processes with the presentation correlating with Mark’s passion for golf.”  

After the incident McAllister gained a forklift licence himself so he would have experience first-hand. “I try and regularly get out there and work with them,” he says. “I get to see the challenges they face, and we work through to improve. It also helps in strengthening our team.”   

A continuous quest

After his incident, Mark Ellis has made a successful return to work; but the effects of his incident at Atlas Steels are long lasting. It has driven a quest to elevate safety so that no one suffers a similar incident. 

Mihaljevic says Atlas’s efforts to improve safety are ongoing. “It’s relentless,” she says. “The importance of having well risk assessed safety systems and processes in place especially where mobile plant is in use is evident.”   

There are learnings for everyone where mobile plant is in use says Pearson, “If you walk or drive into any workplace, follow the signs and directions of the employees and maintain situational awareness to ensure your own safety and the safety of others.”

Pearson adds other businesses can provide ideas that can be trialled and possibly implemented. He says it’s a never-ending search for improved risk management across the board to reduce the potential for injury.  

But Mihaljevic says don’t disregard incidents that occur in other businesses. “If you read something that happened in another company, don’t just think ‘that’s horrible’, act on it. Ask yourself if that incident or similar could happen in your business and what do you have to do to control that risk.”  

Good safety leadership is paramount and its important to lead by example McAllister says. “Continue to engage and encourage open conversations regarding safety. Some of the best ideas will come from the warehouse floor.”

 

Atlas Steels acknowledges that this article was produced as a result of a SafeWork NSW Enforceable Undertaking.

 

This article is featured in Australian Stainless Magazine issue 65, 2019.

Stainless Steel and Fire Resistance

What is the fire rating of stainless steel? This is a common enquiry from ASSDA Members and the construction industry, especially with the current concerns about flammable cladding. The three major branches to this question are covered in this article.

Will stainless steel burn, and if it does, will it give off fumes or facilitate the spread of fire?  

This question is readily answered because stainless steels are steels. It is recognised that steels do not burn and only start to melt at about 1400oC. This means that stainless steels do not have a “fire rating” as such, so the tests of AS/NZS 1530.3 (or the equivalent tests in BS 476) are not required.

Heating in a fire will obviously have an appearance effect because, unlike the transparent nanometer-thick passive layer formed in moist air, stainless steels heated above about 300oC in air discolour as they grow a less dense oxide layer. This develops from the rainbow colours seen beside welds to a dark and non-protective oxide layer whose thickness depends on the time of exposure and temperature reached. The street rubbish bin shown suffered from a fire but remained functional for almost a year (until the repair cycle reached it) with a decorative rainbow oxide. By way of comparison, powder coated bins would suffer from unsightly burn marks and corrosion. 

For austenitic alloys such as 304 and 316, the temperature limits for lifetime section loss due to oxidation is about 870oC (with temperature cycling) so they are routinely used in high temperature furnaces and ductwork. The current trend to apply decorative coatings to stainless steels would require an assessment to determine the combustibility, potential fumes and flame spread of the coating. Tests to AS/NZS 1530.3 would be appropriate. 

Microstructural effects of a short-term heat cycle (less than a couple of hours of exposure, such as a fire) could include carbide precipitation (sensitisation) in an austenitic alloy which was not an L grade (i.e. carbon >0.03%). Duplex and weldable ferritic grades should not have sufficient carbon for sensitisation. Sensitisation would degrade the corrosion resistance but not affect mechanical properties. Both duplex and ferritic grades can suffer 475oC embrittlement, however data produced by the International Molybdenum Association (IMOA) shows that this requires more than two hours in the 400oC to 500oC range for a 50% reduction in toughness. This duration is unlikely in most fires.

 

Will stainless steel provide a barrier to flames and if it does, how rapidly will the heat penetrate the barrier sufficiently to cause damage (usually a specific temperature rise) on the far side? 

