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Lost Time Injury Alert

Acids used to etch, pickle or passivate in stainless steel fabrication shops are highly corrosive and, under some circumstances, highly reactive. Where these acids are stored, mixed or used, good occupational health and safety practices need to be implemented.

When working with corrosive chemicals, good, safe working practices should be adopted.In July 1996, the laboratory supervisor at a major stainless steel processing facility sustained a severe eye injury when a mixture of 25ml concentrated hydrochloric acid, 25ml concentrated nitric acid and 50ml iso-propyl alcohol burst through the top of the storage bottle and splashed into his right eye. He also sustained acid burns to his temple, the back of his head, behind his ear, and to the inside of his right forearm.

The supervisor had a Metallurgy Certificate and fifteen years' laboratory experience.

WorkCover subsequently supplied information on one of the root causes of the accident, a similar accident having occurred about a month earlier in another workplace in the same suburb. The following information is published in Bretherick's Handbook of Reactive Chemical Hazards (edited by P G Urben, 5th Edition, Volume 1, published by Butterworths Heinemann):

"Mixtures of nitric acid and alcohols ('Nital') are quite unstable when the concentration of the acid is above 10%, and mixtures containing over 5% should not be stored. The use of a little alcohol and excess nitric acid to clean sintered glassware (by 'nitric acid fizzing') is not recommended. At best, it is a completely unpredictable approximation to a nitric acid-alcohol rocket propulsion system. At worst, if heavy metals are present, fulminates capable of detonating the mixture may be formed."

When working with corrosive chemicals, good, safe working practices should be adopted, including the following:

  • Personal Protective Equipment (PPE) - face mask, apron, rubber gloves - should be worn at all times;
  • Acids and alcohols should only be mixed in a fume cupboard or vented area;
  • The acid should be added to the diluent, not the other way around;
  • Mixed acids should be stored in vessels with ground glass stoppers which allow venting - not screw top containers;
  • Goggles should be worn during all work with alkalies, e.g. sodium hydroxide, as alkalies are particularly injurious to the eye; and
  • No assumptions should be made if unexpected reactions occur.

Today, environmental factors are at the forefront of material selection for specifiers. Stainless steel’s long service life, 100 percent recyclability and its valuable raw materials make it an excellent environmental performer.

Stainless steel objects rarely become waste at the end of their useful life. Recycled stainless objects are systematically separated and recovered to go back into the production process through recycling.

As well as iron, stainless steel contains valuable raw materials like chromium and nickel which makes recycling stainless steel economically viable.

Stainless steel is actively recycled on a large scale around the world by recyclers who collect and process scrap (recycled stainless steel) for re-melting all around the world.

Specialised expertise and sophisticated technology is needed in recycling to separate and prepare each type of alloy for remelting by stainless steel mills. Scrap collection

The use of stainless steel scrap is fundamental to the steelmaking process. There are two types of scrap - reclaimed scrap (old scrap) and industrial scrap (new scrap).

Reclaimed scrap includes industrial equipment, tanks, washing machines and refrigerators that have reached the end of their service life.

Industrial scrap includes industrial returns or production offcuts from manufacturing by industrial engineering and fabrication sources.

Today, stainless steel is made up of approximately 60% recycled content including:

  • 25% reclaimed scrap
  • 35% industrial scrap
  • 40% new raw materials

The useful service life of stainless steel products is long so the availability of scrap is dependent on levels of production from decades ago.

With an average content of 25% of old scrap, stainless steel is close to the theoretical maximum content of material from end-of-life products.

Recycling the scrap

Specialised expertise and sophisticated technology is needed in recycling to separate and prepare each type of alloy for remelting.

A recycling processor feeds the scrap into a large shredder to break it into smaller pieces.

It is then chemically analysed and stored by type.

This process may include ‘blending’ the scrap into chrome steels, nickel alloys and other types of stainless steels.

After blending into piles for specific customer requirements the scrap is then loaded into containers for export to overseas mills.

The global market for scrap

Virtually, all Australian stainless steel scrap goes overseas. There’s a small market for stainless steel scrap in Australia for use in the foundries business. Foundries often use profile offcut or plate material scrap products.      

At least 30,000 tonnes of stainless steel scrap in Australia will be exported a year to stainless steel mills in countries including China, South Korea, Taiwan, India and Japan.

China, for example, is using approximately 800,000 tonnes of industrial scrap. Reclaimed scrap is also on the increase in China and is expected to reach 2.5 million tonnes in 2005.

For mills, scrap is important because recycled stainless steel contains valuable raw elements including chromium, nickel and molybdenum that are gathered, processed and reused in the production process. The more scrap used in furnaces by mills, the less raw materials are required in the production process.

