Diesel engine unsealing In order to prevent the diesel engine from rusting, when the product leaves the factory, both inside and outside is sealed with oil. Therefore, after the new unit is installed and meets the installation requirements, it must be unsealed before it can start. Otherwise, it will cause the danger. So it should be taken seriously. The steps to remove the oil seal are as follows: 1) Heating the diesel above 45 ℃ to 56 ℃for cleaning and removing the external anti-rust oil. 2) Heating water aover 90 ℃, then continuously pouring water through the water jacket outlet, flowing out from the plug assy Irain (or water pump inlet) on the side of the cylinder body, continuously for 2--3 hours, and rolling the crankshaft discontinuously to make the anti-proof oil of piston top, cylinder liner surface and elsewhere dissolves and flows out. 3) Clean the oil sump with clean diesel oil and replace it with new oil. Cooling and fuel system, fuel injection speed regulation system, water pump and starting drive system should be cleaned and checked in accordance with the requirements of the instructions, and sufficient clean cooling water should be added, starting batteries should be fully charged, and preparations should be made for the start up of the machine. Inspection before the genset has a test 1. Inspection procedures 1) Check whether the surface of the unit is clean. The anchor nut, flywheel screw and other moving parts are not loosened. It must be fastened if any problems found. 2) Check whether the clearance of each part is correct, especially check the intake & exhaust valve clearance to make sure it meets the requirements. 3) Put each cylinder in the pressure reducing position, rotate the crankshaft to check if there is any abnormal sound in the operating sound of the cylinder parts, and whether the crankshaft rotates freely. At the same time, pump the engine oil into the friction surface. Then, close the pressure - reducing device, shake the crankshaft, and check the cylinder for air leakage. If the crankshaft is very difficult to shake, it indicates that the compression is normal. 4) Check fuel supply system, steps are as follows: ① Check whether the venthole on the fuel tank cover is smooth and clean if there is dirt in the hole. Whether the diesel added meets the required brand number, whetehr oil mass is adequate, and turn on the oil circuit switch. ② Open the mechanism of decompressor to shake the crankshaft. If each cylinder has a clear injection sound, it indicates that the injection is good. Whereas, there may be air in the oil line. This moment, you should rotate the fuel filter and injection pump air bleed screw to eliminate the air in the oil line. ③Check whether there is oil leakage in the oil pipe and joint, and deal with the problems in time if found. 5) Check water cooling system, procedures are as follows: ①Check whether the cooling water in the tank is sufficient. If the water is insufficient, clean soft water should be added. ②Check whether there is water leakage in the joint pipe and solve the problem in time. ③Check that the impeller rotation of the cooling water pump is flexible and the belt is tight and appropriate. When checking whether the belt is tight, push the middle of the driving belt. It is suitable if the driving belt is pressed down 10-15mm. 6) Check lubricating system ①Check the oil pipe and pipe joints for oil leakage and solve the problem in time ②Check the oil mass of the oil pan, draw out the oil dipstick next to the crankcase, observe whether the height of the oil surface is in accordance with the rules, otherwise, add oil to the diesel engine, add No.8 or 11 engine oil in winter, and add No.14 oil in summer. Check again, if found that the oil surface height is above the normal, should be carefully analyzed the reasons for the increase in oil, usually there are three reasons. a. Add too much oil b. Diesel oil leaks into the crankcase and dilutes the oil. c. The cooling water leaked into the oil. 7) Check starting system a. First, check whether the specific gravity of starting system is within the range of 1.240 ~ 1.280. If the specific gravity is less than 1.180, it indicates that the battery power is insufficient. b. Check whether the power line is correct. c. Check whether there is contamination or oxidation on the battery terminal, it should be cleaned up. d. Check whether the electric contact of starting motor and electro-magnetic control is good.
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This post is mainly written to introduce how to adjust crosshead, injector and valves of Cummins NT diesel engines correctly. Pay attention to reading and you will learn more. Crosshead Adjustment Note: Crosshead adjustment should always be made before attempting to adjust the valves. 1. Loosen the locknut on the crosshead adjusting screw. Turn the adjusting screw out at least one turn. 2. Hold the crosshead down against its mating valve stem. Turn the adjusting screw back in until it touches the valve stem. Hold the adjusting screw in this position and tighten the locknut. 3. Tighten the adjusting screw locknut to 25 to 30 ft-lb [34 to 41 N*m] torque. Note: When ST-669 Torque Wrench Adapter is used, tighten the locknut to 22 to 26 ft-lb [30 to 35 N*m] torque. 