When To Use Stainless And Alloy Steel In Place Of Plastic Or Carbon Steel. There are many times when it is false economy to use carbon steel and plastic items. It is often better to use stainless and alloy steels instead. They last longer and deliver a lower life cycle cost.
Keywords: steel tank, steel pipe
The only way to convince people who don’t have their own experience with building and maintaining plant and equipment is to do a life cycle cost analysis and show them the money they will lose if they make poor choices!
Here are some typical situations when it’s usually better to use high quality stainless metals (not less than 316 marine grade stainless steel).
Stainless Steel Tanks
- If you factor in the cost of first painting a carbon steel storage tank, and then repainting it every 10 to 12 years to protect it against atmospheric and/or chemical vapour corrosion, you could have paid for a stainless steel tank at the start. It’s likely that a stainless tank would never need to be maintained again once it’s installed.Unlike painted carbon steel, you can’t chip a stainless tank wall and start a corrosion cell. Underfloor corrosion on a carbon steel tank is a major risk and many tanks need floors replaced at sometime in their working lives. Provided there is not a chloride problem under a stainless steel tank floor, then underfloor corrosion is not an issue.
- One important factor with stainless steels and alloy steels is that they have much higher tensile strengths than carbon steels. This means you can use thinner material to make the tank. As a consequence you need less mass of metal and so the costs look more reasonable when compared to a thicker carbon steel tank that you have to paint and maintain.The next time you need to build a carbon steel tank also do the design and cost calculations to make it out of stainless steel (or alloy steel in corrosive environments). Compare the life time costs – you will be surprised at how sensible it could be to go with stainless or alloy steel instead of painted carbon steel.
Stainless Steel Pipe
- Here too if you factor in the cost to replace and repaint corroded piping over the life of the plant you will probably find stainless piping is cheaper my quite a margin.
- One other place to consider using stainless instead of plastic is for instrumentation sensing lines and air-actuated valve connections. Plastic piping is easily damaged, cut, burnt by weld splatter, driven over, pierced, snagged and made unusable by atmospheric contaminants. Stainless steel (or maybe even copper) tubing is often a better life-time choice.
Stainless Steel For Cable Ties; Pipeline And Electrical Conduit Wall Mounting Clamps
- In the Australia sun ultraviolet-protected plastic electric cable ties last about 5 years. Then they perish and break. The cables fall off the walls and from bracketing. It’s a waste of time and costs unnecessary money putting the cabling back up again.Back in 1999 I ask my electrical maintenance people to come up with an alternate way to tie-up electric cabling that would last at least 20 years without maintenance. They chose stainless steel bandit strapping with stainless crimps. They don’t use plastic cable ties in outside locations any more because they failed so quickly.
- Using galvanised wall mounting clamps for piping and electrical conduits in corrosive environments is a waste of money. It usually better to use stainless steel (or for very corrosive locations get special clamps made from alloy steel) than to replace corroded galvanised wall clamps every three to five years for the next 40 years of a production plant’s life.
Stainless Structural Steel Frames
- If you use mobile equipment, like pumps, mounted on transportable frames in corrosive chemical environments, it’s probably more cost effective to make all the metal mounting structure from stainless steel. It’ll last longer and look better than painted carbon steel will after a couple of months of service.
- You often see the lower portion of structural steel members corroding if they stand in wet and/or corrosive environments. If corrosion will destroy the support feet and lower portions of a structure it may be more cost effective to make the lower portions of non-corroding metals.
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