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Savings for Stainless


Posted 30 November 2003

Researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Cooperative Research Centre for Welded Structures (CRC-WS) have developed a welding process for stainless steels and other corrosion-resistant metals that is significantly faster, cheaper and easier than current practices.

The patented process is an elaboration of standard gas-tungsten arc welding (GTAW), and uses a specially designed torch that establishes and maintains a ‘keyhole’ at the joint.

The weld then proceeds, zipper-like, with the melted sides of the keyhole fusing at the back as the torch melts new material in front of it.

Keyhole GTAW is most effective for materials of low thermal conductivity, such as titanium and stainless steel, but does not work with good thermal conductors such as aluminium.

‘In comparison to conventional GTAW, machining of the edges to be joined is greatly reduced, it uses about one-twentieth the filler material, and reduces the welding time by about tenfold’ says Dr Ted Summerville, a commercial manager at CSIRO Manufacturing & Infrastructure Technology in Adelaide.

Applications of the technology include tube making, welding of rotatable products such as pipes and the joining of large sheets. The technology is particularly advantageous for welding thicker materials.

In keyhole welding, the arc melts the metal right through on both sides of the joint. Via surface tension, this establishes a stable structure which joins the front and rear surfaces through the width of the material. The weld pool is thus anchored, preventing the ejection of molten material.

The result is a process which is not only relatively inexpensive to acquire, but is also cheap to operate. The torch melts right through the joint where the two metal pieces to be welded abut, and molten metal extends through the depth of the material – up to 12mm thick for steels and 16mm for titanium alloys.

Very little filler material is needed to make the joint – about 50g/m for welding 12mm thick stainless steel, compared with about 1kg/m using conventional GTAW. And the joint is made in one pass, compared with up to seven for the thickest steels and titanium alloys.

Reduction to a single pass means that the metal at the site of the weld is only at risk of contamination once, whereas if it is welded seven times, there are seven opportunities for contamination.

The lack of multiple passes also vastly increases welding productivity. Typical examples of keyhole performance include single-pass welding of 12mm thick austenitic stainless steel at speeds of 300mm/min, 8mm carbon–manganese steel at 500mm/min, and 3mm ferritic stainless steel at 1000mm/min.

In one comparison, the welding time of 35min/m for 12mm stainless steel plate using conventional GTAW was reduced to <3.5min/m using the keyhole method.

And the quality of the welds is generally excellent. ‘We have qualified the process against a range of American standards’, says Dr Summerville, ‘and it has always passed’.

In addition, it is clean welding process. Fume generation using conventional GTAW is very low, and the same is true for keyhole GTAW.

The drawback to keyhole GTAW is that the torch can only be used in the conventional downhand position – the joint must be made between horizontal sheets with the torch vertical.

Recent work, however, has demonstrated that it is possible to operate the technology ‘out-of-position’, and this could lead to many new applications in the future.

‘If keyhole welding could be done in any position – for instance, if you could rotate the torch around pipe – it would increase the market for the technology by about ten times’, says Dr Summerville.

The technology is currently being licensed by the joint owners of the technology – CSIRO and the CRC-WS – and licencees are already successfully applying the technology in USA and Finland.

A number of licensees in these markets have reported significant productivity improvements.

Licenses for the keyhole welding technology are being offered in Australia, Europe and USA for use in the manufacture of products ranging from spiral-welded pipe to railway rolling stock.

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Specifying Stainless Steel Pressure Piping for High Rise Buildings

Brisbane's tallest residential tower, The Aurora will stand 69 levels and will set an important precedent in the use of stainless steel pressure piping in high rise buildings when the Bovis Lend Lease project is completed in January 2006

 

Situated on the corner of Queen, Eagle and Wharf Streets in the Brisbane CBD, The Aurora utilises stainless steel pressure piping instead of conventional copper piping to ensure adequate water pressure for each of the 478 two and three bedroom apartments in the $250 million development.

ASSDA member, Blucher Australia, supplied approximately 250m x 108mm OD x 2mm Mapress tube and fittings, 90 degree and 45 degree bends, sockets, flange adaptors and tees in grade 316 stainless steel.

The Aurora project is different to conventional installations due to a single metered water supply being provided to a common pump set for both potable and fire fighting services.

The potable supply is then directly pumped to a reservoir at the top of the building, thus eliminating large costs of having to set aside floors for transfer tanks, pumps etc.

The fire service is branched off the potable supply immediately after the pump set and separated with a non-return valve allowing potable supply to continue the 70 storey rise to the top floor gravity feed tank. The potable water supply is to be an approved system and also able to withstand both the head pressure created by the vertical rise and pressure of emergency back up pumps in the event of a fire, which in this case is 2490 kPa.

The Mapress 316 Stainless Steel Press-Fit System was recommended by Mark Tapley of Plumbing Contractor Tapworth and Booth and specified by Hydramellenia, the subsidiary of Brisbane Hydraulic consultants Steve Paul & Partners. The system is able to withstand a high working pressure of up to 2600 kPa or 26 Bar. The system can be pressure tested up to 4000 kPa or 40 Bar.

Blucher Australia is presently proceeding with Standards Australia to obtain MP 52 certification for potable water supply and once obtained, the Mapress System will be the only stainless steel system, complete with tubes and fittings to achieve this certification.