4. Check the clearance between the crosshead and valve spring retainer 1 and 2. Fig. 2-19 with a wire gauge. Tighten must be a minimum of 0.025 inch [0.64 mm] clearance. Valve Adjustment The “VS” markets used when adjusting the injectors is also used when adjusting the valves; however, the valves to be adjusted are not on the same cylinder as the injector. See Table 2-3 for the correct valves to adjust. Example: When 1-6 “VS” is used, the injector on cylinder number 3 is adjusted and the valves on cylinder number 5 are adjusted. 1. Loosen both locknuts on the intake and exhaust valve adjusting screws. 2. Insert the proper feeler gauge between the rocker lever and crosshead contact surfaces. (Fig.2-20). See Table 2-9 for valve clearance valves. 3. Turn the adjusting screw down until the rocker lever just touches the feeler gauge. Hold the adjusting screw in this position and tighten the locknut to 40 to 45 ft-lb [54 to 61 N*m] torque. Note: When ST-669 Torque Wrench Adapter is used, tighten the locknut to 35 to 40 ft-lb [47 to 54 N*m] torque.
Adjust Injector and Valves (Torque Method For Top-Stop Injector Engines) Timing Mark Alignment 1. Loosen the injector rocker lever adjusting nut on all cylinders. This will aid in distinguishing between cylinders adjusted and not adjusted. 2. Bar the engine in the direction of rotation until a valve set mark aligns with the mark or pointer on the gear case cover. 3. Check the valve rocker levers on the two cylinders aligned as indicated on the pulley. On one cylinder of the pair, both rocker levers will be free and the valves closed; this is the cylinder to be adjusted. 4. Adjust the injector plunger first, then the crossheads and valves to the clearances indicated in the following paragraphs. 5. For the firing order see Table 2-5 for Inline Engines. 6. Continue to bar the engine to the next “VS” mark and adjust each cylinder in the firing order. Note: Only one cylinder is aligned at each mark. Two complete revolutions of the crankshaft are required to adjust all cylinders. Injector Plunger Adjustment The injector plungers must be adjusted with an inch-pound torque wrench to a definite torque setting. A torque wrench with a screwdriver adapter can be used for this adjustment. Turn the crankshaft in the direction of rotation until one of the “VS” marks are aligned with the pointer. Check both of the cylinders indicated on the pulley to see which valve rocker levers, this is the cylinder to be adjusted. 1. Turn the adjusting screw down until the plunger contacts the cup and advance an additional 15 degrees to squeeze the oil from the cup. 2. Loosen the adjusting screw one turn; then using an inch torque wrench with screwdriver adapter tighten the adjusting screw to the valve shown in Table 2-6 and tighten the locknut to 40 to 45 ft-lbs [54 to 61 N*m] torque. If ST-669 Torque Wrench Adapter is used, torque to 30 to 35 ft-lbs [41 to 47 N*m]. Crosshead Adjustment Crossheads are used to operate two valves with one rocker lever. The crosshead adjustment is provided to assure equal operation of each pair of generator set valves and prevent strain from misalignment. Valve Adjustment The same engine position used in adjusting the injectors is used for settings the intake and exhaust valves. Adjust the injectors and the valves on the same cylinder at the same time. 1. While adjusting the valves, make sure that the compression release, on those engines so equipped, is in the running position. 2. Loosen the locknut and back off the adjusting screw. Insert a feeler gauge between the rocker lever and crosshead. Turn the screw down until the lever just touches the gauge and lock the adjusting screw in this position with the locknut. Tighten the locknut to 40 to 45 ft-lbs [54 to 61 N*m] torque. When using ST-669 torque to 30 to 35 ft-lbs [41 to 47 N*m]. 3. Always make final valve adjustment at stabilized engine lubricating oil temperature. See Table 2-7 for the appropriate valve clearances. 1. Each component of the gas generator set must be maintained in accordance with the method and time specified in the manual. No maintenance exceed the time limit or improper maintenance method will lead to the performance of the unit decline, and even cause serious accidents. 2. When carrying out maintenance on the generator set, care should be taken to prevent the cotton yarn from being caught in the rotating parts, and the protective net is no exception. 3. Gas pipelines, valves, flanges, joints, etc., should be inspected regularly. There should be no gas leakage or damage. There should be no accumulation around the valve that interferes with the operation of the valve. The valve should be opened and closed regularly for maintenance. If the valve is unable to open or close, it should be repaired or replaced in time. 4. The hose on the gas pipeline should be replaced regularly. It is strictly prohibited to use expired and aging rubber hose. In particular, the rubber pipe connected with the supercharger (specific to individual models), such as aging will cause gas leakage, which will lead to fire explosion and other serious accidents. 5. Regularly check the cable connections for tightness or insulation. 6. When operating, maintaining and repairing the gas gen sets and gas pipelines, the gas source must be reliably cut off and the internal gas should be blown clean. No gas supply shall be restored to the gas facility until the cause of the accident is ascertained and necessary safety measures are taken. When performing maintenance and overhaul, explosion-proof measures or explosion-proof tools shall be taken. It is strictly forbidden to use tapping tools such as irons. 