Repair of the KamAZ automobile compressor
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In process of work in the compressor the cylinder-piston group wears out, valve tightness is broken.
In case of these malfunctions, the filling time of the pneumatic system (before the control lamps are extinguished) at an engine crankshaft speed of 2200 rpm exceeds the set by the technical conditions, i.e. 8 minutes, or the compressor does not develop the set pressure of 7. 7.5 kgf / cm2 at all.
In addition, the wear of the piston-cylinder group leads to the absorption of oil mist from the compressor crankcase into the cylinders, and then the oil, together with the air, goes to the pneumatic system.
After filling the pneumatic system with air in the pressure regulator, the unloading valve opens, oil and air are thrown out and settles on the regulator and frame. It should be noted here that the oil flow through the compressor increases due to contamination of the engine air filter.
The fact is that the compressor draws in filtered air from the intake manifold of the engine.
As the filter becomes dirty, the vacuum in the intake manifold increases, and the compressor, even with a working piston group, draws oil mist from the crankcase, and then throws it into the pneumatic actuator during the exhaust stroke.
Leakage of the gasket 18 of the cylinder head, internal cracks in the head or block lead to the fact that the liquid from the cooling system is sucked into the cylinders, and then together with the air goes into the pneumatic drive. The coolant level in the expansion tank drops and the fluid in it boils.
This is because the piston in the compression stroke pushes air into the compressor cooling jacket, and then the air and liquid merge into the expansion tank. There is one more dangerous consequence of the considered malfunctions.
The liquid entering the compressor cylinder, through the gaps between the cylinder, piston and rings, seeps into the compressor crankcase, and from it flows into the engine oil pan. If liquid enters the oil when searching for a leak, keep in mind the compressor as well.
Otherwise, due to a faulty compressor, a serviceable engine may be erroneously sent for repair, and the faulty compressor can be reinstalled on another serviceable engine.
Oil for lubricating the compressor is supplied from the central oil channel of the engine to the mechanical seal 4 installed in the crankshaft. The seal is pressed against the flywheel housing with a spring 5.
With significant wear of the mechanical seal, as well as breaking the spring, oil, bypassing the compressor, directly flows to the block of distribution gears and further to the engine sump.
This malfunction can be the cause of failure of not only the compressor (jamming due to lack of lubrication), but also of the engine (cranking of the crankshaft liners due to oil starvation).
Incomplete opening of exhaust valves leads to overheating of the air at the compressor outlet.
Disassembly of the compressor, mounted on a stand, begin with the removal of the cylinder head. Then the intake valves, their guides and seats are removed from the cylinder block sockets. Clamping the head of the block in a vice, turn off the plugs of the discharge valves, remove the valves, seats and gaskets.
By bending the antenna of the lock washer 2, and unscrewing the nut 3 for fastening the gear wheel of the crankshaft drive, remove the lock washer. Then, with the help of the device, the compressor drive gear is removed and the key 6 is removed from the groove of the crankshaft.
In order to remove the end seal and spring from the crankshaft, the thrust ring must first be removed from the crankshaft.
Turning the compressor on the stand with the bottom cover up, unscrew the mounting bolts and remove the bottom cover with gasket 24. Then you need to unscrew and unscrew the nut securing the connecting rod covers, remove the covers.
Tapping the handle with a hammer at the end of the lower head of the connecting rod, take out the piston with the connecting rod. After removing the liners, it is necessary to connect the covers and connecting rods in pairs with bolts so as not to confuse them in the future.
The connecting rod with the cover is processed in the assembly, so they are replaced only in pairs.
Turning the compressor with the cylinder block up, unscrew the nuts securing the block to the crankcase and remove the cylinder block with the oil reflector plates 21. After that, unscrew the bolts securing the rear cover of the crankcase 23 and remove the cover. Before pressing the crankshaft out of the crankcase, the thrust ring of the main bearing, mounted on the side of the drive gear, is removed.
Clamping the connecting rod in a vice, the compression oil rings are removed from the piston, the thrust ring of the piston pin is removed. After pressing out the piston pin 14, the piston is disconnected from the connecting rod, and then the sleeve is pressed out from the upper connecting rod head.
Compressor parts fault detection
In the event of a defect, parts with cracks, chips, scratches and risks on work surfaces, and other mechanical damages are subject to rejection.
When the inner surface of the cylinders is worn by more than 0.02 mm, it is necessary to bore the cylinders for the repair size (Table 1). The bore diameter under the intake valve seat must not exceed 17.027 mm.
