Jaw crushers’ working principle, installation, commissioning and maintenance guide

What is Jaw crusher?

Jaw crushers play an important role in coarse and medium crushing in many fields such as mining, building materials, and infrastructure. According to the width of the feed opening, it can be divided into three types: large, medium, and small. The feed opening width of large machines exceeds 600 mm, the feed opening width of medium-sized machines is between 300 and 600 mm, and the feed opening width of small machines is less than 300 mm. This crusher has a compact structure, simple manufacturing, stable operation, and easy maintenance.

Its core working parts include two jaw plates: one is a fixed jaw plate, which is fixed vertically (or slightly outward) on the front wall of the machine body; the other is a movable jaw plate, which is set at an angle and together with the fixed jaw plate forms a crushing chamber with a large top and a small bottom. The movable jaw plate reciprocates periodically, sometimes opening and sometimes closing. When it is open, the material can enter the crushing chamber; when it is closed, the material is squeezed, bent, and split, thereby achieving crushing.

In addition, jaw crushers can be further classified according to the swinging mode of the movable jaw plate, including simple swinging, complex swinging and comprehensive swinging.

Advantages of jaw crushers:

High efficiency: jaw crushers significantly increase the output of limestone and reduce the operating rate, thus providing valuable maintenance time.

Large block crushing: The crusher can easily cope with the crushing of large blocks of limestone, with a maximum crushable particle size of 1000*1200mm, effectively solving the problem of tight limestone supply and a large number of large blocks of limestone that cannot be used.

Optimized mixing: The mixing uniformity of the two materials has been significantly improved, and the addition amount of desulfurized limestone has been greatly increased to 60%, thereby reducing the cost of raw materials.

Energy saving and consumption reduction: In terms of power consumption, the crusher has also been significantly reduced, with the power consumption per ton of limestone reduced by 1-2KWh/t, and an average annual electricity bill saving of 10,000 USD.
Fine particle size: The particle size of the crushed limestone is controlled at 2-15mm, which effectively solves the problem of chute blockage and reduced mill output caused by excessive original limestone particle size.
Improve the environment: The high level of automation of the jaw crusher means that workers do not need to directly contact the material, which greatly reduces the labor intensity and improves the working environment.

• Regular inspection and maintenance: For any stone crushing equipment, including the jaw crusher, it is crucial to shut down and check the internal wear regularly. This involves the wear degree of the center feed pipe, cone cap, impeller, upper and lower flow channel lining, circumferential guard plate and wear-resistant block. Once severe wear is found, it should be replaced immediately, and ensure that the weight and size of the new part are consistent with the original part.

• Conveyor belt inspection and adjustment: The jaw crusher conveyor belt plays a key role in the stone production line. In order to ensure its stable operation, it is necessary to check its tightness regularly and keep the force uniform. When using dual motor drive, the triangular tapes on both sides should be selected in groups to try to keep the length consistent. Once the conveyor belt is found to be severely worn, it should be replaced in time.
• Lubrication management of mechanical parts: Jaw crushers require specific grease, such as Mobil automotive grease extra or 3 lithium grease. In daily use, an appropriate amount of grease should be added for maintenance every 400 hours of work. After 2000 hours of work, the main shaft assembly should be opened to clean the bearings. Generally speaking, new bearings should be replaced every 7200 hours of work to ensure the long-term stable operation of mechanical parts.

In addition, in order to ensure the continuous and stable operation of the jaw crusher, in addition to daily operation and maintenance, planned maintenance work is also required. This includes daily maintenance inspections, minor repairs, medium repairs and major repairs to ensure the overall performance and safety of the equipment.

• The scope of minor repairs covers the inspection and repair of the jaw crusher adjustment device and the adjustment of the discharge port gap. In addition, it also includes the adjustment or replacement of the wear liner, and the inspection and maintenance of the transmission part and lubrication system, and the lubricating oil needs to be replaced. The frequency of minor repairs is usually set to once every 1-3 months.

• Medium repair is based on minor repair, and further involves the replacement of thrust plates and linings, as well as the inspection and repair of bearings. The cycle of medium repair is usually about 1-2 years.
• Overhaul is more comprehensive. In addition to all the contents of medium repair, it also includes the replacement or turning of the eccentric shaft and the movable jaw mandrel, the casting of babbitt alloy on the upper part of the connecting rod head, and the replacement or repair of various wear parts. The overhaul cycle of the jaw crusher is usually set at about 5 years.

