Cone crusher is a crushing machine suitable for raw materials in metallurgy, construction, road construction, chemical and silicate industries. According to different crushing principles and product particle size, it is divided into many models. Cone crushers are widely used in mining, smelting, building materials, highways, railways, water conservancy and chemical industries and many other sectors. The cone crusher has large crushing ratio, high efficiency, low energy consumption, and uniform product particle size. It is suitable for medium and fine crushing of various ores and rocks.
The models are mainly divided into spring cone crusher, hydraulic cone crusher and high pressure hydraulic spring cone crusher. Their working principle and structure are introduced respectively. Here, our company will introduce the development history, working principle, composition, influencing factors, technical advantages, operation matters, common faults, inspection and maintenance of cone crusher in detail for you.
Cone Crusher Features and Structure
With the continuous development of mining technology, cone crushers are also divided into several categories, including spring cone crushers, rolling mortar cone crushers, hydraulic cone crushers and compound cone crushers according to their types; PY cone crusher, Simmons cone crusher, compound cone crusher, standard hydraulic cone crusher, single-cylinder hydraulic cone crusher and multi-cylinder hydraulic cone crusher and many other models. The hydraulic crusher is developed on the basis of digesting and absorbing various types of cone crushers with the international advanced level in the 1980s. It is clearly different in design from the structure of the traditional cone crusher and concentrates the main advantages of the various types of cone crushers known so far. It is suitable for fine crushing and ultra-fine crushing of hard rocks, ores, slag, refractory materials, etc.
The structure of cone crusher mainly includes frame, horizontal shaft, moving cone, balance wheel, eccentric sleeve, upper crushing wall (fixed cone), lower crushing wall (moving cone), hydraulic coupling, lubrication system, hydraulic system.
Cone Crusher Performance Improvement
The improvement of the working performance of the cone crusher has become a new goal of the mining machinery processing industry. Our company's crushing equipment technical experts have made some basic research results on cone crushers. The researchers will start from different perspectives of the crusher's working mechanism and performance. Conduct detailed research on laminated cavity model, cavity design planning, particle size distribution of crushed products, and cavity multi-objective optimization design:
- 1. The researchers analyzed the current situation of the research and development of the cone crusher cavity at home and abroad, and deeply understood the importance and urgency of the optimal design of the cone crusher cavity structure and the improvement of the working performance of the cone crusher.
- 2. The motion characteristics of the crushed materials in the crushing cavity of the cone crusher are deeply studied, and three different forms of particle flow states are discussed, which are sliding, free fall, and coexistence of sliding and free fall. The influence of the movement state of the bulk material in the crushing cavity on the working performance of the crusher is analyzed, and the movement trajectory of the bulk material in the crushing cavity of the cone crusher is simulated and analyzed, and the stratified crushing characteristics of the cone crusher are obtained. Layer research and design accumulate theoretical foundations.
- 3. By analyzing the influence of the crusher cavity type on the particle size distribution of rock products, a calculation method of the particle size distribution of crushed products based on the overall balance model is established, and a new calculation method of the production capacity of the cone crusher is deduced.
- 4. Committed to the development of high-efficiency laminated cone crusher, on the basis of the research on the working mechanism and performance of the cone crusher, a multi-objective optimization design scheme for the production capacity of the cone crusher, the particle size of the crushed products and the cavity structure has been established. Combined with the multi-objective optimization problem of the cavity structure of the spring cone crusher, the solution method of the multi-objective optimization model of the crusher cavity is deeply studied.
The new hydraulic cone crusher is an advanced level cone crusher developed by absorbing the world's advanced crushing technology. It is widely used in metallurgy, construction, hydropower, transportation, chemical industry, and building materials industries. It is suitable for crushing hard, medium hardness and above. of various ores and rocks. The new hydraulic cone crusher is a high performance cone crusher.
Working principle of cone crusher
During the working process of the cone crusher, the motor drives the eccentric sleeve to rotate through the transmission device, and the moving cone rotates and swings under the force of the eccentric sleeve. The static cone is broken by multiple squeezing and impact. When the moving cone leaves this section, the materials that have been crushed to the required particle size fall down under the action of their own gravity and are discharged from the bottom of the cone.
