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Use of Stainless Seel in the Wine Industry

Stainless steels are widely used in the food industries, including wine production, because of their corrosion resistance and ease of cleaning which result in negligible product contamination.

Long life can be expected from stainless steel equipment provided care is taken with:

> Vessel design
> Grade selection
> Fabrication procedures
> Maintenance practices.

The precautions to be taken are not complicated but are most important - neglecting to follow them can lead to rapid failure.

VESSEL DESIGN
Much can be done in the detailed design to improve corrosion resistance. The two cardinal rules are:

1. Design for complete and free drainage
2. Eliminate or seal weld crevices.

A series of drawings, with accompanying narrative, comparing good and bad design practices, are set out in Part Ill of Nickel Development Institute publication #11 007: Guidelines for the welded fabrication of nickel-containing stainless steels for corrosion resistant services.

GRADE SELECTION
Two stainless steel grades are particularly used in the wine industry, grades 304 and 316, and both 'standard' and 'low carbon (L)' versions are available. Their compositions are shown in Table One below.

Table One: Stainless Steel Grade Selection
GRADE CHROMIUM NICKEL MOLYBDENUM CARBON
304 18.0 - 20.0 8.0 - 10.5 - 0.08 max
304L 18.0 - 20.0 8.0 - 10.5 - 0.03 max
316 16.0 - 18.0 10.0 - 14.0 2.0 - 3.0 0.08 max
316L 16.0 - 18.0 10.0 - 14.0 2.0 - 3.0 0.03 max

The 'L grades are specified w here welding is to be carried out and there is concern that time-at-temperature may be sufficient to precipitate chromium carbides and hence cause sensitisation of the metal, resulting in susceptibility to intergranular corrosion.

The molybdenum content of grade 316 significantly improves its resistance to p1tting and crevice corrosion, particularly in the presence of chlorides. It also increases the material cost by about 20 to 25 percent.

For handling waters, grade 304 is satisfactory up to about 200 parts per million (ppm) chlorides, while grade 316 can be used up to 1 000 ppm chlorides.

Tartaric, acetic, tannic, malic and citric acids are not corrosive to stainless steel at the concentrations found in juices or wines. However, the level of su lphur dioxide is an issue. Grade 304 is generally regarded as resistant to corrosion when immersed in juice or wine at free SO2 levels up to 700 ppm. Above this, grade 316 is recommended. The problem is greater in the vapour space where sulphurcontaining acids can form. Grade 304 is not recommended for use in areas where there is more than 75 ppm SO2 in the liquid. This can lead to composite tanks using grade 316 in the ullage zone and grade 304 in the submerged zone.

FABRICATION PROCEDURES
Cracks and crevices in stainless steel welds can act as initiation points for pitting and crevice corrosion. They can also result in product contamination . The aim should be for smooth weld beads without porosity, slag inclusions or undercut.

During the welding of stainless steels, 'heat tint' is formed. This is a high temperature oxide, rich in chromium which has been drawn from the stainless steel. The result is a very thin low-chromium layer on the underlying stainless steel surtace. For best corrosion resistance, both the oxide film and underlying chromiumdeficient layer must be removed. This can be done by pickling using a nitric/hydrofluoric acid mix, either in a bath or as paste, or by mechanical removal.

Since stainless steel depends for its corrosion resistance on the presence of an extremely thin, continuous chromium oxide film, any contaminants which disrupt this film will reduce its corrosion performance and can initiate pitting. A common contaminant is embedded iron particles from nearby grinding of carbon steel fabrications or the use of iron-contaminated tools. Such contamination can be removed by passivating the stainless steel with nitric acid, followed by a thorough water rinse.

After hydrotesting and before being put into service, tanks should be drained and thoroughly dried. There are too many instances of new stainless steel systems failing due to pitting or crevice corrosion because either:

> Contaminated test water has been left stagnant in the system, or
> The system has been drained but not dried, leaving pools of water to evaporate, concentrating dissolved salts and resulting in corrosive attack.

MAINTENANCE
Stainless steel is inherently a low maintenance material - but it is not zero maintenance. The main requirements are:

> Deposits which build up on stainless steel surfaces should be regularly removed. This is because crevices exist under deposits and crevice corrosion can be initiated in such areas.
> Following cleaning, regular inspection is necessary to establish the condition of the equipment. This will ensure early detection of any developing problems so that steps can be taken to prevent further deterioration.

If guidelines such as these are followed, long and trouble free service can be expected from stainless steel equipment.

Words by David Jenkinson from the Nickel Development Institute.

This article featured in Australian Stainless magazine - Issue 18, May 2001.

Vats Stack Up in New Application

A stainless steel stackable wine storage and fermentation system has been adapted to carry water for use in hospitals. 

STAKVATs feature internal temperature control tubes and a sloped design for complete drainage and radius corners for protection against crevice corrosion and bacteria collection.

Each vat has a storage capacity of 900 litres, can be stacked five high and easily transported on a tray truck. They are also fork-liftable four ways.

The vats are made from grade 316 stainless steel sheet and grade 304 tube. Standard BSM grade 316 fittings are used for the outlets, with door handles and locking pins made from grade 304.

The original STAKVAT design featured replaceable French and American Oak sides used for wine enhancement. The modified STAKVAT has a stainless steel side instead of oak, but maintains the cooling/heating tube system and sloped design.

Oxygenated water is created in the STAKVAT via the airspace in the top of the vat. The water will be circulated through a system of STAKVATs at approximately 30 litres per minute.

Managing Director of Ausvat, Peter Warren said the STAKVAT helped meet an industry need for efficiency in storage space.

"Stainless steel internal cooling systems and the space saved by using STAKVATS produces many cost-effective advantages," Mr Warren said.

