The routine maintenance and overhaul of induction furnaces is very important. It can detect all kinds of hidden dangers in time, avoid major accidents and ensure long-term safe production, and promote the improvement of casting production and quality.
For lining induction furnaces, induction coil, flexible wires, lid, hydraulic systems, cooling systems, electrical systems, maintenance and overhaul content, in the table below. The methods provided in the table are mainly based on the working characteristics of the induction-type induction furnace, and many of the contents are also applicable to the grooved induction furnace.
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
furnace
lining |
Whether there is crack in the lining | See if there is any crack | Cold furnace before each furnace | If the crack width is less than 22 mm , if the chip or the like is not embedded in the crack, it is not necessary to repair it, and it can still be used.Otherwise it needs to be patched before it can be used. |
Repair of the tap hole | Observe whether there is crack at the junction of the side refusal lining and the taphole | When tapping | If there is a crack, repair it | |
Repair of furnace bottom and slag line lining | Observe whether the lining of the bottom of the furnace and the slag line is partially corroded. | After tapping | If there is obvious erosion, it needs to be repaired. | |
sense
should
line
ring |
Visual inspection | ( 1 ) Is the coil insulation part bumped and carbonized? ( 2 ) Whether there is adhesion to the surface of the coil ( 3 ) Does the insulation pad between the coils protrude? ( 4 ) Is the mounting bolt of the top tight coil loose? | 1 time / day 1 time / day 1 time / day 1 time / 3months | Compressed air in the workshop
Tighten the bolt |
Coil compression screw | Visually check if the coil compression screw is slack | 1 time /week | ||
rubber tube | ( 1 ) Is there any leakage at the rubber pipe joint? ( 2 ) Check if the rubber tube is cut | 1 time / day 1 time /week | ||
Coil anti-corrosion joint | Remove the rubber hose and check the corrosion resistance of the corrosion joint at the end of the coil | 1 time / 6months | When this corrosion joint is corroded by 1/2or more, it needs to be replaced with a new one.Usually changed every two years | |
Cooling water temperature at the coil outlet | Under the rated amount of molten iron and rated power, record the maximum and minimum cooling water temperature of each branch of the coil | 1 time / day | ||
Dust removal | There is compressed air in the workshop to blow off the dust and molten iron on the surface of the coil. | 1 time / day | ||
Pickling | Pickling of the sensor hose | 1 time / 2years | ||
can scratch Sex guide line |
Water cooled cable | ( 1 ) Whether there is leakage ( 2 ) Check if the cable touches the pit ( 3 ) Record the cable outlet temperature at rated power ( 4 ) Preventive measures taken to prevent accidents ( 5 ) Check if the connection bolts at the terminal end are discolored | 1 time / day 1 time / day 1 time / day 1 time / 3years 1 time / day | According to the number of tilting, the life of the water-cooled cable is determined to be three years. It needs to be replaced after three years. If the bolt is discolored, re-tighten. |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
furnace
cover
|
Dry cable | ( 1 ) Eliminate dust on the busbar splint of insulating rubber ( 2 ) Check if the chain of the suspension busbar is broken ( 3 ) Is the busbar copper foil disconnected? | 1 time / day
1 time /week 1 time /week | When the copper foil area is 10% of the busconductive area , a new busbar needs to be replaced. |
Refractory pouring material | Visually inspect the thickness of the refractory watering layer in the lining of the furnace cover | 1 time / day | When the thickness of the refractory potting material is 1/2, the lining of the furnace cover should be rebuilt. | |
Hydraulic furnace cover
| ( 1 ) Whether there is leakage at the sealing part ( 2 ) Leakage of piping ( 3 ) Leakage of high pressure pipe | 1 time / day 1 time / day 1 time / day | If so, repair it Exchange | |
High pressure pipe | ( 1 ) There are traces of iron scald on the high-pressure pipe, etc. ( 2 ) To ensure safety, exchange | 1 time /week 1 time / 2years | ||
Lubricating | ( 1 ) Manual type: part of the fulcrum of the furnace cover ( 2 ) Electric type: sprocket drive bearing for shaft adjustment chain for shaft cover wheel ( 3 ) Hydraulic type: guide bearing | |||