The diameter for ball bearings in the compressor crankcase should be no more than 72.05 mm. With a larger diameter, an interference fit of the bearing is not ensured.
The non-flatness of the contact surface of the compressor head to the cylinder block should be no more than 0.1 mm. Risks, traces of development on the surface of the seats of the pressure valves are eliminated by grinding and grinding the valves. The diameter of the hole for installing the discharge valve should be no more than 28.8 mm.
The diameter of the crankshaft for ball bearings and gears should be at least 35 mm, for the face seal not more than 25.05 mm, the width of the keyway not more than 5.02 mm. If the connecting rod journals are worn, they must be regrind to the next repair size (Table 3).
The device and principle of operation of the KamAZ Euro compressor (53205-3509015)
This single cylinder compressor 53205-3509015 KamAZ car consists of a cylinder head with a cover (pos. 2), a suction valve (pos. 10), a piston (pos. 4), a cylinder (pos. 7), a crankshaft (pos. 12), sliding bearings, a crankcase (pos. 1 ), connecting rod (pos. 5), back cover (pos. 3), discharge valve.
When the piston (key 4) moves down under the valve (key 10), a vacuum occurs. In this case, the external atmospheric pressure presses the valve (pos. 5) through the suction pipe from the bottom of the cylinder head.
The suction valve (key 10) bends, opening the suction openings, and through them air enters the cylinder cavity. the suction process.
The discharge valve is currently in the closed position.
When moving upward, the compressor piston compresses the air that is in the cylinder cavity. In this case, under the pressure of the air, the suction valve is pressed against the bottom of the cylinder head and the suction port is closed.
Under the action of compressed air passing through the discharge openings, the discharge valve is squeezed, which, bending, opens the discharge holes.
There is a flow of compressed air through the discharge pipe into the pipeline, which leads to the brake system of the car. This is a pumping process.
Grease compressor Euro KAMAZ (53205-3509015) comes from the oil line of the unit under pressure. The oil in the compressor is fed to the front main plain bearing, which is pressed into the crankcase (pos.
1), through an inlet made in the flange of the crankcase. The connecting rod bearing (key 5) as well as the main rear plain bearing are provided with oil through the oil channel, which passes through the crankshaft (key 12) of the engine.
Oil is drained from the crankcase through the drain hole.
The water jacket of the cylinder head is cooled by a fluid, which is supplied by the engine circulation system.
Coolant enters the compressor through an opening that is located on the air discharge side of the cylinder head.
During compression that occurs during operation, heat is released that the coolant absorbs through the walls of the cylinder head. Coolant is discharged through the opposite hole. Both holes are sealed with plugs during transport (key 24).
Fig. 1. KAMAZ 53205-3509015 compressor (single-cylinder)
1. a case; 2. cylinder head with cover assembly; 3. back cover; 4. the piston; 5. connecting rod; 6. a sealing ring; 7. cylinder; 8, 9. head gasket; 10. suction valve; 11. hairpin; 12. a cranked shaft; 13. gear; 14. a nut; 15. transport flange cover; 16. piston pin; 17. a stopper of a piston pin; 18. a sealing ring; 19. traffic jam; 20. cork with gaskets; 21. a bolt with a washer; 22. nameplate; 23. rivet; 24, 25. traffic jam.
Piston compressor operation and repair
The compressor is a fairly sophisticated technical equipment, as it operates, it has the right to wear out and break. In this article, we consider all the methods of maintenance and operation for its maximum life extension. Run DIY compressor repair, if it still broke, maybe.
Reliability of compressor equipment largely depends on timely and high-quality maintenance. A large number of breakdowns of reciprocating compressors is a consequence of poor-quality cleaning of compressible air (abrasive dust, water, and other inclusions). Application and timely replacement and cleaning of filter elements will delay compressor repair for a long time.
The main reasons why an air piston compressor fails:
- Adverse operating conditions
- No scheduled maintenance
- Not competent staff
To ensure high-quality maintenance, operation and repair of the compressor with your own hands, it is necessary to solve all the above points.
The main difference between maintenance and compressor repair is that during the repair, forced replacement of certain parts is carried out, and during maintenance, the parts are replaced as necessary, depending on their actual condition.
Principle of operation and components
A compressor is a device for increasing pressure and moving gas to the desired source (spray guns, grinders, wrenches, airbrushes and any other pneumatic equipment).