Stainless steel for the STAKVATS were supplied by ASSDA member Stirling Stainless Steel, with fabrication by ASSDA members Simcraft Products and Unique Metal Works Pty Ltd.

This article featured in Australian Stainless magazine - Issue 18, May 2001.

2205 Golden Choice for Mine Upgrade

Two 2205 duplex stainless steel elution columns over 12 metres long have been installed in a replacement project at Kalgoorlie Consolidated Gold Mines in Western Australia. 

Elution columns are used in the mettalurgical process of extracting gold from carbon.

Carbon impregnated with gold is hot washed with caustic cyanide in the elution columns to dissolve the gold out of the carbon. The gold solution is pumped away while the barren carbon remains in the columns and then is removed for reuse.

The columns hold temperatures of 140°C and operate under pressures of 550 kilopascals (KPa).

he previous columns, constructed from grade 304 stainless steel, were beginning to fail due to pitting corrosion caused by chlorides carried over in the process water, combined with erosion corrosion on the internal surface. The tanks were in service for a total of five years.

Stainless steel supplier, ASSDA member Sandvik Australia, worked with a consultant to find a more suitable grade of stainless steel for the job.

2205 was chosen for its ability to provide a higher resistance to chloride attack. The grade also has improved hardness over grade 304, thereby offering better resistance to the erosion effect of the activated carbon.

Kalgoorlie Consolidated Gold Mines Mechanical Engineer Adrian Rowell, said the grade change was made to try to ensure the columns lasted the life of the mine.

"The plant is planned to operate for another 15 to 20 years," Mr Rowell said . "By shifting to 2205 we anticipate that the columns will last that long."

Fabricated by ASSDA member Specialised Engineering Services (WA) Pty Ltd, the columns were constructed from 2205 duplex stainless steel
8 millimetre plate, which offered a significant weight saving over the original 10 millimetre grade 304 vessel. The columns were fabricated to AS 1210 class 28 Pressure Vessels with a maximum design temperature of 150°C.

Each elution column is 12.4 metres long, 1.7 metres in diameter and positioned vertically.

This article featured in Australian Stainless magazine - Issue 18, May 2001.

Stainless Metamorphosis for WA Winery

Nearly four tonnes of stainless steel has been used to extend and upgrade facilities at Cape Clairault Winery in Western Australia's Margaret River region.

The project involved the installation of four 5 000 litre red wine hopper fermenters, four 12 000 litre and one 4 500 litre white wine storage tanks and the upgrade of 15 existing tanks of 1 000 -12 000 litre capacities.

Each hopper has a 20 degree sloping bottom to allow complete drainage after service. The design reduces the need for manual cleaning, a potentially dangerous practice due to the build-up of carbon dioxide in the enclosed tank space.

The white wine storage tanks have a conical bottom, also for drainage, and a two piece controllable heating/cooling system constructed from grade 316 stainless steel high pressure cavity plate. If the tank is only half full, refrigeration can be pumped through just the bottom cavity plate.

The cavity plate, constructed by ASSDA member Simcraft Products also features off-centre dimples for greater distribution of the cooling brine.

To convert the winery's existing tanks from storage to fermentation, high pressure cavity plate and temperature probes were added for cold stabilisation, while one of the 5 000 litre tanks was converted to a fermentation hopper.

The tanks were fabricated or upgraded with grade 316 stainless steel in coil, with all welds acid cleaned with post-fabrication polishing to ensure greater corrosion resistance.

The tanks were fabricated in sections then joined together, stacked one on top of the other. Plug welds were used to reduce the risk of cracking at contact points and for improved corrosion resistance.

Simcraft Products undertook all fabrication for the project. Stainless steel and stainless steel components for the tanks were supplied by ASSDA member Austral Wright Metals.

This article featured in Australian Stainless magazine - Issue 18, May 2001.

Tourists Supported by Stainless

Stainless steel spiral handrails provide a stunning support for climbers of Perth's new Bell Tower complex.

Grade 316 stainless steel tube was used to construct handrails for an internal spiral staircase and for an observation platform on the building's sixth floor.

170 metres of tube was used for the staircase, which was spiralled and fixed to the mild steel structure of the building. Washers and neoprene gaskets were used to separate the stainless steel from the mild steel, avoiding corrosion issues caused by dissimilar metal contact.

The handrails were fabricated by Tubelok Metals Australia in their Cannington (Western Australia) workshop and brought into the Bell Tower in six metre lengths.

Handrails on the sixth floor observation platform were secured to the structure with patch fittings through toughened glass, with 40 metres of stainless steel pipe used in total.

All handrail for the project was polished to a AWBP finish (as welded buff polished)_ Stainless steel for the project was supplied by ASSDA member Austral Wright Metals.

This article featured in Australian Stainless magazine - Issue 18, May 2001.

Food Processing Plants Built on Stainless

A combination of grades 304 and 316L stainless steel has been utilised for all contact surfaces in Murray Goulburn's milk processing plant in Rochester, Victoria, which was upgraded in 2000.

The plant comprises an evaporator to concentrate cow's milk and spray dryer to produce various milk powders. Approximately 100 000 litres of milk is processed per hour, with the majority of product for export to over 100 countries. The evaporator and dryer represent more than half of the total project, a capital investment of around A$50 million.

The stainless surfaces and components carry milk feed, evaporated vapour, milk concentrate, milk powder, hot drying gas and cleaning chemicals of alkali and acid.

Ardmona tomato processing plant constructed entirely in stainless steel using grade 304.All product contact surfaces are of austenitic stainless steel grade AISI 304, with the 12m long evaporator tubes being produced from strip then rolled with the seam welded and bead rolled; the tubes have a 2B internal finish.