7. The emergency repair of gas leakage should be carried out after reducing the gas pressure or cutting off the gas source. When the leakage place has been burned, the measures should be taken to control the fire and then reduce the pressure or cut off the gas source. Negative pressure in the pipeline is strictly prohibited. 8. It is strictly forbidden to use electric welding on gas generating set to avoid the spark ablation alloy layer caused by the bearing bush gap. In special cases where welding must be used, the ground wire should be connected to the welded parts, and the ground wire must be connected before the bearing bush to ensure that the current does not pass through the bearing pad. 9. When the engine is in normal working condition or when the temperature of the body and cylinder head is high, cold water is strictly prohibited. Otherwise, the body and the cylinder head will crack under the sharp change in temperature, causing serious accidents, and make the body, cylinder head scrapped. 10. Due to the influence of environmental and interference signals, sometimes unit false alarm and shutdown will appear. The operating personnel must not remove the protection device casually, otherwise, engine racing will occur, causing malignant accidents such as pull shaft, top cylinder, broken rocker arm, broken connecting rod, broken piston, broken cylinder, and broken body. 11. Electric butterfly valve (or solenoid valve) damage should be timely repaired and replaced, can not be tied! Otherwise, it will also cause engine racing, resulting in malignant accidents. 12. All seal parts are strictly forbidden to be opened during use. 13. The fusible and explosive diaphragm of each explosion-proof device must be used in accordance with the technical design requirements, and materials shall not be replaced or thickened at will. 14. It is strictly forbidden to dismantle and unload the parts of the gas generator set. When it is necessary to disassemble the inspect, you should carefully read the instructions of relevant parts, understand and master its internal structure and working principle, clarify the disassembly, inspection, assembly procedures and related technical requirements and precautions, and carefully operate according to the specified procedures and requirements. Parts that have an impact on various technical parameters (such as valve clearance, ignition advance angle, etc.) must be re-inspected and adjusted after disassembly. 15. Electronic governor, generator voltage regulator, monitor and other components have been adjusted by the technical service personnel of the factory. Unless new parts are replaced, the user shall not change the parameter settings at will. 16. When the gas genset is not in use for long time, it shall be sealed up. Before the new machine exceeds the storage period or is re-enabled after long-term storage, a comprehensive inspection must be carried out. Usually, open the cylinder head, check the internal condition of the cylinder liner, move the turbocharger turbine, check the turbine rotation, and carry out the insulation inspection to the generator, etc. If there are obvious corrosion, moisture and other abnormal conditions, must be completely dismantled, it can be used after the treatment is completed and maintenance is qualified. Bonding Repair Method For Diesel Generator Set Spare Parts The method of repairing or connecting the failed parts of the diesel generator set by applying the adhesive and restoring the function of the parts is called the bonding repair method. In recent years, bonding repair technology has developed rapidly and has been widely used in the repair of diesel generator set. The following describes in detail the electroplating repair method of the diesel generator set parts - the characteristics of the bonding process. 1. Unlimited by materials, all kinds of the same or different materials can be bonded. 2. The bonding process temperature is not high, it will not cause changes in the metallographic structure of the base metal and thermal deformation, and will not cause cracks and other defects, so that it can adhere to cast iron parts, aluminum alloy parts, thin parts, small parts and the like. 3. The strength of the original is not damaged during bonding, and local stress concentration is not easily generated. Compared with riveting, threaded connection and welding, the structure quality is reduced by 20%-25%, and the surface is beautiful and flat. 4. The process is convenient, the cost is low, and the construction period is short, which is convenient for on-site repair. 5. The glue joint has the properties of sealing, abrasion resistance, corrosion resistance and insulation, and some also have heat insulation, moisture proof and shockproof performance. The glue between the two metals also prevents electrochemical corrosion. The disadvantages are: high temperature resistance (generally only 150 ° C, up to 300 ° C, except for inorganic glue); poor impact resistance, peeling resistance, anti-aging properties; low bonding strength (compared with welding and riveting); The inspection is more difficult. Therefore, it is necessary to fully understand the characteristics of the bonding process, and rationally select the bonding agent and bonding method to make full use of it in the repair work. Bonding Method 1. Hot melt bonding The method uses electric heating, hot gas or frictional heat to heat and melt the bonding surface, and then superimposes and adds