Issues related to the major overhaul of gas generators
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Our company has a single-stage 2.6m gas generator that has been in use for 1.5 years and now requires major maintenance; please help provide a maintenance plan and approach.
For a 2.6m furnace that has been in operation for 1.5 years and is now undergoing maintenance, after shutting down the furnace it is necessary to inspect the closed-loop assembly and the large gear ring at the furnace bottom; replace worn-out components such as steel balls if needed. Additionally, check the wear level of the furnace grates as well as the refractory bricks at the furnace bottom.
1. Inspect the furnace bottom, jacket, ash bin, ash plow, furnace grates, ash tray, steel balls, and the pipes above and below. 2. Weld and repair the gas cleaning box and cyclone dust collector, and replace the air ducts. 3. Inspect the valve station and all oil pipelines, and maintain the valves and cylinders.
I recommend that you obtain a maintenance plan from the manufacturer, as they have a great deal of experience.
When designing and installing a gas generator, it is advisable to establish corresponding maintenance procedures; you can also search on Baidu for maintenance procedures related to such gas generators, as there are quite a few available.
The grates, jackets, and ash scoops of various sizes must be inspected; the hydraulic system needs to be cleaned, as well as the ash tray at the bottom of the furnace – unless it’s made of tofu!
Here is another version with all items included (this is what we do by principle): 3 Maintenance Procedures 3.1 Preparatory work before maintenance 3.1.1 For maintenance tasks that involve electric or gas welding, a fire permit must be obtained. 3.1.2 Measure the gas concentration inside and outside the furnace; maintenance can only be carried out once the standards are met. 3.1.3 When maintaining related pipes and valves, they must first be purged and inspected using steam. 3.1.4 The maintenance site should be equipped with complete fire prevention tools and facilities. 3.2 Quality Standards for the Maintenance of the Generator Furnace
Serial Number | Item | Maintenance Quality Standards
1 | Generator Furnace Body | Horizontal tolerance: less than 0.2 mm/m; Deviation from the center line: less than 0.3 mm
2 | Ash Pan | Horizontal tolerance: less than 0.2 mm/m; Deviation from the center line: less than 0.1 mm
3 | Top Cover and Outer Shell | Tolerance for the center line of the top cover and outer shell: ±2 mm; Tolerance for the center line of the furnace shell and grate: ±5 mm; Vertical tolerance of the furnace shell: 2 mm over the entire length; Horizontal tolerance of the top cover: less than 1 mm/m; Tolerance for the elevation of the furnace outlet and the inlets of the double vertical pipes: ±2 mm
4 | Water-Cooled Jacket | Horizontal tolerance of the water jacket: less than 1 mm/m; Vertical tolerance of the water jacket: less than 2 mm; Tolerance for the center line of the water jacket relative to the reference center line: less than 2 mm. The interior of the water jacket and steam drum should be clean, and the steam and water pipelines should be unobstructed. Accessories such as the steam drum level gauge and safety valve should be functional and reliable.
5 | Ash Pan and Ash Knife | Fill the ash pan with water, rotate it once, and if no leakage occurs within 24 hours in a stationary state, it is considered qualified. When the ash pan rotates, the minimum distance between the edge of the ash pan and the edge of the pillar should be greater than 5 mm. The distance from the lower end of the ash knife to the bottom surface of the ash pan should be greater than 30 mm. The installation angle of the ash knife should be correct.
6 | Grate | Eccentricity tolerance of the grate: 150 ± 10 mm. Each layer should be properly assembled and fit together tightly, with the center bolts tightened. There should be no cracks or damage on the surfaces of each layer. The ventilation gaps between layers should not be blocked.
7 | Ball Bearings | Elevation tolerance of the ball ring: ±2 mm; Tolerance for the center line of the lower ball ring relative to the reference center line: ±1 mm; Horizontal tolerance of the lower ball ring: less than 0.5 mm/m. The lower ball ring can be installed without shims. The diameter of the balls should be checked, with a tolerance of ±0.10 mm. Appropriate lubricating grease should be applied to the balls and the grooves in the ball rings.