Principal contractor Niro Australia received instructions to proceed in July 1999 and conducted the first powder trials 14 months later, with commercial production starting November 2000.

To carry out the project, Niro involved Victorian fabricators Stainless Technology and PLC Engineering, though some fabrication was also conducted in New Zealand.

ASSDA member Alfa Laval supplied food grade stainless steel pumps, process valves, tank equipment, fittings and tubing worth over $2.5 million. The total supply was in excess of 40 tonnes and included 40km of tubing in sizes 1" to 6".

Grade 316L stainless steel was used for wetted parts (parts in contact with process fluids) and 304 for non-wetted areas. Products were generally supplied with a no.4 external surface finish; AS 1528 was used as the guideline for component standards.

Many of the process pumps and valves were chosen for their product handling characteristics. Specialist mixproof valves, which allow two different products to travel through the same valve without fear of intermixing, and high efficiency pumps were selected. Spillage-free mixproof valves were specified to prevent accidental discharge onto process floors and ensure a clean process environment, and rotary lobe pumps were selected for their gentle handling of cream products.

Pre-fabrication of many of the valve and pipework assemblies was carried out off-site in controlled environments. Due to the critical nature of the process applications, importance was placed on welding techniques and subsequent cleaning of welds. Valve manifolds were pre-fabricated and transported to site on completion, minimising the number of critical welds performed on site.

TOMATO PROCESSING
Fifty thousand tonnes of tomatoes have passed through Ardmona's processing plant in Mooroopna, Victoria, since it began operation a year ago.

The $15 million plant, which produces whole peeled and crushed tomatoes, was constructed entirely in stainless steel using grade 304 for the structural components and 316 tube and fittings for the wetted parts. Stainless steel was specified for its corrosion resistance and low maintenance, and to meet the health and safety requirements of a food processing plant.

Designed with a life expectancy of 30 years, the plant is capable of processing 40 tonnes of tomatoes per hour.

Ardmona's Engineering and Production Department, in conjunction with Italian firm Sasib Foods, were responsible for the design, engineering and construction aspects of the nine-month installation.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Monumentally Successful

The first edition of Australian Stainless featured the flagpole which towers over the new Federal Parliament building in Canberra. Ten years on and fifteen years since it was erected, the flagpole is well on the way towards its planned 200 year life. A condition survey was recently carried out by an ASSDA member for the Joint Houses of Parliament Committee.

The statistics: the 81m high structure is constructed mainly from 16mm thick hot rolled 304L plate: the base plates are 321 and the clusters supporting the flagpole proper are unpolished, cast 304 equivalent (CF-8). The four triangular legs rise diagonally for 28m from the top of walls to the east and west, before curving to vertical 4m below the lower cluster. The legs continue for a further 15.5m to the upper cluster and terminate 5.1m above the upper cluster. The circular tapered flagpole extends 25.7m above the upper cluster.

The corner and face welds of the leg plate joins were ground using grits down to #120 to match the bold plate surfaces.

As the flagpole was assembled 18 months before Parliament House was completed, it was exposed to the dust and pollution of a construction site; since Parliament opened it has experienced air quality of a rural environment.

Although quite safe, the inspection required a good head for heights while using a "lie back and enjoy it" lift up one leg or the less steady 7m scissor lift to reach the lower plates of the legs. A 40 power theodolite lent by the ACT Survey Office completed the inspection of inaccessible areas.

SURVEY RESULTS
The overall appearance of the flagpole is outstanding. The rib marks, plate to plate welds and polishing patterns along the legs all add to the visual impact. The multiple heated weld joins are as bright as the rest of the surfaces. Slight deposits at drip points aren't obvious to the casual observer and were easily removed with a damp cloth. The location of these deposits was determined by the prevailing weather.

Encouragingly, neither design crevices nor minor fabrication anomalies have caused obvious corrosion in 15 years' exposure.

Occasional small round rust spots, probably caused by pollution during construction, were visible at a distance of about 30cm. There were fewer spots near the masthead probably due to better rain washing and less pollution. The spots were readily removed with water and a plastic scourer and when examined at X30 did not show pitting. Consistent with surface profile expectations, the unpolished top of the legs showed no signs of spots. Surface profile measurements around the base of the legs showed surface roughness between 1 and 1.5 micrometres with a vertical polish direction.

And the future? 304 is ideal for this environment and with the decision to clean off drip line deposits and monitor selected areas for changes in appearance, it is expected that the flagpole will still be brightly glistening in the sun in 2200.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Stainless Steel Evokes Korean War

Polished stainless steel poles represent a barren wartime landscape at the Korean War Memorial in Canberra. The history of the conflict is etched in curved stainless steel panels. 

ASSDA member MME Surface Finishing polished 1000 lineal metres of 25 nominal bore schedule 10, grade 316 pipe to make 260 poles standing 3.8m high. These were welded and gusseted to 12mm thick plates, chemically anchored to a concrete slab, by the fabricator, ACT Stainless Steel.

The other main components of the Memorial,also fabricated and installed by ACT and polished by MME, are the curved stainless steel panels inside a central viewing platform, which record the history of the war with maps and illustrations.

There are eight 3000 x 1200 x 3 mm sections and two 3000 x 3000 x 5 mm. The 5 mm sections were formed by TIG welding sheets together, then polishing, as joins were not desirable. The polished finish enabled the welded areas to be blended after joining. The sheets were coated with 80 micron polyethylene film to prevent damage to the polished surface during etching and fabrication.

MME also polished the stainless steel lettering provided by Waterjet Dynamics to a uniform roughness of 0.5 microns.

The whole project was completed under the $1.6million budget, which was raised by Korean War veterans and donations from the two countries.The construction time frame was 23 weeks, and practical completion was achieved 17 April 2000,the day before the dedication ceremony attended by then Governor-General Sir William Deane and Prime Minister John Howard.

