In the production process of my country’s press plants, unplanned downtime caused by conveying equipment accounts for 60% to 80% of all unplanned downtime. Improving the operation performance of conveying equipment and reducing failure rates are the focus of all press plants. Improvement The performance and configuration of the conveying equipment are issues that are of great concern to the designers of conveying equipment.
The conveying equipment of a large-scale press plant is mainly scraper conveyors, bucket elevators and screw conveyors. The following introduces the technical points of improving the design of these conveying equipment under the condition of full load operation, and briefly introduces the situation of pipeline conveyors.
Horizontal scraper conveyor of conveying equipment
The horizontal scraper conveyor has problems in the production process
Generally, the supplier designs the conveying capacity of the conveying equipment to increase by 5% to 10% on the basis of the contractual amount. When the conveyor fails during production, it is difficult to restart with the material and the chain may be deformed. The observation window of the scraper mirror is generally configured on one side, and it is difficult to see the internal operation. Residual materials are likely to exist at the tail after the scraper is running and stopped, and the return stroke of the guide rail is designed as a parallel guide rail, which cannot make uniform contact. Without special requirements, the shell, track, and chain are mostly made of carbon steel, which is easy to wear. Reducers and motors are mostly general-purpose types. According to the national safety management requirements, the original granary group area was changed to dust explosion-proof; as the leaching oil plant upgraded the safety protection level, the design of the leaching meal storage was changed to explosion-proof type; the motor began to promote the configuration of energy-saving type in accordance with the new national regulations.
Improve design requirements of this scraper conveying equipment
Case
The design of the scraper conveyor should have a 15% overload starting and continuous operation capacity while meeting the rated production. The observation windows of the scraper mirrors should be arranged symmetrically at both ends. The middle section of the sight glass observation windows are about 10 m apart, arranged symmetrically on both sides of the scraper, and the sight glass observation windows are tempered glass. A hinged observation door is provided at the top of the shell at the head and tail ends of the scraper. The head of the horizontal square scraper is equipped with an overflow door (with limit switch), and the overflow door is automatically opened when needed to discharge the material stored in the scraper. The sweeper is made of flame-retardant high molecular polyethylene material with a thickness greater than or equal to 25 mm. The return path of the chain is provided with a guide rail, and the upper guide rail is supported in a “eight” shape, and the bottom edge of the entire blade can evenly contact the guide rail. The conveying material inlet, discharge port and discharge position are customized according to the production process.
The cover and side plates are made of Q235, the inner lining and bottom plate are made of wear-resistant steel NM360 or NM400, the thickness of the inner lining of the side plate is greater than or equal to 6 mm, and the top plate is 4 mm carbon steel. Use galvanized U-shaped buckles and bolts to fix on the side plate, no need to drill holes on the cover plate and side plate flange, use M10 galvanized bolts, the middle partition thickness is 10 mm, the material is NM360, the head and tail section The thickness of the side plate is greater than or equal to 8 mm; the thickness of the bottom plate is greater than or equal to 6 mm, and the thickness of the inner liner plate is greater than or equal to 10 mm. The cover plate adopts the “roof” structure, with a section of 1.5 m. During the manufacturing process, the NM360 board has to undergo secondary quenching and tempering.
Head and tail wheel part
The head and tail wheel shaft of the scraper conveyor conveying equipment should be processed as a whole, and the transition of the shaft diameter should be as smooth as possible.
The head and tail wheel shafts are made of 42CrMo, subject to heat treatment. The sprocket adopts Martin split, which adopts assembled split or split type. Use 10.9 grade anti-corrosion bolts to fasten. If a bent plate chain is used, split sprockets can be used. The head is equipped with a de-chain cleaning device, which is convenient for the scraper chain to detach and remove the accumulated material in the tooth groove. The discharge port of the head is opened directly to the end to effectively prevent material accumulation. The head is also equipped with an anti-clogging switch to prevent material blocking. The protective cover uses oil-immersed sprocket protective cover. It adopts split type bearing with seat, and adopts vertical installation or horizontal installation according to the situation. It can also adopt slider-type seat bearing with packing seal and packing seal. The tail wheel adopts a split sprocket, which is easy to disassemble and assemble.