pour
move
oil
Cylinder | Cylinder lower bearing and high pressure pipe | ( 1 ) There are traces of iron scald on the bearing part and the high pressure pipe ( 2 ) oil leakage | 1 time /week
1 time /month |
Remove the cover for inspection |
Cylinder | ( 1 ) Whether there is leakage at the sealing part ( 2 ) abnormal sound | 1 time / day 1 time / day | Observe the cylinder block when tilting the furnace When a sound such as a knocking cylinder is issued, most of the bearings are short of oil. | |
Inclined limit switch | ( 1 ) Action check Press the limit switch by hand and the pump motor should stop running. ( 2 ) Whether there is splashing molten iron on the limit switch | 1 time /week
1 time /week | ||
Lubricating | All the fuel ports | 1 time /week | ||
High pressure control cabinet |
Cabinet inspection | ( 1 ) Check the operation of each indicator light bulb ( 2 ) Whether the parts are damaged or burned out ( 3 ) Clean the inside of the tray with compressed air in the workshop | 1 time /month 1 time /week 1 time /week | |
Circuit breaker vacuum switch | ( 1 ) Cleaning pass is the contact The vacuum tube is milky white, blurred, and the vacuum is reduced. ( 2 ) Measuring electrode consumption | 1 time / 6months
1 time /month |
If the gap exceeds 6 mm, the vacuum tube should be replaced. | |
Main switchgear |
Electromagnetic air switch | ( 1 ) the roughness of the main contact, the amount of wear
( 2 ) Come on
( 3 ) Whether the fire extinguishing board has carbonization | 1 time / 6months
1 time / 6months
1 time / 6months | When the roughness is severe, grind with a trowel, sand, etc. When the contact wear exceeds 2/3 , change the contact Adding spindle oil to each bearing and link The carbonized part is ground with sand
|
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
Main switchgear | ( 4 ) Dust removal | 1 time /week | Clean with compressed air in the workshop and wipe off the dust on the insulator with a cloth | |
Insulation resistance | Use a 1000 volt megger to measure the main loop with greater than 10M Ωbetween | |||
Converter switch |
Transfer switch | ( 1 ) Measuring insulation resistance ( 2 ) Rough switch main connector ( 3 ) The main circuit connecting bolt is loose and overheated | 1 time / 6months 1 time /month 1 time / 3months | Measuredbetween the conductor and the ground with a 1000volt megger 1M Ω Polish or exchange |
control
system
cabinet
station | Cabinet inspection | ( 1 ) Whether the component is damaged or burned out ( 2 ) Whether the component is slack or falling off | 1 time /week 1 time /week | |
Action test | ( 1 ) Check if the indicator light is on ( 2 ) Alarm circuit Should check the action according to the alarm condition | 1 time /week 1 time /week | ||
Dust removal inside the cabinet | Use workshop compressed air to clean | 1 time /week | ||
Auxiliary machine contactor | ( 1 ) Check the roughness of the joint, and use a fine sand to smooth it when it is rough. ( 2 ) Exchange contacts Change when the contact wears badly | 1 / March
1 time / 2years | In particular, the contactor for the furnace cover that is often used | |
Transformer reactor | Check appearance | ( 1 ) Is there any oil leakage? ( 2 ) Whether the insulating oil is added to the specified position | 1 time /week 1 time /week | |
Transformer and reactor temperature | Check the daily thermometer indication, below the specified value | 1 time /week | ||
Sound and vibration | ( 1 ) usually check by listening and touching ( 2 ) Instrument measurement | 1 time /week 1 time /year | ||
Insulating oil pressure test | Should meet the specified value | 1 time / 6months | ||
Tap changer | ( 1 ) Check the tap conversion for offset ( 2 ) Check the roughness of the tap adapter | 1 time / 6months 1 time / 6months | Change the new one when it is severely rough with fine sand | |
Capacitor bank | Check appearance | ( 1 ) Is there any oil leakage? ( 2 ) Whether the terminal screws are loose or not | 1 time / day 1 time /week | If slack occurs , theterminal part will change color due to overheating. |
Replacing the contactor of the capacitor
Dust removal | ( 1 ) Rough joint 1 ) Smooth the rough part with a trowel sand 2 ) When the wear is severe, change the joint ( 2 ) Contact temperature rise Wipe the insulator with a cloth cleaning air in the workshop | 1 time / 6months
1 time /week 1 time /week |
At least 1 time/ month | |
