More companies are choosing to build stainless steel tanks over carbon steel tanks and the reasons are simple. Stainless steel is much more versatile, longer lasting, and generally suited to different industries with special needs.
Stainless steel tanks can cost less to manufacture than carbon tanks, are more resistant to temperature induced cracking (necessary for the extreme Australian weather), need little to no maintenance (important for keeping bottom line costs down), and when correctly applied, will not corrode anywhere near as quickly as carbon steel tanks. Finally, they last much longer than carbon steel tanks – tanks made from stainless steel can be used for decades without requiring extensive refurbishment or replacement.
This post covers technical information to consider when your company is deciding between a tank made from stainless steel or carbon steel.
What is stainless steel and carbon steel made of?
Iron and carbon are two of the fundamental elements that make up both materials. Where the two materials differ is that a minimum of 10.5 percent chromium is added to make stainless steel. Chromium is the special ingredient that protects stainless steel from corrosion.
Adding amounts of alloying elements like molybdenum, nickel, manganese, titanium and others determine the type of grade and its suitability to corrosion resistance, strength, hardness and heat resistance.
Stainless steel material grades have advanced in recent years because it can be customised to specific industry needs. LDX2101, for example, provides superior strength and corrosion resistance while maintaining comparable costs to more traditional grades such as 304 and 316.
Stainless steel tank vs carbon steel tank thicknesses and weight
Although stainless steel and carbon steel tank fabrication practices are traditionally similar, welding durations on carbon steel tanks are higher, particularly with coded designs such as API650, AS1210 and AS1692. Consumables for stainless steel tanks are slightly higher; however, it’s offset by the overall reduction in tank weight due to stainless steel’s higher strength.
The table below shows weight comparisons between a 1,500,000L storage tank, 12.5m diameter x 12.5m high shell, material thicknesses as per API650 design code, including a corrosion allowance of 0.25mm for stainless steel and 3mm carbon steel.
Table 1: Weight Comparison of 1,500,000L API650 Storage Tank.
|Material||Thickness (mm)||316SS (kg)||Thickness (mm)||LDX SS (kg)||Thickness (mm)||Carbon Steel (kg)|
|Shell||5, 6, 8||24,565||5||20,069||6, 8, 10||30,249|
Cost savings from fabricating stainless steel tanks
Continuing with the 1,500,000L tank example, there are additional costs associated with surface treatment on carbon steel tanks, while stainless steel tanks don’t incur these costs. With properly selected types and grades, stainless steel is resistant to tank contents, the external environment and doesn’t need painting. Your life cycle cost of ownership becomes significantly less.
Some more points to consider:
- Fabricating carbon steel tanks requires preheating and post heating for welds. Carbon steel tanks also need post welding treatment and radiography testing inspection. Depending on design parameters, these processes aren’t required for stainless steel tanks
- Grit blasting for paint preparation creates airborne particles that can contaminate surrounding properties, and dirty equipment
- Grit blasting and painting for carbon steel tanks requires personnel to work at heights. Stainless steel tanks eliminate the need to paint at heights, reducing the risks of falls and WHS issues
- On-site duration – fabrication of an A&G stainless steel tank is generally much quicker than a carbon steel tank, specifically field-erected vessels
- Painting outdoors can affect the environment, the environmental impact is reduced with a stainless steel tank
Comparing maintenance costs: Stainless steel tanks vs carbon steel tanks and vessels
Painting, maintenance and rework costs are indicative of scheduled cycles and vary depending on type of product stored and facility location.
Tanks storing aggressive materials, or near coastal environments, may cost more in maintenance. Please use the table below as a general guide only. Depending on the individual application and process, costs can vary greatly. Of significant consideration (not listed below), is the ‘Out of Service Costs’ (when the tank is not being used) for carbon steel tanks during regular maintenance works.
Table 2: Based on 810m2 surface area @ $240 m2
|304 SS||316 SS||LDX 2101||SAF 2205||Carbon Steel|
|Maintenance 10-12 Years||Ø||Ø||Ø||Ø||$279,000|
|Maintenance 20-22 Years||Ø||Ø||Ø||Ø||$335,280|
|Maintenance 30 Years||Ø||Ø||Ø||Ø||$402,350|
Advantages of a stainless steel tank:
- Initial manufacture costs of stainless steel tanks can be lower than carbon steel tanks and vessels
- Little to no ongoing maintenance costs for the life of the stainless steel tank, hence no loss of productivity
- Stainless steel tanks look better aesthetically at a facility, compared to discoloured, rusting, painted carbon steel tanks
Stainless steel tanks are superior and cost less
It’s a myth that stainless steel tanks cost more than carbon steel. As shown above, stainless steel tanks cost your business significantly less and provide many other benefits, from the initial capital outlay phase and over the life of the vessel.
A&G Engineering is Australia’s leading stainless steel tank manufacturer, providing different capacity storage and processing tanks for the petrochemical, winery, brewery, dairy, food and beverage and other industries. Call us on (02) 69643422 or email to find out more about whether a stainless steel tank is the right solution for your needs.