Common faults of the most popular reciprocating pl

2022-08-19
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Common faults of reciprocating piston air compressor

reciprocating piston air compressor plays an extremely important role in the flexible packaging plastic industry. For example, when making bags, it is used on the punching machine for air punching; When printing plastic, it is also used on the cylinder to lift the offset press roll. Reciprocating piston compressor has excellent performance and has the advantages of low noise, low fuel consumption and low specific power, but it is prone to faults such as reduced exhaust volume, high exhaust temperature, high oil temperature, cylinder knocking sound, piston seizure or seizure in production

reciprocating piston air compressor plays an extremely important role in the flexible packaging plastic industry. For example, when making bags, it is used on the punching machine for air punching; When printing plastic, it is also used on the cylinder to lift the offset press roll. Reciprocating piston compressor has excellent performance and has the advantages of low noise, low fuel consumption and low specific power, but it is prone to faults such as reduced exhaust volume, high exhaust temperature, high oil temperature, cylinder knocking sound, piston seizure or seizure in production

I. working principle of reciprocating piston air compressor

generally, the motor drives the shaft to rotate through the triangle belt, and then drives the piston to produce reciprocating motion through the connecting rod, so that the volume of the piston cavity composed of air valve, piston and cylinder changes, so as to achieve the purpose of compressing air. The compressed air is compressed by the intercooler and finally enters the air storage tank

the air storage tank is mainly composed of cylinder and pressure gauge, with the main features of, safety valve, etc., which can stabilize the pressure of the air pipeline and reduce the pressure fluctuation caused by the operation of the compressor. If the compressed air inside exceeds the rated pressure for some reason, the safety valve will automatically open to discharge the compressed air into the atmosphere to ensure safe operation. Our factory uses v-0.3/10 and w-0.6/10 air compressors produced by Fujian compressor General Factory, and the opening pressure of the safety valve is 1.05 ~ 1.08 times of the rated exhaust pressure. Of course, the opening pressure of the safety valve is different for air compressors of different specifications

II. Inspection before production

before starting the air compressor, it is necessary to make some inspections to eliminate hidden troubles. The inspection before startup mainly includes the inspection of power supply voltage and oil level

power supply voltage: the fluctuation range of power supply voltage is required to be about 5%

oil level inspection: the oil level is generally 1/3 ~ 2/3 of the oil standard. When it is lower than 1/3 of the oil standard, the filtered lubricating oil of the same brand should be added in time. In winter, 1 Sigri should be used to develop high elongation carbon fiber thermoplastic composite 3 compressor oil, and in summer, 19 compressor oil should be used. If the temperature is above 10 ℃, use sae30, and if the temperature is below 10 ℃, use sae10

III. reduction of exhaust volume

1 Oil shortage

the reduction of exhaust volume is directly related to oil shortage

once in our production, the air compressor had the fault of reducing the exhaust volume, which not only failed to lift the press roll of the printing machine, but also accompanied by a certain cylinder knocking sound. We first check and clean the air silencer, and then observe the oil level. If the oil level is lower than 1/3 of the oil level, we immediately fill it with oil of the same brand, and then start the power switch. When we try it on, there is still a knocking sound. Later, the crankshaft, connecting rod, piston and cylinder of the moving mechanism components were disassembled one by one for inspection. It was found that the crankshaft was cracked and was about to break. It must have been short of oil for some time. Due to the lack of oil, the moving parts have dry friction, and the overload operation causes various parts to be damaged to varying degrees. We clean and grind the damaged moving parts, replace them seriously, and then re develop and use non-metallic materials, install and test the machine. The sound of cylinder knocking disappears, and the exhaust volume is normal. It can be seen that oil must not be lacking, otherwise there will be endless trouble

2. Poor tightness of air silencing filter and air valve

the reduction of exhaust volume is also related to the tightness of air silencing filter and air valve. The air silencing filter must be cleaned frequently. Cleaning the dirt on the air valve plate and valve plate is conducive to ensuring the normal exhaust volume of the air compressor. Normally, the filter should be cleaned every 200 hours, and the air valve should be cleaned every 500 ~ 800 hours

3. Poor quality of lubricating oil

poor quality of lubricating oil will cause the piston ring to be sucked, thereby reducing the exhaust volume. Therefore, high-quality lubricating oil should be selected. After long-term operation, the lubricating oil will contain impurities, dust, etc., so it needs to be filtered. Generally speaking, the engine oil should be changed every 500 ~ 800 hours, and the engine oil used previously should be filtered

4. Excessive exhaust temperature

excessive exhaust temperature will also cause the piston ring to be sucked, resulting in reduced exhaust volume. As long as the temperature is reduced, the problem can be solved. Here we should pay attention to two points:

(1) the ambient temperature should not be too high, generally not more than 40 ℃

(2) if the air valve leaks, the discharged high-temperature gas will return to the cylinder. At this time, we should carefully check the air valve, grind the valve plate or replace the valve plate to eliminate air leakage, so as to solve the problem of over high temperature

IV. causes and Countermeasures of crash phenomenon

air compressors are also prone to crash during operation. The causes of the air compressor crash are both electrical and mechanical

1. Electrical reasons

Liang Xiaoli, general manager of air pressure company, said that the electrical part of the compressor is mainly composed of motor, automatic air pressure switch, etc. When the air compressor operates normally, the automatic air pressure switch is closed. When the pressure of the air storage tank reaches the rated exhaust pressure, the compressed air pushes the rubber and makes the spring jump through the jump bridge, so that the moving contact in the bakelite seat is separated from the static contact, cutting off the circuit and stopping the motor. On the contrary, when the pressure of the air tank decreases to a certain value, the spring springs back, the circuit is connected, and the motor runs (see Figure 1)

if the contactor C coil is not energized, the air pressure switch will not work, resulting in a crash. For example, when there is a lack of phase, the power switch K cannot be closed, and the coil C cannot be energized, resulting in a crash

2. Mechanical reasons

the mechanical reasons for the crash are: the connecting rod is broken, the piston is stuck in the cylinder, and the piston assembly clearance is too large or too small

the fracture of connecting rod is mostly related to overload operation, so overload operation should be avoided to avoid the fracture of connecting rod. At the same time, attention should be paid to the assembly clearance and lubrication state of cylinder and piston

in addition, when the air compressor is shut down and not in use, open the blowdown valve at the bottom of the air tank and discharge the sewage. If it is not used for a long time, pay attention to moisture resistance, keep the air valve and oil seal clean, apply oil to the surface openings of cylinders, pistons, etc., and seal them with oil paper. In short, daily maintenance is very important to ensure the good operation and long service life of the compressor. At the same time, the maintenance workers are required to have a strong heart to find and eliminate faults as early as possible

paper cutter failure and blade grinding

some small faults caused by blades in paper cutting often make many operators confused and unable to find the problem. The following excerpts are for peer reference

fault 1 When the newly ground blade is put into use, it will suddenly fall off a bit of the blade without touching any hard foreign matter during cutting

the main reason for this problem is that the feed amount of the blade in the grinding process is not properly controlled (the feed amount is too large), resulting in too high temperature in the grinding process (that is, the temperature at the contact point between the blade and the grinding wheel is too high), which will burn the blade out

fault 2 The cutter cannot cut to the end when cutting

this is mainly because the straightness of the blade is out of tolerance

fault 3 When the blade is used just after grinding, there are knife flowers on the cutting surface of the cut paper, or poor cutting occurs in the cutting process

this is mainly because the grinding edge is too soft due to overheating

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