A satisfactory demonstration is supplied by reference BS 647 Part 22 tests carried out for a British Stainless Steel Association (BSSA) member, Stewart Fraser, who manufacture 316 framed doors which include a cavity filled with non-combustable boards. The results are given at www.bssa.org.uk/topics.php?article=106.

It showed slight discolouration and distortion on the flame impingement side with the sheltered side of the door reaching only 98oC after 60 minutes. The test was continued for another 80 minutes without the failure of flame containment or subsequent opening of the door in its frame. Similar testing was carried out on a 1.5mm thick 2304 duplex sheet fabricated into a simulated ship’s bulkhead with enclosed ceramic wool insulation. With a bright orange glow of an 1100oC metal temperature on the flame side, the “safe” side reached 30oC after 40 minutes and 110oC after 60 minutes. The test was terminated after 120 minutes with containment still satisfying IMO resolution A518 (XIII).

 

What are the effects (both during and after an event) to the mechanical properties of stainless steel? How do these compare with structural carbon steels? 

There are tests as well as a theoretical basis which demonstrate that both austenitic and duplex stainless steels have superior high temperature properties compared to carbon steel. The table below shows the deflection and failure modes of three metre long commercial electrical cable trays loaded to simulate actual loadings. They were heated with 18 LPG burners to obtain an average temperature of 1000oC  to 1050oC for at least five minutes. [Nickel Institute publication No. 10042]

    

 

The publication also considers the life cycle costs (LCC) of the use of aluminium, galvanised steel or stainless steel for stairways, handrails, gratings and firewalls, as well as cladding for corridors and accommodation modules on North Sea platforms. Fire risk controls are obviously a major concern although corrosion resistance is also critical. On an LCC basis, stainless steel was most economical especially when its reduced requirement for maintenance periods were included. 

In addition to the above testing in cable tray applications, substantial research and application work has since been carried out and codified. Installations include 2205 duplex hangers suspending the slab which forms the floor of the emergency ventilation duct in the CLEM7 tunnel in Brisbane [ISSF].

In short term fires such as on balconies or stairways, the temperature rise exposed to an ISO 834 fire temperature profile depends on thickness and emissivity. Polished stainless steels typically have low emissivity of <0.1 and hence a slower temperature rise. Conservatively, after 30 minutes a 12mm sheet of stainless steel with 0.2 emissivity would reach 620oC whereas steel (with no rust) and 0.4 emissivity would reach 750oC.   

When considering strength and deflection, the metal temperatures in a conventional fire do not reach levels to anneal the material so any cold work strengthening will raise the temperature for a 50% strength reduction. In addition, as shown in the graph, the reduction in Young’s Modulus, i.e. deflection from a specific load, is less than that of carbon steel for temperatures above ~200oC. By 600oC the modulus retention for stainless steel is 0.75 compared to 0.3 for carbon steel, i.e. less than half the deflection for a given load.

 

         

 

In summary, stainless steel has substantial advantages in structural use when fire risk is considered, and these advantages continue into higher strength and lower deflections at elevated temperatures.

CLEM7 image above courtesy of Ancon.

This article is featured in Australian Stainless Magazine issue 65, 2019.

 

 

 

Stainless Steel for  High Performance Enclosures

Stainless steel is the ultimate materials solution for electrical enclosures in safeguarding the network and communications technology invested in underground mining sites.

Olympic Dam is a large polymetallic underground mine located in South Australia, approximately 550km northwest of Adelaide.

Home to a major source of oxide copper gold deposit, Olympic Dam produces combined quantities of copper, gold, uranium and silver through an underground mining system integrated with a metallurgical processing plant. The large deposit was discovered in 1975 and in 1988, the mine was opened by WMC Resources. Today, Olympic Dam is owned and operated by BHP, following its acquisition of WMC Resources in 2005. 

ASSDA Member and Accredited Fabricator B&R Enclosures was contracted by MPS Building & Electrical to assist with finding a solution to a fibre enclosure hub capable of linking four mining shafts to the surface.