Stainless steel mills

Scrap along with other raw materials, ferrochromium (chrome/iron), ferro moly (molybdenum/iron) and nickel are blended into an electric furnace.

After melting, impurities are removed, the molten metal is refined and the chemistry analysed to determine what final adjustments are necessary for the specific type of stainless steel being produced.

The molten stainless steel is then cast into slabs or billets before production of plate, sheet, coil, wire and other forms in preparation for use by industrial manufacturers.

The stainless returns to you

Industrial manufacturers produce stainless steel items that you use everyday including cutlery, pots and pans, kitchen sinks and many architectural, industrial and other components.

At each stage of the production and use process, stainless steel retains its basic properties and utility value. Unlike many industrial and engineering materials, stainless steel may be returned to its original quality in the supply chain without any degradation.

You can be assured that even after its long service life, your environmentally-efficient stainless steel will always return to you bright, shining and new!

For more information about stainless steel, submit your query via the Technical Hotline.

ASSDA acknowledges the assistance and contribution of Ignatius Brun of ELG Recycling Processors, the International Stainless Steel Forum (ISSF), the Nickel Institute and Peter Moore of Atlas Steels in the production of this article.

Consumption of stainless steel scrap - 2004

  • China — 2.8 million tonnes of production using 900,000 tonnes of scrap.
  • Japan — 2.4 million tonnes of production capacity using 900,000 tonnes of scrap.
  • South Korea — 2.3 million tonnes of production using  800,000 tonnes of scrap.
    Product mix 80% austenitic, 20% ferritic.
  • Taiwan — 2.6 million tonnes of production using 600,000 tonnes of scrap.
  • India  — 1.4 million tonnes of production using 300,000 tonnes of scrap.

Note: Australia sends a proportion of stainless steel scrap to all of the above countries.

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

Piercing Questions

In today's age of experimentation with body art, the issue seems not to be 'to pierce or not to pierce', but what to pierce and how many times. Material selection for body piercing jewellery is just one of a number of factors influencing the successful and safe enjoyment of body piercing.

While a variety of hypo-allergenic materials are used for body piercing, including titanium, niobium and solid 14K gold, the predominant material used for initial piercings in Australia is grade 316L stainless steel. 316L is used for its aesthetic appeal, its ease of fabrication and, most importantly, its established position as an inert and acceptable material for surgical implantation.

Several standards exist for the specification of stainless steel for surgical implants, some of which can be used as a reference point for the manufacture of body piercing jewellery, eg: ASTM F138 Standard specifications for stainless steel bar and wire for surgical implants (special quality) and ISO 5832-1 Implants for surgery - Metallic materials - Part 1: Wrought stainless steel. There is no standard which specifically covers materials for body piercing jewellery. Piercers should, however, check state health regulations and seek medical advice on health aspects of the piercing process.

For further information on the use of stainless steel for body piercing jewellery, contact ASSDA.

Life-Cycle Costing (LCC) has long been used in planning for reliability and maintenance for complex engineering systems in defence, airline, railway, offshore platform, power station, and other applications.

A basic attribute of stainless steel is the ability to provide long-term performance with a minimum of downtime and cost associated with maintenance. As a result LCC is of particular importance to the stainless industry.

Whilst the mathematics of LCC can be quite complex, there is a program available which can be easily applied to most examples. ASSDA can make this program available to any interested party on request.

LCC analysis provides a more secure basis for comparing and selecting material options than the traditional method of judgments based on comparing acquisition costs alone. This particularly applies to situations where the initial cost is high and downtime for unplanned maintenance is costly.

In circumstances where stainless is being considered or introduced into new fields of applications, comparisons are often made with materials of a lower initial cost such as coated carbon steel or plastics.

Here the reasoning should progress well beyond the simple initial cost comparison and take account of the long term cost assessments associated with maintenance replacement and operating stoppages.

LCC is the tool to make this assessment and the International Chromium Development Association (ICDA) program makes it easy.

Calculating LCC

In the LCC calculation, consideration is given only to relevant costs which are directly or indirectly affected by the material options being considered. Besides the cost of material, these include costs of installation, operation, maintenance, stoppages, replacements and possibly the residual value at the end of the service life. The time intervals at which the various costs arise during the selected life cycle period must also be taken into account.

Before the various cost items can be put together, those that arise every year and those that occur at certain time intervals during the service life must be converted into present values.

Again the complexities of the mathematics are catered for by the PC program.

Examples are the best way of demonstrating LCC principles and application and two are offered to illustrate the point.

The first is from Swedish practice and features roofing.

