Choosing the Right Blow Bar for Your Horizontal Shaft Impactor (HSI)
When it comes to crushing operations, selecting the right blow bar is critical for maximising efficiency and minimising costs. Blow bars are the sacrificial workhorse of a Horizontal Shaft Impactor (HSI), designed to break down materials like concrete, asphalt, and rock. This guide will help you understand how to choose the best blow bar for your application, ensuring optimal performance and longer wear life.
What Are Blow Bars and Why Are They Important?
Blow bars, also known as hammers, are the main wear components of a HSI. These thick metal slabs are mounted on the rotor and strike feed material, throwing it against impact plates to reduce its size. The right blow bar not only improves crushing efficiency but also reduces downtime and costs by lasting longer and performing reliably.
Selecting the right blow bar ensures better compatibility with your crusher and feed material, improving overall operational efficiency. Understanding the types and applications of blow bars is key to choosing the right one for your needs.
Choosing the Right Blow Bar Material for Your Application
Blow bars are made from various materials, each offering unique benefits depending on the application. Here’s a breakdown of common materials to help you select the best blow bar for your needs:
1. Manganese Steel –
- What Is It: Manganese steel is highly valued for its excellent impact resistance and unique ability to work-harden under stress. This means the surface becomes harder with repeated impact, enhancing its durability over time. However, its wear resistance remains relatively low compared to other materials. Manganese steel is a top choice for blow bars used in primary or secondary crushers, especially for handling large feed sizes over 800mm in diameter or in applications with a high presence of unbreakable objects. A typical application is crushing limestone in quarry operations for cement plants.
- Why Choose It: Typically in 18 and 22% Mn, their high impact resistance makes it ideal for primary crushing and applications with large feed sizes.
- Best For: Crushing limestone or large rocks in cement plants or quarry operations.
2. Manganese Steel with Titanium Carbide Inserts
- Why Choose It: These blow bars have Titanium Inserts along key wear areas significantly enhancing their performance. Offers up to 60% longer wear life than standard manganese steel.
- Best For: Applications where abrasive materials are present and longer life is needed from your blowbars.
3. Martensitic Steel
- What Is It?: Martensitic steel is an alloy steel enriched with elements like molybdenum and nickel, designed for enhanced wear resistance compared to manganese steel. However, this comes at the cost of reduced impact resistance. These properties make martensitic blow bars ideal for applications with smaller feed sizes or dealing with possible contamination from items that cannot be crushed. A common use case is in impactors recycling concrete with rebar,
- Why Choose It Balances wear resistance and impact performance, making it suitable for medium feed sizes.
- Best For: Recycling concrete with moderate contamination, such as rebar.
4. Martensitic Steel with Ceramic Inserts
- What Is It: As per Manganese Steel bars, Martensitic Steel bars can be manufactured with ceramic inserts in key areas. In certain applications, this can result in up to 100% longer wear life.
- Why Choose It: Ceramic inserts enhance wear life, doubling durability in demanding applications.
- Best For: Concrete recycling and abrasive applications with controlled feed sizes.
5. Chrome White Iron
- What Is It?: Chrome white iron, with its higher carbon and chromium content compared to manganese and martensitic steel, offers exceptional wear resistance but limited impact tolerance. Chrome white iron is classified based on chromium content: medium chrome contains around 20%, while high chrome typically has approximately 25%. These blow bars are ideal for secondary or tertiary crushers handling highly abrasive materials like natural stone or granite. However, strict control over feed size—typically less than 300mm in diameter—is essential, and unbreakable objects or tramp iron must be excluded to prevent damage. A common application for chrome white iron blow bars is in aggregate production and sand-making plants.
- Why Choose It: Exceptional wear resistance but requires careful handling due to lower impact resistance.
- Best For: Crushing abrasive rocks like granite or sandstone in secondary or tertiary applications.
6. Chrome White Iron with Ceramic Inserts
- Why Choose It: Combines the wear resistance of chrome with the durability of ceramics for extended life.
- Best For: Highly abrasive materials in sand-making or aggregate plants.
Factors to Consider When Choosing the Right Blow Bar
Selecting the right blow bar involves more than just material choice. The following factors are equally important:
Material Characteristics
- Feed Size: Larger feed sizes require blow bars with higher impact resistance, like manganese steel or martensitic steel with ceramic inserts.
- Abrasiveness: Materials like asphalt or silica-rich rock demand wear-resistant options, such as high chrome or chrome with ceramic inserts.
- Moisture Content: Excess moisture can accelerate wear, so choose materials designed for durability under such conditions.
Crusher Settings
- Rotor Speed: Higher rotor speeds result in finer output but increased wear. Balancing speed with your application is crucial.
- Closed Side Setting (CSS): Proper crusher settings reduce unnecessary wear and improve blow bar performance.
Operational Practices
Operational practices are critical in reducing wear and ensuring efficient performance in impact crushers. Pre-screening is one of the most effective ways to minimise blow bar wear by removing fines and contaminants before they reach the crusher. Fines, if left unchecked, can act like abrasive agents, accelerating wear on blow bars and other components. Similarly, contaminants like tramp iron or other uncrushable materials can cause significant damage if not removed in advance. Another essential practice is maintaining a steady material flow into the crusher. Consistent feeding prevents uneven wear on blow bars, as irregular or fluctuating material flow can cause one side of the rotor to experience higher stress than the other. Proper material preparation and ensuring smooth, even feeding help extend the life of wear parts, optimise crusher efficiency, and reduce the frequency of costly downtime for maintenance.
Benefits of Choosing the Right Blow Bar
By selecting the right blow bar for your application, you can:
- Extend the wear life of your blow bars.
- Reduce downtime and operational costs.
- Maximise crushing efficiency and output.
The right blow bar material tailored to your specific needs ensures smooth operation and improved cost-per-ton efficiency.
Be Prepared for Downtime
Blow bars will eventually wear out, so it’s vital to plan for replacements. Ordering replacement blow bars in advance minimises downtime and keeps your operation running smoothly. High-quality, application-specific blow bars not only increase productivity but also reduce long-term costs.
A good enterprise resource planning tool can help you manage your stock to ensure you maintain your critical safety levels. ACBG offers an Inventory Management Program whereby we can hold stock at our warehouse or at your site to ensure your never caught out.
Why Choosing the Right Blow Bar Matters
The blow bar is a small yet essential component that determines the efficiency of your HSI. Making an informed decision when choosing the right blow bar ensures durability, optimised crushing performance, and cost savings. Whether you’re processing abrasive materials or managing large feed sizes, the right blow bar can make all the difference.
Ensure you select the best blow bar for your specific application to maximise efficiency and minimise downtime in your crushing operation. For expert advice or to explore our range of high-quality blow bars, contact us today.