B&R’s design and engineering team worked closely with MPS Building & Electrical to design and fabricate an enclosure specific to BHP’s requirements. The customised solution was supplied through Auslec Electrical and Data located in Wingfield.

The outcome was a double door stainless steel field cabinet, 1000mm deep and capable of housing electrical and monitoring equipment. Due to the remote location of the project and the type of equipment installed, stainless steel sunshades and lockable handles were included to reduce heat within the enclosure and prevent vandalism.

Grade 316 stainless steel with a No. 4 surface finish was specified for the custom-designed enclosures, with material supplied by ASSDA Member Outokumpu in 1.5mm thick sheet. 

Underground communication networks are a critical link between operations below ground and at the surface to ensure efficiencies in production and personnel safety. Protecting the equipment that delivers these communication networks is vital and stainless steel offers the durability and longevity required to deliver a robust structure to ensure preservation of the internal hardware.

In addition, grade 316 stainless steel offers excellent corrosion resistance, particularly to pitting corrosion which can occur in inland Australia due to high salinity in the ground water. 

B&R have worked alongside BHP and MPS Building & Electrical on past projects, installing enclosure solutions into a variety of different applications. B&R’s ability to design custom solutions along with their reliable service meant MPS Building & Electrical could confidently deliver this project and supply an enclosure suitable for harsh mining environments and extreme weather conditions.

As a result of good collaboration and local technical expertise, the project’s stainless steel enclosure design is now a standard specification for future installations across Olympic Dam.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.

Stainless Shines in Darling Harbour

Mirror finished stainless steel sign blades can be found scattered along the central boulevard of Sydney’s revitalised Darling Harbour.

Through a recent $3.4 billion transformation, Darling Harbour has become Australia’s largest entertainment and events precinct boasting world class facilities, including over 40,000 square metres of exhibition space. This urban rejuvenation builds on the success of Darling Harbour and in turn, will generate $200 million annually in economic benefit for the NSW economy.

The Harbour is ringed by attractions, entertainment and extraordinary waterfront restaurants. The Boulevard creates an active north-south pedestrian connection between Central Station and Cockle Bay. Its prime location is within walking distance of most points in the Sydney CBD therefore wayfinding signage is pivotal in navigating people through and around the precinct.

ASSDA Member and Accredited Fabricator Stoddart were engaged by Lend Lease to manufacture and install 19 stainless steel wayfinding sign blades for Darling Harbour’s ‘once in a generation’ re-development. The sign blades are featured in groups of two and three, each standing seven metres tall and two metres wide.

258 panels of grade 316 stainless steel were used for the sign blades in order to provide housing for LED display screens throughout the precinct. The structural stainless steel frame also mounts speakers and power outlets. All stainless steel used in this project was supplied by ASSDA Member, Fagersta Steels

Featuring a mirror profile finish, the stainless steel signs create a stunning visual effect through the reflection of the countless city lights and surrounds of the bustling tourist and entertainment mecca.

Stainless steel was specified by landscape architects, Hassell, for its aesthetic appeal and high-quality attributes. The Harbour’s salt water environment and location was also a consideration in the materials specification, being adjacent to the city centre.

It is only fitting for quality material such as stainless steel to be showcased in one of the world’s most desirable entertainment and event destinations.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.

Pickling and Passivation of Stainless Steel

One of the most common misunderstandings in specifications for stainless steel fabrication relates to the post-fabrication treatments to restore or enhance the corrosion resistance. 

The surface treatment processes invoked vary between pickle and passivate, passivate, or sometimes simply pickle. Needless to say, whilst pickling and passivation are two distinct processes, a lack of clarity can cause some confusion between the owner and the builder/fabricator about what is expected and required. 

This article briefly outlines the factors that affect the corrosion resistance of stainless steels, what surface treatments can be used and how they affect the steel’s surface to improve corrosion resistance.