The head and tail are designed with quick-opening nut or handle fixed waterproof sealing observation window on the cover, which is convenient to observe the tightness of the chain and the degree of wear of the head wheel; all the inlets are installed with observation windows on the side plates 50 cm in the direction of material movement. The body material is a plexiglass plate greater than or equal to 10 mm thick, and the fixed frame is detachable and replaceable. The installation position must be on one side plate within the height of the design material.
Reducer, coupling and motor
When the reducer is in the dust danger zone (the same below), the maximum surface temperature should not exceed 85 ℃. The explosion-proof gear reducer and the explosion-proof gear reducer are in accordance with CE specifications, F grade insulation, and protection grades IP54 and IP55. If a shaft-mounted reducer is used, the brake arm must be placed in tension at all times. All reducers must use internal injection or forced lubrication, and the lubricant must reach all moving parts such as gears, bearings and seals. The oil seal must be able to withstand pressure changes in the reducer due to clogged ventilation or temperature changes.
Flexible couplings are used for couplings. Rigid couplings are forbidden to facilitate coupling disassembly and assembly. The safety factor of the coupling is greater than or equal to 2. When the power of the driving device motor is 18 kW and above, a hydraulic coupling should be installed on the shaft. The shaft of the drive device whose motor power is equal to or less than 15 kW should be a rubber sleeve type or other type of coupling approved by the owner.
In the past, the motor was designed according to the dust-proof design, that is, the dust-proof squirrel-cage motor, and the regulations were divided into 11 zones according to the grain dust explosive danger zone. Now adopts YE3 series high-efficiency motors, YVF2 series frequency conversion special motors are changed to YXVF series high-efficiency frequency conversion speed-regulating motors. It is required that explosion-proof motors should be designed in leaching restricted areas and soybean meal warehouses. Flameproof motors YB3 type are changed to YBX3 series high-efficiency explosion-proof motors , All exposed parts of the motor should be protected by approved and suitable reinforced metal protective nets. The motor should be equipped with lifting bolts, and the motor lifting bolt holes should not penetrate the motor casing to expose the iron core of the stator. The energy efficiency standard of the motor is not lower than the latest level 2 of the country, and a fuel nozzle is required.
Safety protection device
The protection and explosion-proof levels must meet the national standards and IEC standards, including the following: ① stall sensor; ② slide pipe blockage sensor at the feeding and unloading; ③ tensioning device limit switch (gravity tensioning device); ④Rotation speed monitoring; The level device of the scraper conveyor is of resistance selection type and capacitive type; ⑤The head wheel bearing temperature measurement system.
Chain
The chain speed of the 500 t/h scraper conveyor conveying equipment for raw grain receiving in the factory is less than or equal to 0.60 m/s, and the chain speed of the scraper conveyor in the workshop is 0.35~0.40 m/s.
For the scraper chain, select welded bent plate chain, the material is 40Cr, 45CS quenching, and the mass of the welded bent plate chain with a width of 500 mm is greater than or equal to 30 kg per meter, and the tensile strength is greater than or equal to 600 kN. The material of the pin is 40Cr, which must be carburized and high-frequency treated. The tensile force of the die forging chain is 1500 kN. Key components such as chains, sprockets, and axles must undergo quenching, tempering, carburizing, shot blasting heat treatment and quenching and tempering. The thickness of the guide rail on the chain is 8-10 mm, and the guide rail material is wear-resistant steel greater than or equal to NM360.
Each link of the chain plate is equipped with ultra-high molecular polyethylene wear-resistant plates, the thickness is greater than or equal to 19 mm, the curved scraper is greater than or equal to 25 mm, and the relative molecular mass of the ultra-high molecular polyethylene wear-resistant plates is greater than or equal to 3.5 million, using 8.8 grade hot plating Zinc stop bolts are fixed to the chain plate.