The building industry is one of the most rapidly expanding markets for stainless steel and roofing is a major growth application. A method based on seam welding 0.4 mm strips of cold rolled stainless steel was invented in Sweden in the 60s and has since found favour in Europe and Japan. An LCC calculation was carried out based on these material options:

  • Galvanised and plastic coated carbon steel, double folded edges
  • 0.4 mm stainless steel strip, seam-welded and single folded edges (type 316 for coastal areas or polluted atmospheres, otherwise type 304)

In this example the LCC period is 50 years and a real interest rate of 3% is used (comparative figures are given per sq metre):

MATERIAL MATERIAL COST INSTALLED COST LCC
Carbon steel 1.1 2.1 2.2
Stainless Steel
Type 316 2.0 2.8 1.4
Type 304 1.6 2.6 1.3

 

The LCC result shows that stainless steels are less costly than galvanised and plastic coated steel. Galvanised carbon steel requires replacement after about 20 years. The calculation does, however, not take into account the risk of damage to building substructures each time the covering is replaced. The stainless steel alternative is the only one which is virtually maintenance free.

The second example is a mixing tank for a water treatment plant.

The example is of a simple rectangular, open-top tank for the initial mixing of waste streams from a water processing plant. The requirement is for a projected 20-year life, to coincide with a similar requirement of other components of the water treatment plant. The tank is to take a variety of waste streams, mainly rinse waters and spills from both acidic and basic solutions.

The dimensions of the tank are 3 metres long, 1.5 metres wide and 1.5 metres high. The entire tank is raised off the floor by four steel channels beneath the tank; these ensure that spills do not accumulate beneath the tank.

The design brief requested evaluation of three materials.

  • Mild steel with applied fibreglass lining,
  • Stainless steel alternatives of type 304 and duplex grade 2205 (UNS S31803).

As the 2205 was not readily available in angle and channel products, these were substituted by type 304 for the 2205 design as these components were not to be in regular contact with the corrosive environment.

The evaluation was carried out using the LCC PC program from the International Chromium Development Association (ICDA) available in Australia through ASSDA.

Experience suggested that both the 304 and 2205 would probably survive without replacement for the full twenty years, whereas the mild steel was expected to last for only about eight years before replacement. In addition both the stainless steels were expected to require only minimal inspection and cleaning as regular maintenance in comparison with fairly extensive patching of the mild steel and its lining.

The 'Summary of Present Value Costs' table of Figure 1 shows the resulting LCC analysis - the type 304 stainless steel is lowest cost, closely followed by the 2205 and with mild steel substantially more expensive due to its higher maintenance and replacement costs.

The "Value of Lost Production" in the summary table is shown as zero - this implies all maintenance and replacement is carried out in scheduled shut downs for other plant maintenance. Shut downs causing lost production could substantially add to the Total Operating Cost of the option requiring this unscheduled maintenance.

The ICDA LCC software also gives a more detailed breakdown of the contributions to the initial costs and operating costs, and a "sensitivity analysis" on all the inputs which is shown in Figure 2. The latter gives the effect on the total LCC for each material option of an independent change (e.g. of 20%) in each of the inputs. This information is vital in determining which of the input items must be accurately known and which are of lesser importance. In this case the sensitivity analysis indicates that the most critical data is the time before replacement becomes necessary. The assumption was that the 304 and 2205 would both survive for the full 20 years; from the sensitivity analysis it is apparent that if the 304 fails before this time (possibly due to its lower pitting corrosion resistance compared to 2205), the 2205 duplex stainless steel becomes by far the cheaper option. Clearly a good knowledge of the actual operating conditions to be encountered is crucial to the correct selection.

Figure 1

Sensitivity Analysis on Life-Cycle Costing for a WTP Mixing Tank
Cost of capital 7.90 %
Inflation rate 3.5 %
Real interest rate 4.25 %
Desired life cycle duration 20.0 years
Downtime per maintenance/replacement event 3.0 days
Value of lost production 0 Mu/day

 



Type 304 2205 Mild Steel
-20.0% +20.0% -20.0% +20.0% -20.0% +20.0%
Cost of capital 5320 5404 5773 5822 12826 10590
Inflation rate 5389 5351 5814 5792 11107 12133
Desired life cycle duration 5371 7707 5804 8328 9169 13751
Downtime per maint/replace event 5371 5371 5804 5804 11600 11600
Value of lost production 5371 5371 5804 5804 11600 11600
Material's cost 4559 6183 4918 6690 11271 11929
Fabrication and installation cost 5115 5627 5548 6060 11344 11856
Other installation costs 5371 5371 5804 5804 11300 11900
Cost per maintenance event 5307 5435 5740 5868 11326 11873
Elapsed time between maintenance event 5479 5347 5912 5780 12707 11416
Cost per replacement event 5371 5371 5804 5804 11600 11600
Elapsed time between replacement events 7968 5416 8639 5839 13977 9437
Material-related operating costs 5371 5371 5804 5804 11600 11600
Base Case LCC 5371 5804 11600