The main equipment in demand for body repair was a piston oil compressor.
In reciprocating, the volume of the working chambers is changed using pistons reciprocating.
They have a different number of working cylinders and distinguish them by the following structural arrangement:
- V and W shaped
The main design flaws: incomplete balance of their moving parts, the presence of a large number of friction pairs, etc. All this is the cause of failure and subsequent repair.
Before you repair the compressor yourself, you need to study its technical structure. In the photo below is a diagram of a single-stage compressor, a piston group.
- Connecting rod
- Piston pin
- Cylinder head
- Valve plate
- Oil seals
- Crankshaft bearings
On the case near the electric motor there is an automation unit called a presostat. With it, you can adjust the compressor. It is possible to lower the inflation pressure or increase it.
Piston compressor malfunctions
If any defects are found (the appearance of knocks, jamming of the rubbing parts, strong heating, increased consumption of lubricant, etc.), it is necessary to repair.
It is important to establish the type and amount of repair at the stage of diagnosing the condition of an object before repair. Compressor malfunctions can be divided into two groups: technical malfunctions (piston group working part and electrical equipment malfunctions). Below are the most common breakdowns:
- Compressor (electric motor) does not start
- The electric motor is buzzing and does not rotate
- The compressor is not gaining momentum
- Knock in the cylinder-piston group
- Too hot cylinder
- Performance dropped
- Strong vibration
Compressor (electric motor) does not start
The compressor does not turn on, the most common problem. The main and commonplace that may be in this breakdown is that there is no voltage in the network. The first thing to check is the plug and wire for an open circuit that feed the electric motor.
Using a special “tester screwdriver”, check if voltage is applied at all phases. Check fuse, if equipped. Make sure the starting capacitors are working (single-phase compressors have a voltage of 220V).
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Pay attention to the pressure level in the tank (receiver). Perhaps the pressure is sufficient and the automation does not start the compressor, as soon as the pressure drops to a certain level, the motor will start automatically. This is not a breakdown, many forget about this nuance and worry ahead of time.
Check valve can also be a problem if the compressor does not turn on. Also, a faulty automation unit (presostat) affects the breakdown (on, off), the button on the unit itself may have become unusable.
If the electric motor does not start buzzing, buzzing does not gain the necessary speed or stops during operation, this does not always mean its breakdown.
The main malfunctions of the electric motor that can interfere with its proper smooth operation:
- Low motor power (insufficient mains voltage)
- Loose connections, poor contact
- The non-return valve is out of order (leaking), thereby creating a back pressure
- Incorrect compressor start (see operating instructions)
- Jammed piston group (due to lack of oil level, overload)
If the electric motor of the compressor does not turn on at all and does not make sounds, then this indicates the following:
- The mains fuse has tripped
- Overload protection tripped
- Poor electrical contact (wiring problems)
- The worst thing is that the electric motor burned out (often there is a characteristic smell)
Knock and rumble in cylinder and piston group
One of the causes of compressor failure is a faulty piston group. Recognizing a defect in this system is quite simple.
Usually they are accompanied by a knock, rumble, rattle, and other sounds of a metallic nature.
If the compressor knocks, then its discharge part is faulty, where there are a lot of metal parts that interact with each other. Due to their friction and wear, extraneous noises and unpleasant sounds appear.
You should not start with such a breakdown, if possible, it is necessary to eliminate it as soon as you hear the first signs of their manifestation. The main malfunctions if the compressor began to knock and work loudly than before:
- Crashed bearings, connecting rod bushings
- Faulty bearings on the crankshaft.
- Worn piston, rings, finger on the piston
- Worn cylinder
- The cylinder and head bolts loosened
- Particle hit the cylinder
- Cooling impeller loose on pulley
In order to repair these breakdowns, in simple cases it is enough to extend all the bolts and nuts. If the piston, the crankshaft cylinder or the connecting rod are worn out, then a comprehensive overhaul is needed.
When repairing a piston group, it may be necessary to bore the cylinder, if it is very worn and has external defects, select a repair piston for new dimensions.
The following are possible defects in the piston system:
- Changing the diameter of the piston, cylinder
- Cylinder Mirror Shape Distortion
- Risks, scratches, scuffs on cylinder walls
- Cracks in the main working part
- Cracks and breakage of flanges
During long-term operation due to wear, risks appear on the cylinder mirror, the inner diameter of the sleeve for the eccentric shaft increases. During the repair, the cylinders are restored by pressing liners into them. Worn bushings under the eccentric shaft are replaced.