Install 2~3 cleaning scrapers evenly on the scraper chain. The size of the cleaning scraper is slightly larger than the rubber plate of the scraper. Fix the cleaning scraper on the scraper with screws.
Generally, fixed chains are set every 3 m. One end of the inner pin of the group is stepped, and the other end is hot riveted. The movable pin between the group and the group adopts a D-type plug on one side. The interference fit is 6~ 8 mm T-shaped pin or directly fixed with threaded pin, each whole chain can reserve 3~5 m full joint.
Curved scraper conveyor conveying equipment
In addition to the problem of the horizontal scraper conveyor in the production of the curved scraper conveyor, how to reduce the amount of returned material should be considered in the design of the curved scraper, and the amount of returned material must be controlled within 5%. Used in the workshop: ①used for conveying high temperature and humid materials, such as softened materials, blanks, extruded materials and finished dregs at 55-65 ℃, and DC discharge with a temperature of more than 100 ℃; ② conveying inflammable and flammable materials Explosive materials such as wet meal. Pay full attention to the following matters in the design:
Head and tail wheel
Use standard chains with half-pitch odd-numbered teeth. Split bearing Dodge TAKE-UP integral slider bearing or return tension slider bearing for tail bearing. The safety factor of the speed reducer of the green sheet scraper, the leaching workshop, the scraper conveyor from the leaching workshop, and the wet meal scraper is greater than or equal to 2.0. The head of the conveyor scraper and the DT meal scraper conveyor from the pretreatment workshop to the extraction workshop should be equipped with exhaust holes.
Curved section
The chain is tightly combined, the bending section selects the optimal radius of curvature for natural transition, and the inner lining is made of NM360 or NM400 high-strength wear-resistant plates. The side panel of the curved structure is 6 mm NM360, the lining height is greater than the material height, the thickness of the guide rail on the chain is at least 10 mm, and the guide rail material is not less than wear-resistant steel NM360 or Mn65. The distance between the sight glass observation windows is about 10 m, and a pair of sight glass observation windows are provided in the vertical section housing close to the curved section. It adopts welded curved plate chain, and the form of scraper adopts full-face scraper.
Seal
The flanges are required to be flat, and the head and tail wheel shafts adopt double PTFE packing oil seals, copper sleeve bearing seals, and integral sealing. The assembly seal test should be done before leaving the factory.
Special requirements for wet meal scraper
According to the design treatment capacity of 30% solvent, the scraper treatment capacity from DT to DC is designed according to the water content of the meal at 16%, and the linear velocity is less than or equal to 0.35 m/s. Adjust the amount of return material of the wet meal scraper to within 3% as much as possible. In order to reduce retained materials and friction, plastic lining, shell material Q235 or SS304, shell thickness of scraper bearing section 8 mm, partition thickness 10 mm, detachable assembly form for bending section, sight glasses, bending section sliding The material of the channel is Mn65, NM360 or NM400, the thickness is 10 mm, the shell thickness of the non-load-bearing material section is greater than or equal to 6 mm, the flange plane of the cylinder connection should be finished, the reaming hole is positioned, the thickness is greater than or equal to 18 mm, and the chain is used Welded curved plate chain, liner material is PTFE (density 2.1~2.3 t/m3), thickness is greater than or equal to 15 mm, chain load factor is greater than or equal to 8 times, the thickness of head and tail plate is greater than or equal to 10 mm, adopt frequency conversion start Or soft start, select sealing packing for easy replacement. The shell of the straight section adopts upper and lower welding, and the curved arc section is connected by bolts (consider the replacement of the grinding section of the intermediate diaphragm).
Use thicker plates for inlet and outlet positions (best movable type, easy to replace), resistant to erosion; pay attention to the contact surface of the scraper track plate and the chain to be wide; from the extractor to the wet meal scraper of DT, from DT to DC The hot meal scraper should be kept warm; the top of the scraper should have an air valve to prevent liquefaction and vaporization of the grease in the shaft seal. The bearing seat of the scraper should be fixed with top wire to prevent the rotation shaft from moving.