The design was by ANKWM Design Group and documentation was completed in conjuction with architectural firm Daryl Jackson Pty Ltd. Manteena Pty Ltd was the project manager.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

 

Aspects of Mig Welding Thin Stainless Sheet

Principles of Mig Welding

According to the AWS Welding Handbook volume 2, MIG welding is "an arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. The process is used with shielding from an externally supplied gas and without the application of pressure". The wire is usually supplied in spools and fed through to the welding arc by an electric feed motor, with no manual control ofthe wire feeding process ie semiautomatic.

Most materials, except aluminium, use what is termed a ‘constant potential power source’, and this automatically regulates the arc gap by varying the burn off rate of the wire.

MODES OF METAL TRANSFER
There are four modes of metal transfer possible with the standard MIG welding system: short circuiting (or dip), globular, spray and pulsed modes.

Short circuiting transfer is the mode which uses the lowest amperage range, hence the lowest heat input of the four variants. Essentially the electrode contacts the molten weld pool, completing the electrical circuit. Resistance heating of the electrode takes place until the tip of the wire is melted off and transferred to the weld pool. The arc is then extinguished, until the tip of the wire comes back into contact with the weld pool, and the cycle begins again. This process is repeated between 20 to 200 per second.

Globular transfer uses slightly higher currents than for short circuit transfer, but lower than those used for the spray mode. The arc is continuous, but the molten metal is transferred across the arc in a characteristic globular fashion, with the globule diameter greater than that of the electrode.

Spray transfer uses the highest current ranges, having a continuous arc, and the weld metal transferred across the arc in many tiny droplets. The droplet diameter is equal to or less than the electrode diameter, and is also accompanied by an electric force propelling these droplets across the arc, hence the term spray transfer.

Pulsed transfer is achieved by using a lower welding current at which conventional spray transfer would not be possible, and then imposing background pulses of power through the system. Typical pulsing frequencies can be up to 40 kilohertz and this in turn transfers one droplet across the arc per pulse, thus achieving spray transfer at lower welding currents.

SHIELDING GASES
A variety of shielding gases are available from many suppliers, which have been refined to suit various applications. A major effect that these gases have, is their ability to influence arc stability and mode of metal transfer.

The common MIG shielding gases are Argon and CO2. At all usable welding currents, CO2 will commonly produce a drip or globular transfer, whilst the full range of transfers can be obtained with Argon.

Mixtures of these two gases as well as a one or two percent addition of oxygen are also common when MIG welding the carbon and low alloy
steels. They have been designed to get the best characteristics of both gases, and improve arc stability, metal flow, sidewall fusion, wetability
etc.

PROBLEMS ASSOCIATED WITH MIG WELDING SHEET MATERIALS
It should not come as any surprise that welding sheet metals by the MIG process must have limits, especially on the thinner sections. MIG welding is a relatively high heat input process, and hence the rate of heat transfer away from the weld pool becomes important. The surrounding material must be able to support and maintain the weld pool until it solidifies. The final weld must also have an acceptable bead profile, with visual and surface quality within the specification requirements. Heat input must be kept to a minimum, and this in turn implies a
short circuit or globular transfer mode. Unfortunately, these modes are prone to spatter.

A compromise must be reached between heat input, travel speed, weldability and bead shape, which are all influenced by specific gas compositions.

The table shows some results of MIG welding austenitic stainless steel sheet using a one millimetre diameter wire, with a variety of gases. The volts and amps recorded indicate the lowest settings which achieved the stable transfer mode indicated.

The values of interest, and which formed the basis for the experiment, are the electrical settings, namely the amps and volts. Travel speed is obviously important in reducing heat input, but the effect of gas composition on the stable mode of transfer was the primary objective.

CONCLUSIONS
The results obtained not only confirmed the expected problems when welding thin stainless sheet, but also produced some interesting points
when using the pulsed transfer mode. As expected, spray transfer is not recommended for thin sheet.

Helium, as an alternative addition to shielding gases definitely has advantages in achieving an acceptable weld profile over the more common
gas mixtures, even in semi-automatic welding, but a greater degree of competency is required by the welder to be able to handle the necessary faster travel speeds.

Pulsing helps to overcome the problems associated with bead shape and burn-through, and if the equipment is available, it negates the advantages offered by a helium containing gas. Higher travel speeds in the pulsed mode are still necessary with the helium addition. The use of a helium-containing mixture with the pulsed mode should offer a combined benefit of a lower heat input and faster production rates, and, hopefully, less distortion as a result.

Words by Jim Henderson.

Reproduced with permission from the Australasian Welding Journal Volume 45 Fourth Quarter page 21.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Stainless at Sea World

Sea World's latest attractions, polar bear cubs Lia and Lutik, have captured the public's attention since their arrival from Russia late last year. The one-year-old siblings join resident polar bears Kanook and Ping Ping, who have already given the park one of its most successful years since Polar Bear Shores was built in 2000.

The use of stainless steel in the construction of the polar bear enclosure contributes to giving park visitors a close look at the playful cubs and the adult bears. Large underwater viewing windows, supported by stainless steel frames, allow the public to watch the bears swimming and diving in a four-metre deep pool.

The health and well-being of the bears is a prime consideration in the design of their custom-built enclosure, which Sea World says "leads the world in providing a naturalistic and stimulating environment utilising the latest in polar bear technology, drawing on international research and knowledge."

The exhibit features natural landscaping, chilled water pools, shade cover, water misters and streams, wind generators and diving and climbing opportunities. Stainless steel plays a significant part. The larger bears are powerful animals, and strong stainless steel doors onto the exhibit ensure their security as well as the keepers'. The four air-conditioned den areas are made of grade 316 stainless, selected to withstand the corrosive effect of bear urine and daily hosing out.