The Mapress Stainless Steel Press-Fit System carries European pressure certification suitable for this particular application and the pressure rating for the system. No other stainless steel 'system' holds an MP 52 certification so the major change was acceptance by Brisbane City Council.

The Mapress Stainless Steel Press-Fit System was chosen for a combination of reasons including longevity, ease of installation and the system's ability to handle high pressure.

As a part of Blucher Australia's guarantee and OH&S requirements, Blucher Australia Technical Manager, Ian Johnson trained Project Manager Mark Tapley, Site Foreman Steve Woods and four other employees involved in The Aurora project in the use of the specialised Hydraulic Press-Fit tool and installation procedures.

Blucher Australia hold stock of all the stainless steel components required to do the installation. Delivery, in conjunction with the good organisation skills of Steve Wood of Tapworth and Booth, was straight forward.

Hydramellenia, the subsidiary of Steve Paul and Partners, is convinced of the benefits and is currently specifying the Mapress system for other projects. Blucher Australia has already supplied to the smaller Metropole Apartments Project, also in Brisbane, and has received inquiries from other consultants who have heard of this project.

This article featured in Australian Stainless magazine - Issue 30, January 2005.

Reducing risk with stainless flameproof technology

Where flammable or combustible materials are stored or handled, there can be a severe risk of an explosion or fire if handling equipment such as forklift trucks are not flameproofed.

A Combilift with stainless steel exhaust conditioner from Chess FlameproofFlameproofing of material handling equipment is the science of reducing the risk of an explosion or fire by means of specialised principles and technologies.

Three components are needed in order to generate an explosion or fire.

  1. A flammable or combustible material eg. liquid, gas or dust.
  2. Oxygen eg. air.
  3. Ignition source eg. electrical sparks,  mechanical sparks, hot surface and static discharges.

Sources of ignition include flames and sparks from exhaust systems, arc and sparks from electrical equipment, hot surfaces and static build up.

Chess Flameproof, a division of ASSDA member Chess Engineering Pty Ltd, specialises in the conversion of materials handling equipment for use in hazardous areas.

Materials handling equipment such as forklift trucks, tow tractors, sweepers, scissor lifts and boom lifts ranging from 1 ton to 32 tonnes have all been designed and manufactured to remove or reduce the risk of the equipment becoming the source of ignition. Both diesel and battery electric powered forklifts can be flameproofed. Note spark ignition engines ie. LPG and petrol are not permitted in any hazardous areas.

Left to right: A stainless steel flame arrestor, a corrugated stainless steel exhaust flex, a stainless steel final flame trap element and a stainless steel flame arrestor. In addition to flameproofing, Chess Engineering manufactures custom forklift attachments, engine protection systems, speed sensors/controllers and cabins as well as custom modifications and general forklift engineering.

To overcome the possible sources of ignition, a number of protection techniques are used:

Stainless steel water cooled exhaust manifold

Extreme temperatures of the gases leaving the cylinder head of the engine can easily cause the exhaust manifold to climb in temperature to a level where it may possibly ignite surrounding hazardous area atmosphere. To overcome this problem a stainless steel water cooled exhaust manifold is fitted.

Stainless steel exhaust conditioner

An exhaust conditioner is a water tank that channels the hot exhaust gases and particles through a labyrinth thus cooling and filtering.

Depending upon the area classification, a final flame trap element may be fitted as a secondary measure. Inside the exhaust conditioner is a very corrosive environment because of the exhaust gases, water and elevated temperatures.

Toyota forklift built to Zone 1 hazardous areas For standard conditions, grade 316 stainless steel has proved to be more than adequate for this application and withstands the harsh environment providing welding and post welding procedures are correctly followed. Alternatively for extremely corrosive conditions, a duplex stainless steel has been used.

This article featured in Australian Stainless Issue 32, Winter 2005.

Images:

Main image - Stainless steel flame arrestor or flame trap used on the engine inlet to cool and quench flames that may arise from combustion malfunction.

Top right - A Combilift with stainless steel exhaust conditioner.

Above - A stainless steel final flame trap element (centre) and (left) a corrugated stainless steel exhaust flex with braided sleeve used to absorb engine movement and vibration.

Right - Toyota forklift built to Zone 1 hazardous area.

Stainless Steel Bulk Solvent Storage Facility Completed

When coatings manufacturer, PPG Industries’ original bulk solvent storage facility had come to the end of its economic life, the company elected to install a new $8m facility that is both efficient and fully compliant with numerous safety, environmental and good design principles on its Clayton, Victoria site

 

Established in the 1950s, the bulk solvent storage facility receives a diverse range of bulk solvents and monomers, sourced from petrochemical producers in particular and delivered to the site by bulk road tanker.

PPG Industries Project Manager, Tom Van Loon, said he went in search of a stainless steel fabrication contractor with both the experience and capacity to undertake the major components on a qualitative and timely basis.

“Projects of this nature are normally awarded to a contractor on a turn key basis, but we elected to engage a competent team of designers and supervisors, outsource most services and work in close cooperation with our appointed fabricator Furphy Engineering and the suppliers of the process equipment” Mr Van Loon said.

On site at Clayton, the tanks are fully enclosed within a three-compartment concrete ‘vault’. The 400mm thick vault has dimensions of about 28 metres by 22 metres with a depth of 5.5 metres.

The tanks have been backfilled with washed silica sand to maintain low ambient product temperature and provide additional fire protection. As an additional safety protection each solvent tank is nitrogen blanketed.

