Design of a specialized engine repair facility

Contents

Summary

1. Process layout of the production building

1.1 Definition of Repair Plant Production Program

1.2 Determination of total scope of work

1.3 Repair Process Diagram

1.4 We distribute labor intensity by areas and types of works

1.5 Determination of main parameters of production process

1.6 Calculation and selection of repair and process equipment

1.7 Determination of production building area

2. Work coordination schedule

3. Occupational Safety Design

4. Calculation of energy needs

5.Process Design

5.1 Analysis of working conditions

5.2 Defect Analysis

5.3 Analysis of possible process recovery of the part

6. Technical and economic evaluation of the project

Conclusion

List of used literature

Summary

This course project in the discipline "Engineering of technical service enterprises" on the topic "Designing of a specialized engine repair enterprise" consists of an explanatory note, which includes the following sections:

1) Process layout of the production building.

In the first section we define the production program, the total scope of work, the scheme of the technological process of repair, we distribute labor intensity to the areas and types of work, we select repair and technological equipment, we determine the areas of the production building

2) Design of work approval schedule.

We give the process parameters, draw up a schedule of work approval.

3) Occupational safety design.

4) Energy demand calculation.

We calculate all the energy resources required by the enterprise.

5) Process design.

We carry out analysis of operating conditions, analysis of defects, analysis of possible technological restoration of the part.

6) Technical and economic assessment of the enterprise.

We find indicators of the cost of repair, wages of workers, profit of the enterprise, profitability.

The graphic part consists of 3 drawings of A1 format:

1) Technological layout of the enterprise.

2) Work approval schedule.

3) Part repair drawing.

3. Occupational safety design.

Safety and industrial sanitation requirements. Production, storage and auxiliary rooms shall meet the requirements of SNiP and sanitary design standards of industrial enterprises CH24571.

They provide insulation of premises in which dust, vapors and gases are released according to production conditions. Gas generators must be designed in one-story rooms, with a light roof and located near the external walls.

Doorways of rooms shall have no thresholds and doors shall have windows. Guides for machine wheels are installed on inspection ditches and racks and stairs are equipped on both sides. In niches of inspection pits and ditches there must be low-voltage lighting (voltage is not more than 36 V). Racks shall be equipped with railings not less than 1 m high with side skin not less than 0.15 m high.

Passages between racks, shelves and cabinets in storage rooms shall be not less than 1 m, which ensures free movement of personnel.

In the sanitary sector there should be washbasins and showers with uninterrupted supply of cold and hot water. Washbasins are equipped with electric dryers. Portable lighting luminaires, as well as general lighting luminaires at suspension height less than 2.5 m and in rooms with increased danger must be connected to the network with voltage not higher than 36 V.

Transformers for the lighting network 12... 36 B are used only with separate primary and secondary windings. One of outputs of transformer secondary winding and core are grounded.

Emergency lighting is arranged in the workshops, providing illumination of the passages. The lights are turned on automatically when the working lighting is suddenly turned off.

In garages, sheds and under canopies there should be only a low voltage (12 V) network for connection of portable electric power supplies.

Natural and artificial lighting of production premises and workplaces must be accepted according to SNiP 114-79. Production ,

sanitary and auxiliary rooms are equipped with central heating and ventilation to ensure uniform temperature and air condition. The average internal temperature shall be: for production premises 15 ° С; hot shops 12,.. 14 ° С; administrative public buildings 18... 20 ° С. Thermometers shall be installed to control temperature in all rooms in a visible place at a distance of 15... 20 m from the gates and exit doors.

To provide workers with drinking water, water supply columns with fountain cranes or saturator plants with carbonated water are provided. Enameled tanks with foundry cranes may be installed.

Lifting machines and load-lifting devices shall comply with the requirements of the "Rules for the construction and safety of load-lifting cranes."

Rollers and conveyors, located at a height of more than one meter, are equipped with sides with a height of at least 7z of the height of the transported cargoes.