The crushing process of the cone crusher is completed between the fixed fixed cone and the rotating moving cone. When the cone crusher is working, the horizontal shaft of the crusher is driven by the motor through the V-belt and the pulley, and the horizontal shaft drives the eccentric sleeve to rotate through the large and small gears. , so that the surface of the crushing wall is sometimes close to the surface of the fixed cone, and sometimes away from the surface of the fixed cone, so that the stone is continuously crushed, broken and impacted in the crushing cavity. The crushed material is discharged from the discharge port at the lower part of the crusher under the action of its own weight. The upper cavity of the cone crusher is supported on the spherical bearing bush at the upper end of the fixed main shaft, and the lower cavity is sleeved on the outside of the eccentric sleeve, and its movement is directly driven by the eccentric sleeve. When the eccentric bushing rotates around the main shaft, the moving cone not only rotates around the center line of the machine with the eccentric bushing, but also rotates around its own axis. The moving cone performs a space swing movement around its spherical support center. The axis of the moving cone and the center line of the main shaft intersect at a fixed point, that is, the center point of the spherical surface, and the included angle is the precession angle. When the cone crusher is running, the axis of the moving cone moves on a conical surface relative to the center line of the machine, and the top of the cone is the spherical support center, which always remains stationary during the movement of the moving cone. Therefore, the motion of the moving cone can be regarded as the rotation of a rigid body around a fixed point, that is, the motion of the moving cone is composed of two kinds of rotational motions: precession motion or implicated motion (the moving cone rotates around the center line of the machine) and rotational motion or relative motion. Movement (rotating movement of the moving cone around its own axis).
In the case of no-load operation of the cone crusher, the rotation of the moving cone is determined by the friction torque given by the spherical bearing to the moving cone and the frictional force given by the eccentric bushing to the moving cone. direction turn. Under normal circumstances, the moving cone rotates along the rotation direction of the eccentric sleeve, and the rotation speed is determined by the difference between the two torques. And this type of cone crusher is between the spherical bearing and the lower bushing of the moving cone to control the rotation of the moving cone. In the case of loaded operation, the friction torque of the stone on the cone surface of the moving cone far exceeds the friction torque generated by the eccentric bushing on the moving cone.
The composition of hydraulic cone crusher
The machine has a hydraulic system to adjust the size of the crusher's discharge port, and the hydraulic system can effectively ensure the safe operation of the equipment. When there is a foreign body in the crushing chamber, the hydraulic system can make the moving cone move down automatically. When the foreign body is discharged, the system makes the moving cone automatically reset.
The crushing cavity refers to the geometric space formed between the moving cone and the fixed cone. The shape of the crushing cavity has a great influence on the performance of the whole machine. Cavity type of crusher is the main technical index of crushing. The machine is designed with four cavity types from coarse crushing to fine crushing, and it has six possible combinations, which means that it can best suit the special requirements of users;
The labyrinth sealing device replaces the water seal used in the past, so that dust and impurities cannot enter the body, thus ensuring the cleanliness of the lubricating oil, prolonging the service life of the sliding bearing and the thrust ball bearing, and making the machine run reliably;
Cone Crusher Structural Features
- 1. Higher production capacity, better quality.
- 2. Due to the safety device, the downtime is greatly reduced.
- 3. The body is a cast steel structure, and there are reinforcing ribs in the heavy-duty parts.
- 4. With adjuster, it can quickly adjust the size of crushing and discharging granularity.
- 5. Provide spring protection device.
- 6. With a complete lubrication system, it will automatically shut down when the temperature is too high or the flow rate is too slow.
- 7. The internal structure has good sealing performance, which can effectively protect the equipment from dust and other small particles.
- 8. Long service life and strong applicability.
The structure of cone crusher
Cone crusher is mainly composed of frame, drive shaft, eccentric sleeve, spherical bearing, crushing cone, adjustment device, adjustment sleeve, spring and discharge port.
- (1) Crusher main frame assembly: The crusher main frame is composed of an upper frame body and a lower frame body, which are connected by a hydraulic cylinder, with wear-resistant lining plates and protective covers inside: the upper frame body is a welded part, and its upper mouth is welded There is wear-resistant copper plate, and the lower frame is an integral steel casting.
- (2) Main shaft assembly: The main shaft and the center wheel of the lower frame of the main frame are assembled with a small interference fit on the tapered surface, and the main shaft is provided with axial and radial lubricating oil holes.