Furphy Engineering purchased the majority of the stainless steel for the project from ASSDA member, Midway Metals.

“The tanks for the UST project required a total of 70 tonnes of 6mm thick, grade 304 stainless steel which were fabricated at the Furphy Engineering workshops in Shepparton, Victoria.

“The welding of each tank was subject to non-destructive testing by radiography during fabrication, followed by hydrostatic testing of each tank prior to delivery” said Darren Leeder, Furphy Engineering’s Sales and Marketing Manager.

Located above the underground storage is the process control system, extensive delivery pumping and pipework and three tanker unloading bays.

Furphy’s also fabricated all the stainless steel pipe spool work, comprising over 1,500 individual spool pieces amounting to more than 4,500 metres of stainless steel pipe work to deliver the solvent raw materials to the manufacturing centres on the site.

All fabrication was undertaken to various standards including AS 1692-1989: Tanks for flammable and combustible liquids and other best practice standards for the environment, plant safety and related quality aspects.

As Project Manager for PPG Industries, Tom Van Loon says that the project was completed on time and to budget.

“The project outcome has been particularly pleasing as the storage facility has scope to handle PPG’s anticipated growth in the future.”

This article featured in Australian Stainless magazine - Issue 33, Spring 2005.

Alloy C-276: A Super Alloy for Processing Plants

OMG Cawse Pty Ltd is the owner and operator of a nickel and cobalt mining operation and processing plant that is located 55 kilometres north east of Kalgoorlie.

Extracting nickel involves acid leaching using sulfuric acid in a high temperature and pressure autoclave to dissolve the nickel and cobalt from the oxide ore.

The wastes from this process are very acidic and require a highly corrosion resistant material for the lining of the sump tank.

When various concrete coatings for the sump tank were trialed and failed, OMG Cawse opted to install Alloy C-276 to engineer out the continuous maintenance of the concrete coatings.

Alloy C-276 is a super nickel alloy (not a stainless steel), a material that remains resistant in the most corrosive environments such as in chemical processing, waste treatment, pollution control and pulp and paper production.

ASSDA member, Specialised Engineering Services (WA) fabricated a 3mm thick liner for a sump tank from Alloy C-276 plate supplied by ASSDA Major Sponsor, Atlas Steels.

Measuring 9m long x 2.5m wide x 1m to 1.3m deep, the tank is filled with water and receives up to 98% sulphuric acid.

Alloy C-276 is also one of the few materials that can withstand the corrosive effects of chlorine dioxide, wet chlorine gas and hypochlorite.

This article featured in Australian Stainless Issue 34 - Summer 2005.

Australian Stainless Products

Built on Reputation

Alistair Patterson has a flair for the food and beverage industry that borders on obsession. As the sole proprietor for ASSDA Accredited Fabricator, Australian Stainless Products, Patterson's reputation within the industry means when projects are on, he is onto it!

Australian Stainless Products are custom manufacturers of quality stainless steel food, beverage and pharmaceutical process products and equipment.

Established more than 20 years ago, Australian Stainless Products started out building basic dairy machinery, primarily small repairs and maintenance of equipment for a few of the local food processing equipment plants.

“Back then the business was basically building milking machinery. We did small repairs and maintenance and equipment for a few of the local food processing plants in the area.”

Now, the Melbourne-based company manufactures original equipment from large tanks, vessels and hoppers including process equipment up to 50,000 litre capacity.

Working with a small but loyal client base, Patterson has worked with some engineering consultants such as dairy equipment supplier DeLeval for more than a decade.

“It's quite a small industry. We operate by word of mouth and references of jobs. It takes a long time to build, grow and develop a business within this industry,” said Patterson.

This article featured in Australian Stainless magazine - Issue 35, Autumn 2006.

Nickel Mine Uses 400 Tonnes of Stainless Steel

When ASSDA Accredited Fabricator Nepean Engineering was awarded the tender for the manufacture of the stirring mechanisms for 10 thickeners for the Goro Nickel Mine in New Caledonia, they had no idea of the enormity of the venture. But having now completed the two-year undertaking they reflect on what has been their biggest stainless steel project to date.

 

 

Although the nickel mine was a massive development, Nepean Group Owner and Managing Director David Fuller admits the initial stages of commencement were a little “stop-start”.

“We won the tender 2 years before from GLV Australia Pty Ltd (Dorr-Oliver Elmco) but the project was cancelled,” he says. “We then had to re-tender and were lucky enough to win it again.”

Manufacturing finally commenced in August 2005 and was completed in March 2007.

Nickel Mine uses 400 tonnes of stainless steelDavid says the project resulted in 410 tonne of stainless steel product, including an additional 370 tonne of carbon steel. The contract export value was $10 million. Varying grades were used including 338 tonnes of 316L, 65tonne of 904L and 7 tonne of AL6XN. The thicknesses ranged from 1.6mm up to 80mm.

Six of the thickeners were 70 metres in diameter and required the manufacture of 33 metre long raking arms. Because a highly corrosion resistant material was needed where the nickel extraction occurred, Nepean Engineering used 904L for its high nickel and chromium content. The thick sections required meant that 316L and 904L were used to avoid sensitisation and the subsequent risk of intergranular attack.