Types of jaw crushers:

• Single-swing jaw crusher

In the single-swing jaw crusher, the jaw plate is suspended on the mandrel and can swing left and right. The rotation of the eccentric shaft drives the connecting rod to reciprocate up and down, and then drives the two thrust plates to reciprocate, so that the movable jaw can realize the functions of crushing and unloading. This crusher adopts a crank double-connecting rod mechanism. Although the crushing reaction force on the movable jaw is large, the force on the eccentric shaft and the connecting rod is relatively small. Therefore, it is often made into large and medium-sized machines in industry for crushing hard materials. However, the motion trajectory of each point on its movable jaw is in the shape of an arc, with a small arc at the upper end and a large arc at the lower end, resulting in a slightly lower crushing efficiency, and the crushing ratio is usually 3-6. Because its motion trajectory is relatively simple, it is called a simple swing jaw crusher.

• Simple swing jaw crusher

The simple swing jaw crusher has a compact and simple structure, and the transmission parts such as the eccentric shaft are subjected to less force. Due to the limited vertical displacement of the movable jaw, the material rarely suffers from over-crushing during processing, thereby reducing the wear of the movable jaw plate.

• Compound swing jaw crusher

The upper end of the movable jaw of the compound swing jaw crusher is directly suspended on the eccentric shaft, and as the connecting rod of the crank-connecting rod mechanism, it is directly driven by the eccentricity of the eccentric shaft. The lower end of the movable jaw is supported on the rear wall of the frame through the thrust plate. When the eccentric shaft rotates, the motion trajectory of each point on the movable jaw gradually changes from the circumference of the suspension point to an ellipse, and the lower it is, the more biased the ellipse is. When it reaches the connection point between the lower part of the movable jaw and the thrust plate, the trajectory becomes an arc line. Since the motion trajectory of each point on the movable jaw in this machine is relatively complex, it is called a complex swing jaw crusher.

Compared with the simple swing type, the compound swing jaw crusher has the advantages of light weight, fewer components, more compact structure and better filling degree in the crushing chamber. The forced ejection of finished product discharge function at the lower end of its movable jaw improves productivity, which is 20-30% higher than that of the simple swing jaw crusher of the same specification. In addition, the large-scale up and down rolling movement of the material block under the movable jaw helps the finished product to be discharged in a cubic shape, reducing the flaky components and thus improving the product quality.
Jaw crushers can be divided into two types according to the motion trajectory of the movable jaw: simple swing and complex swing. The working principles of these two crushers are similar, but the motion trajectory of the movable jaw is very different. In the simple swing jaw crusher, since the movable jaw is suspended on the support shaft, its reciprocating motion causes the trajectory of each point on the movable jaw to be in the shape of a circular arc, and the arc is the largest at the bottom (i.e., at the discharge port). However, there are some problems with this design. Since the ore in the upper part of the crushing chamber is mostly large ore blocks, it is difficult to achieve the necessary compression, so it needs to be crushed repeatedly to crush. This causes the crushing load to be mainly concentrated in the lower part of the crushing chamber, reducing the production capacity. In addition, its vertical stroke is small, and the grinding and discharging speed are relatively slow. But the advantage is that the jaw plate wears less and the product is less over-crushed.

In contrast, the design of the complex swing jaw crusher is more outstanding. Its movable jaw acts as the connecting rod of the crank connecting rod mechanism. Driven by the eccentric shaft, the motion trajectory of each point on the movable jaw is approximately elliptical, and the upper part is approximately circular. This design significantly improves the production capacity. Since the horizontal stroke is large in the upper part and small in the lower part, the horizontal stroke of the upper part is about 1.5 times that of the lower part, thereby meeting the compression required for the large ore in the upper part of the crushing chamber. At the same time, the vertical stroke of the entire movable jaw is greater than the horizontal stroke, especially at the discharge port, the vertical stroke is about 3 times the horizontal stroke, which further promotes discharge and improves production capacity. Practice has proved that under the same conditions, the production capacity of the compound swing jaw crusher is about 30% higher than that of the simple swing jaw crusher. However, it should be noted that the jaw plate wears quickly and the product is over-crushed.