Temperature around the capacitor bank | Mercury thermometer measurement | 1 time / day | Ventilated, so that the surrounding temperature does not exceed 40 ℃ | |
Oil pressure device |
Hydraulic oil | ( 1 ) Whether the oil level of the oil level indicates the color of the oil changes ( 2 ) Check the amount of dust in the hydraulic oil and the quality of the oil ( 3 ) Measuring temperature | 1 time /week
1 time / 6months
1 time / 6months | If the oil level drops ,the circuit leaks When the quality is poor , change the oil. |
pressure gauge | Whether the pressure of the tilting furnace is different from normal, when the pressure drops, adjust the pressure to normal value. | 1 time /week |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
oil
Pressure
Loading
Set |
Pump | Check if the noise of the pump is abnormal | 1 time /week | When the pump is noisy , there are the following reasons : (1) Inhaling air from a suction filter (2) The suction side of the pump draws in air |
Pressure regulating valve | (1) When the time lag occurs from the start of the pump to the pressure rise and the noise of the pressure regulating valve becomes louder ,disassemble the pressure regulating valve for cleaning. (2) When the speed of the tilting furnace is too slow , increase the setting of the pressure regulating valve within the maximum operating pressure range of the device . The set pressure does not rise , and the cleaning is performed for cleaning. | |||
Pipeline filter | Disassemble the filter for cleaning
Exchange parts | The first time a month laterfor the 1/3months 1 time / 2years | ||
Piping Emergency generator Petrol Engine Hand pump | Visually check for oil leaks on the piping Prevent rust , start engine pump Check by attached inspection book Take measures to prevent rust and start the hand pump | 1 time /month 1 time /month
1 time /month | ||
Blower |
Fan belt | Whether the belt is slack
Whether the belt is disconnected | The first time is one month , and thefuture is 1 time / 6months | |
Gas filter | Visually check the vacuum status and clean with workshop compressed air | 1 time /month
| ||
Noise, vibration | The noise and vibration of the blower are different from usual. | 1 time /week | ||
Lubricating | Blower bearing | 1 time / 3months | ||
Cooling water circuit |
Cooling water pump | (1) Bearing temperature and motor case temperature (2) When the pump bearing has water leakage , thereinforced bearing (3) The noise and vibration of the motor and pump are different from usual. (4) after long-term operation, or in the winter, night stops running, should be excluded from surplus water (5) gland seal electrical wear | 1 time /week 1 time /month 1 time /month
1 time / 1.5to 2 years | |
Cooling Tower | (1) Blockage of the nozzle (2) Filtration of the filter : Clean or exchange when there is serious pollution (3) Whether the fan belt is slack
(4) Fan bearing lubrication |
Initialinspectionis a once a month,after 1/3months 1 time / 3months | Check the nozzle for blockage from the inspection window during operation | |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
Cooling water circuit
|
Cooling water circuit | (1) Is the flowmeter flow different from usual? (2) Cleaning filter (3) Water pressure gauge Whether the alarm value is normal or not, the pressure indication is different from usual. (4) Thermometer The thermometer indicates whether it is normal Whether the alarm contact point is abnormal (5) Piping Whether the piping has leaked | 1 time / day 1 time / 3months 1 time /week
1 time /month 1 time /week
1 time / day | |
Emergency equipment | (1) gasoline engine pump Run weekly, half-hour time (2) Gasoline engine inspection according to subsidiary inspection (3) Emergency solenoid valve | 1 time /week
1 time / day | ||
Leakage alarm device | Electrode lead line inspection | (1) Is the electrode lead wire connection normal? (2) Whether the electrode lead wire is grounded | 1 time / day | Check with a test stick |
Coil check | When removing the furnace : Whether the coil is burnt out due to molten metal Whether there is bump in the coil Is there any other damage to the coil? | It is more appropriate tofill the coil insulation with asbestos plaster for 3 to5 years. |
The routine maintenance and overhaul of induction furnaces is very important. It can detect all kinds of hidden dangers in time, avoid major accidents and ensure long-term safe production, and promote the improvement of casting production and quality.