Corrosion Resistance and its Controls

Stainless steel is resistant to aggressive environments because of a very thin, self-repairing, chromium-rich complex, oxide film present on the surface of the steel. It is not completely impervious, but it dissolves many orders of magnitude more slowly than it reforms. The passive layer is more resistant for alloys with more chromium, molybdenum and nitrogen. This is the reason for the empirical, composition based Pitting Resistant Equivalent (PRE(N)) index which is often used as a ranking tool in selecting which stainless steel will be used in new applications. However, the alloy composition is not the only control of the passive film’s strength, and hence its corrosion resistance. There must also be an adequate supply of oxygen and moisture to maintain the integrity of the passive film. This requires either good design or a maintenance program – and preferably both.  

For a specific alloy, i.e. a specific PRE(N), the passive film (and hence the corrosion resistance) can be improved by chemically oxidising the steel’s surface. Air and water are good and the ASTM standard dealing with passivation (A967 Standard Practice for Chemical Passivation Treatments for Stainless Steel Parts) advises that for many environments, no further treatment is required for satisfactory service. However, oxidising or chelating chemical treatments will provide better corrosion resistance.

Roughness

Corrosion resistance is indirectly improved if the surface is smooth and clean (free of contaminants) to facilitate the self-renewal of the passive film. For abraded surfaces there is also a critical surface roughness of 0.5μm Ra that should not be exceeded. This is recognised in surface finish 2K in EN 10088.2. It seems that for steels, the size of abrasives causing this roughness is too large to cut the surface cleanly and leaves rough edges and metal debris which can accumulate dirt and corrosives – hence more rapid corrosion with coarser polishing.

Contamination

The bête noir of stainless steel: carbon steel contamination. If it is not removed, the stainless steel will rust. In marine environments, it will collect chlorides and cause large rust stains and small pits in the stainless steel. If it is mechanically removed, it is likely that the smeared steel will leave a larger rust stain, although it may be less intense. Acid treatments can remove carbon steel deposits and have the added advantage that they can also remove surface breaking manganese sulphide (MnS) inclusions. These MnS inclusions do not have a passive film and act as initiating points for corrosion.

Welding

If you have welded your fabrication and there are rainbow coloured bands along the welds, they are zones where the passive film has been destroyed. Under the darker colours, there will be a wedge-shaped layer with a lower chromium content than the bulk stainless steel. Corrosion will initiate in these coloured bands. The weld tint colours can be mechanically removed provided the grinding is not too rough. Chemical removal by pickling is often a better option.

Pickling

Pickling uses a mixture of nitric and hydrofluoric (HF) acids. The wide range of concentrations and exposure times are described in ASTM A380 Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems. Typically the nitric concentration is up to 10 times the HF concentration, but pickling is slow unless the HF is more than about 3%. Longer pickling times are required at lower temperatures or if a high alloy is being used, i.e. super duplex takes longer than duplex which requires longer than 304. If a paste is used, the contact area acid gets exhausted unless it is stirred, e.g. with the application brush. Thorough washing is needed to remove all residue even from crevices and, to avoid stains, it is important not to allow acid or rinse water to dry on the surfaces.  

OHS and environmental considerations mean that using a pickling contractor is easier, safer and ensures the appropriate disposal of acid and pickled heavy metals. Contractors will often use a temperature-controlled, stirred tank or, sometimes, a spray pickling solution in an acid-proof and bunded bay. Unless an additional level of passivation is required for a very aggressive environment, the outcome is a pickled item that is passive.

Chemical Passivation

The traditional and very effective acid is nitric, typically between 15% and 25% for about two hours, although it is not uncommon to drop machined parts into a bucket of nitric acid for half a shift. The passive film is significantly strengthened and the ratio of chromium to iron in the surface layers can exceed 1 – compared to <0.4 in the bulk. Nitric acid will also remove rust stains and sulphide inclusions plus, more slowly, carbon steel smears. Phosphoric acid will remove rust and sulphide inclusions, but it is not oxidising and will not strengthen the passive film. Another method of strengthening the passive film of a chemically-clean surface is to use a hydrogen peroxide solution – lots of free oxygen and only water residue.