- (3) Eccentric bushing assembly: The high-lead bronze bushing fixed by screws is installed inside the eccentric bushing; the lower part is equipped with a large bevel gear and a thrust bearing through bolts, of which the upper thrust bearing is forged steel, and the lower one is made of forged steel. The thrust bearing is a high-lead bronze part; in addition, the eccentric shaft sleeve is also equipped with a bolt-fixed counterweight assembly, which is filled with lead and installed with a wear-resistant protective liner.
- (4) Moving cone assembly: the upper part of the moving cone is bolted and fixed with the feeding plate assembly, and the lower part is equipped with a spherical bearing bush, which can be matched with the spherical steel bush installed in the sleeve; high manganese steel is installed on the outside of the moving cone The manufactured moving cone lining plate, the space between the moving cone and the lining plate is filled with epoxy resin; the upper and lower high lead bronze bushings are installed inside the moving cone.
- (5) Fixed cone assembly: the upper part of the fixed cone is installed with a feeding hopper; the inside is installed with a high-manganese steel wear-resistant lining plate fixed with large-diameter bolts, and epoxy resin is also filled between the fixed cone and the lining plate. ;The outside of the fixed cone is a trapezoidal thread matched with the adjusting ring.
- (6) Adjustment ring: The adjustment ring is a component, which consists of an adjustment ring, a clamping ring, a cam follower and a hydraulic motor; there are trapezoidal threads in the clamping ring, which can be connected with the fixed cone; the upper part of the adjustment ring is equipped with a main frame Retaining pin and guide rod to prevent adjustment ring from rotating within main frame.
- (7) Lubrication device of the unit: it consists of lubricating oil tank, motor oil pump, filter device, cooling device and control device. For example, the cone crusher of Yantai Xinhai Mining Machine adopts two sealing methods of dry oil or water, so that dust and impurities cannot enter the machine body and ensure the cleanliness of the lubricating oil.
- (8) Horizontal drive shaft assembly: a high-power main drive motor, through the V-belt drive device, the small bevel gear on the horizontal shaft drives the large bevel gear and the eccentric bushing: the box body of the horizontal shaft is an integral cast iron, with Bolt to main frame.
- (9) Hydraulic clamp frame and over-iron release device: The upper components of the adjustment ring are connected to the main frame of the crusher through a double-acting hydraulic cylinder.
- (10) Adjustment mechanism assembly: use the hydraulic motor to drive the pinion, and the pinion drives the large ring gear on the adjustment cap, thereby driving the fixed cone to rotate to achieve the purpose of adjusting the gap between the fixed cone lining plate and the moving cone lining plate.
- (11) Hydraulic control station: The control station includes an oil tank with an oil meter, a motor oil pump, a filter device, an energy storage device, a control device, a pressure switch, a safety protection device, etc.; a terminal box and button control are also installed beside the crusher cabinet.
- 1. The feeding particle size ratio is appropriate
- 2. Automatic control device;
- 3. Cone crusher discharge to pass
- 4. Correctly select the crushing cavity for the crushed materials
- 5. The feeding distribution is uniform in the 360° range of the crushing cavity
- 6. The specifications of the conveyor belt are adapted to the maximum output capacity of the crusher;
- 7. Proper selection of sieve specifications for pre-screening and closed-circuit screening.
Easy to replace
In the past, the crusher was very slow to replace the crushing wall, and the new structure of the cone crusher replaced the crushing wall very quickly. Because there are clips on the upper crushing wall, the crushing wall is fixed by jacking up with bolts. The lower crushing wall is fixed with hydraulic nuts. The back of the upper and lower crushing walls does not need any filling material, so the replacement is fast, reducing the labor intensity of workers;
Adjust the opening
The machine uses a high-pressure displacement sensor, and the adjustment of the position of the discharge port is carried out in the operating room. As long as you press a button, there will be a display on the console, and you can see the size of the discharge port that needs to be adjusted, which is very convenient and accurate.