This repair is quite difficult to do it yourself without the necessary tools and equipment. Since the most time-consuming and crucial step is the restoration of the cylinder.
Boring is performed on a vertical boring machine using a special tool.
This, as regards the cylinder, below we consider the main malfunctions of the compressor crankcase.
- Cracks in the walls of the cavities of the crankcase block
- Deviations in the size and shape of landing sites
- Warping of seats
- Crashed seats under the crankshaft bearings
When these components are worn, they must be replaced with new ones. The hole for the bearings is bored on a horizontal boring machine for a larger diameter of the bearings or for pressing the sleeve with the subsequent boring of the pressed sleeve for the required diameter. Compressor repairs of such complexity should be performed by qualified specialists.
Below, spare parts are “repair kits” for overhauling a compressor, a piston group.
The compressor is hot
If the compressor is very hot, then this indicates its some kind of malfunction. There may be several reasons for overheating. Starting simple, it is blocked by blowing air from the cylinder and crankcase. Check if the impeller is covered by foreign objects.
One of the main reasons for a warming compressor is the lack of oil level. The working units work for wear, high friction is created, and as a result it is very hot. With further such work, the equipment will quickly fail. Check the oil level; if it is not enough, add to the correct level.
Valve malfunctions as a result of carbonated contamination or their weakening. There may also be clogged air ducts.
Look at the pressure level, maybe the automation has broken and the compressor is “hammering” to a lot of pressure, this causes overheating. Repair or replacement of the safety valve may be required.
Try to place the compressor in a cool, spacious place, especially in the hot season. No matter how much cooling he has, it will heat up much less, which will affect his positive and durable work. ” Also, do not forget that the colder the air, the less moisture and oil impurities in it.
A drop in performance may be due to several reasons. Clogged, clogged suction air filter. Remove and clean the filter with compressed air or replace it. Basically in reciprocating compressors it is made of ordinary foam rubber.
There may be an air leak somewhere. Inspect all suitable and escaping tubes and hoses. As in the previous case, wear and malfunction of the valves is possible, this greatly affects performance.
With long enough use, the piston rings wear out and the seal disappears.
In more serious cases, the cylinder and pistons are worn, scratched or have other external defects, which leads to a loss of compression and the compressor stops pumping air.
It is worth checking the tension of the belt connecting the electric motor and the crankshaft of the piston system. When loosening, slippage is possible and the compressor stops pumping air properly.
Oil enters the working chamber
If the oil enters the working chamber, the signs are rather bad, of course, this will not lead to a complete failure of the compressor, but it can very much harm the paintwork and the occurrence of defects during painting.
The main reasons for getting oil to where it doesn’t need: Low viscosity oil is poured, that is, the oil is too liquid, it seeps through seals and rings. Oil level is too high. Due to excess oil, it is squeezed out with force and enters the chamber.
Inappropriate oil used. Fill in special compressor oil only.
Worn pistons and rings in the cylinder block. Also, the wear of the cylinder itself affects the ingress of oil into the working chamber. To eliminate the malfunction, repair of the piston group compressor is required, which is described above.
Operation and maintenance of the compressor
A piston compressor, like any technical equipment, requires certain maintenance. Proper operation will help extend the life of your compressor equipment. Consider the main activities for maintenance, repair and operation of the compressor.
1. Replacing and cleaning the air filter. The filter element is mainly made of non-woven material, foam rubber or sintonin.
If the compressor is located in the same place where the car is painted, then it is clogged up (sticking) by dust from paint, varnish and other paints and varnishes.
The filter prevents abrasive dust from entering the cylinder; the piston and cylinder wear less. Change and clean the filter as often as possible, as this will significantly increase the service life and delay the compressor repair.
2. Oil change is a very important point. Check the oil level on a special indicator (window) in the compressor housing. Work at a low level or without oil leads to serious overhaul.
Top up if necessary. Periodically, it is necessary to completely drain and fill in a new one. Use only special compressor oil.
Mobil, Fubug, Shell VDL 100, KC 19, 46 piston compressor oil or any other proprietary.
3. Condensate drain An important point in compressor maintenance. The air is saturated with moisture; it inevitably enters the receiver with intake air. Over time, it accumulates in large quantities.
With a high condensate content, it can be released into the air hoses, which leads to defects during painting. Also, condensation begins to corrode inside the receiver.
Drain condensate as often as possible, at least once a week, especially in hot and humid seasons.