Structure of jaw crusher

The main components of the jaw crusher include: fixed jaw plate, movable jaw plate, frame, upper and lower guard plates, adjustment seat and movable jaw tie rod. A deep understanding of these components is essential for the use and maintenance of the jaw crusher.

Crushing ratio of jaw crusher

The crushing ratio of jaw crushers is generally between 4 and 8, but in some large or specially designed jaw crushers, the crushing ratio may reach 10 or even higher.

The crushing ratio refers to the ratio of the raw material particle size to the particle size of the crushed product, which reflects the crushing ability of the crusher to the material. A larger crushing ratio means that larger-sized materials can be crushed into smaller-sized products, which is suitable for processing situations where the original material particle size is larger.

For example, for some large pieces of ore in mining, the jaw crusher can crush them into smaller particles through the relative movement of its movable jaw and fixed jaw to meet the requirements of subsequent processing technology. In some building materials industries, such as cement production, jaw crushers are also often used for the initial crushing of raw materials such as limestone, and the size of its crushing ratio directly affects the processing capacity and production efficiency of subsequent processing equipment.

However, the increase in crushing ratio is not unlimited. As the crushing ratio increases, the structural complexity and energy consumption of the crusher will increase accordingly, and the wear resistance and reliability requirements of the equipment will also be higher. Therefore, in actual applications, it is necessary to select the appropriate jaw crusher model and crushing ratio according to specific production requirements and material characteristics in order to achieve the best production effect and economic benefits.

Features of jaw crusher

• Low noise, less dust, and provide a comfortable working environment.
• The crushing ratio is large, the product particle size is uniform, and it meets different production needs.
• Simple structure, reliable operation, low operating cost, and easy maintenance.
• The lubrication system is safe and reliable, the parts are easy to replace, and daily maintenance is easy.
• The crushing chamber is designed to be deep and without dead zones, which enhances the feeding capacity and increases the output.
• The energy-saving effect is good, with a single machine saving 15% to 30%, and the system saving more than doubled, reducing energy costs.
• The discharge port has a wide adjustment range and can flexibly adapt to the needs of different users.
• The gasket-type discharge port adjustment device is easy to operate, has a large adjustment range, and improves the flexibility of the equipment.

Working principle of jaw crusher:

The jaw crusher crushes materials through the reciprocating motion of the movable jaw plate against the fixed jaw plate. When the movable jaw plate approaches the fixed jaw plate, the material is crushed by squeezing, splitting and impact; when leaving, the crushed material is discharged from the discharge port by gravity. In the process of crushing huge stones into small stones, the jaw crusher is often used as the first “main” crusher. It has a long history and a solid structure. It is an important equipment in the fields of mining, construction and road construction.

• Hydraulic jaw crusher
• Non-grinding jaw crusher
• Impact jaw crusher
• Direct drive jaw crusher
• Dual-chamber jaw crusher
• Wedge-roller jaw crusher
• European version jaw crusher
• Powerful jaw crusher
• Modular jaw crusher

Detailed explanation of main components:

• Frame: As a rigid frame with four walls opened up and down, it not only supports the eccentric shaft, but also bears the reaction force of the crushed material. Therefore, the frame must have sufficient strength and rigidity. It is usually cast as a whole with cast steel, and small machines may use high-quality cast iron instead. The frame of a large machine needs to be cast in sections and firmly connected into a whole by bolts. The casting process is relatively complicated. In addition, the frame of a homemade small jaw crusher can also be welded with thick steel plates, but it should be noted that its rigidity may be slightly inferior.
• Jaw plate and side guard plate: Both the fixed jaw and the movable jaw are composed of a jaw bed and a jaw plate, of which the jaw plate is the working part and is fixed to the jaw bed by bolts and wedges. The jaw bed of the fixed jaw is usually the front wall of the frame, while the jaw bed of the movable jaw is suspended on the periphery. It must have sufficient strength and rigidity to withstand the crushing reaction force, so it is mostly made of cast steel or cast iron.
• Transmission parts: The eccentric shaft, as the main shaft of the crusher, bears huge bending and torsion forces and is usually made of high-carbon steel. Its eccentric part needs to be finely processed, heat treated, and the bearing bushing cast by babbitt alloy. A pulley is installed at one end of the eccentric shaft and a flywheel is installed at the other end to store and release energy to make the machine work more evenly.
• Adjustment device: The adjustment device is used to adjust the size of the discharge port. Common types include wedge type, pad type, and hydraulic type. Among them, the wedge type adjustment device consists of two front and rear wedges, and the size of the discharge port is adjusted by moving the rear wedge up and down through a screw. The discharge port adjustment of a small jaw crusher is usually achieved by increasing or decreasing the number of gaskets between the rear thrust plate support and the frame.
• Flywheel: The function of the flywheel is to store the energy of the movable jaw during the idle stroke and release it during industrial formation, making the machine work more evenly. The pulley also plays a similar role. The flywheel is often made of cast iron or cast steel, and attention should be paid to the static balance during manufacturing and installation.
• Lubrication device: The eccentric shaft bearing is usually lubricated by centralized circulation, while the support surface of the mandrel and thrust plate is generally lubricated by grease through a manual oil gun. Since the swing angle of the movable jaw is very small, the lubrication between the mandrel and the bearing may be difficult, so axial oil grooves and annular oil grooves are often opened at the bottom of the bearing, and dry butter is forced to be injected through an oil pump for lubrication.