 

Figure 2

 

Sensitivity Analysis on Life-Cycle Costing for a WTP Mixing Tank
Cost of capital 7.90 %
Inflation rate 3.5 %
Real interest rate 4.25 %
Desired life cycle duration 20.0 years
Downtime per maintenance/replacement event 3.0 days
Value of lost production 0 Mu/day

 



Type 304 2205 Mild Steel
-20.0% +20.0% -20.0% +20.0% -20.0% +20.0%
Cost of capital 5320 5404 5773 5822 12826 10590
Inflation rate 5389 5351 5814 5792 11107 12133
Desired life cycle duration 5371 7707 5804 8328 9169 13751
Downtime per maint/replace event 5371 5371 5804 5804 11600 11600
Value of lost production 5371 5371 5804 5804 11600 11600
Material's cost 4559 6183 4918 6690 11271 11929
Fabrication and installation cost 5115 5627 5548 6060 11344 11856
Other installation costs 5371 5371 5804 5804 11300 11900
Cost per maintenance event 5307 5435 5740 5868 11326 11873
Elapsed time between maintenance events 5479 5347 5912 5780 12707 11416
Cost per replacement event 5371 5371 5804 5804 11600 11600
Elapsed time between replacement events 7968 5416 8639 5839 13977 9437
Material-related operating costs 5371 5371 5804 5804 11600 11600
Base Case LCC 5371 5804 11600

 

Percentage Change from Base Case Data
  Type 304 2205 Mild Steel
-20.0% +20.0% -20.0% +20.0% -20.0% +20.0%
Cost of capital -0.9 0.6 -0.5 0.3 10.6 -8.7
Inflation rate 0.3 -0.4 0.2 -0.2 -4.3 4.6
Desired life cycle duration 0.0 43.5 0.0 43.5 -21.0 18.5
Downtime per maint/replace event 0.0 0.0 0.0 0.0 0.0 0.0
Value of lost production 0.0 0.0 0.0 0.0 0.0 0.0
Material's cost -15.1 15.1 -15.3 15.3 -2.8 2.8
Fabrication and installation cost -4.8 4.8 -4.4 4.4 -2.2 2.2
Other installation costs 0.0 0.0 0.0 0.0 -2.6 2.6
Cost per maintenance event -1.2 1.2 -1.1 1.1 -2.4 2.4
Elapsed time between maintenance events 2.0 -0.4 1.9 -0.4 9.5 1.6
Cost per replacement event 0.0 0.0 0.0 0.0 0.0 0.0
Elapsed time between replacement events 48.4 0.8 48.8 0.8 20.5 -18.6
Material-related operating costs 0.0 0.0 0.0 0.0 0.0 0.0

 

ACKNOWLEDGMENTS:

1. This article has drawn on material contained in a publication Life Cycle Costing - Evaluation of a Method of Use For Stainless Steel Applications by Sten Von Matern of Avesta AB, Sweden. This has been made available to ASSDA through Avesta Sheffield Australia Pty Ltd. This contribution is gratefully acknowledged.

2. The program "Life Cycle Costing" was developed by and supplied to ASSDA by the International Chromium Development Association.

In response to the growing awareness that our quality of life depends upon protection of our environment, consumers and regulators are directing their resources towards products less harmful to the environment. The challenge to specifiers is clear: understand the "cradle to grave" characteristics of materials and make ever more satisfying products from ever more benign materials.

In use stainless steel is durable and requires a minimum of maintenance, outlasting many competing products and eliminating requirements for additional potentially hazardous materials such as paint, fire protective coatings, cleaners and solvents.

Stainless steel is a valuable scrap material. It is 100% recyclable and a preferred raw material input by steel makers. Stainless steel production incorporates high levels of scrap use (as high as 80% of charged materials will be scrap stainless steel). New stainless steel comprises at least 50% recycled stainless steel product and more than half the stainless steel produced today has already been another useful stainless steel product in the past. Even beer kegs wear out eventually. Power is expensive and modern stainless mills operate close to the theoretical minimum.

Despite the very high recycling of old stainless steel products, some stainless steel will find its way to landfills or other disposal sites. In these circumstances no detrimental effect to soil or ground water is expected.

Why Join ASSDA?

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