Paddy is a highly abrasive material due to the presence of silica in its husk. When transported through chutes and spouts, it causes significant wear and tear, leading to frequent maintenance and operational downtime. Choosing the right material is crucial for ensuring durability, cost-effectiveness, and smooth material flow. However, due to ignorance many people in industry choose wrong material which ultimately doesn’t work.
In rice industry I have seen people using following material for Chutes and Spouts
1. Mild Steel or GI
2. Mild Steel or GI with UHMWPE Liner
3. ASTM AR400
4. ATSM AR400 with UHMWPE Liner, and
5. Stainless Steel SS-304
We must understand that the property of metal that helps resist Abrasion is hardness and friction. Higher Hardness reduces wear and tear caused by friction and mechanical forces. We must also understand that we are only talking about abrasion not corrosion here. Corrosion is entirely different phenomenon.
Let us understand the properties of each type of metal before concluding the results
Mild Steel (IS 2062)
Mild steel has a hardness of 130-180 BHN and hence offers low abrasion resistance, making it prone to wear in paddy handling applications. It has a high friction coefficient of approximately 0.6, leading to material sticking and higher energy consumption. However, it has excellent weldability and formability, making it an easily acceptable choice for fabrication of chutes and spouts.
Galvanized Steel (GI - Zinc Coated MS)
Galvanized steel has similar properties like mild steel however since it is basically as mild steel coated with zinc hence it improves its corrosion resistance properties. Hence, for abrasion resistance it is not a good material as its cost is high as compared to Mild Steel and also its zinc coating wears off in no time. It also has high friction (~0.6), similar to mild steel, leading to material sticking.
It costs around 1.2 to 1.5 times that of plain mild steel.
ASTM AR400
AR400 is an abrasion-resistant steel with a hardness of 360-440 BHN, offering high durability in wear-prone applications. It has moderate friction coefficient (~0.3) and better abrasion resistance than mild steel but lacks smooth material flow. Weldability is moderate, requiring preheating for proper joining, and formability is limited due to its hardness.
The cost is about 1.3 to 1.5 times higher than mild steel.
Stainless Steel (SS304/SS316)
Stainless steel has a hardness of 190-220 BHN and moderate abrasion resistance, making it suitable for corrosion-prone environments rather than high-abrasion applications. It has a moderate friction coefficient (~0.4), and though weldability and formability are good.
However, it is expensive—about 3 to 4 times the cost of mild steel.
Mild Steel with UHMWPE Liner
By adding a UHMWPE (Ultra High Molecular Weight Polyethylene) liner to mild steel, abrasion resistance significantly improves. UHMWPE has a hardness of 63-69 Shore D and an extremely low friction coefficient of around 0.1, ensuring smooth paddy flow. Since the base metal is Mild Steel hence Weldability and formability remain the same as mild steel, while abrasion resistance improves a lot due to the liner’s protection.
The cost is about 1.3 to 1.7 times higher than plain mild steel.
Conclusion: The Best Choice
After comparing the materials based on abrasion resistance, friction, cost, and durability, the best choice for paddy chutes and spouts is Mild Steel with a UHMWPE Liner.
It is the most cost-effective solution compared to all other metals including AR400 and Stainless Steel.
It provides high abrasion resistance, significantly reducing wear compared to plain mild steel as there is no direct contact of paddy with mild steel as paddy flows over UHMWPE liner only.
It ensures smooth material flow due to low friction, preventing blockages and reducing energy consumption.
Fabrication is simple, as mild steel is easy to weld and form.
The liner provides moderate corrosion resistance too, protecting the mild steel base from direct exposure to paddy.
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