Super-austenitic grade AL6XN with 6% molybdenum and high nitrogen, offered better corrosion resistance and was used in one of the smaller thickeners, which extracts cobalt. This material was imported from America.

When manufacturing commenced Nepean Engineering experienced quite a few challenges as a large amount of material was non-standard size.

“316L angle was unavailable so all angles were pressed from flat plate,” David says.

Pressing was performed across the grain. This required joining 2 x 8 metre sheets using sub arc welding so that the longer angles could run across the sheet. The sheets were then cut to fit the plasma cutter, which could handle 6 x 17 metres. Some of the angles were formed in Nepean's 1000 tonne press and others were subcontracted for specialist pressing.Nickel Mine uses 400 tonnes of stainless steel

Special dies were made for Nepean's press to allow larger angle radius. Furthermore, pipe unavailability due to wall thickness requirements meant up to 2 semi-circular half sections of pipe had to be pressed then sub arc welded together to achieve a die of the required length and diameter. For quality purposes, all welding required procedures. Nepean Engineering created a procedures manual for approval by the client.

Contamination from processing and handling was an issue that required focus. Nepean Engineering built a new factory dedicated to stainless steel with inserts at work stations, on forklift tines and on cranes plus separation sheets on presses and rolls to avoid cross contamination. All welds were pickled after fabrication. However, it became evident that not all contamination had been removed with further contamination also occurring due to airborne grinding particles. In order to provide a clean surface with a uniform overall appearance, flap disc grinding and garnet blasting was performed which removed any contamination, excess flux, heat tint and oxides.

With such a large quantity of stainless steel on site and with varying grades and material thicknesses, clear identification was imperative. Traceability was adopted on all parts and processes of the project with the introduction of a colour coding system to identify the different grades of stainless steel.

Material heat numbers were stamped on all components. Maps and naming schedules were used so that each component had a part number and could be identified on a drawing. A spreadsheet was produced to advise the client of the heat number of the plate from which each part was cut. This then could be traced to a material certificate to provide the chemical and mechanical properties of that particular plate or item.

Weld traceability was also adopted on all parts of the project. Again maps and naming schedules were used so that all welds could be identified. Each welder was assigned an identification number, which was then traced against the weld number and placed on a spreadsheet similar to the material traceability spreadsheet.

Other parameters traced were the type of wire used, wire batch numbers, flux type and batch and welding procedures.

Non-destructive testing (NDT) was employed with dye penetrant and ultra sonic tests on the non-magnetic, austenitic stainless steel components and magnetic particle and ultrasonic on the carbon steel components.

David Fuller said “the job was a major challenge but one that Nepean Engineering rose to”. “The experience we have acquired, along with the additional infrastructure built puts us in good stead for future projects of this magnitude.”

This article featured in Australian Stainless magazine - Issue 39, Autumn 2007.

Stainless advance for water treatment plant

Never has there been a time in Australia when water preservation was so critical.  As populations rise and dam levels fall, the importance of treating and reusing water has become not a question of “if” but a question of “when”.

bundambaThe construction of Bundamba Advanced Water Treatment Plant (BAWTP) west of Brisbane is aimed at alleviating pressure on South East Queensland’s existing dams and waterways by providing an alternate water supply for end users in the region, initially Swanbank power station.  

The project has had great flow on benefits for the Australian stainless steel industry as infrastructure requirements point to the material for its strength, corrosion resistance and application performance.

The world-class BAWTP is a joint venture between Thiess Pty Ltd and Black & Veatch, who are responsible for the engineering, design, procurement and construction. Management of the project is in alliance with the Queensland Government. A number of ASSDA members were sub-contracted by Thiess Pty Ltd for various stages of the project, including ASSDA Accredited Fabricator D&R Stainless, Perfab Engineering and Stainless Pipe and Fittings Australia.

Following a tender process, D&R Stainless was engaged for off-site pipe spooling. The quantity of stainless steel used for the job, including around 3000 flanges, meant that D&R Stainless was issued with the materials by Thiess Pty Ltd as needed.  

Many of the piping materials for the first two stages of the project were supplied to Thiess Pty Ltd by Stainless Pipe and Fittings.  Materials were in excess of 350 tonnes and included pipe, pipe fittings and flanges in grade 316L with sizes ranging from 25-600nb.

 

bundamba2Once delivered, D&R Stainless cut and bevelled the pipe and then welded and passivated internally and externally before undergoing hydro testing.

D&R Stainless Director Karl Manders said that, not only did the pipes use grade 316, but they were also fabricated to Australian Standard 4041, class 1.

“Because the pipework adhered to such a high standard, 10% of all welds were x-rayed for quality,” he says. Passivation of the pipe welds involved applying pickling paste inside and out, and then scrubbing and flushing to avoid loose scale, important for the fine filtration of the water treatment plant.

Karl says quality was something Thiess Pty Ltd took very seriously, with a welding inspector and quality checker appointed at their premises.

“This was to ensure all welding and passivation was performed at the highest standard, and also to ensure that production off-site was consistent with installation schedules onsite”.

Perfab Engineering was also sub-contracted by Thiess Pty Ltd for the manufacture of the reverse osmosis (RO) skids at its workshops in Newcastle, working closely with the designers from suppliers Koch Membrane Systems in the United States.

The work carried out by Perfab included fabrication and surface treatment of the carbon steel skid frames, fabrication of the stainless steel pipework, full mechanical installation of the valves, instrumentation and RO pressure vessels, pneumatic fitout, electric fitout and testing.

