What is a blow bars? What are the functions?

Our last article mainly introduced the parts of the impact crusher, including the blow bars. At that time, there were comments and comments under the article. Is there a more detailed introduction about the blow bars? We saw that message, so we wrote this article to introduce the blow bars. I hope it can help everyone.

A photo of a blow bars

What is a blow bars?

A photo of a blow bars

The blow bars is an important part of the crusher. The blow bar is made of high-chromium alloy material and the latest manufacturing technology. It has a special structural design. The finished product is cubic, without tension and cracks, and the particle shape is quite good. It is a very reliable and wear-resistant casting. When the plate hammer is worn to a certain extent, it should be adjusted or replaced in time to avoid damage to other components.

The importance of the blow bars?

A photo of a blow bars

I believe that users of all crushers know the importance of the blow bars. When the blow bars is made of high wear-resistant materials, the entire rotor will have good static and dynamic balance and impact resistance. When the machine is working, it is not easy to fail.

In the initial stage of the impact crusher, the blow bars rotates with the rotor and the blow bars itself also makes a 360-degree autobiography. With the increase of the rotor speed, the centrifugal force of the blow bars also increases continuously. When a certain value is reached, the blow bars is fully opened and enters the working state. When the material falls from the feeding port to the working range of the blow bars, the blow bars starts to break. The crushed small pieces of material enter the second crushing cavity for secondary crushing, and the crushed materials fall to the screening machine for screening.

And because the impact crusher is a crushing machine that uses impact to crush materials, when the material enters the action area of the plate hammer, it is impacted at high speed by the plate hammer, so that the crushed objects are continuously thrown to the impact device installed above the rotor. Then, it bounces back from the counterattack lining plate to the action area of the blow bars to be counterattacked again. The material enters the first, second and third counterattack chambers from large to small for repeated crushing. Until the material is crushed to the required particle size, it will be discharged from the machine again.

Therefore, the whole working process of the impact crusher is mainly to use the plate hammer to achieve crushing.

What is the method of fixing the blow bars?

A photo of a blow bars

Wedge fixing

Wedges are used to fix the blow bars on the rotor. Under the action of centrifugal force during operation, this fixing method can ensure that the faster the rotor speed is, the more stable the blow bars are fixed, the work is reliable, and the replacement is convenient. This is a better fixing method for the blow bars at present, and this is the current mainstream fixing method. The wedge is made of cast steel, which has certain toughness and plasticity, high strength and hardness, and good machinability.


The blow bars is inserted axially into the corresponding slot of the rotor from the side of the rotor. To prevent axial movement, the two ends are positioned with pressure plates. Since the fastening bolts are removed, the reliability of the plate hammer operation is improved.

The centrifugal inertia force generated by the rotation of the plate hammer and the reaction force during impact and crushing are used to fasten the self-locking, and the rotor is easily worn in a replaceable structural form, so the assembly and disassembly are simple and easy to manufacture. However, the bolt is exposed on the striking surface and is easily damaged, and the bolt is subjected to a large shearing force, which will cause a serious accident once it is sheared.

Platen fixation

There is also a blow bars inserted into the groove of the rotor from the side, and the two ends are pressed by pressing plates, but this fixing method makes the blow bars not firm enough, and the blow bars is easy to loosen during work. Alloy materials such as manganese steel are not easy to process.

Is the blow bars only fixed in two directions?

A photo of a blow bars

Does the impact crusher only use blow bars in 2 directions, and 2 are installed lower? Indeed, this is the common design of some impact crushers on the market. The higher blow bars hits large materials, and the lower Combat small materials.

When the crusher is crushing materials with high hardness, the problem of high replacement frequency of blow bars has always troubled many personnel in the sand and gravel industry. The improvement also has certain requirements on the material of the blow bars.

What is the solution to the problem of the blow bars?

A photo of a blow bars

The size of the discharge particle size is different

After using for a period of time, if the product size of the crusher is too large, you can adjust the gap between the front and rear counterattack frames, or replace the severely worn liner. The position of the counterattack frame can also be adjusted to maintain a relative gap between the two sides of the frame lining plate to ensure the discharge granularity.

Severe impact sound inside the crusher cavity

If this happens, turn off the power immediately, stop working, clean the crushing chamber, and check whether there is any foreign matter in the crushing chamber. If the condition of the crushing chamber is normal, check the fastening of the lining plate and the gap between the blow bar and the lining plate, and whether the wear-resistant lining plate falls off.