4. Watch the general condition, periodically blow out from dust and other pollution. Pay special attention to the impeller on the electric motor, the ribs of the cylinder, and the air radiator; during operation, dust adheres to them and dusts off the paint, which reduces cooling ability.
5. Inspect the belt drive for wear and tension. When you press the belt at a midpoint, it should not bend more than 12.15 mm. Do all the bolts and nuts. Periodically check the operation of the safety valve, which serves to protect against overpressure, due to breakage of the pressure switch.
Follow all of the above methods and you will delay the compressor repair for a long time.
KAMAZ compressor diagnostics
In order to evaluate the technical condition of the compressor of a KAMAZ automobile, it is necessary to check the supply, the tightness of the head valves and the oil discharge.
1) Check feed. We raise the car cabin, disconnect the discharge line tube from the compressor, and instead install the apparatus for checking the compressor.
Then we open the isolation valve of the device for checking the compressor, start the engine. In this case, the rotational speed value on the tachometer should be 1100-1200 rpm, which corresponds to the compressor shaft rotation frequency equal to 1200-1300 rpm.
The operation of the car engine at a given frequency is carried out until the pressure indicator in the manometer stabilizes. Pressure from 588.4 kPa (6 kgf / cm²) indicates a normal compressor flow.
2) We check the tightness of the valves of the head.
We reduce the engine speed to the idle speed, turn off the isolation valve, bring the pressure in the device receiver to 588.4 kPa (6 kgf / cm²) and stop the engine.
Now you need to register the drop in air pressure in 60 seconds. Exceeding 39.2 kPa (0.4 kgf / cm²) indicates a malfunction.
3) Checking oil discharge. We disconnect the device from the compressor, start the engine and leave it for 3-5 minutes at a speed of 1600-1800 rpm.
Then, without changing the speed, we set a screen of glossy paper at a distance of 5 cm from the outlet of the compressor elbow, and hold it for about 10 seconds. After this time, we remove the screen and trace the oil stain with a pencil. Its diameter should not exceed 2 cm.
If the screen remains clean or several separate spots of oil appear on it as dots, the compressor is in good condition.
If the oil slick in diameter exceeds 2 cm (increased emission), dismantling and repair of the compressor is required.
In case of failure to take measures, the devices of the supply part of the pneumatic actuator due to the ingress of oil condensate into them may refuse to work.
A decrease in compressor flow, as well as depressurization of the head valves, indicates a loose fit of the disks of the discharge valves. The troubleshooting is done by replacing the compressor head or valve seat.
The feed determines the compressor’s operability: its reduction increases the load on the compressor and further reduces its resource. Operation of the car with a compressor producing insufficient supply is unacceptable due to a decrease in braking efficiency.
Checking the compressor supply should be done regularly by evaluating the filling time of the pneumatic actuator.
The filling time with a working compressor and a sealed pneumatic actuator is no more than 6 minutes. Filling time when checking the road train is 12 minutes.
Maintenance, repair and malfunctions of the GAZ-66 compressor
On GAZ-66 cars, a compressor is installed (Fig. 1), designed to inflate tires with air.
Car compressors with a tire pressure regulation system (GAZ-66-01, GAZ-66-02, GAZ-66-04, GAZ-66-05) differ from car compressors without this system (GAZ-66 and GAZ-66-03 ) in that in the threaded hole of the compressor head above the inlet valve instead of the plug
the unloading cylinder is screwed (Fig. 2).
The piston type compressor, single-cylinder, air-cooled, is driven through a pulley together with the power steering pump with two belts from the engine crankshaft pulley. A compressor clutch is installed on the splines of the crankshaft of the compressor. The coupling moves with a fork mounted on a roller, the position of which is fixed with a ball lock.
The air in the compressor comes from the air filter of the engine. Lubricant comes to the compressor from the car engine.
Periodically check the compressor belt tension. Belts are tensioned by tilting the power steering pump. The angle of the pump should ensure that the oil is filled to the mark “oil level” on the pump tank, and if there is no mark, to the filler filter of the tank.
If the belt tension is not ensured by tilting, reposition the pump. With a very large exhaust hood, rearrange the pump brackets to the additional holes in them.
The tension is considered normal if, when you press a finger on the belt between the pulleys of the pump and the crankshaft of the engine, the belts will bend by 15-20 mm.
Removing and disassembling the compressor is carried out in the following order.
Checking the technical condition and repair of compressor parts
After disassembling the compressor, to eliminate any malfunction, check the technical condition of its main parts.