8 | Ash Pan Transmission Mechanism | Horizontal tolerance of the motor and reducer housing: less than 0.2 mm/m; Horizontal tolerance of the worm: less than 0.2 mm/m. The clearance between the worm and the worm gear teeth should be 6–8 mm, while the lateral clearance should be 3–4 mm. The transmission should be smooth. The clearance between the shaft and the bearing should be between 0.05–0.21 mm.
9 | Blower Box | No leakage should occur at any connection points. Tolerance for the clearance between the blower box and the inner wall of the water seal: ±5 mm.
3.3 Types and Frequency of Generator Furnace Repairs
Repair Type | Frequency | Main Tasks
Minor Repair | Every 3–6 months | Check and adjust the travel of the coal feeder; inspect and repair the water seal at the furnace bottom; check the coal distribution tray and coal stop plates; clean the water-cooled jacket and the drain pipe of the steam drum; inspect and clear the pressure measurement pipes at the furnace outlet and at the furnace bottom; clean the furnace outlet pipe, blower box, and bell valve; check the wear condition of the grate and ash knife.
Major Repair | Every 6–12 months | Includes all tasks specified for minor repairs; check and replace the grate; replace the water seal at the furnace bottom; refill the refractory material in the top cover; replace the furnace outlet pipe; inspect and clean the hydraulic systems of the coal feeder and slag remover; check and adjust the wear of the ratchet mechanism; check and replace the nozzles of the double vertical pipes; replace the insulation layer on the furnace body and pipes; inspect and weld any defects in the furnace skirt.
Overhaul | Every 1–2 years | Includes all tasks specified for major repairs; check and measure the thickness of the steam drum and water-cooled jacket, and perform flaw detection and repairs; check and replace the top cover of the furnace; check and replace the double vertical pipes; check and replace the ash pan and ash knife at the furnace bottom; calibrate safety valves and various instruments; check and measure the wear of the balls and ball rings; check and adjust the levelness of the lower ball ring; check and replace the double bell valves and bell valve; check and replace the furnace skirt; check and adjust the verticality of the furnace body.
3.4 Safety Precautions During Maintenance:
3.4.1 It is prohibited to use flammable liquids such as gasoline, kerosene, or alcohol to clean the equipment. If cleaning is necessary, the components to be cleaned should be removed from the equipment and cleaned outside. 3.4.2 When maintaining, inspecting, or shutting down the equipment in use, repair personnel must contact the relevant duty officers and make proper arrangements before proceeding. 3.4.3 At the hot work site, combustible materials should be removed and fire extinguishing equipment should be prepared. 3.4.4 When performing maintenance on the equipment while it is in operation, care should be taken to use copper tools for hammering; if iron tools are used, glycerin must be applied to them. Welding must be carried out using electric welding only, and gas welding is not permitted.
Serial Number | Item | Maintenance Quality Standards
1 | Generator Furnace Body | Horizontal tolerance: less than 0.2 mm/m; Deviation from the center line: less than 0.3 mm
2 | Ash Pan | Horizontal tolerance: less than 0.2 mm/m; Deviation from the center line: less than 0.1 mm
3 | Top Cover and Outer Shell | Tolerance for the center line of the top cover and outer shell: ±2 mm; Tolerance for the center line of the furnace shell and grate: ±5 mm; Vertical tolerance of the furnace shell: 2 mm over the entire length; Horizontal tolerance of the top cover: less than 1 mm/m; Tolerance for the elevation of the furnace outlet and the inlets of the double vertical pipes: ±2 mm
4 | Water-Cooled Jacket | Horizontal tolerance of the water jacket: less than 1 mm/m; Vertical tolerance of the water jacket: less than 2 mm; Tolerance for the center line of the water jacket relative to the reference center line: less than 2 mm. The interior of the water jacket and steam drum should be clean, and the steam and water pipelines should be unobstructed. Accessories such as the steam drum level gauge and safety valve should be functional and reliable.