For lining induction furnaces, induction coil, flexible wires, lid, hydraulic systems, cooling systems, electrical systems, maintenance and overhaul content, in the table below. The methods provided in the table are mainly based on the working characteristics of the 感应-type induction furnace, and many of the contents are also applicable to the grooved induction furnace.
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
furnace
lining |
Whether there is crack in the lining | See if there is any crack | Cold furnace before each furnace | If the crack width is less than 22 mm , if the chip or the like is not embedded in the crack, it is not necessary to repair it, and it can still be used.Otherwise it needs to be patched before it can be used. |
Repair of the tap hole | Observe whether there is crack at the junction of the side refusal lining and the taphole | When tapping | If there is a crack, repair it | |
Repair of furnace bottom and slag line lining | Observe whether the lining of the bottom of the furnace and the slag line is partially corroded. | After tapping | If there is obvious erosion, it needs to be repaired. | |
sense
should
line
ring |
Visual inspection | ( 1 ) Is the coil insulation part bumped and carbonized? ( 2 ) Whether there is adhesion to the surface of the coil ( 3 ) Does the insulation pad between the coils protrude? ( 4 ) Is the mounting bolt of the top tight coil loose? | 1 time / day 1 time / day 1 time / day 1 time / 3months | Compressed air in the workshop
Tighten the bolt |
Coil compression screw | Visually check if the coil compression screw is slack | 1 time /week | ||
rubber tube | ( 1 ) Is there any leakage at the rubber pipe joint? ( 2 ) Check if the rubber tube is cut | 1 time / day 1 time /week | ||
Coil anti-corrosion joint | Remove the rubber hose and check the corrosion resistance of the corrosion joint at the end of the coil | 1 time / 6months | When this corrosion joint is corroded by 1/2or more, it needs to be replaced with a new one.Usually changed every two years | |
Cooling water temperature at the coil outlet | Under the rated amount of molten iron and rated power, record the maximum and minimum cooling water temperature of each branch of the coil | 1 time / day | ||
Dust removal | There is compressed air in the workshop to blow off the dust and molten iron on the surface of the coil. | 1 time / day | ||
Pickling | Pickling of the sensor hose | 1 time / 2years | ||
can scratch Sex guide line |
Water cooled cable | ( 1 ) Whether there is leakage ( 2 ) Check if the cable touches the pit ( 3 ) Record the cable outlet temperature at rated power ( 4 ) Preventive measures taken to prevent accidents ( 5 ) Check if the connection bolts at the terminal end are discolored | 1 time / day 1 time / day 1 time / day 1 time / 3years 1 time / day | According to the number of tilting, the life of the water-cooled cable is determined to be three years. It needs to be replaced after three years. If the bolt is discolored, re-tighten. |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
furnace
cover
|
Dry cable | ( 1 ) Eliminate dust on the busbar splint of insulating rubber ( 2 ) Check if the chain of the suspension busbar is broken ( 3 ) Is the busbar copper foil disconnected? | 1 time / day
1 time /week 1 time /week | When the copper foil area is 10% of the busconductive area , a new busbar needs to be replaced. |
Refractory pouring material | Visually inspect the thickness of the refractory watering layer in the lining of the furnace cover | 1 time / day | When the thickness of the refractory potting material is 1/2, the lining of the furnace cover should be rebuilt. | |
Hydraulic furnace cover
| ( 1 ) Whether there is leakage at the sealing part ( 2 ) Leakage of piping ( 3 ) Leakage of high pressure pipe | 1 time / day 1 time / day 1 time / day | If so, repair it Exchange | |
High pressure pipe | ( 1 ) There are traces of iron scald on the high-pressure pipe, etc. ( 2 ) To ensure safety, exchange | 1 time /week 1 time / 2years | ||
Lubricating | ( 1 ) Manual type: part of the fulcrum of the furnace cover ( 2 ) Electric type: sprocket drive bearing for shaft adjustment chain for shaft cover wheel ( 3 ) Hydraulic type: guide bearing | |||
pour
move
oil