Bucket elevator conveying equipment
Head
The shape of the machine head is split cover, parabolic arc, and the height of the throwing shell is relatively small. It is lined with an A8-grade steel mesh lining board. The thickness of the steel plate is greater than or equal to 8 mm. The thickness is greater than or equal to 8 mm, with appropriate reinforcement ribs to increase the rigidity. The inner surface that is impacted by the material should be lined with polyurethane wear-resistant material (or ceramic sheet material), the thickness is greater than or equal to 10 mm, and fixed with galvanized standard countersunk bolts. All wheel widths should be at least greater than the width of 100 mm, and the barrel width should be at least 50 mm greater than the width of the wheels. Equipped with a hinged inspection door, installed on both sides to prevent deviation. In the discharge chute, an adjustable and detachable return baffle (using polyurethane material) and a bucket movable intercepting rod are set. The machine head cover should be equipped with a lifting ring.
The material of the wear-resistant plate is UHMW-PE with a relative molecular mass of 3.7 million. If the relative molecular mass exceeds 1.4 million, the wear resistance will increase to over 3.5 million, which is very brittle. When the hardness is high, the hardness should be reduced and the toughness should be increased.
The taper connecting shaft between the wheels and axles must be machined as a whole. When the diameter of the shaft changes, the stress concentration must be minimized during the design. For the shaft shoulder, the largest possible chamfer radius should be given according to the actual situation, and the axle and the bearing seat should be connected with a jack wire. The head wheel is equipped with oil-resistant, flame-retardant, anti-static rubber layer, which can be disassembled and assembled. Its hardness is 60 DURO, the thickness is not less than 20 mm, and the thickness of the relief is not less than 10 mm. The bucket elevator roller should use solid wheels, and an adjustable baffle is designed inside the machine head to prevent material return.
The bucket elevator is equipped with a backstop to prevent reverse operation when fully loaded or at full load. The backstop is of multi-tooth type. The bucket elevator can be 100% full load on the bucket in the upper cylinder and the base is 1/3 full Starts smoothly under the conditions of, without slipping.
Case
The bucket elevator has its own barrel on the up and down sides. The difference between the inner width of the barrel and the belt width shall not be less than 150 mm, and the minimum gap between the back of the belt and the barrel shall not be less than 50 mm. The minimum gap between the largest protrusion of the bucket and the barrel shall not be less than 75 mm. The cylinder is made of low-carbon steel and angle steel (or galvanized steel), and the sections are connected by bolts, and the thickness is greater than or equal to 4 mm. The height of a single cylinder is less than or equal to 3 m to ensure vertical positioning in each direction under various load conditions, with a tolerance of ±3 mm. Flanges should be fully welded on both ends of the barrel or sealed to prevent corrosion. When assembling the barrel, welding deformation should be prevented. The joints of each section of the barrel should be flush. The inner surface of any section should not protrude from the inner surface of the adjacent section. Above 2 mm. Before all joints are screwed together, flexible materials such as silicon sealant shall be applied to the flange for sealing. A sliding joint should be set in the cylinder to adjust the vertical movement between the head and tail of the bucket elevator conveying euipment. The design of the conveying equipment should prevent the collision between the bucket and the joint. Where the bucket elevator is installed in the closed structure, the sliding joint should be Carry out sealing treatment to prevent dust from escaping. The barrel adopts a stamping and undercut structure, the barrel is fully opened to observe and repair, and the scissor support is strengthened. Every two sections are equipped with explosion-proof inspection sections. The diagonal error of the 3 m standard section is less than or equal to 2 mm. The barrel is connected by standard flanges, and the connecting bolts are 5.6 grade chrome-plated bolts.
Bucket belt, bucket
According to my country’s industry standard, the belt speed is 2.8~3.5 m/s, and the line selection speed in the press workshop is 2.6~3.0 m/s.