When the machine is working, the motor drives the large bevel gear at the bottom of the eccentric sleeve through the hydraulic coupling and the small bevel gear, so that the eccentric sleeve rotates, causing the cone to swing and crush the material. The main shaft of the crusher is not moving, but only supports the spherical tile to bear the crushing force. Because the main shaft of the crusher does not move and the eccentric sleeve transmits the crushing force, the structure can withstand a large crushing force, and is very suitable for fine crushing and ultra-fine crushing, because the crushing force of ultra-fine crushing is very large. It is estimated that the product particle size (for ultrafine crushed liner) can reach 50^80% (depending on the nature of the material) when the circuit is opened. The crusher is suitable for the third stage crushing or the fourth stage crushing of metal mine concentrators; it is suitable for building materials or non-metallic mines and civil engineering. Especially in areas where the supply of natural sand required for civil engineering is insufficient.
Types of cone crushers
Hydraulic Cone Crusher
On the basis of summarizing the advantages of various crushing cavity types, the hydraulic cone crusher designed by engineers has a variety of crushing cavity types to choose from under the condition of theoretical analysis and practical inspection. Choosing the appropriate crushing cavity type and eccentric distance can meet the production requirements of customers to the greatest extent and achieve high output. In the case of full feeding, lamination and crushing can be achieved, so that the final product particle shape is better.
Spring Cone Crusher
When the unbreakable foreign matter passes through the crushing cavity or the machine is overloaded for some reason, the spring safety system of the spring cone crusher realizes the insurance, and the ore discharge increases. The foreign matter is discharged from the crushing cavity. If the foreign matter is stuck in the discharge port, use the cavity cleaning system to continue to increase the discharge of the ore, so that the foreign matter can be discharged from the crushing cavity. Under the action of the spring, the discharge port is automatically reset, and the spring cone crusher resumes normal operation.
Spring cone crusher is divided into three types: coarse crushing spring cone crusher, medium crushing spring cone crusher and fine crushing spring cone crusher. Among them, the spring cone crusher for coarse crushing is also called a Gyratory Crusher; the spring cone crusher for medium crushing is a standard type cone crusher;
Hydraulic Spring Cone Crusher
The high-efficiency hydraulic spring cone crusher has the world's advanced level of high-energy crusher, which is a perfect combination of crushing speed, eccentric distance (stroke) and high-performance crushing cavity design. It not only improves the production capacity and crushing efficiency, but also expands the scope of application, from limestone to basalt, from stone production to various ore crushing, it can provide unparalleled crushing performance in a variety of medium, fine and ultra-fine crushing operations . Its high rotating speed, high crushing capacity and unique patented design make the crushed products have an extremely high-quality cubic shape, and the easy maintenance features ensure extraordinary high-stability operation, and are well-known all over the world.
Factors affecting the performance of cone crushers
- 1. The cavity shape of the cone crusher is the working space formed by the crushing wall (moving cone) and the rolling mortar wall (fixed cone). The quality of the cavity design has a significant impact on the economic and technical indicators of the crusher (productivity, energy consumption, particle size and shape of the crushed product, and wear of the crushing wall and rolling mortar wall, etc.). In this regard, the unique design makes the final product material more uniform, in the shape of a cube, and the wear of the working surface of the moving cone is more uniform.
- 2. The working parameters of the crusher have a direct impact on the movement characteristics of the bulk material in the crushing cavity, which is mainly reflected in the influence of the swing speed of the main shaft of the crusher on the movement state of the bulk material, which in turn affects the working performance (productivity and particle size distribution of the crushed product) of the crusher. etc.) have a significant impact.
- 3. The swing stroke of the crushing chamber of the cone crusher has an important impact on the working performance of the crusher. When the swing stroke is increased, the actual feed compression ratio of each crushing layer in the crushing chamber increases, the quality of the crushed products is improved, and the calibrated discharge particle size is increased. Swing stroke, the actual feed compression ratio of each crushing layer in the crushing chamber decreases, the quality of the crushed product deteriorates, and the calibrated discharge particle size decreases. Considering the improvement of the quality of the crushed products, the swing stroke of each crushing layer in the crushing chamber also takes a large value.
Technical advantages of cone crusher
- 1. Large crushing ratio and high production efficiency
Combining higher speed and stroke, the rated power and throughput of SMH crusher are greatly improved, and the crushing ratio and production efficiency are improved. The hydraulic cone crusher is designed with the combination of crushing stroke, crushing speed and shape of crushing cavity .
- 2. Less consumption of wearing parts and low operating cost
The structure is reasonable, the crushing principle and technical parameters are advanced, the operation is reliable, and the operating cost is low; all parts of the crusher are protected against wear, which reduces the maintenance cost to a minimum, and the general service life can be increased by more than 30%.
