PXZ1422 hydraulic gyratory crusher is coarse crushing equipment in the rock discharging system of Sijiaying Iron Mine, which processes 30000 tons of rock every day. Its operation directly affects the completion of the iron ore production plan. The eccentric sleeve of the heart part of the equipment bears a great impact load when it breaks rocks, also it is a key crusher wear part for the gyratory crusher. After long-term bearing excessive impact load, the Babbitt alloy of the original eccentric sleeve falls off seriously, and the wear debris blocks the oil circuit so that there is a lot of Babbitt alloy debris in the oil return pipeline, and the lubricating oil temperature rises sharply, which accelerates the damage of the eccentric sleeve, The service cycle of the eccentric sleeve is very short (about 2 months), which directly affects the completion of production tasks. Using modified nylon new material instead of Babbitt alloy to pour eccentric sleeve, applied in pxz1422 gyratory crusher, can be more suitable for non-impact load in crushing, reduce cost, increase service life by 4 times, and create good economic and social benefits.
The eccentric sleeve used in the pxz1422 hydraulic rotary crusher was originally made by pouring Babbitt alloy inside and outside the steel matrix. When the shaft sleeve is subjected to the impact load, it is easy to form cracks (cracks extend when it is cracked and stressed) and spalling. When it is used under excessive impact load, its disadvantages are more prominent.
The crushing process of the 1422 rotary crusher is driven by the motor through the belt pulley and bevel gear. When the eccentric sleeve rotates, it drives the crushing cone to rotate around the center of the crusher, so that the surface of the crushing cone sometimes approaches and sometimes leaves the surface of the fixed cone. The material fed into the crushing cavity is continuously crushed by extrusion and bending. From the analysis of the operation process, the axial force on the inner wall of the eccentric sleeve is very uneven, only more than 1 / 3 of the parts are under great force, impact, and extrusion force, and the radial force is even more uneven. When the eccentric sleeve is squeezed and the impact force is too large,
Babbitt alloy has low compressive strength, easy to wrinkle, and even the alloy is extruded from the bearing. When it is subjected to impact load, its impact toughness is low, and it is easy to form cracks and spalling. The service life of the eccentric sleeve is only about two months. As soon as this problem occurs, the equipment will be shut down for maintenance. The eccentric sleeve is a spare part in the heart of the crusher. It needs to be disassembled and unloaded, and the manpower and material resources are greatly lost. Therefore, if the transformation of the eccentric sleeve is successful, the workshop will get rich practical benefits.
Comparison of material selection
In order to solve the above problems, we try our best to find more suitable materials in the market and network to solve this problem. Through market research, we decided to use the domestic new high impact and wear-resistant material polymer alloy modified cast nylon instead of Babbitt alloy as eccentric sleeve wear-resistant alloy.
In the selection of this new material, we first understand the performance of the material, demonstration, and feasibility analysis.
PV value and friction coefficient of two kinds of wear-resistant materials were analyzed
|Material||Allowable stress||Allowable speed (m/s)||PV value (Mpa m/s)||Friction coefficient HR (unlubricated)||Friction coefficient HP (lubrication)|
We can see that the PVA (standard value) of the modified nylon is slightly larger than that of the bearing alloy, that is to say, the PV value of the product of the load per unit area p and the surface velocity V can be used to determine the limit of use. Under certain conditions, the PV value of the material is constant, and the change of the sliding speed of the workpiece is far more sensitive to the PV value than the pressure P. If the PV value is too large, it is easy to cause the temperature rise of the shaft sleeve. When the speed is low and the load is heavy, the advantages of using nylon shaft sleeve are prominent. The PVA ratio of modified nylon is 12MPa M / s, so the PVA value of modified nylon is suitable for the use requirements of the pxz1422 hydraulic gyratory crusher.
Performance comparison of two kinds of wear-resistant materials
|Material||Tensile strength δ(MPA)||Yield strength δ(MPA)||Elongation δ （%）||Compressive yield strength δ(MPA)||Brinell hardness HB|
As the conventional mechanical properties of compressive strength, elongation, and impact strength, the modified cast nylon is better than Babbitt alloy. The wear-resistant layer of eccentric sleeve needs better plastic wear-resistant materials. The failure mode of Babbitt alloy under compression is comminuted, but the modified cast nylon is not damaged at all or just to the edge of damage. The impact value of modified cast nylon is much higher than that of Babbitt alloy. Under the condition of impact load, the bearing capacity of modified nylon is better than that of Babbitt alloy. The modified cast nylon has high initial modulus and relative creep, which shows good loading performance. Modified nylon is a kind of material with high fatigue resistance in practical use. When there is an impact between the shaft and eccentric sleeve, Babbitt alloy will break and peel off, but the cast nylon has better elasticity than metal material, so nylon is not easy to be damaged.
Friction comparison between modified nylon and Babbitt alloy
|Material||Test time (min)||Friction coefficient (u)||Wear width (mm)|
The comparison of the wear mark width shows that the wear-resistant layer of cast nylon instead of Babbitt alloy as an eccentric sleeve is feasible.
Since September 2011, Our foundry has changed the eccentric sleeve of the 1422 gyratory crusher into a modified nylon eccentric sleeve. The method of the copper tube through water cooling is to weave a one-inch copper tube into a screen-type and place it in the oil tank of the lubrication station. The inlet end is connected with a water pipe, and the outlet end is connected with a water pump to pump water into the cooling pool (the cooling pool of the original thin oil station). After this method is installed, the test run is carried out, At this time, the temperature has dropped to about 32 degrees. After idling for half an hour, the material is cut and the oil temperature is observed. After running with material for one hour, the oil temperature rises to 40 degrees and does not rise again. After 3 months of operation, no abnormality has been found so far, and the output is constantly improving. The service life of the eccentric sleeve is at least 3 times longer than that of Babbitt alloy.
The practice has proved that it is feasible to use modified cast nylon as a new material to replace Babbitt alloy casting eccentric sleeve in pxz1422 gyratory crusher. Because modified cast nylon has concession under extrusion pressure, it also has high impact strength and good flexibility, especially when it bears uneven impact load, It can be seen that the application of new technology and new materials in our construction engineering field can not only improve work efficiency, save the cost of raw materials, but also create high economic and social benefits.