Failure analysis of semi-automatic paper cutting machine in Wenzhou
The semi-automatic paper cutting machine is a very important protective valve. It is widely used in various pressure vessels and piping systems. When the pressure in the pressure system exceeds the specified value, it can automatically open and discharge the excess medium into the atmosphere to ensure the safe operation of pressure vessels and piping systems and prevent the occurrence of accidents. And when the system pressure drops back to the working pressure or slightly lower than the working pressure, it can automatically shut down. The reliability of semi-automatic paper cutter is directly related to the safety of equipment and human body, so we must pay attention to it.
Impulsive semi-automatic cutting of paper machine after the main semi-automatic paper cutter does not move.
For example, in 2001, before the overhaul of furnace No. 3, the main safety door was refused to move when the main safety door was running over. The disassembly inspection found that there was a lot of rust and impurities in the piston chamber. The piston could not move in the piston chamber, causing the main safety door to refuse to move. When the piston, bulging and piston chambers are removed, the defects such as the piston groove mark are grinded. The piston chamber wall is evenly coated with lead powder before assembly, and the valve is assembled in strict order. In the water pressure test of the boiler, the pulse tube is flushed, then the main safety door is connected with the impulse semi automatic paper cutter, and the semi automatic paper cutting machine run again after the overhaul.
The two is the large leakage of the piston chamber of the main safety door. When the gas leakage of the valve piston chamber is large, the effect of F1 in type (1) on the piston is small. In the case of other conditions, F1 < F2 F3 FM so the main safety door is refused.
The main cause of the large leakage of the piston chamber is related to the air tightness of the valve itself and the non conforming to the size of the piston ring or the excessive wear and tear of the piston ring.
For example, the quality of the piston ring in the main semi-automatic paper cutter of No. 3~9 furnace is that the piston ring's edge angle should be smooth, the opening clearance of the free state is not more than 14, the opening clearance after assembly is delta =1 to 1.25, the gap between piston and piston chamber is B=0.12 to 0.18, the gap between piston ring and piston chamber is S=0.08 ~ 0.12, and the piston ring is in good contact with the piston chamber. Light transmittance should not be more than 1 / 6 of the perimeter. For the piston chamber, the groove depth of the piston chamber should not exceed 0.08 ~ 0.1mm, its ellipticity is not more than 0.1mm and the coning degree is not more than 0.1mm. The piston ring, piston and piston chamber of the main safety door of each furnace are not in conformity with the requirements of the maintenance regulation, but the piston ring and the piston ring at present are not in accordance with the requirements of the maintenance regulation. The clearance of the piston chamber is more than 0.20 in the S, and the defect of the piston chamber is more serious, which seriously affects the steam tightness of the piston chamber and causes the large leakage of the piston chamber.
The way to eliminate this defect is to deal with the piston interior surface, replace the qualified piston and piston ring, turn off the opening of the throttle valve in the throttle valve safety device system, increase the intake of the piston chamber of the main safety door, and increase the semi automatic paper cutter by increasing the impulse in the condition that the condition is allowed. To increase the intake volume of the piston chamber in the main safety door, the main semi automatic cutter action is promoted.
Three, the matching between the main semi-automatic paper cutter and the impulse semi-automatic paper cutter is improper, and the steam flow rate of the impulse semi-automatic paper cutter is too small. The nominal diameter of the impulse semi-automatic paper cutting machine is too small, resulting in the inadequacy of the steam flow in the piston chamber of the main semi-automatic paper cutting machine, and the driving force of the piston downward movement is not enough, that is, the F1 < F2 F3 FM causes the main semi-automatic paper cutting machine from moving. This phenomenon occurs mostly in the semi-automatic paper cutter impulse semi-automatic paper cutter when it is replaced, it is caused by poor consideration.
For example, when the No. 5 furnace was overhauled in 2002, two heavy hammer impulse semi-automatic paper cutting machines were replaced by two Harbin valve plants to produce A49H P54100VDg20 pulse semi-automatic cutting machine. The semi-automatic paper cutting machine is generally used with the main safety match of A42H P54100VDg125 type spring type, and it will cut it with the old type of Dg150 * 90 x 250 type of the old main semi-automatic cutting paper. The main semi-automatic paper cutting machine and A29H P54100VDg125 type spring type main semi-automatic paper cutting machine not only have large nominal diameter and poor air tightness, but also finish the weight of the saturated semi automatic paper cutting machine in No. 5 furnace, and make the main semi-automatic paper cutting machine refusing to move when the weight test is tested. Then we disintegrate the semi automatic paper cutting machine and expand the gap between the guide sleeve and the valve core, in order to increase the flow area, and once again the run weight test is successful. Therefore, the matching between the impulse semi-automatic paper cutter and the main semi-automatic paper cutter is not proper, and the nominal diameter is smaller, which will also cause the main semi automatic cutter to refuse to move.