Introducing the bears to one another had to be carefully managed. A specially designed stainless steel mesh screen known as the "howdy window" separated the older bears during the quarantine period, while allowing them to see and smell each other. Kanook, who was 16 when she was brought to the Gold Coast from Arizona, has taken the dominant role while Ping Ping, a young curious five-year-old when he arrived from China, is more submissive. The screen was a success with the two now getting along well together. The same method is being used to familiarise the bears and the new cubs without any risk to Lia and Lutik.

Bringing the polar bears to Australia was the culmination of three years of research and planning. Sea World says there has been overwhelming interest and support from the public which in turn can only assist conservation efforts for the polar bear.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Stainless Strength for Bridge Projects

The Tasmanian Government has embarked on a series of bridge renewal projects, using stainless steel reinforced pre-cast concrete to replace old timber structures.

The Barnes Creek bridge is the first of three to be rebuilt on Brunie Island, south of Hobart. It utilised 7.5 tonnes of grade 316 and duplex 2205 stainless reinforcing bar in a size range of 12 to 25mm supplied by ASSDA member Arminox Australia Pty Ltd.

The Tasmanian Department of Infrastructure, Energy and Resources specified stainless steel for the reinforcing to save on ongoing maintenance costs. The location of the bridge presents construction and maintenance challenges, with the site only accessible by ferry.

The grade was selected to meet the demands of an aggressive marine environment. The bridge is subject to salt-laden winds and salt water covers the foundations at high tide. The 6.5m bridge, which connects local rural and residential areas, has a service life expectancy in excess of 100 years.

SORELL CAUSEWAY
Another of the Department's major projects is the construction of a new 490m bridge connecting the Tasmanian east coast to the Tasman Peninsula. The new Sorell Causeway has been designed to cater for heavy vehicles, a high volume of local traffic and tourists travelling from Hobart to Port Arthur. A small quantity of only 6.5 tonnes of stainless steel 316 and duplex 2205 reinforcing is being used in the critical area of the pile cappings.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Architectural Stainless

World Class and Australian Made

The Australian stainless steel industry is committed to providing high quality, durable products for the architecture industry.

Vee-cut technology is an example of precision fabrication catering to the demands of architects and designers.

Following the importation of a Japanese vee-cutting machine, Australian manufacturers now offer extremely accurate sheet metal folding, resulting in excellent optical features.

The Amada machine operated by Vee-Cut Australia in Sydney produces tight radius curves with precision, while hardly altering the surface tension of the stainless sheet. This produces minimal distortion even with the use of mirror finishes. The machine is capable of handling heavy gauge (up to 6mm) material allowing the manufacture of very strong architectural elements with the precision and high polish associated with light-weight constructions.

GUCCI STORES
Vee-cut technology is typically used for architectural features where clean, sharp lines and a high level of finish are desired, such as shop and hotel fittings and joinery items. The machine has been utilised in the manufacture of stainless steel shop fittings for fashion house Gucci, with the Sydney store the latest in a series which includes Saipan in the Pacific, Auckland and the Gold Coast.

Each fit-out includes illuminated stainless steel and glass showcases made to Gucci's worldwide store design (pictured), and miscellaneous stainless fittings such as shelving, belt straps and lettering totalling around $100 000 per store. About a dozen cabinets have been built for each store using grade 304, 2mm gauge material polished to no.8 mirror finish.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Style + Strength

The superior strength of stainless steel has long made it the material of choice for prison toilet facilities. Innovative styling has now opened up a new market in public restrooms. Increasingly, venues are turning to stainless steel to make their facilities safer and reduce costs in the long term. 

Vandalism in public facilities is a widespread occurrence, with some pub and club owners forced to replace a toilet every few weeks. While the initial outlay may be higher for stainless fittings, the cost of replacing and installing a ceramic pan can be recouped after just one instance of vandalism. Unbreakable stainless steel also eliminates the risk of injury from sharp ceramic shards and the inconvenience of effluent overflow.

Stylish designs mean that aesthetics aren't sacrificed for practicality. Martin O’Brien, General Manager of the recently refurbished QA Hotel in Brisbane’s Teneriffe, says stainless steel was the logical choice because it’s "tough as teeth, durable and looks good. Stainless steel was the best way to go - its clean lines never go out of date." As part of a total makeover, the QA replaced ceramic tiles and fittings with stainless steel. O’Brien says vandalism in pubs is a big issue, with "punters" taking out their frustrations in the bathrooms and causing a lot of damage to conventional fittings.

ELEGANT AND FUNCTIONAL
Metal, timber and black are the predominant themes in the $3 million refurbishment of the 120-year-old Regatta Hotel, overlooking the Brisbane River. Conceived by owner-developer Steve Hammond, the renovation juxtaposes high tech and rustic, with gleaming metal and glass surfaces set against timber frames and sandblasted brick walls. The metallic theme continues outside with stainless steel topped café tables on the pavement and verandahs, and aluminium louvres replacing traditional lattice.

Stainless steel is integral to the washroom design, combining clean, minimalist lines with durability, vandal-resistance and minimum maintenance. Push pad controls replace vulnerable taps, while moulded stainless steel pans with in-wall slimline cisterns and push pad flush eliminate other targets for vandals. Stainless steel is used for mirrors, air-towels, soap and toilet paper dispensers.

Stainless steel fabricator Stoddart, who drew on the resources of ASSDA to develop a commercial product range, says their pans are often specified as part of a suite to fit in with a high-tech, architectural look. This project used Stoddart's standard shrouded toilet made from satin finished, 316 stainless to withstand heavy duty cleaning products. A pin inside the bowl prevents objects like wine glasses being flushed into the plumbing. The flat plate design of the rim flush makes the toilet contraband-proof and the unit has the advantage of being able to be fixed onto a wall from the inside.