The bucket belt core of the conveying equipment is composed of polyester, nylon and PVC materials, oil-resistant, flame-retardant and anti-static, with a tensile strength of 600~800 N/mm. The thickness of the surface layer of the bucket belt is not less than 2 mm, and the bucket belt is 5~7 Layers, number of layers and thickness should meet the standards of tensile force and bucket bolt tensile strength, with a safety factor of 15-18, and the stretch of bucket belt after 12 months of initial use shall not exceed 1%. The width of the bucket belt should be at least 75 mm wider than the sides of the bucket fixed on it.
The bucket belt should have a certain thickness of the outer edge layer. The bucket belt connection should be mechanically connected to the board. At least 6 rows of bucket bolts should be used to connect the board on each side of the connection. The bucket bolts should be 8.8 hot-dip galvanized anti-return bolts. . The rated maximum allowable working tension of the bucket belt should exceed the maximum operating tension by at least 15%, and the ratio of the breaking tension to the working tension is greater than or equal to 9. The protruding part of the bucket fixed to the bucket belt connection board of conveying equipment shall not exceed the bucket protruding line fixed on the remaining part of the bucket belt.
There are three types of bucket materials of the conveying equipment: polyethylene, polyurethane and steel. Generally, polyethylene (life 1.5 years) and polyurethane (3 to 4 years) are used. When the material temperature is lower than 70 ℃, polyethylene or polyurethane buckets are used. Steel bucket is used when the temperature is higher than 70 ℃. The deep bucket and shallow bucket are configured according to the requirements of the conveying materials. The bucket can be punched in the factory or on site, using a belt connector.
Feed inlet, outlet and equipment connection slide pipe
The inlet, outlet and connecting slide pipe are made of 6 mm NM360 or NM400 steel plate, and are connected to the body with bolts. Or choose a polyurethane material or wear-resistant ceramic sheet with a thickness of not less than 10 mm as the wear-resistant liner. It is better to install anti-blocking sensors on the feed chute and the discharge chute.
Inspection doors and explosion vent doors
Detachable inspection doors and observation windows are provided at the head, base and barrel of the bucket elevator. The size of the door and window should be sufficient for the removal and replacement of the head, base, guide wheels and bucket. One access door and observation window should be installed every 12 m. The position where the observation window is installed can see the internal head wheel running.
The surface area to be vented on the bucket hoisting fuselage should be no less than 1 m2 for every 8 m equipment volume. Set an appropriate number of explosion vents at the appropriate positions of the cylinder. The explosion vents and the dust collector are located in the nose, middle, and tail of the machine. The explosion vent membrane is made of approved low-inertia lightweight materials, and the pressure should not exceed 1.5 kPa. It should be completely released in no more than 1 ms. It is required to be detachable, replaceable and fixed with M8 nylon bolts.
Bottom section and base
The bottom section of the bucket elevator conveying equipment uses a steel plate with a thickness greater than or equal to 6 mm and has been strengthened. The material can enter the base of the elevator through the feed chute at the front or rear, and reverse feed should be used as much as possible. The bottom section should be designed such that the feeding tube of the upstream cylinder should be above the center line of the tail wheel when it is at the highest position of the stroke, and the feeding tube of the descending cylinder should be at the tail when it is at the lowest position of the stroke Above the center line of the wheel. Install the plug-in board on the front and back of the base, or design the bottom plate into an arc shape to minimize the accumulation of materials and facilitate the emptying of the base. Slots should be provided on both sides of the base, and their length should meet the specified full stroke of the tail wheel shaft.
The front and rear parts of the bottom section are provided with inclined inserting plates driven by a rack. Both sides of the bottom shell are equipped with a “cleaning chute” or a mouth equipped with a hinged cover, and the cleaning door is a roller structure or a rack and pinion structure. The bottom can be equipped with double inlets, self-cleaning rollers. A sealing device is installed between the base shell and the sliding bearing plate, so that no material and dust will leak at any position of the bottom wheel during the entire tensioning stroke. The tail wheel can be designed with a squirrel-cage type tail wheel with self-cleaning function. The tail wheel is made of a grid bar and a ceramic backing plate is used for the position where the machine seat is washed by the material.