The high pressure pipe spools were fabricated from Sch 40S pipe with 300# flanges and low pressure pipe spools from Sch 10S pipe with 150# flanges.

Perfab has three orbital Gas Tungsten Arc Welding (or TIG) machines that were operated around the clock to ensure the tight delivery times were achieved, however Perfab Engineering General Manager Damien Ryba says “the biggest contributor to the success of the job was having a well trained, highly skilled and productive workforce committed to the success of the project”.

At present, the BAWTP 1A is in full operation and delivering water to the Swanbank Power Station. Thiess Black and Veatch Director, Gus Atmeh, said that the BAWTP 1A project was delivered ahead of schedule and this was due to the support of the project by high quality stainless steel fabrication shops from across Australia and particularly from South East Queensland, who provided stainless steel components for state of the art process equipment and piping: “Without them we could not have made it on time.”

This article featured in Australian Stainless Issue 41

Stainless Steel and Plumbing Standards

After three years of development, the first stage of a Standard covering the grade and dimensions of stainless steel pipes and tubes suitable for water supply and drainage systems has been completed. This interim Standard will be converted to a full Australian Standard in 2009.

The Standards Committee included ASSDA representative Neil McPherson of OneSteel, supported by the Technical Committee.

To avoid possible confusion and protect against corrosion problems in aggressive water supply areas, grades 316 and 316L are specified for the plumbing installation Code of Practice. All materials that satisfy the requirement for water supply and drainage systems must be included in the installation Standard AS/NZS 3500 Parts 1 & 2, which covers the material, grade and approved jointing method for piping systems.

If a material is included in Part 1 Water Supply (for drinking water), it will need to be certified against a product standard to Level 1, while Part 2 Drainage & Sanitary Plumbing requires Level 2 certification. The main difference is that Level 1 products require testing under AS4020 Material in Contact with Drinking Water to confirm lack of water contamination. Stainless steel product readily passes this testing.

All fittings, including the mechanical jointed pressfit and roll grooved types used for the plumbing services, are also tested and certified. AS3688 Metallic End Connectors defines the criteria against which these fittings are certified, including the additional pressure and fatigue testing to demonstrate strength of joint assembly.

Stainless steel using mechanical jointing systems

Mild steel, copper tube and plastic pipes have dominated building water systems for many years. However, high rise developments over recent decades have changed the building industry requirements for water supply and fire protection systems. These systems now require materials with a much higher pressure rating and corrosion resistance.

Stainless steel is recognised as a material most suited to meet these requirements. However, older on-site methods for jointing and fabrication has limited the use of stainless steel.

The approval of mechanical pressfit and roll grooved systems for all water systems has provided a major market for stainless. Stainless steel pipes and fittings have been installed as a solution to specific technical issues including a corrosive environment, high pressure requirements of the hydraulic services system, high operating temperature, or where the project owners are looking for a whole-of-life sustainable product solution.

The following projects illustrate some design and installation specifications around Australia.

Casey Aged Care Facility, Heidelberg, Victoria

108mm and 76mm tube in 316L was supplied by Blucher for a low pressure system feeding rainwater from storage tanks to pumps. Stainless steel was chosen due to concern of longevity and water contamination from other materials due to water levels in storage tanks being low or empty for long periods during dry spells. The Mapress stainless steel pressfitting system was familiar to the plumbing contractor who felt it was labour saving and easy to install. Plastic pipes were used from the roof to the plastic rainwater storage tanks.

Western Corridor Recycled Water Project, SE Queensland

The Mapress 316 pressure system was chosen for rapid, simple installation. There was a lack of pipe fitters available so socket welding was not possible and other trades made the installation. Sizes ranged from 15 to 54mm with butyl rubber sealing rings containing pressures up to 1,000kPa. The stainless steel was used for potable, treated and fire water as well as compressed air. The Mapress system supplied by Blucher has been used in all three waste water treatment plants in the Western Corridor as well as in the Gold Coast Desalination Plant.

Centre Court Business Park, North Ryde, NSW

Heating and chilled/condenser water installations used 316L schedule 5 pipe in both 50 and 100mm diameter in this 30,000m2 low rise complex. Stainless steel offered reliable protection from corrosion and the Victaulic roll grooved system offered ease of assembly.

Suncorp building, Sydney CBD

Refurbishment of the combined fire and drinking water system in a 1972 building used OneSteel Building Services supplied 316L schedule 10 pipe and fittings in 3m, pre grooved lengths for assembly in restricted duct spaces. The 43 floors plus 3 basements ensured high pressure requiring strong stainless steel which also met the drinking water AS4020 requirements.

Centrepoint Tower, Sydney CBD

Stainless steel pipe and fittings were supplied by OneSteel Building Services to replace corroded carbon steel in the 305m tall tower. Systems changed were the fire and potable water and the gas lines. 300m of 316L was supplied in 2.7m lengths which were roll grooved and assembled using Victaulic couplings in a very constricted service duct. Sizes used were 100mm and 50mm in schedule 10 except for gas lines in schedule 40.

This article featured in Australian Stainless magazine - Issue 45, Summer 2009.

Stainless Refinery First of its Kind
Australia’s first grain-to-ethanol refinery has begun production in Queensland, with an expected output of more than 80 million litres a year.