Bearing temperature is too high

When this kind of problem occurs in production, it is necessary to first check whether the lubricating oil has been reduced to less than 50% of the bearing volume, and also need to clean the bearing regularly, replace the lubricating oil, and replace it in time when the bearing is seriously worn.

How to check the tightness of the blow bars?

A photo of a blow bars

The machine wear-resisting parts plate hammer is embedded and fastened, which means inserting the plate hammer into the groove of the rotor from the side. Both ends need to be positioned with pressure plates, which can prevent axial movement. Because the fastening bolts are removed, the plate hammer is improved. reliability of work. The centrifugal force generated when the hammer head rotates and the reaction force when it is impacted and broken are used to fasten and self-lock, and the parts that are vulnerable to wear are made into replaceable structural forms, so the assembly and disassembly are simple and the production is simple.

The metal utilization rate of this method is low, but the improved embedded fastening method adopts a slotted plate hammer with longitudinal grooves on the hammer surface, which greatly reduces the metal consumption rate, and the working surface can also be replaced four times. Extend the service life of the blow bars.

In addition, there are machines that use the wear-resistant parts hammer wedge fastening method. This method is mainly to insert the wedge into the corresponding slot between the blow bars and the rotor to tighten it. The wedge block fastening method is more reliable and more convenient for loading and unloading. Since the relative movement between the plate hammer and the rotor is eliminated, the wear of the rotor is reduced. It can greatly reduce the wear degree of the plate hammer and the rotor, but the utilization rate of the metal may be low.

In addition, machine wear-resistant parts, plate hammer bolt fastening methods are also more common. In this method, the blow bars is fastened to the blow bars seat of the rotor by means of bolts. The plate hammer seat has a tenon shape, which can use the tenon to withstand the impact force of the plate hammer during operation, avoid bolt shearing, and improve the reliability of bolt connection. The tightening of the bolts must be carried out in 2 times, the first time being the initial tightening.

The initial tightening torque should be 60% to 80% of the standard axial force of the bolt, and the initial torque value should not be less than 30% of the final torque value. The second tightening is the final tightening, and the torsion shear type high-strength bolts should be screwed off during the final tightening. In order to make all bolts in the bolt group evenly stressed, the initial tightening and final tightening should be carried out in a certain order.

How to extend the service life of the blow bars?

A photo of a blow bars

Before using the number of axes to control the machine, it is necessary to check the machine in detail to see if its parts are loose, check whether the belt is tight, and also check whether there are other materials or waste remaining in the crushing cavity of the crusher.

Since it is carried out in the open air, it is necessary to avoid the corrosion caused by rain, snow and air pollution to the machine as much as possible, and take effective protective measures according to the corresponding weather conditions.

The hammer pin of the machine is very easy to wear. When it is worn, the productivity will drop, and it will directly affect the service life of the machine. Therefore, the hammer and the pin should be replaced in time.

During the production of machines, lubricants are key to ensuring the proper functioning and production of individual components. Add oil from the bearing housing to ensure good lubrication between parts. The bearings of the machine should be cleaned every 2 months to ensure smooth operation of the equipment.

There is also the casting material of the blow bars, which is also a way to ensure the service life of the blow bars. To choose a wear-resistant material, you cannot choose an alloy material casually.

The importance of blow bars material?

A photo of a blow bars

High chromium is the material of the blow bars. Such a blow bars has a low cost and high hardness, but it generally has the shortcomings of insufficient toughness and easy breakage. Therefore, alloys were added. The successful promotion of this technology made up for the disadvantage of poor toughness of high-chromium blow bars.

Inlaid cemented carbide not only improved the toughness of the blow bars, but also the hard alloy embedded in them undoubtedly replaced the high-chromium blow bars. The hardness of other alloys has also been improved, and the service life is twice as long as that of ordinary high-chromium hammer plates. This reduces the long downtime caused by frequent replacement of blow bars and the waste pollution caused by frequent replacement of blow bars, and improves the performance of blow bars.

A photo of a blow bars

The above is the introduction of the blow bars in this article, I hope it can help you. At the same time, if you have any questions or doubts that are not clear, you can leave a comment below the article. We will check your comments one by one and reply to your comments. At the same time, there are other excellent articles on our website, you are welcome to read them.

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