Impact Crusher Wear Parts Guide: Blow Bars, Impact Plates & Liners Exp

Impact crushers are workhorses in the aggregate, mining, and recycling industries. They use high-speed impact to fracture material, making them ideal for producing cubical products from medium-hard rocks, recycling concrete and asphalt, and shaping aggregate.

But here’s the challenge: impact crushers consume impact crusher wear parts faster than any other crusher type. The blow bars (also called hammers), impact plates, and liners are subjected to extreme impact energy and sliding abrasion with every revolution of the rotor. Choosing the wrong material for your impact crusher wear parts can mean changing blow bars every few hundred hours — driving up your cost per ton and stealing valuable production time.

The right choice? You can achieve 1,500–2,000 hours of blow bar life in many applications, or even longer with advanced materials like ceramic composites.

In this guide, we cover everything you need to know about impact crusher wear parts — how blow bars, impact plates, and liners work, how to select the right material (high chrome, manganese, or ceramic composite) for your feed material, how to identify wear patterns, and how to extend wear part life. Whether you operate a horizontal shaft impactor (HSI) in a Canadian quarry or a recycling crusher on a demolition site, this guide will help you make better decisions about your impact crusher wear parts.

What Are Impact Crusher Wear Parts and How Do They Work?

Unlike jaw or cone crushers that use compression, impact crushers use kinetic energy to break rock. Material is fed into the crusher and struck by blow bars attached to a high-speed rotor. The fractured material is then thrown against impact plates (also called breaker plates or aprons) for secondary breakage, before falling through the crushing chamber.

The three main types of impact crusher wear parts are:

How the crushing process affects wear parts

The impact crusher wear parts experience different types of wear depending on their position:

• Blow bars take the direct impact of incoming material, plus high-velocity abrasion as material slides across them before being thrown

• Impact plates experience secondary impact from material thrown at high speed — more impact than compression

• Liners face sliding abrasion as material bounces off the housing

Because the wear mechanisms differ, the optimal material for each impact crusher wear part can also differ. However, most operators standardize on one material family (high chrome or manganese) for simplicity.

Blow Bars (Hammers) – The Most Critical Impact Crusher Wear Part

Blow bars are the most frequently replaced impact crusher wear parts. They are attached to the rotor — typically in sets of three, four, or six bars depending on the crusher size and design — and rotate at speeds of 400–800 RPM (or faster in some designs).

How blow bars wear

As the blow bar strikes material, it gradually loses mass. The wear pattern is rarely uniform:

• The leading edge (the front face that first contacts material) wears fastest

• The top surface (the strike face) wears from abrasive sliding

• The heel (back edge) and ends typically wear slower

Most operators replace blow bars when the leading edge has worn back 50–60% of the original thickness, or when performance noticeably drops.

Standard vs. reversible blow bars

Reversible blow bars can extend impact crusher wear parts life by 2x compared to non-reversible bars in the same application. BDI Wear Parts offers reversible blow bars for most major crusher models.

Material Selection for Impact Crusher Wear Parts – High Chrome, Manganese, or Ceramic Composite?

The material of your impact crusher wear parts is the most important decision you’ll make. The three main options each have distinct advantages and trade-offs.

Comparison: Materials for impact crusher wear parts

How to choose the right blow bar material

⚠️ Critical warning: Never use high chrome blow bars if your feed contains tramp iron (rebar, bolts, tools, etc.). High chrome is brittle — a single piece of rebar can crack a high chrome blow bar, leading to catastrophic rotor damage. Use manganese steel blow bars for any feed with tramp iron risk.

Impact plates and liners – material selection

For impact plates and liners, the material decision is simpler:

• Impact plates: Usually the same material as blow bars (high chrome or manganese). In some designs, impact plates can be reversed or rotated to extend life.

• Liners: Often made of wear plate steel (AR400, AR500) or manganese steel. For highly abrasive applications, replaceable liner sections in high chrome or ceramic composite are available.

Blow Bar Profiles – Which One Is Right for Your Material?

Beyond material, the profile (shape) of your blow bars affects how the crusher performs and how the impact crusher wear parts wear.

Common blow bar profiles

How to choose the right blow bar profile

BDI Wear Parts offers all of these blow bar profiles and can customize impact crusher wear parts for your specific application and crusher model.