Seven pressure vessels and five columns were fabricated by ASSDA Accredited D&R Stainless from 30 tonnes of grade 304 stainless
steel supplied by ASSDA member Sandvik.

The column sizes range from an acid reduction column 750mm in diameter and 14.2 metres long to a beer column 1900mm in diameter and 24 metres long. 

The columns were fabricated to tight tolerances set by process design engineers Detla T Technology, in the United States.

Chief Executive Officer of Dalby Bio-Refinery Limited, Kevin Endres, has worked with Delta T technnology in the US.

Mr Endres said stainless was the obvious choice for its durability. A project of this size requires a low maintenance and reliable material.

All design and manufacturing was carried out by D&R Stainless to ASME VIII complying with AS1210.

D&R also fabricated 6000 metres of grade 304 piping in sizes from 20NB to 500NB requiring over 6100 elbows, flanges and fittings from ASSDA member Stainless Pipe & Fittings Australia.

All piping was x-ray quality and met ASME B31.3.

Mr Endres said the refinery will eventually expand to output over 200 million litres of ethanol per year.

This article appeared in Australian Stainless Magazine -  Issue 45, Summer 2009.

 

Stainless frameless tankers make big Australian debut

McColl's Transport carts a variety of chemicals such as caustic soda and formaldehyde. The tanker barrel has been wrapped and not rolled, with full length stainless steel sheets used to eliminated circumferential welds. There’s a new breed of tanker being put through its paces along Australia’s east coast carrying aggressive chemicals and class three petroleum products for McColl’s Transport.

 

Dandenong based tanker manufacturer, Marshall Lethlean, has constructed FACT, a Frameless Aggressive Chemical Tanker with some unique operating attributes.

Marshall Lethlean constructed the 25,800 litre, 11.5m long stainless steel tanker with a chassis that’s up to 300 kilos lighter than conventional full frame designs.

Carting a variety of chemicals for McColls, such as caustic soda, formaldehyde and methanol, the barrel has been wrapped and not rolled, using full length stainless sheets to eliminate circumferential welds, a feature unique to Marshall Lethlean stainless steel tankers.

ASSDA Major Sponsor, Atlas Specialty Metals, supplied grade 316 stainless steel sheet to Marshall Lethlean for the fabrication of what is believed to be the industry’s first frameless chemical tanker.

Finally, to give the tanker a bright, durable corrosion resistant finish, the coaming, chassis rails and tank rings were all electropolished by ASSDA member, MME Surface Finishing.

Orlando Iluffi, Marshall Lethlean’s Business Development Manager, says the FACT product was one of many new developments which will be released onto the market to better improve running costs and operating safety.

“We have worked on this new tanker in partnership with McColl’s for nearly two years just to get it right.

“Along the way, we have been able to improve our engineering skills to the point that it has led us toward other new concepts which we are all equally excited about.”

In June 2005, the Frameless Aggressive Chemical Tanker prototype began a six month trial period to test for ‘accelerated durability’.

After three and half months of the trial, McColl’s Workshop Manager, Rob Harrison said the company intends to “buy the tanker after the period” has completed in late December 2005.

This article featured in Australian Stainless magazine - Issue 33, Spring 2005.

Grade 431

A versatile, high strength martensitic stainless steel

Martensitic stainless steels are a less well-known branch of the stainless family. Their special features – high strength and hardness – point to their main application area as shafts and fasteners for motors, pumps and valves in the food and process industries.

The name “martensitic” means that these steels can be thermally hardened. They have a ferritic microstructure if cooled very slowly, but a quenching heat treatment converts the structure to very hard martensite, the same as it would for a low alloy steel such as 4140. Neither the familiar austenitic grades (304, 316 etc) nor the duplex grades (2205 etc) can be hardened in this way.

Grade 431 (UNS 43100) is the most common and versatile of these martensitic stainless steels. It combines good strength and toughness with very useful corrosion resistance and in its usual supply condition can be readily machined.

Chemical Composition

The composition of 431 specified in ASTM A276 is given in Table 1 below.
Grade 431_Table 1

 

 

 

The inclusion of a small amount of nickel in grade 431 is different from most other martensitic grades. This small but important addition makes the steel microstructure austenitic at heat treatment temperatures, even with such a high (for a martensitic grade) chromium content. This high temperature austenite enables formation of hard martensite by quenching.

Corrosion Resistance

The relatively high chromium content gives grade 431 pitting, crevice and general corrosion resistance approaching that of grade 304, which is very useful in a wide range of environments including fresh water and many foods.

Grade 431 has the highest corrosion resistance of any of the martensitic grades. Corrosion resistance is best with a smooth surface finish in the hardened and tempered condition.

Grade 431 is sometimes used for boat shafting and works well in fresh water but is usually not adequate for sea water.

Heat Resistance

Grade 431 has good scaling resistance to about 700°C but, as martensitic steels are hardened by thermal treatment, any exposure at a temperature above their tempering temperature will permanently soften them. 600°C is a common limit.

Mechanical Properties

The application of grade 431 is all about strength and hardness. Table 2 below lists mechanical properties of the grade annealed and in hardened and tempered “Condition T”.

Grade 431_Table 2

 

 

 

 

 

 

 

 

 

 

 

Heat Treatment

A feature of grade 431 is that it can, like other martensitic steels, be hardened and then tempered at various temperatures to generate properties within a wide spectrum, depending on whether the requirement is for highest possible hardness, or best ductility, or some balance between these. Hardening is by air or oil quenching, usually from 950-1000°C.