There are other acids that will strengthen the passive film and dissolve carbon steel and inclusions, but by a different method. Citric and oxalic acids and EDTA all have a carboxylic acid [O-C-OH] atomic structure, and once the acid dissolves the unwanted metal, the positive ion is trapped by the negative oxygen atoms in a process called chelating or sequestering. This process is used in wastewater treatment to remove metals. In passivation, it is important to rinse thoroughly. Chelating treatments are widely used in the food industry as formulations which include biocides, so the citric acid does not contribute as a food source.

There are a number of special cases detailed in ASTM A380 which require care when pickling:

• Sensitised or hardened (nitrided or carburised) areas may suffer intergranular attack.

• Free machining stainless steels requires an inhibitor or it will pit.

• Martensitic stainless steels can suffer hydrogen embrittlement.

All of the above methods are chemical treatments which are quite traditional and generally well applied. Further information is provided in ASTM A380, which also details test and inspection methods to confirm surface cleanliness.

Three Definitions

CLEANING Removal of contaminants such as soil, grease, oil, etc. using low-chloride detergents and/or solvents to allow free access for water and oxygen to grow the passive film.

The bulk material is not affected and the surface looks brighter. Chlorinated solvents may be a risk as residues can degrade if heated and may cause pitting. In vessels or pipework, it is important to drain and dry the surfaces.

PICKLING The removal of any high temperature scale and any adjacent low chromium layer of metal from the surface of stainless steel by chemical means.

It also removes embedded or smeared carbon steel, inclusions and loose flakes of stainless steel left from abrasives.

It will leave a matt finish, which may be paler if the pickling is extended. It provides a passive surface immediately on rinsing – hence you pickle and get a passive surface.

PASSIVATION The treatment of the surface of stainless steel, often with acid solutions (or gels), to remove contaminants and promote the formation of the passive film on a surface that was freshly created, e.g. through grinding, machining or mechanical damage. It will remove acid soluble inclusions such as MnS.

Clean humid air will form a passive film on clean stainless steel and the appearance will not change.

Chemical passivation strengthens the passive film and typically takes an hour or so at ambient temperatures. Air passivation is adequate unless the environment is very aggressive for the grade.

1. Rusting steel contamination from shearing stainless sheet. Photo courtesy of Graham Sussex.

2. Rainbow oxide from poor gas shielding during welding. Photo courtesy of HERA.
3.Before (left) and after (right) pickling of welded fitting. Photo courtesy of Graham Sussex. 4. Welded components after pickling to remove heat tint and possible steel contamination. Photo courtesy of Australian Pickling & Passivation Service.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.


Stainless Opulence

Exemplary stainless steel craftmanship has delivered a sophisticated and lavish cocktail lounge in the heart of the Gold Coast’s entertainment hub.

Cocktail connoisseurs have been flocking to Cherry, The Star Gold Coast to experience the designer drinks on offer in the grandeur of the lounge featuring a 22m long bar. Refurbished in 2017 as part of the first stage of the property’s major transformation, its upmarket look and feel was inspired by its sister venue at The Star Sydney.

Central to Cherry’s luxury design is the intricate, gold metalwork featured in the VIP booth screens, lounge surrounds and balustrades. ASSDA Member and Accredited Fabricator Minnis & Samson fabricated these elements using grade 316 stainless steel tube and flat bar supplied by ASSDA Member Australian Stainless Distributors

The stainless steel was mirror polished prior to the electrostatic application of a special coating to achieve the gold colour finish. Crystal hardware and lush red velvet furnishings complement the gold stainless steel to deliver the opulent design and vision of the cocktail lounge.

Stainless steel is a high quality and high strength material, and was specified for its longevity, hygienic properties and aesthetic appeal. In addition, stainless steel offered better weldability to achieve the detail in the metalwork’s curvature design.

This article featured in Australian Stainless magazine - Issue 63, Spring 2018