sufficient pressure until it cools and solidifies. Mainly used for bonding between thermoplastics, most thermoplastic surfaces can be bonded by heating to 150~230 °C. 2. Flux bonding method Non-finished amorphous thermoplastics, joints plus simple solvents or plastic-containing solutions melt the surface to achieve bonding days. 3. Adhesive bonding method Adhesives are used to bond two materials or two parts together to achieve the desired strength. The method is the most widely used and can bond a variety of materials such as metals and metals, metals and non-metals, non-metals and non-metals. There are many types of adhesives, and there are many classification methods. According to the chemical composition of the adhesive, it can be divided into organic adhesive and inorganic adhesive; it is divided into natural adhesive and synthetic adhesive according to the source of raw materials; it is divided into structural adhesive and non-structural according to the strength characteristics of the bonded joint. The adhesive is divided into a liquid adhesive and a solid adhesive according to the state of the adhesive; the shape of the adhesive is powder, rod, film, paste and liquid; and is classified into a thermoplastic adhesive according to thermal properties. Thermosetting adhesives, etc. The natural adhesive composition is simple, and the synthetic adhesive is mostly composed of a plurality of components. Additives such as a curing agent, a plasticizer, a toughening agent, a diluent, a filler, a coupling agent, a solvent, an antioxidant, and the like are usually added to a base material of a natural material or a polymer material having viscosity and elasticity. Whether or not these additives are added depends on the nature of the adhesive and the requirements of use. Synthetic adhesives can be further divided into thermoplastics (such as acrylates, cellulose polyphenols, polyimides), thermosets (such as phenolic, epoxy, polyester polyurethanes), rubbers (such as chloroprene, butyronitrile), and blends. Type (such as phenolic-butyronitrile, epoxy-polysulfide, phenolic-nylon). Among them, epoxy resin adhesive has strong bonding ability to various metal materials and non-metal materials, and has good water resistance, organic solvent resistance, acid and alkali resistance and corrosion resistance, small shrinkage, and electrical insulation. Good performance and the most widely used. Bonding process 1. Selection of the agent When selecting the adhesive, the material of the bonded material, the force and the environment to be used are mainly considered, and the shape, structure and process possibility of the bonded member are comprehensively considered, and the cost is low and the effect is good. 2. Joint Design When designing the joint, the bonded joint should be subjected to or subjected to shearing force as much as possible; the peeling and uneven pulling force should be avoided as much as possible; the bonding area should be increased as much as possible to improve the bearing capacity of the joint; Practical, economical and reliable. For parts that are impacted or subjected to large forces, appropriate reinforcement measures such as riveting, threaded connections, etc., may be employed. 3. Surface treatment The goal is to obtain a clean, rough, and active surface to ensure that the bonded joints are identical. It is the most important process in the entire bonding process and is related to the success or failure of bonding. For surface cleaning, remove the dust with a dry cloth or cotton yarn, remove the thick grease, and then wipe with an organic solvent such as acetone, gasoline or trichloroethylene, or degrease with oil. The rust and oxidation treatment layer is removed by boring, grinding, roughing, sand blasting, electric sparking, etc., and the surface can be roughened. Among them, sandblasting works best. The surface roughness of the metal parts should be mechanically treated with Ra12.5um, and then the surface should be cleaned and dried for use. If necessary, a uniform, dense oxide film can be obtained by chemical treatment to ensure a firm bond between the bonding surface and the adhesive. Chemical treatment generally uses pickling, anodizing, and the like. When steel, iron and natural rubber are bonded, copper and iron can be copper-plated to greatly improve the bonding strength. 4. Glue Different coating methods should be selected according to the different forms of the adhesive. For liquid glue, brush coating, spraying, and roller coating can be used. When applying glue, care should be taken to ensure that the glue layer is free of air bubbles and uniform without lack of glue. The amount of glue applied and the number of times of glue application vary depending on the type of glue, and the thickness of the glue layer should be thin. For most adhesives, it is advisable to control the thickness of the adhesive layer in the range of 0.05~o.2mm. 5. open assembly The adhesive containing the solvent should be left to dry for a certain period of time after the glue is applied, so that the solvent in the adhesive layer is sufficiently volatilized, otherwise bubbles are generated in the adhesive layer after curing, and the bonding strength is lowered. The length of the open time, the temperature is different from glue, should be strictly controlled according to their respective regulations. 