Stainless steel features heavily elsewhere in the bar frames and counters and in a microbrewery. Three 2 000 litre stainless steel tanks with decorative copper cladding have been incorporated into the design of the downstairs bar. The beer is piped to fermentation tanks in the upstairs bar, which form a backdrop to the dancefloor. Apart from providing a theming enhancement to a predominantly beer pub, the installation of a microbrewery was a commercial decision in response to a growing demand for boutique and specialty beers, says project manager Rob Forbes.

BEACHFRONTS AND PARKS
Local authorities present another significant market for stainless steel amenities. Gold Coast City Council, which for some years has had a policy of replacing vandalised ceramic toilets with stainless steel ones, is now installing stainless steel pans in all new public convenience blocks. To improve safety, the Council is also considering installing stainless steel woven security mesh near the entrance of public toilets. The one-way screen allows people to see if is there is a threat outside the building before exiting.

STYLISH STAINLESS SHOWERS
In conjunction with Stoddart, Gold Coast City Council is developing a prototype stainless steel shower to eliminate the corrosion problems of beachside installation. Ian Munro, Supervisor in the Council’s Building & Maintenance section, says the project has attracted interest from other councils on the coast. Seven showers are currently being tested. ASSDA member Stoddart has also manufactured stainless steel street furniture for Casuarina Beach on the Tweed Coast in northern NSW including beach-themed showers in 316 stainless. These are designed to be vandal and weather resistant and feature automatic water cut-off to prevent wastage.

Image on left: Casuarina Beach 316 stainless surfboard shower. Design by Hutton-Harris. Fabrication by Stoddart.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

Coated Abrasives for Surface Finishing - Part 1

Accurate specification of a surface finish is vital for extracting maximum functionality and durability from stainless steel components. Read Part 2. Read Part 3.

Coated abrasives are important in generating the right surface finish for corrosion resistance, cleanliness, aesthetics or other requirements.

MANUFACTURING PROCESS
Primary manufacturing processes such as casting, forging or rolling produce a surface finish which may be adequate for the end function. If not, there are secondary processes such as machining, cutting, grinding, lapping or mass finishing using tumbling techniques or barrel finishing.

Surface finishing techniques may be mechanical, electrical, thermal or chemical or a combination. The finish depends on grit size, pressure and
product selection.

COATED ABRASIVES
Coated abrasives in the form of belts, rolls or discs are used during both the primary and secondary manufacture of stainless steel into coils, sheets or fabrications. Methods and machinery may vary but the broad principles are:

> do not abrade unnecessarily – start at the finest grit which will produce the desired finish quickly

> never skip more than two grit sizes in a polishing sequence or previous grit lines cannot be removed

> don’t use excessive pressure – coated abrasives cut well with minimal pressure

> don’t persist with a worn abrasive product – when a disc or belt stops cutting it should be replaced.

DEVLOPMENTS
The drive for better manufacturing has yielded improvements to grinding and polishing machinery, accompanied by developments in abrasive products. Better abrasive grains give faster stock removal and longer life which has led to increased horsepower being specified and this has necessitated improvements to the quality of backing materials.

COATED ABRASIVES AND SURFACE FINISH GENERATION
A coated abrasive has three components – backing, adhesive and grain – each of which affects the outcome.

BACKINGS are manufactured from paper, cloth, fibre or a combination, non-woven material or polyester film. The type selected should:

> have sufficient tensile strength to transmit the power loading of the machine

> be flexible enough to conform to component shape

> provide a substrate suitable for the relative strength of adhesive required

> not stretch unduly during use

> in the case of very fine grit coatings, provide a flat and true surface.

Paper backings come in a variety of weights designed for specific tasks. In the stainless steel market belts are most commonly manufactured in E (180-200gsm), F (230gsm) or G (300gsm) weights. They may also have anti-static surface treatments to minimize dust adherence.

Cloth backings come in many varieties. Most commonly, X weight (cotton) and Y weight (polyester) are used in heavier stock removal operations such as the grinding of castings and J weight, which is lighter and more flexible, is used for contour work – polishing complicated shapes. Different cloth backfills applied to the rear of the coated abrasive belt allow it to be used for dry and wet operations (oil or water) according to the type of operation.

Cloth belts are normally used on higher horsepower machines and need to be strong enough for the transmission power which can be as high as 10HP per inch width of belt (7.5kW per 25mm).

Vulcanised fibre is used extensively in the manufacture of resin fibre discs. It is less flexible than paper and cloth backings but has the strength required to withstand high operational speeds and heavy grinding pressures.

Combination backings consist of an E weight paper reinforced with an open weave cotton scrim cloth. They are usually used for very coarse grit operations.

Non-woven backings such as lofted nylon are used in the manufacture of hand polishing pads and rolls. This material also forms the basis of many convolute wheels and flap brushes (pictured) which are used to impart a special brushed finish.

BONDING ADHESIVES are used to anchor the abrasive grains in place on the backing. They can be natural animal glues but thermosetting synthetic resins are the norm. They are stronger, tougher and resist heat and fluids better. Different types and strengths have been developed according to the product’s end use. As a rule of thumb, if belts or discs are shedding (losing grain) then the bond strength needs to be increased; if the product is showing signs of glazing (metal pick up) then the bond needs to be less strong.

ABRASIVE GRAINS Most of the grains in use today are synthetically manufactured to be hard enough to penetrate the substrate being ground while still fracturing under dynamic impact to present new cutting facets. They are designed for high thermal and chemical resistance at grinding interface temperatures.