- 3. Lamination and crushing, excellent grain shape of finished products
By adopting the special crushing cavity designed by the principle of inter-granular lamination and the matching rotating speed, it replaces the traditional single-particle crushing principle, realizes the selective crushing of materials, and significantly improves the proportion of fine materials and cube content of the product, which is extremely The needle-like material is greatly reduced.
- 4. Hydraulic protection and hydraulic cavity cleaning, high degree of automation, reduce downtime
Hydraulically adjusted discharge port and overload protection greatly improve the operation level of the crusher, making maintenance easier, more convenient to operate, and shorter downtime; The crushing chamber, the machine can hydraulically lift the top and automatically discharge material in the case of over-iron and instantaneous congestion, which greatly reduces the trouble of the original spring cone crusher that needs to be shut down for manual discharge.
- 5. Thin oil lubrication, reliable and advanced, improve service life
The unique thin oil lubrication system design greatly improves the service life of the equipment. The high-performance non-contact labyrinth seal has no wear, improves the reliability of blocking dust, and fundamentally eliminates common faults such as oil-water mixing of the original spring cone crusher.
- 6. Various crushing cavity types, flexible application and strong adaptability
The cone crusher only needs to replace the fixed cone lining plate and the moving cone lining plate, and the shape of the crushing cavity can be arbitrarily changed from the standard ultra-coarse cavity to the short-head ultra-fine cavity, which can meet the requirements of a wide range of product size.
- 7. Easy maintenance, easy operation and use
All parts of the cone crusher can be disassembled and maintained from the top or the side. The moving cone and the fixed cone are easy to disassemble and assemble, and there is no need to disassemble and assemble the frame and fastening bolts, so the daily replacement of the liner of the cone crusher is more convenient. Utilize hydraulic motors to maximize crusher production efficiency.
- 8. High production capacity and good discharge shape
It provides higher production capacity, optimal product grain shape, and easy automatic control, with maximum reliability and flexibility, and truly creates more value for users.
Operation of cone crusher
Start and stop
- 1. A suitable starter should be selected according to the motor model, and the starter should be started .
- 2. The equipment should be started and stopped in sequence.
- 3. The equipment should be started with no load, and the material can be fed after the operation is stable. When feeding, it should be uniform and not overloaded.
- 4. The feeding should be stopped before the machine is shut down, and the machine can be shut down after all the materials in the standby are emptied.
- 1. The material entering the machine should meet the technical requirements of the machine, the particle size should not exceed the specified range, and the water content is related to the physical properties of the material, and should not be greater than 15%, so as to avoid blocking the feeding port and causing the phenomenon of pasting.
- 2. Feeding should be uniform to improve crushing effect and improve working conditions.
- 3. Metal materials are strictly prohibited from entering the machine to prevent damage to bearings and other components.
- 4. The ore must be given in the middle of the distribution plate, and it is not allowed to directly feed the ore into the crushing chamber. This causes uneven wear of the liner in order to prevent the crusher from being overloaded. The correct ore feeding conditions are: the ore is evenly dispersed in the crushing cavity by the distribution plate, and the fed ore cannot be higher than the level of the rolling mortar wall.
- 5. The maximum feeding size of the crusher is less than or equal to 85% of the size of the feeding port.
- 1. The discharge port of the cone crusher should be unblocked, so as to avoid equipment overload accidents caused by poor discharge.
- 2. The discharge situation should be checked regularly. If it is found that the discharge particle size does not meet the specified discharge particle size, the wear of the hammer head, the lining plate and the tension of the V-belt should be checked. If problems are found, the worn parts should be replaced in time and the V Belt tension.
Replacement of rolling mortar wall
There are U-shaped screws on the rolling mill wall on the adjusting ring, and zinc alloy is injected between the two to make them tightly combined. When the rolling mill wall is newly installed or replaced, after 6-8 hours of operation, the tightening condition should be checked. and tighten the U-shaped screw again.
Replacement of broken walls
The cone crushing wall is fixed on the cone body with a cone head, and zinc alloy is cast between the two. After the newly installed or newly replaced cone crushing wall works for 6-8 hours, its fastening should be checked, and if it is found to be loose, it should be checked immediately. Fasten.