The tempering diagram in Figure 1 shows properties typically achieved when the hardened steel is tempered at the indicated temperature. A tempering temperature within the range 580 – 680°C is usual. Tempering between 370 and 570°C should be avoided because of resulting low impact toughness.

Tempering should follow quenching as quickly as possible to avoid cracking. Softening is usually by sub-critical annealing, by heating to 620 – 660°C and then air cooling.

Grade 431_Figure 1

Physical Properties

Density

7700kg/m3

Elastic Modulus

200GPa

Thermal Expansion (0-100°C)

10.2µm/m/°

Fabrication

Machining is readily carried out in the annealed condition, and also in the common Condition T. Modern machining equipment enables high speed machining at this hardness of about 30HRC.

Welding of 431 is rarely carried out — its high hardenability means that cracking is likely unless very careful pre-heat and post-weld heat treatments are carried out. If welding must be done this can be with 410 fillers to achieve high strength but austenitic 308L, 309L or 310 fillers give softer and more ductile welds.

Cold bending and forming of hardened 431 is very difficult because of the high strength and relatively low ductility.

Forms Available

Grade 431 is available in a wide range of bar sizes — virtually exclusively round but some hexagonal. Most other martensitic grades are only available in round bar, although the higher carbon 12% chromium “420” series of grades may also be available as hollow bar and as blocks and plates intended for tooling applications.

Alternatives

Another approach to high strength stainless steel bar is a precipitation hardening grade, such as 17-4PH. These grades have similar corrosion resistance and offer some advantages in producing long, straight, higher strength shafts.

Shafts to be used in more corrosive environments are likely to be a duplex or super duplex or nitrogen-strengthened austenitic grade. These, however, have lower achievable strengths than martensitic or precipitation hardening grades.

Specifications

Grade 431 is usually specified by ASTM A276, with composition as in Table 1. In the Australian market, however, there are usually two deviations from A276:

  1. It is most common to find this grade supplied in the hardened and tempered “Condition T” to AS 1444 or BS 970, with specified tensile strength of 850-1000MPa. Yield and elongation are typically in conformance with the limits listed above. ASTM A276 only lists a Condition A version of grade 431 — this is the annealed condition that would normally require hardening heat treatment after machining.

  2. The second deviation is that it is usual for cold finished stainless steel bars stocked in Australia to be with the all-minus ISO h9 or h10 diameter tolerances. Hot finished “black” bars with all-plus ISO k tolerances may also be available.

 

This article was prepared by ASSDA Technical Committee member Peter Moore from Atlas Steels. Further technical advice can be obtained via ASSDA’s technical inquiry line on +617 3220 0722.

This article featured in Australian Stainless magazine - Issue 48, Autumn 2011.

stainless integral to design

Posted 17th December 2009

LWA44 101 650x250 for web

A dam upgrade project in South Australia has achieved a world-first zero carbon footprint for water infrastructure and has used stainless steel as part of the unique design. The Little Para Dam upgrade incorporates a Hydroplus Fusegate System, with stainless steel fabrication carried out by ASSDA Accredited Fabricator LWA Engineering.

The Fusegates are similar to those built at Jindabyne for the Snowy Hydro in 2007, featuring a cast in-situ concrete design with stainless steel inlet wells and seal fixings in order to provide a 100 year design life and virtually no maintenance. However, for the Little Para dam upgrade, SA Water accepted the lean duplex stainless steel (LDX 2101) proposed by CivilTEC for the superstructure of the units for the following reasons:

  • it would provide similar corrosion resistance to 316 grade stainless steel, but with a higher tensile strength (450N/mm²) and at a much lower price;
  • an off-site fabrication system would reduce the amount of time required on site at Little Para from eight months to just six weeks, thereby reducing site administration overheads and running costs for all parties involved; and
  • the extremely efficient design (by WSP Group) used far less construction materials than would normally be required for a project of this nature and LDX 2101 is manufactured using approximately 65 per cent recycled material.

LWA Engineering Managing Director Larry Watson said LWA Engineering had been working with ASSDA Major Sponsor Sandvik on the stainless steel components of the project.

“With a Carbon Pollution Reduction Scheme on the agenda, a zero carbon footprint has never been more important,” Mr Watson said.

“One of the main reasons SA Water wanted to use this design with this material came down to the reduction in carbon footprint which minimised the offset required to achieve zero emissions. This is the first zero carbon infrastructure project in the country.”

The walls of the Fusegate bucket are formed from a composite steel shell comprising two 4mm thick stainless steel ‘skin’ plates spaced 150mm apart. A lattice work of ribbing is then welded onto the plates.

Around 70 tonnes of LDX 2101 were supplied by Sandvik for the walls and internal ribbing of the five Fusegates. The material was imported in 4mm thick coil form, which was then cut to length at Sandvik’s Sydney premises, with ribs being cut in Melbourne (RCR Laser) and Adelaide. The wall panels were cut on Sandvik’s 2m-4m laser bed to within ±0.2mm of accuracy.