Cylinder | Cylinder lower bearing and high pressure pipe | ( 1 ) There are traces of iron scald on the bearing part and the high pressure pipe ( 2 ) oil leakage | 1 time /week
1 time /month |
Remove the cover for inspection |
Cylinder | ( 1 ) Whether there is leakage at the sealing part ( 2 ) abnormal sound | 1 time / day 1 time / day | Observe the cylinder block when tilting the furnace When a sound such as a knocking cylinder is issued, most of the bearings are short of oil. | |
Inclined limit switch | ( 1 ) Action check Press the limit switch by hand and the pump motor should stop running. ( 2 ) Whether there is splashing molten iron on the limit switch | 1 time /week
1 time /week | ||
Lubricating | All the fuel ports | 1 time /week | ||
High pressure control cabinet |
Cabinet inspection | ( 1 ) Check the operation of each indicator light bulb ( 2 ) Whether the parts are damaged or burned out ( 3 ) Clean the inside of the tray with compressed air in the workshop | 1 time /month 1 time /week 1 time /week | |
Circuit breaker vacuum switch | ( 1 ) Cleaning pass is the contact The vacuum tube is milky white, blurred, and the vacuum is reduced. ( 2 ) Measuring electrode consumption | 1 time / 6months
1 time /month |
If the gap exceeds 6 mm, the vacuum tube should be replaced. | |
Main switchgear |
Electromagnetic air switch | ( 1 ) the roughness of the main contact, the amount of wear
( 2 ) Come on
( 3 ) Whether the fire extinguishing board has carbonization | 1 time / 6months
1 time / 6months
1 time / 6months | When the roughness is severe, grind with a trowel, sand, etc. When the contact wear exceeds 2/3 , change the contact Adding spindle oil to each bearing and link The carbonized part is ground with sand
|
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
Main switchgear | ( 4 ) Dust removal | 1 time /week | Clean with compressed air in the workshop and wipe off the dust on the insulator with a cloth | |
Insulation resistance | Use a 1000 volt megger to measure the main loop with greater than 10M Ωbetween | |||
Converter switch |
Transfer switch | ( 1 ) Measuring insulation resistance ( 2 ) Rough switch main connector ( 3 ) The main circuit connecting bolt is loose and overheated | 1 time / 6months 1 time /month 1 time / 3months | Measuredbetween the conductor and the ground with a 1000volt megger 1M Ω Polish or exchange |
control
system
cabinet
station | Cabinet inspection | ( 1 ) Whether the component is damaged or burned out ( 2 ) Whether the component is slack or falling off | 1 time /week 1 time /week | |
Action test | ( 1 ) Check if the indicator light is on ( 2 ) Alarm circuit Should check the action according to the alarm condition | 1 time /week 1 time /week | ||
Dust removal inside the cabinet | Use workshop compressed air to clean | 1 time /week | ||
Auxiliary machine contactor | ( 1 ) Check the roughness of the joint, and use a fine sand to smooth it when it is rough. ( 2 ) Exchange contacts Change when the contact wears badly | 1 / March
1 time / 2years | In particular, the contactor for the furnace cover that is often used | |
Transformer reactor | Check appearance | ( 1 ) Is there any oil leakage? ( 2 ) Whether the insulating oil is added to the specified position | 1 time /week 1 time /week | |
Transformer and reactor temperature | Check the daily thermometer indication, below the specified value | 1 time /week | ||
Sound and vibration | ( 1 ) usually check by listening and touching ( 2 ) Instrument measurement | 1 time /week 1 time /year | ||
Insulating oil pressure test | Should meet the specified value | 1 time / 6months | ||
Tap changer | ( 1 ) Check the tap conversion for offset ( 2 ) Check the roughness of the tap adapter | 1 time / 6months 1 time / 6months | Change the new one when it is severely rough with fine sand | |
Capacitor bank | Check appearance | ( 1 ) Is there any oil leakage? ( 2 ) Whether the terminal screws are loose or not | 1 time / day 1 time /week | If slack occurs , theterminal part will change color due to overheating. |
Replacing the contactor of the capacitor
Dust removal | ( 1 ) Rough joint 1 ) Smooth the rough part with a trowel sand 2 ) When the wear is severe, change the joint ( 2 ) Contact temperature rise Wipe the insulator with a cloth cleaning air in the workshop | 1 time / 6months
1 time /week 1 time /week |
At least 1 time/ month | |