Premium grade aluminium oxide grains are an effective general purpose abrasive. Silicon carbide grain is used to impart a brighter finish, however it has a comparatively shorter product life. Although more expensive, the newly-developed zirconia alumina grain produces a more consistent finish throughout the life of the product.

Words by Charles Fenton. Charles E. Fenton is Managing Director of Klingspor Abrasive Technologies, Australia. The next article in this series will look at how backings, bonding adhesives and abrasive grains are combined.

This technical article featured in Australian Stainless magazine - Issue 22, September 2002.

A Safe Surface for Food Processing

A contaminant-free surface is a critical requirement of the food processing sector and electropolishing is a highly effective way to achieve the level of surface smoothness required for keeping stainless steel components scrupulously clean. 

Pillsbury Australia in Melbourne's outer east is one of a growing number of food processors who have opted for electropolishing for hygienic and durable stainless steel components. Pillsbury produces the fresh pasta brand Latina Fresh. The range consists of filled pasta types like ravioli and tortellini for which the fillings are cooked during manufacture, but the consumer completes the cooking process at home. For some years now, Pillsbury has specified an electropolished finish for all its stainless steel food preparation equipment and related components such as trolleys, cooling racks and other fittings. These are manufactured by GP's Fabrications and electropolished by ASSDA member MME Surface Finishing.

As well as promoting hygiene, electropolishing enhances stainless steel's corrosion resistance. Many fittings in Pillsbury's plant have been in constant operation for eight to ten years and show no sign of surface deterioration despite exposure to steam-laden, high temperature atmospheres.

Electropolishing works by selectively removing surface metal thereby smoothing and levelling the stainless steel. This is done by immersing the component in a chemical bath to which lowvoltage electric current is added. Stock removal is controlled to a high degree of accuracy by adjusting the time, temperature and current density.

The resulting finish is free of surface flaws and impurities, giving no opportunities for deposits to lodge and contaminate the food product. A further benefit is that it makes the components easier to keep clean, allowing for longer periods of processing activity.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Australian Technology Advances Industry

A new technique for manufacturing high pressure cavity plate for heat exchange applications developed by the Australian stainless steel industry increases the options available to the food processing and manufacturing sectors. 

'Laser welded cavity plate' has been developed by ASSDA member J Furphy & Sons, a Shepparton fabricator of stainless steel tanks and processing equipment, as an alternative to resistance or plug welded dimple plate used for the heating or cooling jackets on stainless steel tanks, vessels and silos.

A wide range of industries stands to benefit from the new cavity plate, from dairy, brewing, food, wine, pulp and paper, chemical, pharmaceutical, refrigeration to textiles and manufacturing.

It is designed to be used in jacketed tanks, pressure vessels, shells and heads, troughing, chutes and hoppers, immersion plates, bank assemblies, baffles, ice-making plates, water chillers and food cookers.

The method of manufacture allows design flexibility enabling it to be tailored to specific performance requirements. It can be designed to suit both the flow characteristics of the refrigerant or heating medium and the required performance objective for the equipment by programming the cavity pattern and dimensions into a CNC controlled laser welding system.

The process involves laser welding two sheets of stainless steel in their flat form and inflating to form the cavity through which the cooling or heating medium is transferred.

The laser welds are exceptionally strong and have been burst tested in excess of 13 000 kPa, with most common demand being for operating pressures between 300 and 3 000kPa.

The product is available single embossed for uses where a flat inner wall is required or double embossed for immersion where both sides of the plate are utilised to heat or chill.

It is in use in chocolate crucibles in the confectionery industry as well as in Peerless Holdings’ edible oils processing tanks. Orbis Engineering has used the cavity plate in a cooling tunnel conveyor bed and Barry Brown & Sons has utlised it in on-farm milk silos. It has also been used in various major winery projects, including Peace Wines and Jindalee Estate, for fermentation and storage vessels.

Another ASSDA member, A&G Engineering of Griffith, has specialised in cavity plate for use as a cooling plate in wine vessels for a number of
years. This product also incorporates technology unique to Australia.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Stainless Takes Flight

Lightweight stainless steel sheet, polished to a high level of reflectivity, has been chosen to interpret the layered feathers of one of Australia's national icons, the dancing brolga. 

Designing and creating a trio of life-size sculptures has occupied much of Allen Minogue's time since his retirement as an engineer and designer.

The birds, inspired by a visit to the Northern Territory, have cast grade 316 legs and heads and feathers made from 2B finish 316 sheet in four
thicknesses, from 0.55mm to 1.2mm.

The feathers are all individually shaped using a hand guillotine and other hand tools. They are then screwed into a fibreglass body moulded from a wooden carving. The first figure, which took 700 hours to complete, has 700 feathers. The poses are realistic, with the central male bird
captured at the moment of taking flight.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

 

Stainless Memorial to Rail Workers

Stainless steel responds admirably to the strength and durability imperatives of public art at the Ipswich Workshops Rail Museum, opened to the public earlier this month.

The Workshops began operations in the 1860s and initially assembled components imported from England, but by the early 1900s railway stock was being manufactured from the ground up. During the peak employment period of the 1950s there were over 3 000 workers. To reflect the Workshops’ importance in shaping the identity of the town of Ipswich, west of Brisbane, the design brief called for a monument concentrating on the social history of the Workshops and the contribution of the vast number of workers, interpreted in a contemporary framework.

In response, Brisbane sculptor Brad Nunn designed MARKER, a curving stainless steel column bearing the words spirit and presence,studded with numbered discs representing individual workers.

Each worker had a disc resembling a dog tag known as a check, which he collected from the foreman on arrival at work. He used the check throughout the day, for example to borrow tools, and returned it when clocking off. Railway authorities calculated the workers’ pays by seeing which checks had been collected each day.