Tensioner
The tensioning device is equipped with a limit switch, which adopts hydraulic tensioning or mechanical tensioning. The mechanical tensioning adopts weight box tensioning + screw fine adjustment. The tensioning device should have enough travel, and the unused travel should not be less than 50% of the entire travel. There is a sealing mechanism between the bottom box and the sliding bearing plate. Under the premise of ensuring the sealing effect, it should slide flexibly without jamming.
Safety protection device
The protection and explosion-proof levels must meet the national standards and IEC standards. The content: ① stall sensor; ② pipe blockage sensor at the feeding and unloading place; ③ tension device limit switch; ④ head wheel bearing temperature measurement system; ⑤ speed Monitoring, overload protection, coupling with shear pin; ⑥ anti-deflection device, use mechanical anti-deflection device, the contact part with belt is tail wheel roller, or use pressure plate type deviation detection device.
Screw conveyor (screw auger) of conveying equipment
The screw conveyors used in ports and squeezing plants are only used for horizontal conveying equipment, and can convey normal temperature and high temperature materials. According to process requirements, the screw conveyor adopts variable pitch and variable shaft diameter, with the middle shaft referring to GB/T 12459, in accordance with the Sch80 standard. Material thickness: Shell 5 mm, blade 6 mm, cover 3 mm.
Screw conveyor
The screw conveyor with a conveying distance of less than or equal to 30 m uses a high-strength hollow main shaft, a suspension bearing, and a reinforced triangular-shaped adjustable suspension. If it is used for distributing screw conveyor, the material opening should be opened according to the position of receiving equipment below.
Sealed auger
One end of the sealing auger in the leaching workshop is a discharge port. A section of broken blades is designed before the discharge port. The length of the broken blades is 1.1 to 1.25 times the diameter as the material sealing section. The outer wall at one end of the unloading port is changed to a gravity door, which is hinged on the top of the shell, which also serves as a material seal. It is recommended to use SS304 as the material of the sealing auger in the extraction workshop to prevent failure due to corrosion damage or the gravity door from falling into the extractor. Special reminder to design the material and strength of the hinge of the gravity door. The top of the extruder is used as a feed auger. There is a variable pitch and material sealing section in the middle to feed the extruder stably. The discharge port of the flap cooler under the extruder is used to receive the material and connect the feeding scraper. It plays the role of material sealing and prevents the solvent in the leaching workshop from entering the pretreatment workshop through the scraper conveyor.
Conclusion of conveying equipment
As the processing scale of the press plant now exceeds the actual production needs, there are fewer and fewer new plants, and the technical transformation of the press plant is highly valued. In the production process, if one conveying equipment fails, it will cause the entire line to shut down. It will take a while to resume production, which not only wastes energy, but also the product quality can reach the rated product quality index 2~3 hours after starting up. Semi-finished products need to be added back, resulting in a reduction in processing volume for a period of time. Therefore, the operation stability of the conveying equipment is higher than before, which leads to higher requirements for the quality of materials and accessories required by the conveying equipment. In addition, due to energy-saving and safety requirements, the motor is replaced with a high-efficiency and energy-saving type, and the reducer and motor are designed as explosion-proof in the meal warehouse. Consider the possible influence of dust in the design of bucket elevator, design explosion venting and head safety net.
The medium of the curved scraper conveyor conveying equipment used in the workshop of the press plant is different from that of the outdoor curved scraper conveyor. It contains oil and gas, water vapor, solvent, high temperature, and density of the medium.
In addition, in the long-distance transportation of small particles or powdered materials in the starch and food industries, as well as the transportation of defatted meal and soybean hulls in the crushing plant, pipeline conveyors can be used. The scale of the pipeline conveyor is 40-50 t/h. Two pipes can be laid along the wall. The radius of the bend is required to be greater than 4D. A round plate is welded every 30-40 mm with a steel wire rope in the pipe. The material of the round plate is SS304 or manganese steel. The perforation of the round plate and wire rope welding are key technologies . Compared with wind transportation, pipeline conveyors save electricity and operate stably.