Suspension conveyors at the places of removal and loading are installed at a height of not more than 1.2 m. The movement of goods on roller tables is allowed provided that the load touches three rollers simultaneously. Small-piece loads are moved on the conveyor in a special container. The distance between the wall and the conveyor is at least 0.8 m.

The conveyors shall have a light and sound alarm which is interlocked with the launcher and provides good visibility and audibility. Stop buttons with interval of not more than 20 m are installed in prominent places for urgent stop of conveyor.

All electrical installations shall be arranged in strict compliance with applicable regulations. Metal parts of electrical equipment (electric motor housings, generators; frames of distribution boards; enclosures of instruments, choppers, magnetic starters; lighting equipment parts; metal insulation of cables; pipes in which wires are located, and other non-energized pipes that may be under it due to failure of parts or elements of installations) are reliably grounded.

In three-phase four-wire networks having direct neutral grounding, all metal parts of installations and devices are connected to zero network wire, and in three-wire networks, metal parts are grounded. The grounding circuit is bolted to the object and welded to the wire.

5. Process design.

5.1 Analysis of operating conditions.

The engine is primarily designed to convert the chemical energy of the fuel into the reciprocating motion of the piston, and then into the rotational motion of the crank gear. The engine is the main mechanism of any car, tractor, etc.

During engine operation, its parts wear out due to friction forces, high temperatures, high pressure, etc.

5.2 Defect analysis.

The main failures of the cylinder-piston group (CPG) are wear of cylinders, pistons (skirt, upper groove of the piston ring, pin hole), piston rings and fingers.

There are often various cracks and holes in the cylinder block as a result of breakage of connecting rods, valves and pistons, as well as violation of the geometry and arrangement of various surfaces - the upper plane of the block and crankshaft beds due to overheating due to insufficient cooling and lubrication.

When repairing the engine, parts of the CPG that have great wear or damage shall be repaired or replaced depending on the size and type of wear for each type of part. Thus, the cylinder block, which is expensive, and for many models and a scarce part, it is necessary to strive to repair regardless of its malfunction.

5.3 Analysis of possible process recovery of the part.

Cylinders and liners wear out mainly as a result of friction of piston rings, action of abrasive particles from cylinder surface and corrosion. The greatest wear in the cylinders in height is observed near the upper dead center. In addition, they wear unevenly around the circle.

Cylinders of autotractor engines are deformed in operation, as a result of which the shape is disturbed. Cylinders are deformed as a result of difference tat, incorrect tightening of studs for unit head attachment, uneven heating, insufficient rigidity of unit walls.

The circumferential wear of the cylinders also depends on the skew of the piston when moving in the cylinder, in the rocking plane of the connecting rod, as a result of which a cutting action of the edges of the piston rings occurs. The wear of the cylinders depends to a large extent on the bends of the connecting rod and the crankshaft, as well as on the distortions in the connecting rod piston group. In these cases, the piston operates skew in the cylinder.

The location of the large axis of the cylinder shaft in the plane of the longitudinal axis of the crankshaft indicates the bending of the connecting rod, the non-rigidity of the crankshaft or the skew obtained during the assembly of the connecting rod with the piston. In addition to wear of the inner working surface, the cylinders have the following defects: due to the nose of the lower surface of the supporting collar and landing belts; cavitation destruction of the outer surface; scale deposition.

The repair technology of cylinders and liners mainly depends on their design. The design of the cylinders of autotractor engines is different. In some engines, the cylinders are cast and bored directly in the block, in others, as cylinders, they are pressed into the holes of the cast iron liner block. All modern tractor, combine and truck engines are usually made with replaceable sleeves.

In order to increase the service life of the engines, the casings are cast from alloyed cast iron SCh 2140 and subjected to surface quenching until a hardness of not less than 40 HRC3 is obtained.

Wear, ovality and conicity of cylinder working surface are controlled by indicator nutrometer NI100160. Wear of support collar is installed by means of caliper. It is 0.08... 0.1 mm.

The wear of landing corbels is determined by measurement of their diameter and ovality by STATE THREADS KI3343 adaptation, by beating of a basic face of the burt and landing corbels of rather internal surface of a sleeve - KI3340 GOSNITI adaptation.

To detect wear, the sleeve (or cylinder) is measured by an indicator nutrometer in two mutually perpendicular planes at a distance of 15... 30 mm from the upper edge and in the middle and the repair size under which the cylinder must be drilled is determined.

To the obtained size of the cylinder in the most worn-out area, two allowances are added for the cutter failure and for subsequent processing. The nearest cylinder repair size must be greater than (or equal to) the design size, i.e.

Dr.p > Drasch = dmax + 2 (a + b),

where dmax is the largest diameter of the worn-out cylinder, mm; a - allowance (0.02... 0.05 mm) for cutter failure; b - allowance (0.02... 0.05 mm) for subsequent processing.

For tractor sleeves, one repair size is adopted, increased relative to the nominal value by 0.7 mm. For car engine cylinders, a larger number of repair sizes are adopted, for example, after 0.5 mm. The industry produces repair pistons and rings corresponding to the repair sizes of liners and cylinders.

Cylinders are repaired by stretching to repair size followed by honing. Inner surface of cylinders and liners is spread on vertical boring machines of models 278 and 279 N.

At bore for repair dimension geometrical shape and cleanliness of engine liner (cylinder) surface are restored. Sleeve in conductor is installed on machine table. Axis of machine spindle is aligned with sleeve axis by means of indicator device. The base for such installation is an unworn cylindrical shoulder of the upper part of the sleeve. After centering, CONDUIT is secured on machine stack.

Cutter is mounted in cutter head.

Sleeves are stretched in one pass in the mode: spindle rotation speed 112 min1, tool supply 0.2 mm/v. The ovality and taper of the part after stretching are no more than 0.04... 0.05 mm, surface roughness Ra = 2.5...... 1.25 μm.

The diameter of the casings of tractor diesel engines after stretching should be, mm: YAMZ240B, YAMZ-238NB, YAMZ740, A-01M, A41 -130.45 + 0.05; D240, D-65- 110.6 + 0.05; SMD80 130.6+0.07; SMD20, SMD-22 - 120.6 + 006; D37M, D-21 - 105.6 + 006.

To increase the productivity and quality of the process, it is recommended to use incisors with elborar inserts to stretch the casings. By stretching the sleeves at a rotation speed of 725 min-1 of the machine spindle, a supply of 0.05 mm/v, and a cutting depth of 0.3 mm, it is possible to obtain ovality and cone-shaped 0.01... 0.03 mm, and Ra < 0.63... 0.32 mm. Honing allowance in this case is only 0.04... 0.05 mm.

After stretching, a honing allowance is left, which is carried out on special machines ZMZZ and ZA83. The sleeve is fixed in a special device (Figure 4.32), which reduces its deformation and increases the accuracy of processing.

Honing of the casings is carried out in three operations (Table 4.3): rough, finished and final .

During finishing honing, surface roughness is reduced and hole geometry is corrected again. The processing allowance is 0.03... 0.04 mm per diameter. The ovality and taper of the hole after finishing honing should be no more than 0.03 mm, the surface roughness should correspond to Ra - 0.4 μm. With final honing, the allowance of 0,005... 0.01 μm is removed, which reduces the roughness to Ra = 0.2...... 0.16 μm.

Process performance and tool stability ensure the use of bars with the following characteristics: for rough processing - A250/200M1 Si; FAIR - ACB100/8MC2; Final - ASM28/20MSA. A mixture of 90% kerosene and 10% spindle oil is used as COG.

The honing mode of non-heated casings differs from the above-mentioned. Allowance on draft honing 0.05... 0.08 mm, on semi-pure - 0.03 mm, on finished - 0,005 mm. The ovality and conicity of the inner surface of the sleeves after final treatment should be no more than 0.02 mm, a Ra < 0.32... 0.16 μm. Clipping of sleeve collar is performed before finishing honing on lathe.

The length of the honing head stroke of £ should be such that the output of the bars K for. cylinder edge was not more than 1/3 of their length t in order to avoid painting of bars and formation of cylinder bell. With a smaller course, barrel-shaped sleeve is observed, and with a larger course, corset.

Length of bars is taken equal to half height of sleeve. The number of bars in the honing head should be such that their total width is at least 20% of the circumference of the sleeve being treated.

All cylinders (or liners) shall be treated to one size within the specified tolerance of the new cylinder.

To obtain a high-quality surface of the cylinder, it is necessary, on the one hand, to make it as smooth as possible, and on the other, as rough as possible, so that the depressions are filled with as much oil as possible. This is achieved using the so-called plane-vertex honing. It is carried out in two stages. At first, with the help of fairly coarse-grained bars (100... 120 μm) create the main surface roughness, at which the depth of the depressions is relatively large and reaches 20... 30 μm. Then, the protrusions are smoothed with fine-grained bars (16... 40 μm), as a result of which support surfaces are formed. The removal of metal at the finishing operation is 3... 5 μm, and the surface profile receives a look close to the profile of the already working surface.

The quality of the obtained surface is characterized by the so-called Abbot curve, which is the dependence of the total area of ​ ​ the depressions on their depth. This curve has a bend at the point separating the support surface from the spine recesses

new roughness. According to experimental data, the support surface should be 50... 80% the entire surface of the cylinder, and at least 0.02 mm3 of oil per 1 cm2 of surface area should be retained in the depressions. For diesel engines, due to the heavier operating conditions of the piston rings, the volume of the depressions can be increased, for example, due to the use of coarser bars when creating basic roughness.

It should be noted that when repairing the cylinders, it is necessary to strive to create even deeper depressions on the surface than could be on the new cylinder. Thus, with a slight increase in the oil consumption of the repaired engine, the lubrication conditions of the rings will be improved. This moment in the repair is often very important. The fact is that piston rings produced by various companies can have various materials, coatings, elasticity, which do not always correspond to the material of a particular cylinder and the operating conditions of the rings in a given engine. Then, improving lubrication reduces the wear intensity of rings and cylinders with a not very successful combination of ring-cylinder pair materials.

The troughs of the main roughness should have not only depth, but also certain opening angles, which are implicitly described by the Abbot curve. The angle of the depression is important for oil retention, and far from always wider depressions with a larger volume hold a larger amount of oil. With a large opening of the angle, the oil "falls" into the depression, and with a small angle due to surface tension, it protrudes above the surface of the cylinder, providing lubrication of the parts.

A very important parameter of the cylinder surface is the honing angle a, that is, the angle between the hairlines formed when the head moves up and down. With low angle, it is not possible to achieve the necessary surface profile, which leads to "dry" friction and gouging of rings and cylinders. A large angle usually requires more oil consumption. The optimal honing angle is usually 60... 75 °.

Cavitation damage is most often eliminated by applying to a pre-prepared and heated surface of an epoxy resin composition to a temperature of 60 ° C. A simpler method of electrocontact welding of steel plate has been developed. Steel plate 10 or 20 0.3 mm thick shall be 5... 10 mm cover the damaged area.

The mounting upper and lower belts are restored by electrocontact welding of the tape, metallization, application of polymer materials, galvanic iron, electrocontact deposition (electro-saturation) of iron-zinc alloy.

Worn end face of support collar is cut until wear marks are removed before last honing operation.

Conclusion

In the course project in the discipline "Design of technical service enterprises," a specialized enterprise for the repair of tractor and car engines was designed, with a total area of ​ ​ 540 m2. When analyzing economic indicators, they came to the conclusion that this enterprise is profitable. The amount of the OPF was - 21,600 000rub. At the same time, the cost of repair was - 6,628 848rub. The payback period of the enterprise is 3.26 years, profitability is 29.8%.