Our company's bell-type annealing furnace uses light diesel oil as fuel, has good temperature control effect, and has the function of automatically recording the workpiece temperature in the furnace. The annealing furnace has an inner diameter of 12.5 m and a height of 7 m. The main body of the furnace is composed of a bell-shaped outer cover and a moving furnace bottom plate, and the hoisting machine controls the furnace cover to rise and fall (the furnace cover is opened and closed). The moving hearth chassis is subjected to a load of 600t and the lower part is provided with 14 rigid support chassis. Four special berth trolleys are used to transport the furnace chassis together with its under support, and the berth trolley travels between the outdoor annealing furnace and the factory. Large hydropower station components are subject to annealing heat treatment. For example, after the Three Gorges runner welding, the overall heat treatment is required. The net weight of the runner is 450t, and the maximum diameter is 10.5m and the height is 5.3m. The furnace has completed the annealing process for hundreds of large hydropower units such as runners and lower frames.
The ignition procedure is as follows: first open the bypass flue above the chimney, slightly open the air inlet and the combustion air valve, and ignite the igniter. Send the igniter to the burner port without opening the fuel valve. If ignition, adjust the combustion air and fuel valve opening, so that the ratio of fuel to combustion air is reasonable, that is, the flame is adjusted to stable combustion, then close the bypass flue ram and open the air inlet valve. According to the above procedure, the required burners are ignited one by one, and the flame is adjusted and stabilized before the adjustment is successful.
1. The flame in the furnace is suddenly large and small, and the flame is broken.
When the Xiangjiaba runner was annealed, the operator found that the flame of the burner was suddenly large and small, accompanied by a "beep, bang" sound, and the entire burner tube vibrated. At the same time, it was found that smoke was on the upper respirator of the gas tank and the mouth of the oil tank at a distance. This is a dangerous phenomenon and must be eliminated as soon as possible.
Through analysis, there is air in the oil pipe, and the annealing furnace has three oil passages, which are evenly distributed on the furnace body. There is an oil pressure gauge at each oil pipe inlet pipe, and there is also a hydraulic pressure gauge at the fuel pipe in the pump house. There is a control valve on the tubing behind each watch to adjust the minimum oil pressure in the pipe. At that time, it was found that the oil pressure gauge was unstable and there was vibration. The light diesel oil in the oil return pipe was analyzed, and there was room for it. The smoke from the pipe was returned to the oil tank through the pipeline space. After the operator re-adjusts the oil pressure in the oil pipe to 0.5 MPa or more, the space inside the oil return pipe is eliminated, the fault is eliminated, and the annealing furnace is in normal operation.
2. Observing hole fire failure during annealing
When the annealing is carried out in half, the flame emerges from the observation hole of the outer wall of the furnace, and the length reaches 33 cm, which has been burned to the outer wall of the furnace. The technician and the operator analyzed that the failure indicated a positive pressure in the furnace and a high positive pressure in the furnace.
At the beginning of the combustion, the operator inspected the combustion of each burner along the furnace. During operation, if positive pressure occurs in the furnace, the chimney gate should be opened and the flue gas should be discharged from above until no positive pressure occurs. After the shutter is opened, the fault is eliminated.
3. The electric oil tank cap bolt is broken, and the high pressure oil is sprayed out.
During the annealing process of a product, eight M24 bolts in the fixed electric heating oil tank cover in the pump room are broken, and the high-pressure oil is discharged. The furnace oil supply system is pumped from a storage tank into a heating oil tank by a 125 L/min oil pump. After heating the oil tank, oil is supplied to the burner of the furnace through three 40L/min oil pumps, and each oil pump can be burned by 13 burners.
There is a relief valve on the heating oil return pipe to ensure that the heating oil tank is full of oil. Heating the oil tank is to prevent the fuel viscosity in winter from being large and difficult to atomize. The heating oil tank is built in the oil pump room, and the oil tank is heated by an electric heating tube. Since the heating tank heater has never been used, the overflow valve is rusted and does not play a regulating role for a long time. As the heating oil tank oil is in the annealing process, the oil accumulates more than a certain pressure, so that the eight M24 bolts in the fixed heating oil tank cover are broken due to the high pressure, and the high-pressure oil is sprayed on the wall of the oil pump room, which may cause personal accident.
Since the heating tank is not used, the relief valve is removed and connected directly with a pipe. After replacing the fixed tank cap bolts, the annealing furnace operates normally.
4. Poor failure of combustion flame after replacement of burner brick
The burner brick is fixed on the base of the burner brick by four lengths of 400mm iron and diagonal triangle iron at the front end of the burner. Prevent the furnace from lifting and lowering, and the burner bricks fall off due to heavy weight.
In a major overhaul, due to the change in the size of the burner brick, more than 50% of the combustion-supporting port is sealed when the burner block is fixed, resulting in more flame black smoke per burner and poor combustion of the diesel. In order to make up for the poor combustion flame, redesign, increase the size of the burner brick, re-made 39 sets of burner bricks, to ensure that the burner bricks have enough combustion air to solve the flame failure.
5. The idle burner tube is burned into a red state.
During the lower frame annealing process, when the annealing process is halfway through, suddenly two idle burner tubes are ignited and the burner tube has been burned to a reddish state. Therefore, all valves are turned off and the lower frame annealing is forced to terminate. Cool the burner tube with a fire extinguisher on the outside so that it does not explode. The reason for the analysis is that the shut-off valve on the oil line is not tightly closed, resulting in leakage of diesel fuel, and the leaked diesel oil is stored in the burner barrel. Since the temperature in the overall furnace reaches about 220 ° C, the diesel in the burner barrel is ignited. Replace the shut-off valve on the faulty oil circuit and the annealing furnace operates normally.
6. The furnace body cannot fall down
The total weight of the furnace is 105t and is supported by 3 columns. 30t counterweight iron is assembled in each column, and the furnace body is connected by wire rope and fixed pulley. The hoist pulls the furnace body and the maximum lifting force is 40t. At that time, it was winter. Because the furnace body was tilted, the individual points were scratched, and the proportion of the weight in the column was unreasonable, which caused the furnace body to fail. The furnace body is lowered by its own weight, and the hoist only controls its speed. Using a 20t chain hoist can not lower the furnace. Through on-site technicians to determine the scheme, a certain amount of weights are taken out in the weight-weighted column and added to the light-weight column to ensure the level of the furnace body without tilting, and the fault is eliminated. Class failure.
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