5 | Ash Pan and Ash Knife | Fill the ash pan with water, rotate it once, and if no leakage occurs within 24 hours in a stationary state, it is considered qualified. When the ash pan rotates, the minimum distance between the edge of the ash pan and the edge of the pillar should be greater than 5 mm. The distance from the lower end of the ash knife to the bottom surface of the ash pan should be greater than 30 mm. The installation angle of the ash knife should be correct.
6 | Grate | Eccentricity tolerance of the grate: 150 ± 10 mm. Each layer should be properly assembled and fit together tightly, with the center bolts tightened. There should be no cracks or damage on the surfaces of each layer. The ventilation gaps between layers should not be blocked.
7 | Ball Bearings | Elevation tolerance of the ball ring: ±2 mm; Tolerance for the center line of the lower ball ring relative to the reference center line: ±1 mm; Horizontal tolerance of the lower ball ring: less than 0.5 mm/m. The lower ball ring can be installed without shims. The diameter of the balls should be checked, with a tolerance of ±0.10 mm. Appropriate lubricating grease should be applied to the balls and the grooves in the ball rings.
8 | Ash Pan Transmission Mechanism | Horizontal tolerance of the motor and reducer housing: less than 0.2 mm/m; Horizontal tolerance of the worm: less than 0.2 mm/m. The clearance between the worm and the worm gear teeth should be 6–8 mm, while the lateral clearance should be 3–4 mm. The transmission should be smooth. The clearance between the shaft and the bearing should be between 0.05–0.21 mm.
9 | Blower Box | No leakage should occur at any connection points. Tolerance for the clearance between the blower box and the inner wall of the water seal: ±5 mm.
3.3 Types and Frequency of Generator Furnace Repairs
Repair Type | Frequency | Main Tasks
Minor Repair | Every 3–6 months | Check and adjust the travel of the coal feeder; inspect and repair the water seal at the furnace bottom; check the coal distribution tray and coal stop plates; clean the water-cooled jacket and the drain pipe of the steam drum; inspect and clear the pressure measurement pipes at the furnace outlet and at the furnace bottom; clean the furnace outlet pipe, blower box, and bell valve; check the wear condition of the grate and ash knife.
Major Repair | Every 6–12 months | Includes all tasks specified for minor repairs; check and replace the grate; replace the water seal at the furnace bottom; refill the refractory material in the top cover; replace the furnace outlet pipe; inspect and clean the hydraulic systems of the coal feeder and slag remover; check and adjust the wear of the ratchet mechanism; check and replace the nozzles of the double vertical pipes; replace the insulation layer on the furnace body and pipes; inspect and weld any defects in the furnace skirt.
Overhaul | Every 1–2 years | Includes all tasks specified for major repairs; check and measure the thickness of the steam drum and water-cooled jacket, and perform flaw detection and repairs; check and replace the top cover of the furnace; check and replace the double vertical pipes; check and replace the ash pan and ash knife at the furnace bottom; calibrate safety valves and various instruments; check and measure the wear of the balls and ball rings; check and adjust the levelness of the lower ball ring; check and replace the double bell valves and bell valve; check and replace the furnace skirt; check and adjust the verticality of the furnace body.
3.4 Safety Precautions During Maintenance:
3.4.1 It is prohibited to use flammable liquids such as gasoline, kerosene, or alcohol to clean the equipment. If cleaning is necessary, the components to be cleaned should be removed from the equipment and cleaned outside. 3.4.2 When maintaining, inspecting, or shutting down the equipment in use, repair personnel must contact the relevant duty officers and make proper arrangements before proceeding. 3.4.3 At the hot work site, combustible materials should be removed and fire extinguishing equipment should be prepared. 3.4.4 When performing maintenance on the equipment while it is in operation, care should be taken to use copper tools for hammering; if iron tools are used, glycerin must be applied to them. Welding must be carried out using electric welding only, and gas welding is not permitted.