6. Curing The two bonded parts that are left open can be used for closing, assembly and heating, and pressure curing. Except for the room temperature curing glue, almost all other glues need to be heated and cured. Even if it is a room temperature assimilated adhesive, increasing the cultivating temperature is beneficial to the bonding effect. Slowly heat up and cool down during curing. When the temperature is raised to the flow temperature of the adhesive, it should be kept at this temperature for 20~30 minutes, so that the glue is fully diffused and wetted on the bonding surface, and then raised to the desired temperature. Curing temperature, pressure and time should depend on the specific type of adhesive. An oven, an infrared lamp, an electric furnace, and electric induction heating can be used for heating. 7. Quality inspection The quality inspection of bonding parts is both destructive and non-destructive. The destructive test measures the breaking strength of the bonding member. Non-destructive testing is commonly used in actual production. It is generally tested by observing the appearance and the method of tapping the sound. The accuracy depends largely on the experience of the inspector. In recent years, some advanced technologies such as acoustic resistance, laser holography, and X-ray inspection have also been used for non-destructive testing of bonded parts, and great progress has been made. 8. Post-bonding processing Some bonding parts are bonded to the technical requirements by machining or bench work. The necessary chamfering and grinding should be carried out before processing, and the cutting force and cutting temperature should be controlled during processing. Fault diagnosis and troubleshooting method Generator overheating (1) The generator does not operate in accordance with the specified technical conditions, such as too high stator voltage, iron loss increases; if the load current is too large, the copper loss of the stator winding increases; if the frequency is too low, the cooling fan speed becomes slow, affecting the heat dissipation of generator; the power factor is too low, so that the rotor excitation current increases, resulting in the rotor heating. Check whether the indication of monitoring instrument is normal. If it is abnormal, necessary adjustment and treatment must be carried out to operate the generator in accordance with the specified technical conditions. (2) The three-phase load current of the generator is unbalanced, and the overloaded one-phase winding will overheat; if the difference of three-phase current exceeds 10% of the rated current, it is a serious phase current imbalance, and the three-phase current imbalance will generate negative sequence magnetic field, which will increase the loss and cause heating of components of magnetic pole winding and hoop. The three-phase load should be adjusted to keep the phase current as balanced as possible. (3) The air duct is blocked by dust accumulation, and the ventilation is poor, which results in the difficulty of generator heat dissipation. Dust and oil dirt should be removed from the air duct. (4) If the inlet air temperature is too high or the inlet water temperature is too high, the cooler will be blocked. The inlet or inlet temperature should be lowered to remove blockages in the cooler. Generator load should be limited to reduce the generator temperature before failure is eliminated. (5) Grease should be added to the bearing according to the regulations, usually 1/2~1/3 of the bearing chamber (the upper limit of the low speed, the lower limit of the high speed), and not more than 70% of the bearing room is suitable. (6) Bearing wear. If the wear is not serious, the bearing is partially overheated; if the wear is severe, the stator and the rotor may be rubbed, causing the stator and the rotor to overheat. The bearing should be inspected for noise. If friction between stator and rotor is found, generator should be stopped immediately to repair or replace the bearing. (7) The insulation of the stator core is damaged, which causes short circuit between the sheets, resulting in local eddy current loss and heating, and the stator winding will be damaged if it is serious. Machine should be shut down immediately for maintenance. (8) The parallel wires of the stator windings are broken, causing the current of other wires to increase and heat up. The machine should be stopped immediately for repair. 2. The generator neutral line has abnormal voltage to the ground. (1) Under normal circumstances, due to the influence of high harmonics or manufacturing process, the air gap under each magnetic pole is uneven and the magnetic potential is unequal, and the voltage is low. If the voltage is in the range of one to several volts, there will be no danger, do not have to deal with. (2) The generator winding has short circuit or poor insulation to the ground, which leads to the deterioration of electrical equipment and generator performance, easy to heat. It should be repaired in time to avoid accidents. (3) Neutral line has no voltage to ground at no load, and voltage occurs when there is load. It is caused by three-phase unbalance, and the three-phase load should be adjusted to make it basically balanced. 3. Generator current is too large. (1) If the load is too large, the load should be reduced. (2) If the transmission line has short circuit or grounding fault, the line should be overhauled and restored to normal after troubleshooting. 