Abstract: The inspection and classification of spare parts is an important process in the overhaul process of diesel generator sets, with a focus on the inspection of measuring tools for spare parts and the detection of shape and position errors of spare parts. The accuracy of the inspection and classification of spare parts will directly affect the repair quality and cost of diesel generator sets. This job requires maintenance personnel to understand the main content of diesel generator parts inspection, be familiar with the common inspection methods for diesel generator set spare parts, and master the basic skills of diesel generator set spare parts inspection.
1、 Quality inspection measures and contents for diesel engine spare parts
1. Measures to ensure the quality of spare parts inspection
The fundamental purpose of spare parts inspection work is to ensure the quality of spare parts. Qualified quality spare parts should have reliable working performance that is compatible with the technical performance of the diesel generator set, as well as a service life that is balanced with other spare parts of the diesel generator set. To ensure the quality of spare parts inspection, the following measures should be implemented and executed.
(1) Strictly grasp the technical standards of spare parts;
(2) Correctly select corresponding inspection equipment and tools according to the technical requirements of spare parts;
(3) Improve the technical level of inspection operations;
(4) Prevent inspection errors;
(5) Establish reasonable inspection regulations and systems.
2. The main content of spare parts inspection
(1) Geometric accuracy inspection of spare parts
Geometric accuracy includes dimensional accuracy, shape and position accuracy, as well as the mutual fitting accuracy between spare parts. The accuracy of shape and position includes straightness, flatness, roundness, cylindricity, coaxiality, parallelism, verticality, etc.
(2) Inspection of surface quality
The surface quality inspection of spare parts includes not only surface roughness inspection, but also inspection for defects such as scratches, burns, and burrs on the surface.
(3) Testing of mechanical properties
Inspection of hardness, balance condition, and spring stiffness of spare parts materials.
(4) Inspection of hidden defects
Hidden defects refer to defects that cannot be directly detected from general observation and measurement, such as internal inclusions, voids, and micro cracks that occur during use. The inspection of hidden defects refers to the inspection of such defects.
2、 Methods for Inspection of Diesel Engine Parts
1. Sensory testing method
Sensory inspection is a method of inspecting and classifying spare parts based on the operator’s visual, auditory, and tactile senses. It refers to a method in which inspectors identify the technical condition of spare parts solely based on visual perception (with little use of inspection equipment). This method is simple and cost-effective. However, this method cannot be used for quantitative testing and cannot be used to test parts with high precision requirements, and requires inspectors to have rich experience.
(1) Visual inspection
Visual inspection is the main method of sensory inspection. Many failure phenomena of spare parts, such as fractures and macroscopic cracks, obvious bending, twisting, warping deformation, surface erosion, abrasion, severe wear, etc., can be directly observed and identified. In the repair of diesel generator sets, this method can be used to detect the failure of various casings, diesel engine cylinder barrels, and various gear tooth surfaces. The use of magnifying glasses and endoscopes for examination results in better results.
(2) Auditory testing
Auditory testing is a method of detecting defects in spare parts based on the operator’s auditory ability. During inspection, tap the workpiece to determine if there are any defects in the spare parts based on the sound. When striking flawless components such as shells and shafts, the sound is very clear and crisp; When there are cracks inside, the sound is hoarse; When there are shrinkage holes inside, the sound is very low.
(3) Tactile testing
Touch the surface of the spare parts with your hand to feel their surface condition; Shake the mating parts to feel their fit; Touching parts with relative motion by hand can sense their heating situation and determine whether there are any abnormal phenomena.
2. Instrument and tool inspection method
A large amount of inspection work is carried out using instruments and tools. According to the working principle and types of instruments and tools, they can be divided into general measuring tools, specialized measuring tools, mechanical instruments and meters, optical instruments, electronic instruments, etc.
3. Physical testing method
The physical inspection method refers to the inspection method that uses physical quantities such as electricity, magnetism, sound, light, and heat to detect the technical condition of spare parts through the changes caused by the workpiece. The implementation of this method should be combined with instrument and tool inspection methods, and is often used to inspect hidden defects inside spare parts. This type of inspection has no damage to the parts themselves, so it is called non-destructive inspection. Non destructive testing has developed rapidly in recent years, and currently, various methods widely used in production include magnetic powder method, penetration method, ultrasonic method, etc.
3、 Inspection of wear and tear of diesel engine spare parts
There are many components that make up a diesel generator set, and although various types of spare parts have different structures and functions, their wear patterns and empirical methods are basically the same. The size and geometric shape of diesel generator spare parts change due to working wear. When the wear exceeds a certain limit and continues to be used, it will cause significant deterioration in machine performance. During the repair process of diesel generator sets, strict inspection and determination of their technical condition should be carried out in accordance with the diesel engine repair technical standards. For different types of spare parts, the inspection methods and requirements vary due to the different wear parts. The wear of spare parts can be divided into shell type, shaft type, hole type, gear tooth shape, and other parts of wear.
1. Inspection methods for the quality of shell type spare parts
The cylinder block and pump body shell are both shell type components, which are the framework of diesel generators and the basis for assembling various assembly components. The damage that this component is prone to during use includes cracks, damage, perforation, thread damage, twisting deformation of the joint plane, and wear of the hole wall. The inspection method for these components is generally visual inspection combined with necessary measuring tools.
(1) Inspection of cracks.
If there are significant cracks in the components of the diesel generator set casing, they can generally be observed directly with the naked eye. For smaller cracks, the crack location can be detected by tapping and listening to the sound changes. Alternatively, a magnifying glass or immersion display method can be used for inspection.
(2) Inspection of thread damage.
The damage at the threaded opening can be detected visually. If the thread damage is within two buckles, repair is not required. For the damage to the threads inside the bolt hole, a bolt rotation test can be used to match it. In general, the bolt should be able to be tightened to the bottom without any looseness. If there is a jamming phenomenon during the process of rotating the bolt, it indicates that the thread in the bolt hole is damaged and should be repaired.
(3) Inspection of hole wall wear.
When the wear on the hole wall is significant, it can generally be observed with the naked eye. For cylinder inner walls with high technical requirements, cylinder gauges or inner micrometers are generally used for measurement during maintenance work to determine their out of roundness and cone diameter.
(4) Inspection of wear of shaft holes and hole seats.
There are two methods for checking the wear between the shaft hole and the hole seat: trial fitting method and measurement method. When there is certain wear between the shaft hole and the hole seat, the corresponding spare parts can be used for trial fitting inspection. If it feels loose, you can insert a feeler gauge into it to determine the degree of wear.
(5) Inspection of joint plane warping.
By interlocking two matching spare parts together, such as the cylinder block and cylinder head, the degree of distortion and warping of the cylinder block or cylinder head can be determined. Place the parts to be tested on the platform or flat plate, and measure them from all sides with a feeler gauge to determine the degree of warping of the parts.
(6) Inspection of axis parallelism.
After deformation occurs in the use of shell components, sometimes their axis parallelism may exceed the technical standards specified for spare parts. Currently, there are two methods for detecting axis parallelism: direct measurement and indirect measurement. The method of measuring the parallelism of the axis of the bearing seat hole. This method directly measures the parallelism of the axis of the bearing seat hole.
(7) Inspection of coaxiality of shaft holes.
To test the coaxiality of the shaft hole, a coaxiality tester is generally used. When measuring, it is necessary to make the spherical axis head on the equal arm lever touch the inner wall of the measured hole. If the axis hole is different, during the rotation of the centering axis, the spherical contact on the equal arm lever will move radially, and the amount of movement will be transmitted to the dial gauge through the lever. The value indicated by the dial gauge is the coaxiality of the axis hole. At present, in order to improve the accuracy of axial coaxiality, manufacturers generally use optical equipment such as collimating tubes and telescopes to measure axial coaxiality. Measurement of coaxiality between collimator and telescope optics
(8) Inspection of axis verticality.
When testing the verticality of the axis of shell components, an inspection instrument is generally used for inspection, as shown in. When the handle is turned to drive the plunger and measuring head to rotate 180 °, the difference in the dial gauge reading is the verticality of the cylinder axis to the main bearing seat hole axis within a length range of 70mm. If the length of the vertical hole is 140mm and 140 ÷ 70=2, the difference in the dial gauge reading must be multiplied by 2 to determine the verticality of the entire length of the cylinder. If the length of the vertical hole is 210mm and 210 ÷ 70=3, the difference in the dial gauge reading must be multiplied by 3 to determine the verticality of the entire length of the cylinder.
3. Inspection of hole type spare parts
The inspection items for holes vary depending on the working conditions of spare parts. For example, the cylinder of a diesel generator not only wears unevenly on the circumference but also along the length direction, so its roundness and cylindricity need to be inspected. For bearing seat holes and front and rear wheel bearing seat holes, due to the short depth of the holes, only the maximum wear diameter and roundness need to be measured. The tools used for measuring holes include vernier calipers, inner micrometers, and plug gauges. The cylinder gauge can be used not only to measure cylinders, but also to measure various medium-sized holes.
4. Inspection of tooth shaped parts
(1) The outer and inner teeth of gears, as well as the key teeth of spline shafts and taper holes, can all be considered as tooth shaped parts. The main damages to the tooth profile include wear along the tooth thickness and length directions, peeling of the carburized layer on the tooth surface, scratches and pitting on the tooth surface, and individual tooth breakage.
(2) The inspection of the above-mentioned damage can directly observe the condition of the damage. The area of pitting and peeling on the general tooth surface should not exceed 25%. The wear of tooth thickness mainly depends on the assembly clearance not exceeding the allowable standard for major repairs, generally not exceeding 0.5mm. When there is obvious stepped wear, it cannot be used again.
(3) When inspecting, first observe whether there are any fractures, cracks, grooves, spots, or peeling of carburized and quenched layers on the surface of the gear teeth and key teeth, and whether the end of the gear teeth and key teeth H has been ground into a cone. Then measure the tooth thickness D and the tooth length E and F using a gear caliper.
(4) For involute gears, the wear of the gear can be determined by comparing the length of the common normal of the measuring gear with the length of the common normal of the new gear.
5. Inspection of other worn parts
(1) Some spare parts do not have a shaft, hole, or tooth shape, but rather a special shape. For example, the cam and eccentric wheel of the camshaft should be inspected according to the specified outer dimensions; The wear degree of the conical and cylindrical surfaces of the intake and exhaust valve heads, as well as the valve stem end, is generally determined by observation. If necessary, special sample gauges can be used for inspection.
(2) Some spare parts are a combination and are generally not allowed to be disassembled for inspection. For example, for certain rolling bearings, the first step is to conduct a visual inspection, carefully observe the inner and outer raceways and the surface of the rolling element. The surface should be smooth, the contact should be even, without cracks, pinholes, spots, and scale like delamination. There should be no annealing color, and the cage should not be broken or damaged. The clearance of rolling bearings should meet technical requirements, and their axial and radial clearances can be checked by hand feeling. The bearing should have no jamming phenomenon, but rotate uniformly, with a uniform sound response and no impact sound.
Summary:
The cleaned diesel generator parts should be inspected according to technical requirements, and classified into three categories: usable parts, parts that need repair, and scrapped parts. This process is called part inspection and classification. Usable parts refer to parts that have some damage, but their size and shape position errors are within the allowable range, meet the technical standards for major repairs, and can still be used; Repaired and scrapped parts refer to non usable parts that have exceeded the allowable range of damage, do not meet the technical standards for major repairs, and cannot continue to be used. If the parts cannot be repaired or the repair cost does not meet the economic requirements, such parts are considered scrap parts; If the technical standards for diesel generator set overhaul can be achieved through repair, and the service life is guaranteed to meet economic requirements, these parts are the parts that need to be repaired.
https://www.eaglepowermachine.com/super-silent-diesel-industry-generator-set-product/
Post time: Mar-04-2024