Instructions for use:

• Preparation: Before using the jaw crusher, it is necessary to ensure that all preparations have been properly completed, including checking the equipment status, preparing lubricating materials, adjusting the size of the discharge port, etc. These preparations are essential to ensure the normal operation of the equipment and extend its service life.
• Before starting the jaw crusher, you should first carefully check the lubrication of the bearing and ensure that the toggle plate connection inside the bearing is fully greased to ensure the smooth operation of the equipment.
• Next, check whether all fasteners are tightened in place to prevent equipment failure due to looseness.
• At the same time, confirm whether the protective device is in good condition to ensure that it can effectively prevent unsafe phenomena during operation. Once any safety hazards are found, measures should be taken immediately to eliminate them.
• Finally, check before starting: Is there any ore or other debris in the crushing chamber? If so, it must be removed immediately to ensure the normal start-up and safe operation of the equipment.

1. The jaw crusher can only be started after confirming that the machine and transmission parts are in good condition.
2. The crusher should be started under no-load condition.
3. After starting, if any abnormal situation is found, it should be stopped immediately, and the cause should be found out and the fault should be eliminated before restarting.

Jaw crusher Maintenance and use guide

1. Feeding can only be started after the jaw crusher is running normally and smoothly.
2. When feeding, it should be ensured that the material to be crushed can enter the crushing chamber evenly, and be careful to avoid adding materials from the side to prevent sudden changes in load or sharp increases in unilateral load.
3. When the crusher is working normally, the temperature rise of the bearing should not exceed 35℃, and the maximum temperature should not exceed 70℃. Once it exceeds this range, it should be stopped immediately, and the cause should be found out and handled accordingly.
4. Before stopping, the feeding should be stopped first. Make sure that the material in the crushing chamber has been completely emptied before turning off the motor and stopping the crusher.

Lubrication

1. Be sure to provide sufficient lubrication to the friction surface regularly to ensure the continuous and stable operation of the machine and extend its service life.

2. When selecting grease, factors such as the location and temperature should be considered. It is usually recommended to use calcium-based, sodium-based or calcium-sodium-based grease.

3. The volume of grease in the bearing seat should be controlled between 50-70% and replaced every three months. When replacing new oil, the dirt in the bearing and bearing seat must be thoroughly cleaned with clean gasoline or kerosene.

4. Before starting the machine, add an appropriate amount of grease to the contact between the toggle plate and the toggle plate pad.

No-load test run

(1) Ensure that the bearing temperature rise of the jaw crusher does not exceed 30°C after 2 hours of continuous operation.

(2) Check whether all fasteners are firm and have no signs of looseness.
(3) Observe whether the flywheel and the groove wheel run smoothly without abnormal vibration.
(4) Check all friction parts to ensure that there is no scratch, chipping or grinding, and no abnormal noise.
(5) The adjustment device of the discharge port should be able to smoothly adjust the discharge port and ensure that its adjustment range meets the requirements.

Load test

(1) When the jaw crusher is tested with load, it should be ensured that there is no periodic or significant impact or knocking sound during its operation.
(2) During the test, the maximum particle size of the feed must strictly comply with the design specifications.
(3) After 8 hours of continuous operation, the temperature rise of the bearing should not exceed 30℃.