4. The generator terminal voltage is too high. (1) If the grid voltage of generator parallel to the power grid is too high, and the voltage of parallel generator should be reduced. (2) If the fault of excitation device causes overexcitation, the excitation device should be repaired in time. 5. Insufficient power Since the voltage source compound excitation compensation of the excitation device is insufficient, the excitation current required for the armature reaction cannot be provided, so that the generator terminal voltage is lower than the grid voltage and the rated reactive power cannot be delivered. The following measures should be taken: (1) A three-phase voltage regulator is connected between the generator and the excitation reactor to increase the terminal voltage of the generator, so that the magnetic potential of the excitation device is gradually increased. (2) Change the phase between the voltage magnetic-flux potential of the excitation device and the terminal voltage of the generator to increase the total magnetomotive force. Several thousand ohms and 10W resistors can be connected in parallel at both ends of each phase winding of the reactor. (3) The resistance of the varistor is reduced to increase the excitation current of the generator. 6. Stator winding insulation breakdown, short circuit (1) The stator winding is damped. For generators that have been stopped for a long time or overhauled for a long time, the insulation resistance should be measured before putting into operation. Those who are not qualified are not allowed to put into operation. The damp generator should be dried. (2) The winding itself is defective or improperly repaired, resulting in winding insulation breakdown or mechanical damage. The insulation material should be selected according to the specified insulation grade, the embedded winding and the dipping paint should be strictly carried out in accordance with the technical requirements. (3) The winding is overheated. Insulation overheating will reduce insulation performance, and sometimes the insulation breakdown is quickly caused at a high temperature. Daily inspection should be strengthened to prevent the generator parts from overheating and damaging the winding insulation. (4) Insulation aging. Generally, generator runs for 15 ~ 20 years, winding insulation aging occurs, electrical performance changes, and even make insulation breakdown. If the insulation is found to be unqualified, replace the defective winding insulation in time to prolong the service life of the generator. (5) Metal foreign matter enters the inside of the generator. After repairing the diesel generator, do not leave the metal objects, parts or tools in the stator; tie the binding wire of the rotor and fasten the end parts so as not to be loosened by centrifugal force. 7. The stator core is loose. The core is not fastened due to improper manufacturing and assembly. If the whole core is loose, for small generators, two iron plates smaller than the inner diameter of the stator winding end can be used to tighten the iron core by putting on double head bolts. After the original shape is restored, the original clamping bolt of the iron core is tightened. If the local iron core is relaxed, silicon steel sheet paint can be applied between the slack sheets, and then insert a hard insulating material into the slack parts. 8. Short circuit between iron chips 1) The iron core lamination is slack. When the generator is running, the iron core vibrates to damage the insulation; if the insulation of the iron chip is damaged or the core is partially overheated, it will cause insulation aging. (2) There is a burr on the edge of the iron chip or mechanical damage during maintenance. Use a fine boring tool to remove the burrs, repair the damage, clean the surface, and then apply a layer of silicon steel paint. (3) If there is solder or copper particles short iron core, the metal welding joint should be scraped or cut off to deal with the surface. (4) The arc short circuit occurs in the winding, which may also cause the short circuit of the iron core. The burned part should be removed with a chisel and the surface should be treated. 9. The generator loses remanence and cannot generate electricity when starting. (1) Remanence is often lost after shutdown, because the material used in the magnetic pole of the exciter is close to the soft steel, and the remanence is less. The magnetic field disappears when there is no current in the excitation winding after shutdown. A battery should be provided to magnetize before generating electricity. (2) The magnetic pole of the generator loses its magnetism, and a DC current (in a short time) larger than the rated current should be applied to the winding for magnetization, that is, sufficient remanence can be restored. Selection Principle of Repair Technology for Diesel Generator Set 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. 