Replacement of bushings
The taper sleeve and the hollow eccentric shaft should be grinded together, and zinc alloy should be injected to prevent the taper sleeve from rotating. The zinc alloy should fill all the gaps. The deformation of the taper sleeve may be caused by the hot injection of zinc alloy. It should be corrected in time. When manufacturing spare parts, it should be prepared according to the actual size of the inner diameter of the eccentric sleeve to maintain the original fit.
Installation and maintenance
The maintenance of the machine is an extremely important and regular work. It should be closely coordinated with the operation and maintenance of the machine, and there should be full-time personnel to conduct on-duty inspections.
Maintenance of the machine
- 1. The shaft of the crusher bears the full load of the machine, so good lubrication has a great relationship with the life of the bearing, which directly affects the service life and operation rate of the machine. Therefore, the injected lubricating oil must be clean and the seal must be good. The main oiling places of the machine: (1) Rotary bearing (2) Roller bearing (3) All gears (4) Active bearing, sliding plane;
- 2. The newly installed tires are prone to loosening and must be checked frequently;
- 3. Pay attention to whether the work of each part of the machine is normal;
- 4. Pay attention to check the wear degree of the wear-resistant parts, and pay attention to replace the worn parts at any time;
- 5. On the bottom frame plane of the movable device, dust and other objects should be removed to prevent the movable bearing from moving on the chassis when the machine encounters materials that cannot be broken, resulting in serious accidents;
- 6. If the bearing oil temperature rises, stop immediately to check the cause and eliminate it;
- 7. If there is an impact sound when the rotating gear is running, stop it immediately to check and eliminate it.
Installation and test drive
- 1. The equipment should be installed on a horizontal concrete foundation and fixed with anchor bolts;
- 2. When installing, pay attention to the verticality of the main body and the level;
- 3. After installation, check whether the bolts of various parts are loose and whether the main engine compartment door is tightened. If so, please tighten it;
- 4. Configure the power cord and control switch according to the power of the equipment;
- 5. After the inspection is completed, carry out an empty-load test run, and the test run is normal and the production can be carried out.
Fault 1: The oil pressure in the oil pipes before and after the filter is not the same.
Cause of failure: filter clogged.
Troubleshooting: When the oil pressure difference exceeds 0.04MPa, the filter must be cleaned, first make the oil not pass through the ground filter, and then remove the filter for cleaning, so as to supply oil directly to the crusher, no more than 2-3h
Fault 2: There is no oil flow in the oil flow indicator, but the oil pressure is lower than 0.5MPa.
Reasons for failure: 1. Low oil temperature; 2. Oil switch is not turned on properly; 3. Oil pump is not easy to use;
Troubleshooting methods: 1. Oil heating; 2. Turn on the switch; 3. Stop the crusher and replace the oil pump;
Fault 3: The oil return in the fuel tank is reduced, and the oil level is significantly reduced.
Causes of failure: 1. Oil leakage from the bottom cover of the crusher; 2. Oil leakage from the flange of the transmission bearing shell; 3. The groove of the spherical bearing seat ring is blocked or too much oil is supplied, and the oil leaks from the dust-proof device.
Troubleshooting methods: 1.2 Stop the machine, find out the cause and eliminate it, and then add oil to the fuel tank; (3) Stop the machine, clean the oil return ring groove, adjust the amount of oil supplied, and add oil to the fuel tank.
Fault 4: The oil temperature exceeds 55℃, but the oil pressure does not rise.
Cause of failure: There is something wrong with the eccentric shaft sleeve;
Troubleshooting method: stop the machine to check the straight bushing and tapered bushing, find out the cause of the fault and clear it.
Fault 5: Oil temperature rises while oil pressure rises.
Cause of failure: The oil pipe or the oil circuit inside the crusher is blocked.
Troubleshooting method: stop the machine to find the blockage and clear it.
Fault 6: The temperature of the oil coming out of the cooler exceeds 45°C.
Failure reasons: 1. There is no cooling water; 2. The temperature of the cooling water is high; 3. The cooler is blocked.
Troubleshooting method: supply cooling water; check whether the water pressure is too low, increase the pressure as much as possible, and check the cooling water temperature; clean the cooler.
Fault 7: There is water in the oil, and the amount of oil in the tank increases.
Cause of failure: The water pressure in the cooler is higher than the oil pressure.