Crusher preparation

(1) Be sure to check the lubrication condition of the bearing to ensure that it is in good condition, and confirm whether the joints of the thrust plate are fully greased.
(2) Carefully check all fasteners to ensure that they are tightened in place.
(3) The condition of the drive belt is also crucial and should be carefully checked to see if it is intact. If any damage is found, it should be replaced in time; if there is oil on the transmission belt or pulley, it should be wiped clean with a rag.
(4) Carefully check the protective device to ensure that it is intact and eliminate any unsafe factors.
(5) There should be no ore or debris in the crushing chamber. Therefore, it must be thoroughly cleaned before starting the machine to ensure that the crusher can start with an empty cavity.
(6) Confirm that the top bolts have been returned, the gasket group has been tightened, and the T-bolts have been tightened. In addition, the crusher operator must undergo professional training, master the skills of “three understandings and four skills”, and obtain a certificate of qualification before he can take up his post.
In actual work, the crusher driver should maintain close communication with the working face scraper conveyor driver and the transport lane belt conveyor driver, unify signal communication, and ensure that the equipment is started and stopped in sequence. If large pieces of coal or gangue are found to be accumulated and overflowed at the feed port of the crusher, the working face scraper conveyor should be stopped immediately. During the operation of the equipment, if gangue or other metal objects are found to enter the crusher, the equipment must be stopped immediately to ensure safe and efficient production.

Key points and precautions for operation

(1) Make sure that the crusher is running smoothly before starting to feed.
(2) When feeding, ensure that the material is evenly added to the crusher cavity to avoid lateral or excessive stacking to prevent unilateral overload or total overload.
(3) During operation, pay close attention to the bearing temperature rise, which should not exceed 30°C, and the maximum temperature should not exceed 70°C. If it exceeds this range, stop the machine immediately for inspection and troubleshooting.
(4) Before stopping, stop feeding first, ensure that the material in the crushing cavity is completely discharged, and then turn off the power.
(5) If the machine stops due to blockage of material in the crushing cavity, turn off the power immediately and clean it up before restarting.
(6) If one end of the jaw plate is worn, it can be reversed and continued to be used.
(7) Regularly check and loosen the locking bushing appropriately to prevent machine damage.

Troubleshooting

During the operation of the jaw crusher, the transmission system often fails due to the large torque and vibration. These faults include the gap between the pulley and the shaft head causing wear of the shaft head and the hub, and the eccentric shaft being subjected to force causing wear of the bearing seat.

Traditional repair methods usually use wheel hub expansion, repair welding or brush plating followed by machining repair, but these methods all have disadvantages. The thermal stress generated by the high temperature of the repair welding may not be completely eliminated, causing material damage and even bending or breaking of the components; while the brush plating is limited by the coating thickness and is easy to peel off. More importantly, these metal repair methods cannot change the “hard-to-hard” matching relationship, so under the combined action of various forces, it will still cause wear again.

However, in contemporary developed countries such as Europe and the United States, polymer composite material repair methods are often used to address the above problems. This technology has comprehensive properties such as super strong adhesion and excellent compressive strength, and can achieve on-site repair without disassembly and machining. Compared with traditional metal repair methods, polymer material repair is not affected by repair welding thermal stress, and the repair thickness is not limited. At the same time, its unique yielding property can absorb the impact and vibration of the equipment, effectively avoid re-wear, and significantly extend the service life of equipment components. This not only saves a lot of downtime for the enterprise, but also creates huge economic value.

In addition, when the frame of the jaw crusher is found to be seriously jumping during operation, it should be stopped and checked immediately. Possible reasons include loose or broken belts, damaged eccentric shaft bearings, etc. Take corresponding maintenance measures according to the specific situation to ensure the normal operation of the crusher.

• Check whether the anchor bolts are loose or broken.
• Confirm whether the position of the flywheel is deviated.
•  Check whether the main engine foundation is stable and check whether there are vibration isolation measures.

For the above problems, the following solutions can be taken:

• If the anchor bolts are loose, use a wrench to tighten them; if the anchor bolts are broken, replace them with new bolts.
• For the problem of flywheel position deviation, the flywheel cover plate should be removed first, then the flywheel sleeve bolts should be loosened, and the flywheel position should be adjusted appropriately, and then the flywheel tension sleeve bolts should be tightened.
• If the main machine foundation is unstable and causes the jaw crusher to shake, the stability of the foundation should be strengthened, such as adding sleepers or rubber strips between the machine and the ground to reduce vibration.