Temperature around the capacitor bank | Mercury thermometer measurement | 1 time / day | Ventilated, so that the surrounding temperature does not exceed 40 ℃ | |
Oil pressure device |
Hydraulic oil | ( 1 ) Whether the oil level of the oil level indicates the color of the oil changes ( 2 ) Check the amount of dust in the hydraulic oil and the quality of the oil ( 3 ) Measuring temperature | 1 time /week
1 time / 6months
1 time / 6months | If the oil level drops ,the circuit leaks When the quality is poor , change the oil. |
pressure gauge | Whether the pressure of the tilting furnace is different from normal, when the pressure drops, adjust the pressure to normal value. | 1 time /week |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
oil
Pressure
Loading
Set |
Pump | Check if the noise of the pump is abnormal | 1 time /week | When the pump is noisy , there are the following reasons : (1) Inhaling air from a suction filter (2) The suction side of the pump draws in air |
Pressure regulating valve | (1) When the time lag occurs from the start of the pump to the pressure rise and the noise of the pressure regulating valve becomes louder ,disassemble the pressure regulating valve for cleaning. (2) When the speed of the tilting furnace is too slow , increase the setting of the pressure regulating valve within the maximum operating pressure range of the device . The set pressure does not rise , and the cleaning is performed for cleaning. | |||
Pipeline filter | Disassemble the filter for cleaning
Exchange parts | The first time a month laterfor the 1/3months 1 time / 2years | ||
Piping Emergency generator Petrol Engine Hand pump | Visually check for oil leaks on the piping Prevent rust , start engine pump Check by attached inspection book Take measures to prevent rust and start the hand pump | 1 time /month 1 time /month
1 time /month | ||
Blower |
Fan belt | Whether the belt is slack
Whether the belt is disconnected | The first time is one month , and thefuture is 1 time / 6months | |
Gas filter | Visually check the vacuum status and clean with workshop compressed air | 1 time /month
| ||
Noise, vibration | The noise and vibration of the blower are different from usual. | 1 time /week | ||
Lubricating | Blower bearing | 1 time / 3months | ||
Cooling water circuit |
Cooling water pump | (1) Bearing temperature and motor case temperature (2) When the pump bearing has water leakage , thereinforced bearing (3) The noise and vibration of the motor and pump are different from usual. (4) after long-term operation, or in the winter, night stops running, should be excluded from surplus water (5) gland seal electrical wear | 1 time /week 1 time /month 1 time /month
1 time / 1.5to 2 years | |
Cooling Tower | (1) Blockage of the nozzle (2) Filtration of the filter : Clean or exchange when there is serious pollution (3) Whether the fan belt is slack
(4) Fan bearing lubrication |
Initialinspectionis a once a month,after 1/3months 1 time / 3months | Check the nozzle for blockage from the inspection window during operation | |
Maintenance and repair project | Maintenance and repair content | Inspection time and frequency | Remarks | |
Cooling water circuit
|
Cooling water circuit | (1) Is the flowmeter flow different from usual? (2) Cleaning filter (3) Water pressure gauge Whether the alarm value is normal or not, the pressure indication is different from usual. (4) Thermometer The thermometer indicates whether it is normal Whether the alarm contact point is abnormal (5) Piping Whether the piping has leaked | 1 time / day 1 time / 3months 1 time /week
1 time /month 1 time /week
1 time / day | |
Emergency equipment | (1) gasoline engine pump Run weekly, half-hour time (2) Gasoline engine inspection according to subsidiary inspection (3) Emergency solenoid valve | 1 time /week
1 time / day | ||
Leakage alarm device | Electrode lead line inspection | (1) Is the electrode lead wire connection normal? (2) Whether the electrode lead wire is grounded | 1 time / day | Check with a test stick |
Coil check | When removing the furnace : Whether the coil is burnt out due to molten metal Whether there is bump in the coil Is there any other damage to the coil? | It is more appropriate tofill the coil insulation with asbestos plaster for 3 to5 years. |
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