Limestone is soft. It is widely used. We see it in cement. We see it in roads. But, picking the right crusher is hard. Many people buy the wrong one. They lose money. This article helps you choose. We use data. We use experience. We are SBM. We know mining equipment. We will explain how to pick the best machine. It is simple.
You must know your stone first. Limestone is sedimentary. It is not hard. The Mohs hardness is usually 3 to 4. This is important. Why? Because hard rocks break machines.
Limestone also contains silica. Silica eats metal. If silica is high, wear is high. You must check the content. Is it 5%? Is it 10%? High silica needs special parts. It needs high chrome parts.
Moisture is another key factor. Wet limestone is sticky. It clogs the machine. Production stops. You lose time. We check water content always. It changes the machine choice.
The Jaw Crusher is for big rocks. It is the first stage. We call it the primary crusher. It works like a mouth. It chews the stone.
Working Principle:
A motor spins a shaft. The shaft moves a jaw plate. The plate moves back and forth. This is the “eccentric motion”. The rock falls in. The jaw squeezes it. The rock breaks.
Key Parameters:
We look at the CSS. This is Closed Side Setting. It decides the output size. We also look at the OSS. This is Open Side Setting. It decides the speed.
Standard data from Mining Journal shows jaws are efficient. They handle compression well. But, they make flat shapes. Limestone needs good shapes. So, we need a second machine.
This is the most important section. Please read carefully. For limestone, the Impact Crusher is the best. Why? Because of the physics.
The Impact Principle:
The machine has a rotor. The rotor spins fast. Very fast. It has blow bars. These are heavy metal bars. The rock enters. The bar hits the rock. The rock flies. It hits a liner. It breaks again. Then it hits other rocks.
Advantages for Limestone:
We use SBM impact crushers often. They use high chrome blow bars. This resists wear. The rotor is heavy. This keeps the speed steady.
This is a big pain point. Many customers ask this. “My blow bars break too fast. Why?”
The Problem:
Limestone is soft. But silica is hard. It acts like sandpaper. It grinds the steel. If you use a normal impact crusher, costs go up. You change parts every week. This is bad.
The Solution:
If silica is over 10%, stop. Do not use an Impact Crusher alone. You might need a Cone Crusher. Or, use special alloys. SBM offers ceramic-composite bars. They last longer. We calculate the wear cost. We compare it to profit. We find the balance.
Let us look at numbers. Engineers love numbers. These are typical specs for a medium plant. This is based on SBM field data.
| Feature | Jaw Crusher | Impact Crusher |
|---|---|---|
| Reduction Ratio | 3:1 to 5:1 | 10:1 to 20:1 |
| Output Shape | Flaky / Flat | Cubical / Good |
| Maintenance | Low | Medium |
| Suitable Silica | Any level | Low to Medium |
The table shows the truth. Impact crushers win on shape. Jaws win on tough rock. For limestone, shape usually wins. The market pays more for cubes.
Background:
A client in Vietnam. They make cement. The weather is wet. It rains a lot. The limestone is muddy.
Equipment List:
The Challenge:
The mud was terrible. It blocked the jaw crusher. The capacity dropped. It went from 300 tons to 150 tons. The client was angry.
Our Solution:
We changed the feeder. We added a scalping screen. It removes the mud before the crusher. We also adjusted the impact crusher speed. We increased the rotor speed. This clears the chamber fast.
Result:
Production went up. It hit 350 tons per hour. The client was happy. They said the SBM design saved the project. The maintenance time dropped by 30%.
Background:
A project in Saudi Arabia. It is hot. Very dry. The limestone is pure. They need aggregate for asphalt.
The Goal:
They need specific sizes. 0-5mm, 5-10mm, 10-20mm. The shape must be perfect. No flat stones allowed.
Design Logic:
We skipped the Cone Crusher. Why? Because it makes dust. We used a two-stage Impact Crusher system. One large impactor. One shaping impactor.
Customer Feedback:
“The stone shape is amazing. The asphalt binds well. Our road quality is top tier. The SBM equipment runs in 45°C heat. No overheating. The motors are strong.”
This is another common question. “Why do I pay so much for electricity?”
The Analysis:
Maybe your motor is too big. Or too small. If it is too small, it works too hard. If too big, you waste power.
The Fix:
We match the motor to the load. We use soft starters. This reduces the spike. We also check the belt tension. Loose belts waste power. Simple checks save money.
A good machine needs good care. Installation is the start. If you install it wrong, it breaks.
Installation Tips:
Maintenance Cycle:
Check bolts every day. Tighten them. Grease the bearings every week. Check the liners every month. Flip the blow bars. This doubles their life. Why? Because they wear on one side.
We do not list prices here. Prices change. But we discuss value. We look at OPEX. This is Operating Expense.
Wear Parts:
Limestone is kind to jaws. You change plates rarely. Maybe once a year. But impact bars wear fast. Maybe every 2 months. You must budget for this.
Energy:
Impact crushers use more power per ton than jaws. But, they do more work. They crush and shape. If you use a jaw and a cone, you run two motors. One impactor might be cheaper overall.
Pain point number three. “My crusher is clogged.”
Strategy:
Do not crush wet mud. Screen it out. Use a wobbler feeder. It shakes the mud off. Or, heat the material? No, that is too expensive. Just screen it. SBM feeders are good at this.
Here are three questions users ask us. We answer them simply.
Q1: Can I use a Cone Crusher for limestone?
A: Yes, you can. But why? Cones are for hard rock. Granite. Basalt. They are expensive. They are heavy. For soft limestone, they are overkill. An impactor is cheaper and lighter. It does the job well.
Q2: How often should I change the blow bars?
A: It depends. How much silica? How many hours? Usually, inspect them weekly. If worn 50%, flip them. If worn past the safety line, change them. Do not wait. A broken bar destroys the rotor.
Q3: What is the best reduction ratio?
A: For limestone, try 15:1 in an impactor. If you feed 600mm, you can get 40mm out. This is efficient. Pushing it harder causes stress.
To pick the best crusher, follow these steps. It is a decision tree.
Step 1: Test the rock. Is it hard? Is it abrasive?
Step 2: Check the market. Do they want cubes? Or just rock?
Step 3: Calculate the volume. Tons per hour.
If you have soft, low-silica limestone, buy an SBM Impact Crusher. It is the gold standard. It saves money. It makes good product. If the rock is dirty, add a screen. If the rock is huge, add a jaw.
Do not guess. Use data. Look at the charts. Read the manual. Good luck with your quarry.
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