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. The oil delivery pump of diesel generator set is single acting piston type. It is mounted o n the side of the fuel injection pump of the diesel generator set and is driven by an eccentric wheel on the injection pump shaft. Its function is to inhale fuel from the tank and supply enough fuel to the diesel generator injection pump with a certain pressure. Before starting the diesel generator set, pump the oil with the hand pump on the oil pump and remove the air from the oil circuit. It can smoothly absorb the fuel within 1 m below the center of the pump in 0.5min. The handle nut must be fastened after the pump oil. The technical specifications of the diesel generator pump are shown in figure 1. The 4 and 6 cylinder B series and B series enhanced fuel injection pumps use roller pumps, as shown in figure 2a. The 12-cylinder B series fuel injection pump is equipped with two rolling wheels, the oil pump on the left and right sides of the inlet and outlet oil pipe joint and a hand pump mounted separately on the front end of the diesel engine block, as shown in figure 2b/c/d. The matching clearance between the piston and the housing of the oil pump is 0.005-0.02 mm. If the gap is too large, the fuel supply rate will decrease. The jacking rod and the jacking sleeve of the rolling wheel oil pump are also paired and the gap is too large and there are also the disadvantages of oil leakage. Hand pump piston and hand pump body between the rubber sealing device, unless the rubber ring in the hand pump damage, generally should not be removed. The 12 cylinder V diesel generator has no rubber seal for the hand pump. It is sealed by matching clearance (not greater than 0.02mm). The working principle of the oil pump is shown in figure 3. when the roller and the ejector rod of the oil pump are in the lowest position of the eccentric wheel of the fuel injection pump, the fuel in the upper chamber of the piston is squeezed out because the piston is driven upward by the action of the spring. Then the one-way valve on the oil outlet side closes and the fuel is sent to the fuel filter, and a space is formed in the lower chamber of the piston. The one-way valve on the oil inlet side is opened to absorb the fuel, as shown in figure 3a. the cycle is constant, the fuel is inhaled and discharged. When the oil pipeline resistance is increased to the same oil pressure at both ends of the piston, the piston is no longer in balance with the rod movement, and the oil pump stops working. As shown in figure 3 c. Oil pump maintenance Oil pump is an important component in diesel generator to support combustion power generation. Once failure occurs, it will lead to problems such as coke deposition, insufficient combustion, blocking and so on. So it reminds genset users to pay attention to the maintenance of oil pump is also an important task. 1. Before installing the oil pump, check whether the type and specifications are correct. The thickness of the gasket should be suitable to prevent the piston from dying or running out of place because it is too thin or too thick. Tighten the bolt when the toque to be uniform, to prevent damage to the oil pump. 2. There is rubber seal between the piston and the body of the hand oil pump in the oil pump. Do not remove it at will. The rubber ring should be replaced in time if it is damaged. 3. The coarse screen core in the connection of oil pump is easy to be clogged by dirt such as cotton flor, so it must be checked and cleaned 4. The hand oil pump must be pressed back to tighten the button to prevent air intake or oil leakage caused by the pressure off the pump and rubber ring or between the ball valve and the valve seat. The parts should be inspected after long time use of the pump of the diesel generator set. The points for attention are as follows. 1. If the plane of the one-way valve is worn, sunken and pockmarked, the grinding paste shall be used to grind on the flat plate. As the following figure, serious should be replaced. 2. The surface of the one-way seat on the shell should be replaced when worn seriously or unevenly. 3. The wear between the top rod and the top rod sleeve is so serious that the clearance increases, the seal becomes worse and the diesel oil leak is too serious, it must be replaced together with the shell. Optionally increase the size of the rod, but with the shell replacement, or with the size of the rod, subject to mutual research. 4. The coarse filter core in the oil inlet joint is easy to be blocked by cotton wadding, which affects the oil supply. Therefore, it is necessary to pay attention to the cleaning of fuel and the removal of dirt on the filter core. 5. When the rubber ring of the piston pump is damaged, it should be replaced in time. The leakage of the piston of the hand pump used in the 12 cylinder V diesel generator set indicates that the matching surface is worn and the clearance is enlarged, which needs to be rescheduled. Generator parts such as piston for oil conveyance in diesel generator set after reassembly. In the whole process should be good activity, no block and stuck phenomenon, pressure pump should be light and flexible. The one-way valve spring must be accurately embedded in the spring slot when installing the one-way valve spring. Analysis and treatment method if common faults of oil transmission pump of diesel generator set. Many diesel generators ignore the maintenance of oil pump in operation. In fact, oil pump is an important part of generator. Once the fault occurs, the diesel oil circulation in the low pressure oil circuit will be affected, thus affecting the normal operation of the diesel generator set. 6.1 General Provisions Good maintenance and repair, the key of the long-term service life of the generator set, should be carried out by the qualified technical personnel. Good record shall be made in case of maintenance and repair, which will be helpful to arranging the working procedures of maintenance and repair for diesel generator set in the future. In general, the generator set shall be kept clean without liquids such as: fuel oil or lubricating oil piled up on any internal or external surfaces and on the surface of, under and around the sound absorption (if the device is available) materials. The industrial water solvent shall be used to clean the surface of the machine, but the flammable solvents can not be used for cleaning. For instance, the protection of the sound absorption material is torn down or penetrated, it should be replaced immediately so as to prevent the liquid or oils penetrated and accumulated on the material. 