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Selection Principle of Repair Technology for Diesel Generator Set

Oct. 17, 2018

I Reasonable process and technology

The reasonable selection of repair technology is an important problem in the maintenance of diesel generator sets, especially when there are many kinds of damage forms for one part or several repair processes can be used for one damage form. It is more necessary to select the best repair technology of diesel generator set.

Selection Principle of Repair Technology for Diesel Generator Set.jpg


1. Working conditions


The repair process should be different for load, speed, temperature, lubrication, fit, medium between working surfaces, etc. 


For example, the crack between the cylinder valve ports is generally bonded; the crack between the rear axle and the gearbox housing and the bearing housing hole cannot be repaired by bonding. The crack between the cylinder head valve door is not repaired by the general bonding method because of the high working temperature, but it needs to be combined with the inorganic bonding agent by the planting wire and the perforation, or repaired by the welding repair method. The surface of the sliding-fit parts is subject to high contact stress. Only chrome plating, spray welding, surfacing and other processes can be satisfied; parts subjected to impact loads should be spray-welded or surfacing.


2. Degree of wear


The thickness of the repair layer to be compensated varies from part to part due to the different degree of wear. Therefore, it is necessary to grasp the thickness of the repair layer that can be achieved by various repair processes. When the diameter of the part is more than 1 mm, it is obviously not suitable to use chrome repair.


3. Spear part feature


It includes parts materials, dimensions, structures, shapes, and heat treatments. 


For example, the spraying process has a wide application range on the material of the parts, and is suitable for most ferrous metals and alloys; it is difficult to spray a few non-ferrous metals and alloys (copper, tungsten alloy, molybdenum alloy, etc). Mainly because of the high thermal conductivity of these materials, the spray material is not suitable for spray welding. Ductile iron crankshafts have poor weldability, and just surfacing repairs are not as good as plasma spray or low temperature iron plating.


The dimensional structure and heat treatment characteristics of the part itself limit the adoption of certain processes. For example, parts with smaller diameters are not suitable for submerged arc surfacing and metal spray repair; flat spray coatings are used to repair lower bonding strength. Repairing parts by surfacing will inevitably destroy the heat treatment of the parts. When the threaded car on the shaft is small, it is necessary to consider whether the screwing of the nut is limited by the large size of the nearby shaft diameter; the bearing hole of the motor end cover is worn and should not be repaired by the insert method.


4. Precision and performance


The repair process has different effects on the precision and mechanical properties of the parts. The hardness, workability, wear resistance, compactness and precision of the repair layer should be considered in selecting the repair process. For example, to maintain the lubrication performance of the wear-in surface and improve the wear resistance of the parts, porous chrome plating, iron plating, spray coating, vibration surfacing and the like can be employed. Electroplating, spraying, bonding and other processes have little effect on the structure of the parts, and the deformation by heat is also small. However, arc welding, gas welding, surfacing welding and so on, because of the change of metal structure and mechanical properties in the HAZ at high temperature, it is only suitable for the parts which need to be processed and shaped after welding, not quenched and heat treated after welding.


II Economical


The so-called economic cost-effective means that not only the direct consumption of the process is considered, that is, the repair cost is low, and the service life of the diesel generator set parts must also be considered. Usually used to compare:


S (repair) / T (repair) ≤ S (New) / T (New)


S repair-the cost of repairing old parts

T repair-part repair life, h or km

S New-Manufacturing cost of New parts

T New-the Life of New parts


The above formula shows that if the repair cost per unit service life of the diesel generator unit is lower than the manufacturing cost per unit service life of the newly manufactured part, the selected repair process can be considered to be economical. However, take into account the lack of spare parts and stop production due to economic losses. Even if the repair cost is high, if the overall economic analysis can be taken, it should not be restricted by the above formula. Although the repair cost is very high, the service life of some processes is much longer than that of new ones, so it should also be considered as an economical process.


III Increased efficiency and production possibilities


The two principles of reasonable and economical efficiency in the selection principle of diesel generator set repair process have been introduced. The two principles of reasonable and economical efficiency in the selection principle of diesel generator set repair process have been introduced.


1. Efficiency improvement


The production efficiency of diesel generator repair process can be expressed by the sum of each working procedure time from beginning to end. The longer the total time, the lower the process efficiency. Taking the repair technology of wheel flange as an example, the steel ring made by inlaid welding or forging welding requires a lot of equipment and low production efficiency from ring making to assembly welding. By using surfacing method to repair and omit the two processes of gas cutting and welding steel ring and melt the metal wire directly on the flange, the efficiency is improved, and the mechanical properties of wheel are also improved.


2. Production possibility


When selecting the repair process of diesel generator set, we should pat attention to the existing production conditions, repair technology level, cooperative environment, and consider the feasibility of the repair process. At the same time, efforts to create conditions, constantly update existing repair technology, promote and adopt advanced repair technology. In a word, when selecting the repair technology of diesel generator set, we should not only consider the problem from one aspect but also make comprehensive analysis and comparison to determine the optional scheme, until the process is reasonable, the economy is economical and the production is possible.


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