If the cylinder wear exceeds the permissible or its mirror is damaged, repair the cylinder under one of the repair dimensions specified in table. 2. According to these sizes, pistons and piston rings of repair sizes are produced.
The piston repair size group is indicated by the numbers on the piston bottom: “0.4”, “0.8”.
Repair size piston rings are marked:
one strip with a width of 10 mm corresponds to an increase in the diameter of the ring compared to the nominal by 0.4 mm and two strips by 0.8 mm.
When repairing the crankshaft, use liners of repair sizes, the thickness of which is increased by 0.15 and 0.3 mm. The group of the repair size of the insert is indicated by the numbers on its outer side: “—0.3” and “—0.6” (these inserts have a thickness of 1.9-0.013 and 2.05-0.013 mm, respectively).
If nicks or annular grooves are found on the plate valves of the cylinder head, replace them and rub new valves on the seats to obtain continuous annular contact.
Piston fingers, pistons and connecting rods are divided into four groups, which are sorted by the diameters of the mating surfaces through 0.003 mm (table. 3).
Marking places: piston. on the boss under the finger; piston pin. on the finger plug; connecting rod. on the head under the piston pin.
During assembly, the installation of a finger and a connecting rod of an adjacent group is allowed. The fingers to the connecting rod and piston are selected without lubrication at a temperature of 10-30 ° C. The correct selection of the piston pin to the connecting rod sleeve is checked by touch. When pressed with a thumb, the piston pin without lubrication should move with some resistance in the bushing of the upper connecting rod head.
Compressor assembly When assembling the piston with the finger-connecting rod kit, grease the finger with clean engine oil.
At installation of new rings to check a backlash of a lock after installation in the cylinder. The gap should be equal to 0.20-0.40 mm, and the ring should fit snugly against the cylinder over the entire circumference (check for clearance).
Check that the height of the ring and the piston groove is consistent; the clearance between the groove wall and the ring should be within 0.035-0.080 mm. If the gap is smaller and the ring does not roll along the entire piston groove, the end of the ring can be lightly ground on the smallest sandpaper. Install compression rings in the piston grooves with their recesses facing up, and their joints to be bred 180 °.
During the assembly of the compressor, check the ease of rotation of the crankshaft. The moment necessary for turning it must not exceed; 0.2 kgm. before installing the connecting rod and piston group and 0.3 kgm. after installing this group and tightening the connecting rod bolts (but before installing the head).
When setting the intake valve seat, make sure that the narrower belt of the seat faces the valve. Through the upper hole of the head, check the valve stroke, which should be within 0.7-1.5 mm, and the discharge valve within 1.5-3.2 mm.
Compressor tests after repair. Tests should include running-in (no load), performance tests, leak tests, and the operation of the discharge system.
The running-in of the compressor is carried out for 20 min at 1200. 1350 rpm of the crankshaft. The pressure of the oil entering the compressor should be 1.5-3.0 kg / cm2, the temperature should not be lower than 40 ° C. The pressure of the air cooling the compressor must ensure that the temperature of the compressor head is not higher than 90˚.
Performance test carried out at 1200. 1350 rpm of the crankshaft and when pumping air into the tank with a capacity of 23 l.
At a pressure in the tank of 6.5 kg / cm2, the cavity of the tank communicates with the atmosphere with a calibrated hole with a diameter of 1.0 and a length of 3 mm; under these conditions, the compressor must maintain a pressure in the tank of at least 6 kg / cm2 during continuous operation for 3 min.
At the indicated operating mode of the compressor, the discharge of oil with forced air should not exceed 1 cm3 for 5 mim.
Tightness they check on an idle compressor by supplying air at a pressure of 5. 5.5 kg / cm2 to the discharge pipe of the compressor head from a 1 liter tank. The pressure drop in the cylinder should be no more than 0.3 kg / cm2 for 1 min.
Unloading system operation (for compressors with an unloading cylinder) is checked by supplying compressed air under a pressure of 5-5.5 kg / cm2 to the unloading cylinder. In this case, the piston of the unloading cylinder should lower and fully open the inlet valve.
At the same time, check the tightness of the piston seal of the unloading cylinder. The pressure drop in the tank with a capacity of 1 l and at a pressure of 5. 5.5 kg / cm2 should not exceed 0.25 kg / cm2 for 1 min.
When depressurizing, the piston under the influence of a return spring should clearly return to its original position.