How to Extend the Service Life of Your Impact Crusher Wear Parts

Even with the best impact crusher wear parts, improper operation will shorten their life. Follow these five practices to maximize blow bar and impact plate longevity.

1. Feed material correctly – avoid segregation and oversized feed

Oversized feed is the #1 cause of premature blow bar failure. When rocks are too large for the crusher:

• Blow bars take extreme impact energy — accelerated wear or cracking

• Material can bridge above the rotor, causing plugging

Rule of thumb: Maximum feed size should be significantly smaller than the rotor diameter. For HSI crushers, feed size should typically not exceed 15–20% of rotor diameter for hard rock, or slightly larger for soft rock.

Also avoid: Feed segregation (fines on one side, coarse on the other). This causes uneven wear across the blow bars.

2. Maintain proper rotor speed

Rotor speed affects both product size and impact crusher wear parts wear:

• Too slow: Material isn’t thrown hard enough against impact plates — coarser product, more recirculation, more wear on blow bars

• Too fast: Blow bars and impact plates take excessive impact — accelerated wear, possible cracking

Best practice: Set rotor speed based on your feed material and desired product size. Most manufacturers provide speed guidelines. Monitor wear rates and adjust speed if blow bars are wearing faster than expected.

3. Check and adjust impact plate gap regularly

The gap between the blow bars and impact plates (the primary and secondary impact curtains) affects crushing efficiency and wear:

• Gap too large: Less efficient crushing, more recirculation, more wear on blow bars

• Gap too small: Impact plates wear faster, risk of metal-to-metal contact

Best practice: Check impact plate gaps weekly (or daily in high-tonnage operations). Adjust as blow bars wear — closing the gap as blow bars lose mass maintains product size.

4. Rotate or flip blow bars regularly

If you are using reversible blow bars, follow a regular rotation schedule:

• Rotate blow bars end-for-end when the leading edge has worn 30–40%

• Flip blow bars (turn over to use opposite face) when both ends of the first face are worn

Many operators schedule blow bar rotation every 200–400 hours, depending on application. Tracking wear patterns helps optimize rotation frequency.

5. Replace blow bars as a set (or in matched pairs)

Always replace all blow bars in the same rotor position as a set (or as a matched pair in two-rotor designs). Replacing only one or two blow bars creates imbalance:

• Rotor imbalance — vibration, bearing damage

• Uneven wear — new blow bars take more load, wear faster than their matched counterparts

How to Know When to Replace Your Impact Crusher Wear Parts

Knowing the right time to replace impact crusher wear parts prevents both premature replacement (wasting usable life) and late replacement (rotor damage, poor product quality).

Blow bar replacement indicators

Impact plate replacement indicators

Recommended replacement intervals by application

Note: Ceramic composite blow bars can achieve 1.5–2x the hours listed above in highly abrasive applications.

BDI Wear Parts – Your Source for High-Quality Impact Crusher Wear Parts

At BDI Wear Parts, we supply a complete range of impact crusher wear parts for most major brands and models, including:

• Hazemag

• Kleemann

• Metso (NP series, LT series)

• Sandvik (QI series)

• Terex, Pegson, Powerscreen

• Eagle Crusher

• And many other brands

What makes BDI impact crusher wear parts different:

Frequently Asked Questions (FAQ)

Q1: How do I choose between high chrome, manganese steel, and ceramic composite blow bars?

A: The choice depends on your feed material and tramp iron risk:

| If your feed contains tramp iron (rebar, bolts, tools) | → ALWAYS use manganese steel blow bars |
| If your feed is clean (no tramp iron) and highly abrasive (river gravel, quartzite, iron ore) | → High chrome or ceramic composite (ceramic lasts 1.5–2x longer, higher upfront cost) |
| If your feed is low to medium abrasion (limestone, recycled concrete without rebar) | → High chrome or martensitic steel (cost-effective) |
| If you have extreme tonnage and want maximum life between changes | → Ceramic composite (best cost-per-ton despite higher upfront price) |

Critical warning: Do not use high chrome or ceramic blow bars in any application where tramp iron may enter the crusher — they are brittle and will crack, potentially destroying the rotor.

If you are unsure, BDI Wear Parts can analyze your feed material and recommend the optimal blow bar material for your specific application.

Q2: Why are my blow bars wearing out so fast? How can I extend blow bar life?

A: Fast blow bar wear is usually caused by one or more of these factors: