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Machinery and equipment repair and maintenance of common sense

Source: This websitePopularity: 405Time: 2015-12-28SML

一,First, wear and lubrication Basics

      (一)Category (a) worn
      Surface contact with each other during the relative movement, the surface layer material loss constantly occurring phenomenon known as the wear.
      According to wear to extend the length of time it can be divided into two types of natural wear and abrasion accident.
      Wear and tear caused by the accident is caused by the following factors: machine construction defects, poor quality parts and materials, bad parts manufacturing and processing, machine assembly and installation of components or incorrect, violation of safety rules and technical regulations of the machine lubrication, poor repair or Repair quality is not high, and other causes of accidents and the like.
      In general, natural wear and tear to the rear when there is no time limit to repair, it is the main reason for accidents wear.

      (二) Lubrication
      1, a lubricant
      (1) cooling the cooling effect. Prevent friction and heat to make parts temperature rise, leading to increased wear adhesive wear and corrosion, even burn rubber bearing seals or other accidents.
      (2) sealing protection. Lubricants can effectively isolate the humid air moisture, oxygen and harmful media erosion, also prevents internal leakage of the medium, but also to prevent moisture grease, dust, impurities invade friction.
      (3) washing the dirt effect. Will produce abrasive friction movement, as well as foreign matter, dust and sand will be increased wear of the friction surface, forced liquid circulation lubrication can be abrasive away, to reduce or avoid wear.
      (4) to reduce friction and wear. Since the lubricant film can reduce the friction factor between the two moving parts, it will reduce the wear and tear of parts, while also serving as role and vibration damping effect, thereby extending the life of equipment, reduce power consumption, improve operating characteristics of the device.
      2, the type of lubricant
      Lubricant according to the state can be divided into liquid (oil), semi-solid (grease), solid and gaseous lubricant four categories.
      (1) oil
      Lubricating oil, also known as thin oil, its physical and chemical characteristics are:
      Good flowability; low freezing point; appropriate viscosity and viscosity coefficient; good resistance load performance; good oil resistance and extrusion, abrasion resistance; good corrosion resistance and rust resistance; there is a certain degree of purification; ash, carbon residue and the acid value is small; good thermal stability, less volatile and difficult to fire, have a high flash point and flash point; good antioxidant safety, not aging deterioration; good from water retention, resistance to emulsification; have a certain anti-foam.
      Lubricant appearance quality check points in the table below:
      Color change forecast deterioration causes and reasons for the deterioration of the oil is dirty and Forecast
      New oil darken oxidative degradation have a similar thermal degradation burning smell
      Black mixed with abrasive grains have deteriorated pungent odor of metal inert agent
      Turbid water mixed with foreign matter of a precipitate
      Foam mixed with different oil types
      Lubricant selection principles:
      a. In the fully guarantee the safe operation of the machine under conditions of friction, in order to reduce energy consumption should be preferred small viscosity oil.
      b. friction parts at high load conditions of work should be used in small viscosity oil, while friction at low speed heavy-duty working conditions should be used lubricating oil viscosity.
      c ambient temperature low viscosity oil should be chosen small, the viscosity of the lubricant on the contrary should be chosen; at high temperatures should be used high flash point oil; low temperature low freezing point should be used lubricating oil.
      d. Shock, vibration and reciprocating motion, intermittent motion and so unfavorable for the formation of the film, it should be used in a large viscosity oil or use grease or solid lubricant to ensure reliable lubrication.
      e. friction with a small gap should use low viscosity oil, high precision surface machining Face small viscosity oil should be used.
f mechanical cycling conditions chosen under low viscosity lubricant viscosity should be chosen slightly intermittent fuel oil; vertical lubricating surface, exposed gears, chains, wire rope and so on to be elected the viscosity of the oil.
      g. When the absence of suitable grades of lubricating oil, can be used similar grades of lubricating oil or blending alternative use, when substitute only slightly larger than a predetermined selected lubricating oil viscosity, then try not to choose two different properties when blending different label blended oils and additives.

      (2) Grease
      Grease, also known as dry oil, a semi-solid lubricant, which is a mixture of mineral oil and lubricating liquid thickener made of plastic having a lubricant colloidal structure.
      Grease selection principle:
      a high-speed light-load conditions selected penetration of large grease; use a small penetration grease under shock, vibration, intermittent working conditions.
      b.The next b winter or cold conditions, should use low freezing point and a low viscosity oil modulation grease; in summer or hot conditions should be selected high dropping point of grease.
      c. with the gap is large and a small selection of the surface roughness of the penetration of grease, otherwise the choice of the penetration of large grease.
      d Environmental conditions: under wet conditions in general should be used calcium-based grease, and should be used under high temperature conditions generally sodium based grease.

      (3) solid lubricant
      Do a lot of solid lubricant material, metal, metal compounds, inorganic, organic and so on, one of the most commonly used are molybdenum disulfide and graphite lubricant. Molybdenum disulfide lubricants, is a lead-gray to black shiny powder form, which is characterized by good lubricity, adhesion, heat resistance, wear resistance and compression reduce oxidation resistance to chemical corrosion, etc., for equipment in high-speed, high-temperature, high load, low temperature and chemical corrosion environmental conditions of work, have excellent lubricating effect.
The current production of molybdenum disulfide lubricants are: powder, liquid, oil, grease, grease, crayon and other solid film-forming agent.
Equipment lubrication "five": fixed, qualitative, quantitative, regularly scheduled one.
The use of lubricants quality monitoring technology: key equipment and fuel consumption of a large selection of equipment, determine oil quality testing project, such as kinematic viscosity, water content, acid value
      A water-soluble acid and mechanical impurities, etc., determine a reasonable change criterion, the development of specific project indicators, periodic laboratory analysis of samples (generally once every three months), and then determine whether or not to replace, for new equipment and major precision equipment also available through the visual, for drain intervals appropriate to extend or shorten the testing cycle.

      Second, the maintenance basics
      (一)Failure and mechanical failure (a) mechanical parts
Ability to work incapacity called mechanical failure, machine parts called dead loss provisions. Failure of mechanical failure and parts are inseparable. Due to normal wear and tear parts or parts physical and chemical changes caused by deformation, fracture, pitting the like component failure caused by malfunction, such a failure also called natural fault.
      1, parts wear
      Wear is the most important component failure and popular form.
      2, the deformation of parts
      The machine during operation, due to the force, so that the size and shape of the part is changed in the phenomenon called deformation. Deformation of the metal include elastic deformation and plastic      deformation.
      3, part of the fracture
      Parts in the external load, elastically deforms first, when the stress caused by the load continues to increase beyond the elastic limit of the material may produce plastic deformation, fracture stress exceeds the ultimate strength of the final.
      4, erosion
      Dot parts of the surface occurs under cyclic contact stress the role of fatigue spalling called pitting; parts subject to chemical and electrochemical action causes damage to the surface of the surrounding medium is referred to as metal corrosion occurs; parts at a temperature change and the role of the surface of the medium needle shaped hole, and continue to expand called Cavitation. Fatigue pitting, corrosion and Cavitation collectively referred to as pitting.

      Second, the mechanical fault elimination (repair) method
      For man-made accidental failures primarily by increasing the elimination of the use, management, maintenance staff quality, strengthen accountability of methods to achieve. While the natural fault can only be achieved by adjusting and repair methods, usually mainly the following methods:
      1, the main recovery with the nature of the repair method
      (1) Adjustment Act
General tightness or use of the adjusting bolt fitting relationship with the original, not processed for fitting the repair of (or only scraping), but only by increasing the thickness of the spacer shims or adjustment method of adjusting the shim thickness to recover to restore to the original with the gap.
      (2) repair size method
Conducting fittings for the more expensive parts machined to restore its geometry, but to get a new dimension, and then fitting another waste and replace worn parts with new parts fit when processed repairs parts that coincide with the fitting clearance to return to the initial gap, such as changing the shaft bearing repair, repair, etc. are piston cylinder liner change. To consider the possibility of such repairs and replacement parts can be machined on the part of the structure allows the mechanical strength after repair, in this context should try to increase the number of repairs; on the other hand in order to facilitate the supply of spare parts for its repair size should be standardized.
      (3) Supplementary parts method (Additional parts method)
      This method for each part fitting herein are shaping process, and one of the parts give reasonable necking or reaming, and then supplemented with a similar or higher quality liner material to interference pushed or screwed into or welded onto the original parts, then processed with the size to make with nature to meet the requirements.
      2, both with the nature of the recovery and restoration of parts of shapes and sizes of repair methods
      (1) welding repair method
Metal welding is by diffusion and ligation between atoms of the metal weldments separate firmly bonded into a whole, depending on welding equipment, gas welding and welding and other welding has many faults and wear parts are mostly using welding and surfacing methods repair, some parts in the car and then through welding, grinding, to achieve the restoration of the original geometry and size.
      (2) casting supplement
Babbitt bearing wear to limit, the residue alloy melt drains to re-cast the new process is called the complement babbitt casting method. This method can completely recover the performance standards of the old plain bearings.
      (3) plating (plating, electroless plating) Act
Plating using an electrochemical reaction through the electrolyte DC, to achieve a metal plating deposited on the surface in the process.
      (4) Spray and spray
Spraying the molten material is fine particles deposited in the high-speed air jet has been prepared rough parts of the surface, forming a layer of relatively strong mechanical bonding layer. Spray process is developed on the basis of the spraying process, it is re-sprayed layer remelting process, and in the parts of the surface layer to get a similar performance surfacing coating.
      (5) adhesive and stick fill method
It is the use of an adhesive bond between the parts played by chemical, physical and mechanical forces for bonding integrated part or parts of a sticky patch repair process cracks, holes, wear and other defects.
      (6) non-stop plugging technology features and applications
      a, straight pipe and vessel sealing: Monolithic bonding, clogging of law; clamp method; pressure assisted method
      b, flange sealing method

      三、Third, the mechanical disassembly, assembly, cleaning and inspection
      1, mechanical disassembly
      (1) Preparation before demolition
      a, the workplace must be spacious and bright, smooth and clean.
      b, removal tool to prepare complete specifications appropriate.
      c, according to different uses is ready to put parts of the gantry, separate pots, drums, etc.
      (2) Basic Principles of disassembled machinery
      a, depending on the model and relevant information clearly its structural features and assembly relationships, and then determine the decomposition method of disassembly steps.
      b, the correct selection of tools and equipment, when first identify the cause decomposition of difficulty, take the appropriate solution, allowed Luanqiao too hard to prevent damage to parts and tools, but  can not use measuring tools, pliers, a hammer instead of hand and cause damage .
      c, in the direction of dismantling provisions, mark the part or assembly, we should remember the clear direction and mark, if the mark loses should be re-marked.
      d, in order to avoid the removed parts are damaged or missing, according to different size and precision parts were stored, according to the demolition order placed, precision important parts specialized storage custody.
      e, remove the bolts, nuts, etc. without affecting the case should be repaired back in place, so as not to lose and easy to assemble.
      f, demand removal, disassembly of the individual can not judge the good from time to disassemble, one can save time and labor, on the other hand to avoid damage during disassembly and lower parts assembly precision. But need to disassemble the parts must be removed, can not be the easy way and sloppy, resulting in repair quality can not be guaranteed.

      2, the mechanical assembly
      Mechanical assembly process is to determine the mechanical repair quality was an important part, it must be done:
      (1) is assembled parts itself must meet the technical requirements, any defective parts are not assembled. So we must go through rigorous testing before assembling the parts.
      (2) must be selected with the correct method to meet the requirements with precision. Mechanical repair is a lot of work to restore mutual mating parts with precision, can take optional, repair, adjustment and other methods to meet this requirement. With the gap to consider the impact of thermal expansion, the fitting of a material consisting of different coefficients of expansion, when the ambient temperature during assembly when the temperature difference between the larger work, and the resulting gap change should be compensated.
      (3) analyze and check the accuracy of the assembly dimension chain by matching and adjustment to meet the accuracy requirements.
      (4) deal with the mechanical assembly sequence, the principle is: after the first period, before tackling the difficult first precision after the general.
      (5) Select the appropriate assembly methods and assembly equipment, tools.
      (6) Note that parts cleaning and lubrication. Assembly parts must first be thoroughly cleaned, for dynamic fitting to be coated cleaning meet the job requirements of the lubricant surface in relative motion.
      (7) Note that the assembly sealed to prevent "leakage of water." To use the provisions of the seal structure and sealing materials, we can not take any substitutes. Pay attention to quality and clean the sealing surface. Note assembly methods and tightness of the seal assembly, may be appropriate for static sealing sealant.
      (8) Note that the locking device assembly requirements, compliance with safety regulations.
      (9) The attention to quality check the middle part of the assembly.

      3, mechanical cleaning and inspection
      (A) Mechanical cleaning
      1, clear oil
      Oil and grease and dust, rust and other adhesive material, it does not integrate into the water, but into the organic agent. In addition to mechanical methods of decontamination, but also removed by chemical or electrochemical method.
      (1) chemical degreasing method:
      1, the organic solvent degreasing: common organic solvents are gasoline, kerosene, diesel oil, acetone.
      2, the alkaline degreasing solution: such as sodium hydroxide, sodium carbonate, sodium silicate and sodium phosphate. Improve the solution temperature and were stirred to speed up the cleaning degreasing effect, generally heated to about 80 ℃, washed with hot water rinse, and dry with compressed air.
      (2), electrochemical degreasing method: mechanical stirring and peeling action when the two electrodes by electrolysis so grease from parts of the bubble surface method called electrochemical degreasing method. The method has speed, high efficiency, oil, etc. thoroughly.

      (B) Mechanical test
      Content inspection as follows:
      1 part inspection
      Including parts of the geometric accuracy tests, such as the size of the parts, shape; parts surface quality inspection: such as surface roughness, surface damage and other defects; mechanical performance test parts: parts such as strength, hardness, parts of balance, stiffness of the spring and the like; parts hidden defect inspection: such as voids, plus slag, microscopic cracks.
      2 assembly inspection
Such as the relative position of parts and components, with the gap member or interference; tied for balance between the shafts, concentricity between the front and rear axles and the like.
      3 whole test
      That test machine inspection machine technology conditions. Including mechanical ability to work, dynamic economic performance, has the following test methods:
      A view method: This method alone seeing, touching hands, ears to test and judge, simple and practical, widely used, can be divided into:
      (1) visual method: surface damage to parts such as rough, grooves, cracks, scratches, flaking (peeling), fracture and deformation parts large and obvious, serious wear, surface annealing and ablation so visually or with a magnifying glass Observation OK. Also like the rigid coupling of film rupture, dislocation elastic coupling, screwed and riveted seal add the film rupture can also be judged visually.
      (2) percussion method: For the chassis Parts obvious cracks in connection with the case bottom bearing alloy tile, etc., can be clear or hoarse by tapping listening to judge good or bad.
      (3) Comparative Law: The new standard parts and components to be detected by comparing the technical condition of the subject to identify parts. As spring free length, chain length, bearing quality and so on.
      Measurement Method B: will cause changes in the size and shape of the parts worn or deformed, or due to fatigue caused by technical properties (such as elastic) decline. It can be measured by measuring tools and instruments and controls allow the standard to determine whether to continue to use, or to be repaired or scrapped. For example bearing clearance measurements, temperature measurements, measuring the amount of wear on the gears, the measurement of the elasticity of the spring and the like.
C Detection method: for hiding defective parts, especially important to detect subtle defects in parts and repairs for ensuring quality and the use of safety significance, must be carefully carried out mainly in the    following ways:

      (1) penetration display method: clean the parts immersed in kerosene or diesel fuel in a moment, remove the surface will dry, sprinkle a layer of talcum powder, and then tapping with a hammer parts of non-face, if the part cracks When, due to vibration so immersed in oil leaking cracks, leaving a crack at the talc appear yellow line marks.

      (2) Fluorescent Display Method: Wash the surface of the part being tested first, irradiation with ultraviolet light warm-up 10 minutes, so that the surface was observed under ultraviolet light purple, then with a fluorescent display was uniformly coated on the surface of the parts work, to display a yellow-green defect marks.

      (3) testing method: magnetic particle inspection, ultrasonic inspection, radiographic inspection. The main components used to determine the internal defects and weld quality