Nunn obtained a first-hand account of life at the Workshops from his father, an apprentice there in the late 1940s. He chose the text to communicate the strong spirit of place he felt when touring the Workshops and selected a photo of payday, 16 July 1924, which was reproduced at eye-level using laser marking to retain tonal variations.

Nunn, who has been practicing artist since graduating from the Queensland College of Arts in 1990, has previously designed public artworks
using aluminium. He chose stainless steel for this project because it fulfilled the brief’s requirements for durability, longevity and vandal-resistance.

Fabrication of the sculpture was carried out over 300 hours by two staff members of ASSDA member Stoddart Metal Fabricators. The 3m high structure weighs about 1 tonne. Grade 316 plate in 10mm thickness was used; the hundreds of round recesses were milled out and the column bead-blasted and finished with a no.4 vertical polish. Approximately 600 checks are attached to the sculpture and another 600 appear to have been dislodged and are glued to the concrete base around MARKER.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

New Technology for Design Excellence

The overwhelming response from the architecture community to our earlier article on precision folding of stainless steel sheet using vee-cutting technology has prompted a more in-depth look at the process. 

Thanks to vee-cut technology, stainless steel sheet can be formed into angles as precise as those obtained by extrusion. This technology is now being carried out in Sydney, allowing the local manufacture of a whole range of stainless steel architectural products. The technique is particularly suited to elements such as door fronts, window frames, shopfronts, showcases, elevator doors as well as all forms of cladding.

In a completely new method of manufacture, vee-cutting can also be used to make flat products such as tread plates for lifts and escalators by removing strips of material to the required width and depth.

CLEAN LINES COMPLEMENT SPECIAL FINISHES
Ordinary bends made on a brake press typically produce a corner radius twice the thickness of the sheet, resulting in a finished product with soft, blurred lines. But with the introduction to Australia of vee-cut technology, it is now possible to produce stainless steel with corners as precise as an extruded angle, such as those found on aluminium window frames.

The method is particularly useful when working with textured and patterned stainless sheet. Such finishes are distorted by the traditional bending method. Using the vee-cut machine, the feature finish is preserved without loss of quality. This makes it the manufacturing method of choice for items such as bar fronts, display cases, door furnishings and a myriad of other uses where appearance counts.

THE VEE-CUTTING PROCESS
The machine cuts a continuous vee-shaped notch in the sheet using a series of five tools, which make repeated passes across the surface. The number of passes required varies depending on the thickness of the metal; generally three or four are needed, but up to 15 can be required for thicker product.

The machine can handle thicknesses in the range of 0.6mm to 6.0mm and is capable of cutting to a minimum depth of 0.4mm and processing sheet up to 4m in length. The sheet is then folded along the groove in a brake press. The depth of the groove can be set for acute angles down to 15°.

When used for cladding, up to 70% of the thickness of the sheet can be removed; however, care needs to be taken not to weaken structural components by removing too much of the thickness. One option is to remove material to obtain a tight corner and then stitch weld to restore strength – it is a matter of weighing up cost and other considerations.

A TYPICAL APPLICATION - ENTRANCE DOORS
An example of the finish available can be seen in the revolving doors of the McKell Building in Sydney (pictured). Byrnes Entrance Technology Pty Ltd (BET) worked with ASSDA member the Townsend Group to produce profiles and folded panel sections to clad the central steel and aluminium core of the triple door. The final effect is the appearance of a solid, triangular-shaped central column with lightly inward-curving sides.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Stainless, Sun and Air

Stainless steel is well-known as a versatile and attractive medium for large scale public artworks. Two recent projects by Perth’s Stusha Studio make use of different treatments of the material to deliver attention-grabbing results.

INSPIRED BY NATURE
The Armadale Kelmscott Memorial Hospital in WA commissioned shade structures in two courtyards and Stusha Studio responded with four elements, representing a flower, a seed, a leaf and a fruit, inspired by the orchards of the area and the seasons. The structures provide a shadow-play on the courtyard floors and walls, blushing the areas with shade.

The elements are made of stainless steel mesh, rod and square tube and are suspended at 4.4m. The material supply of grades 316 and 304 and support from ASSDA member Stirling Stainless Steel was crucial to the production of the work, fabricated at Stusha Studio and Art Engineering.

As the shades were installed after the hospital was complete, they were made in sections and re-assembled like a kite inside the courtyards. Because the rib-work for the shade structures was garnet-blasted, installation required care to avoid scuffing and this was provided in ample amounts by Damien Costello at Tension Structures.

COLOUR AND MOVEMENT
Hale School in Wembley, WA commissioned a sculptural interpretation of the theme ‘young hearts run free’. Stusha Studio created four stainless steel winged figures, grounded in four points but able to move with the wind, suggesting freedom no matter what the conditions.

The figures are on internal bearings that allow the whole structure to respond to the breeze. Because of their different dimensions the figures move at varying rates, producing an ever-changing kinetic sculpture.

The wings are made entirely of grade 304 stainless steel, cold forged under the largest hammer in the southern hemisphere at Ferrous Forging in Sunshine, Victoria. The sheets were heated by torch, rippled and fabricated by Kevin Burnett at Red Falcon in collaboration with Stusha Studio, in Melbourne. The wings were then shipped to Perth and combined with the rotating shaft, designed by Michael Ong and machined by Medical Engineering.

STAINLESS FOR PUBLIC ART
In carrying out these and other commissions, Stusha Studio has chosen to use stainless steel to deliver artistic concepts because of its robust quality and the easy access to technical advice and expertise. As an artistic material, stainless steel is versatile in the decorative treatments it supports. Text and graphics can be etched into the surface and paint filled if desired, while forging opens up a whole range of colours and effects.

This article featured in Australian Stainless magazine - Issue 22, September 2002.