LWA Engineering marked out the 2m high inner and outer ‘skins’ to form the composite wall panels and spot welded the vertical and horizontal 40mm-4mm thick LDX ribs in position before pre-setting and stitch welding. When the two ‘skins’ were brought together they were fixed in position using a 12mm diameter stainless steel rod which is pushed through 13mm holes in the overlapping lugs and welded at the top and bottom rib location.

Each Fusegate wall was fixed to a pre-cast concrete base chamber using a continuously welded stainless steel base plate cast into the concrete during pre-casting. Prefabricated inlet wells comprising 8mm thick LDX plate continuously welded along splice points were bolted into place on site.

The composite wall design saved about 40 per cent of the stainless steel required when compared with a traditional single-plate design.

The Little Para Dam spillway upgrade will be completed in early 2010.

CONTACTS

LWA Engineering
www.lwaengineering.com.au

Sandvik Australia
www.sandvik.com

LWA-IMG_0180 600dpi for web

Hydrostatic Testing of Stainless Steels

Guidelines to Ensure Long Service Life

Design engineers frequently specify stainless steel in industrial piping systems and tanks for its excellent corrosion resistance. While stainless steel’s unique characteristics make it a standout leader in the durability stakes of alloys, it is not completely immune to corrosion.

Premature failures of the stainless steel can occur due to Microbiologically Influenced Corrosion (MIC). This corrosion phenomenon usually occurs when raw water used for hydrostatic pressure tests is not fully removed from the pipework and there is an extended period before commissioning of the equipment. The result is localised pitting corrosion attack from microbacterial deposits that, in severe cases, can cause failure within a few weeks. MIC is easily prevented using proper hydrostatic testing techniques.

MIC

MIC failures occur by pitting corrosion, often at welds, where colonies of bacteria may form. A number of different bacterial species are known to cause the problem, but the detailed mechanism is not known.

Iron utilising bacteria appear to be the dominating microbial species involved with MIC occurring in stainless steel. Anaerobic sulphate-reducing bacteria pose a greater risk of instigating or accelerating corrosion often under a layer of aerobic slime or microbial deposits. However others, such as manganese utilising bacteria (generally from underground waters), have also been discovered.

MIC is extremely aggressive and difficult to eliminate once established, so it is surprising and disappointing that there is limited knowledge of MIC within the engineering community. Fortunately, MIC is easily avoided by using good practices during the initial hydrostatic testing. Education and promotion of proven hydrostatic testing practices which prevent MIC are vital to minimising its potential impact on the stainless steel industry.

                    

Hydrostatic testing practices to eliminate MIC

In order to eliminate MIC, it is recommended that the following practices are used.

1. Fabrication practices

Crevices should be eliminated or at least minimised during the fabrication process, as they are the preferred sites for attachment and growth of microbial colonies. They also provide traps for chemicals which could concentrate and cause pits.

The likelihood of MIC will also be reduced by:

  • Using full penetration welds; and
  • Purge welding to prevent the formation of heat tint; or
  • Removing heat tint by grinding or pickling.

Arc strikes and weld splatter should also be ground off and pickled.

2. Use clean water

The cleanest water available should be used in a hydrostatic test, such as demineralised, steam condensate or treated potable water. Untreated or raw water from dams or bores should be avoided when conducting a hydrostatic test but, where this is not possible, the water should be sterilised (e.g. by chlorination) before use. If sterilisation is not practical, the requirements for short residence time and subsequent drying of the system are extremely important. The cleaner the water, the less ‘food’ there is for MIC bacteria to live off and multiply.

It is important to ensure that there is no trace of sediment in the stainless steel system during testing to avoid silting, as the water is normally not circulated during a hydrostatic test. This may require the test water to be filtered to ensure it is free of all undissolved solids. Sediments can provide the conditions for crevice attack.

3. Draining and drying

Thoroughly draining and drying the stainless steel system immediately following a hydrostatic test (preferably within 24 hours, certainly within 5 days) will almost certainly prevent the occurrence of MIC.

Horizontal pipelines should be installed in a sloping direction to make them self-draining.

Drying can be achieved by pigging (cleaning with foam or rubber scrapers), followed by blowing dry air through the system. Beware of blowing higher temperature moist air through cold pipework unless the air is dried before being introduced to the system. If warm air is used, it should not be from a gas burner as condensation may occur.

Draining and drying of systems following a hydrostatic test should only be disregarded when the system is placed into service immediately following the test. Partial draining is potentially very serious as subsequent slow evaporation of even clean residual water can produce very concentrated and aggressive solutions.

4. Chloride content and temperature

During hydrostatic testing of stainless steel equipment, the chloride content of the test water must be within the range to which the stainless steel grade is resistant. Figure 1 shows the maximum temperatures and chloride contents to which stainless steels are resistant in water with residual chlorine of about 1 ppm.

The limits shown in Figure 1 may be exceeded provided the contact time of the water is brief, i.e. 24-48 hours.

If the chloride content of the test water is uncertain, the water should be analysed.

5. Standards

NACE and API standards for a number of products and installations provide guidelines for hydrostatic testing, including limits for water quality and contact times. These standards should be consulted for specific details for the fabrication in hand.

Conclusion

The benefits of stainless steel’s corrosion resistance are well proven in many industrial applications involving piping systems, but failures can occur during hydrostatic testing if care is not taken. Attention to a few simple details will prevent surprises a few months down the track, allowing the long service life available from stainless steel to be fully realised.

This article featured in Australian Stainless Issue 47 - Spring 2010.