6.2 Preventative Maintenance For the situations of the use of generator set is not the same, the requirements for maintenance are different. For the detailed maintenance of the diesel engine, please refer to Manual for Diesel Engine. For it is associated with this chapter, the use shall read the relevant parts to practice by combining this chapter. The maintenance work can be performed more frequently than that according to the requirements of this chapter. 6.2.1 Daily maintenance and after-star-up maintenance per time: for the prepared generator set, these procedures can be performed once to visually check the surrounding area of the machine before start-up per time or day. The check before start-up specified in section 5.2 shall be performed here at the same time. For the check procedures of the diesel engine, please refer to Manual for Diesel Engine, in which the requirements can be seen the supplement of the section 5.2. 6.22 Check (referring to the reserve machines not always started) the machine every two weeks and start the machine to run for five minutes. WARNING! Do remember not letting the diesel machine run under low load. 6.2.3 Check (referring to the reserve sets running without load increased) and start the machine to make run for five minutes and increase at least 50% load to run for 1-2 hours every month. 6.2.4 Check every 6 months or 250 hours: 1. Check the protective devices of the control system by adopting fault simulation method. 2. Clean the exhaust hole. 3. Tighten all connectors of the exhaust pipe 4. Tighten all connects of the electrical equipment. 5. Perform other special maintenance of the diesel machine listed in the Manual for Diesel Machine. 6. Observe all instruments on the control screen to see if the running is normal after starting the machine. 6.2.5 Preventative maintenance of alternator: it’s not necessary to perform daily maintenance of the alternator but it is required to check and clean the coil of the alternator regularly. Please to refer to the maintenance of alternator and Alternator Manual specified in section 8.2. 6.2.6 Preventative maintenance of alternator: in line with the requirements provided by the Manual for Diesel Engine, read this manual and perform frequent maintenance to maintain its highly efficient performance. 6.3 Dismantlement of Generator and Alternator Dismantlement of diesel engine or alternator shall be started according to the following procedures: 1. Dismantle the circuit from power supply to the auxiliary equipment (such as: hot water jacket). 2. Disconnect the circuit for battery charging and battery wire (firstly dismantle the cathode), and move battery if necessary. 3. Provided that the generator has cap, then it is necessary to loosen the bolts fixed at each side of the cap, dismantle the exhaust pipe, and then move the cap away. 4. When dismantling the control screen, it’s necessary to dismantle all lines & bearers and fully ensure all the lines can be connected again. 5. If the diesel engine and alternator are dismantled, the rings of the diesel engine and alternator can be used to life them independently. But the bolts fixed at their chassis initially. 6.3.1 Only Dismantle Diesel Engine 1. In case of only dismantling the diesel engine, the hose pipe of the circuit on the diesel engine shall be dismantled initially. 2. Provided that the only foot of alternator is at the chassis, the front end of the alternator shall be stationed well by using the bearer when dismantling the diesel engine. 3. Removing the chassis bolt on the diesel engine and loosening the fixed bolt of the alternator might be helpful to dismantling diesel engine. 4. Remove the protection cover of the fan of alternator. 5. Use lifting hook or wooden bearer to hold it up, be careful and don’t destroy fan blade. 6. Dismantle the diesel engine and alternator 7. Use the elevated crane or similar devices to lift it at the end of the diesel engine. 8. Dismantle the bolt of joint shell. 9. Now, move the generator forward until it is completely separated from alternator and the chassis can be lifted away. 6.3.2 Only Dismantle Alternator 1. In case of only preparing to dismantle alternator, then it is necessary to station the rear part of the diesel engine firmly. 2. Dismantle hose pipe of the circuit. 3, Dismantle the bolts fixed the chassis of the generator. 4. To dismantle the protective cover the alternator fan, it is necessary to firmly station the front part of the generator. Use a bar to fix the central line at the bottom firmly. In doing so, it is restrained from shifting to the gas gap to prevent the axis and magnetic coil from being destroyed. 5. Dismantle the alternator from the diesel engine according to the descriptions specified in section 6.3.1. 6. Use crane or similar devices to lift the alternator, and make the overall alternator slide back to chassis and then lift it away. |
作者
dieselgenerator 存档
July 2022
类别 |