Reconstruction of the engine section - diploma

2.1 SELECTION OF INITIAL DATA

 The rolling stock of Kamdorstroy Autobaz 48 CJSC includes a large number of cars  of various brands. To simplify the calculation, all cars are divided into technologically compatible groups and each group takes the predominant brand.

In accordance with the Regulation on the maintenance and repair of  rolling stock of road  transport  , based   on data on the zoning of   the country's territory by climatic areas, we define the climate as temperate-cold. Category III operating conditions.

2.2 CALCULATION OF PRODUCTION PROGRAM FOR MAINTENANCE AND MAINTENANCE

2.2.1 Adjustment of standard periodicity of maintenance and resource mileage

The production program of CJSC "Kamdorstroy Autobaz 48" for maintenance is characterized by the number of technical services planned for a certain period of time.

Seasonal maintenance (CO), carried out 2 times a year, is usually combined with TO-2 or TO-1 and is not taken into account as a separate type of planned service when determining the demand program.

For TR performed on demand, the number of impacts is not determined.

The production program for each maintenance type is calculated for 1 year. The program serves as the basis for determining the annual volumes of maintenance and maintenance work and the number of workers      .

To calculate the program, it is previously necessary to select standard values ​ ​ of rolling stock mileage before decommissioning and standard values ​ ​ of periodicity TO-1 and TO2, which are set for certain conditions.

For a particular ATP, the conditions may differ, therefore, in the general case, the normalized estimated resource mileage Lp and periodicity TO-1 and TO-2 Li are corrected using coefficients .

2.6 TECHNO-ECONOMIC ASSESSMENT 

The final stage of the design is the analysis of technical and economic indicators, which is carried out in order to identify the degree of technical excellence and economic feasibility of the developed design solutions of ATP. The effectiveness of the project is assessed by comparing its technical and economic indicators with normative ones, as well as with indicators of the reconstructed ATP.

To assess the results of technological design, technical and economic indicators have been developed for various road transport enterprises. In particular, the following technical and economic indicators are established for autonomous ATPs: the number of production workers and work posts per 1 car, the area of ​ ​ production storage, administrative and household premises per 1 car (in m2), the parking area for 1 storage place (in m2), the area of ​ ​ the enterprise for 1 car (in m2).

Technical and economic indicators represent specific values ​ ​ of the norms of the number of industrial workers, posts, areas of industrial and administrative-domestic premises for the most characteristic (reference) conditions.

CONCLUSIONS ON SECTION

In order to determine the conformity of project and normative indicators, their comparison and assessment of the discrepancy of results were carried out. The process calculation as a whole complies with the requirements of ONTP, since the deviation of the calculated indicators from their reference values ​ ​ does not exceed ± 15%, but for two indicators (the area of ​ ​ production, warehouse and administrative and household premises) there is a deviation of more than 15%. This is due to the design and construction of the enterprise in stages from the beginning of the 70s to the present day. The same is due to the shape of the territory of the enterprise.

Analysis of the state of the production and technical base of CJSC "Kamdorstroy Autobaz 48" shows that the working areas and sections are not sufficiently equipped with the necessary technological equipment, tools, devices, and production areas are irrationally used. All the above indicates the need to reconstruct the enterprise.

Section 3 technical design of the engine section

3 Technical design of the engine section

3.1 Characteristics of the engine section

The engine section is an important link of ongoing repair. This section is intended for high-quality and timely repair of engines and its mechanisms and systems. If increased fuel consumption is detected in the engine, noise increases, there is a drop in traction qualities, acceleration and non-uniformity of its operation, then the car is installed in the area of ​ ​ post TR. In the area of post TR, the engine is removed and transported to the engine section (Figure 3.1).   

The engine section is located in production building No. 1. To perform the production process of engine repair, TR area and mechanical section are located in this housing.

Disassembly, washing, adjustment and control operations on engines are performed on the engine section. Disassembly and assembly works are performed on specialized stands providing free access to the engine to be repaired.

Engine removed from car for repair is subjected to external washing. After external washing, the engine is installed on the bench for its complete or partial disassembly. Lifting and transportation equipment is used to move the engine in the section.

In accordance with the specification for control and defects, the parts are sorted into suitable, unsuitable and requiring repair. Using a measuring tool and special devices, deviations in geometric dimensions and shape of parts are determined, comparing the results with the specifications. Signs of unsuitability of parts for their further use are the presence of burrs, cracks, dents, traces of corrosion. Unsuitable parts are replaced by new parts, suitable parts are installed on the engine, and parts requiring repair are restored in the locksmith-mechanical section.

Then engine is assembled. The final stage is the adjustment, running-in and testing of the engine.

3.2 Engine section after reconstruction

As a result of the analysis of the state of the engine section, shortcomings in the layout and the need for a complete replacement of technological equipment and organizational equipment were revealed. According to ONTP and VSN, the following requirements are imposed on the layout of the engine section:

The motor section may be arranged separately or in a common room.

As part of the engine section, a room for washing the engine and parts should be allocated.

The engine run-in and test room shall be allocated.

A parcel may not have walls or partitions up to the entire height of the space.

Installation of equipment shall be carried out taking into account the necessary safety conditions, convenience of maintenance and installation of equipment.

Taking into account these requirements and the production process of the engine section, the following measures for its reconstruction are proposed:

Organize a washing department with modern equipment.

Remove the internal partition.

Pick up new technological equipment and organising equipment.

Replace crane beam.

To perform the production process on the engine section, the necessary technological equipment and organizational equipment were selected.

3.4 Engine run-in and test

Engine run-in after overhaul is necessary for engine preparation for operation by running-in of friction surfaces of mating parts, inspection of repair quality, detection of defects, determination of engine power and economic parameters. 

The performance of internal combustion engines depends on the mode of its first hours of operation. If the assembled engine is fully loaded at the beginning of its operation, premature wear of the friction surfaces is inevitable with the appearance of clearances on them due to the presence of traces of machining. As a result, considerable specific loads occur on the friction surfaces. To reduce these loads, the surfaces of the parts need to be treated together. Engine is prepared for operation at full load by its preliminary run-in, in the process of which loads are gradually increased on mating parts as they are mutual run-in. For 

All newly manufactured or repaired internal combustion engines are the first mandatory process. As studies show, the complete run-in of parts lasts a long time, sometimes measured in tens of hours. But this process is uneven. The main run-in takes place in the first hours of operation of the engine. 

The engine run-in is also designed to verify the correct assembly and installation of individual units and the engine as a whole, the timely elimination of detected defects before testing and commissioning of the engine. Running-in is carried out according to a special program, which takes into account the nature of the repair, the running-in capacity of the antifriction alloy of bearings and the method of loading the engine .

Rolling is carried out not only for repaired engines, but also for newly installed engines, if their assembly was carried out at the installation site .

The engine shell consists of the following stages:

- cold running-in of the engine by rotating it with an electric motor or another engine.

- engine hot run-in at idle and under load.

- engine acceptance.

Engine run-in is caused by the need to prepare the engine for the perception of operational loads and increase its durability. In the process of running-in, the quality of friction surfaces of the parts is improved, which helps to increase their wear resistance, fatigue strength and corrosion resistance.

At the same time, defects indicating certain deviations from the technical conditions for restoration of parts or assembly of the engine are detected during the run-in.

In the process of running-in, the microgeometry of the friction parts changes significantly. The initial roughness of the surfaces of the parts resulting from their machining is smoothed during the run-in, in fact, the bearing surface of the contact of the parts increases.

 The smooth working surfaces of the parts resulting from the run-in are known to be more wear resistant. In addition, with smooth surfaces, friction losses and the possibility of jamming and gouging decrease. New microgeometry of friction part surfaces, 

installed as a result of running-in is the most favorable (optimal) for further operation and reliability of the engine. The surface roughness obtained as a result of machining of the parts affects the nature and duration of the running-in process and the amount of wear of the parts during this period.

Various methods are used to improve the workability of friction surfaces. Thus, the piston rings are electrolytically tinned or phosphated. The thickness of the coating layer is 5-10 μm. The surface coatings of the piston rings improve the surface quality of the cylinders and rings, thereby increasing their wear resistance and preventing the appearance of hairlines and gags.

Chemical coatings are created on the surface of rubbed parts

 thin porous film, which holds lubricant well during the first period of running-in and easily breaks down to powdery state. The powder-like mass impregnated with oil fills the gap between the piston and the cylinder, preventing rubbing surfaces from appearing and improving their quality.

Improved running-in of the cylinder-piston group of domestic engines is achieved by tanning or phosphating of all piston rings except the upper one. The upper piston ring in all engines, and in the ZIL 130 engine, both upper rings are covered with porous chromium.

The best results are in the run-in with sulfur oil. The addition of sulfur to oil in an amount of 0.8-1.2% accelerates the process of running-in and improves the surface quality of conjugated parts. The duration of run-in on hay oil is reduced by 2-5 and even by 6-8 times. Wear of friction surfaces is reduced by 1.2-1.5 times compared to run-in on  oils

without sulfur additive. The reduction in the duration of the run-in is explained, first, by the proppant action of sulfur molecules adsorbed in the ultramicrotracks of the surface layers of the metal of rubbing bodies, second, by the formation of sulfides FeS, FeS2, etc. Proppant action of sulfur molecules penetrated into microcracks accelerates and facilitates formation of plastic deformation of metal surface layers. On the other hand, due to the high temperatures occurring in the microprotrusion sections, as a result of the high specific pressures, sulfur actively enters the chemical compound with the metal, forming sulfides. The thickness of the sulfide films is 60-120 μm or more. Sulfide films help to more easily deform the microprotrusions of the metal surface layers and reduce the run-in time. The run-in occurs at lower values ​ ​ of the friction coefficient, there are no metal setting phenomena due to the fact that the oil film is more firmly retained on sulfide films than on the metal surface. Under these conditions, the abrasive is also softened 

action of wear products. As a result, wear and tear is significant

 reduced in comparison with run-in on uncoated oils.

Well affects engine run-in disulfide molybdenum. Parts coated with disulfide molybdenum film have wear of 2-3 times less than wear of parts not coated with M0S2 at higher surface roughness. The duration of the run-in depends on the quality of the previous machining, the quality of the assembly, the mode of friction in the run-in (crankshaft speed) and, as indicated, the physical properties and quality of the lubricants.

Running in one continuous mode is not reliable because it does not fully prepare the part for operation under operating conditions. The resulting microgeometry of the surface will correspond only to this friction mode and, when it changes, the microgeometry of the friction surfaces of the part will also change. 

Oil viscosity is also important for the quality of engine run-in. The oil used for the run-in must have not only good lubricity but also good cooling of the rubbing surfaces. For this reason, oil with a reduced viscosity in the range of 20-32 cSt (20-32 μm * m2/s) at a temperature of 50 ° C should be used for the run-in.

During the first period of run-in, a significant amount of wear products in the form of metal particles, which are not captured by fine filters, enters the oil. Wear products fall with oil on the rubbing surfaces of the parts and worsen the run-in conditions. Therefore, it is desirable to supply oil to the engine lubrication system with a special pump from a separately installed oil tank during the first period of run-in. In this case, the oil entering the engine must be pre-cleaned 

cotton filters with large filtering 

ability. With this system, stability of purity, temperature and viscosity 

oil is achieved due to continuous filtration, cooling and change of oil in engine. 

During hot run-in, the operation of the valve mechanism, ignition, oil and water pumps, the presence of knocks and noises, the density of connections, etc., is checked, the temperature of the oil entering and leaving water is controlled. The oil temperature of the tested engine shall not exceed 85 ° C, and the inlet water temperature shall be within 70-80 ° C.

Engine testing is an experimental determination of the values ​ ​ of parameters and indicators of product quality during operation or when simulating operating conditions, as well as when reproducing certain effects on products according to a given program.

Conclusions under section

This section analyses the state of the engine section. In accordance with the standards of ONTP, VSN and taking into account production 

process is proposed to plan the reconstruction object. The necessary technological equipment and organizational equipment are selected. A refined calculation of the area of ​ ​ the engine section was made. Possible engine failures and methods of their elimination are considered.