Design of piston compressor with explanatory note

4 Design, calculation and maintenance of the garage compressor BALMA NS 59 S/500 FT 10

4.1 Principle of operation, arrangement and adjustment of equipment

4.1.1 Classification, characterization and analysis of compressor structures.

Due to the increase in the fleet of domestic cars of new brands and foreign cars, at present a fundamental technical re-equipment of motor transport enterprises, maintenance stations and car repair workshops is required with new modern technological equipment and a specialized tool. Without such equipment, it is almost impossible to carry out a number of maintenance and ongoing repairs of modern cars with original designs of units, units and systems. A level that meets world standards in terms of productivity and quality of technical impacts can only be achieved using specialized equipment, combined with the use of new progressive forms and methods of technical equipment and car repair.

The compressor is the most important power equipment used in the technological processes of many industries, including the automotive industry to increase pressure and move gas.

Compressor machines are divided into three classes:

fans - compressors, with relatively low increase and pressure ratio;

superchargers - machines with increased pressure ratio and without medium cooling during operation;

actual compressors are machines equipped with a device for cooling the medium during operation (pressure ratio is more than 3).

According to the achievable end result, one distinguishes:

low-pressure compressors with final pressure up to 1MPa;

medium pressure compressors with final pressure from 1 to 10MPa;

high-pressure compressors with a final pressure of 10 to 100mPa;

ultra-high pressure compressors with a final pressure of more than 100mPa.

According to the method of operation, compressors can be divided into: stationary, mobile, portable, trailed, self-propelled, transport.

Compressors are divided into:

gas - to compress any gas or gas mixture other than air;

air - for air compression;

circulation - to ensure circulation of air (gas) in the closed process circuit;

multipurpose - for alternating compression of various gases;

multi-service (special) - for simultaneous compression of various gases;

Classification of compressors according to the principle of action and main structural features:

1) volumetric action: piston, piston-membrane, membrane;

2) dynamic action: turbocompressors, jet.

Two types of compressors are used in the car service: piston (more common) and rotor (screw) (for large STOs with an air consumption of more than 1000 l/min).

The main characteristics of compressors are volumetric capacity and maximum pressure. These parameters are decisive when selecting the type and model of this equipment.

So, for pumping tires or working with a blowing pistol, a compressor with a capacity of 150-200 l/min with a small receiver (a storage tank for storing compressed air) is quite suitable. At bus assembly points, a capacity of 300-400 l/min with a receiver volume of 50-100 liters is usually enough. Small car shops at 3-4 stations using a pneumatic tool require a compressor with a capacity of about 600 l/min. One painting pistol of the painting area needs the same amount. For large service centers with a branched pneumatic network with dozens of consumers, you need to purchase an apparatus with a capacity of at least 1000-1500 l/min.

The pressure developed by the compressor must be greater than the required pressure for the compressed air consumers. A compressor with a pressure of 800 kPa (8 bar) is considered to be the standard for STOA use. In case of application exclusively for painting works, a compressor with 600 kpa (6 bar) can be used. As a source of compressed air in branched pneumatic networks, a compressor with a pressure of at least 1.0 MPa (10 bar) will be more suitable. The performance and pressure values are directly affected by the apparatus design.

Modern piston compressors are available in four versions:

- "Hobby" class;

- class of professional oil compressors with direct transmission;

- class of professional reciprocating compressors with belt drive;

- class of industrial reciprocating compressors with belt drive.

Hobby-class compressors. This class of compressors uses a single-cylinder, single-stage dry (oil-free) type compressor group, designated in catalogs - "cycle/tap. - 1/1». This means that the entire compression process takes place in one cylinder.

Rotation from the motor shaft is transmitted directly through the coupling (coaxial type) to the crank mechanism of the compressor. Power consumption does not exceed 2.25 kW, pressure - up to 800 Kpa, recommended duration of operation - not more than 15 - 20 minutes per hour. Compressors are made both without a receiver and with receivers with a capacity of 6 to 50 liters for more intensive short-term use.

Compressors without lubrication of the cylinder-piston group are called unattended. Due to the absence of the crankcase, they can operate in any position, air from them comes without oil. But the resource of such mechanisms is lower than that of similar lubricated models, no matter what antifriction materials and designs of unmasked bearings are used

Compressors of this class are designed for rather rare use, mainly for domestic purposes, for work at home, in the garage, in the country, etc. Therefore, great attention is paid to their consumer properties in the design of these compressors. They have a small weight and dimensions, low noise level, practically no maintenance, can be transported both vertically and horizontally.

The field of application dictates a number of special requirements. Compressor housing is made of impact-resistant polystyrene and is designed to reduce noise level and protect consumer from burns. The use of direct transmission between the electric motor and the compressor group made it possible to extremely simplify the design of the compressor and reduce its cost.

The suction capacity of such compressors is in the range of up to 200 l/min. For single-cylinder single-stage direct-transmission compressors, the correction factor for calculating real productivity is 0.60.65.

This class of compressors is not designed for high-intensity work during the working day, so this equipment has practically not been used at STOA, but it can be found in small car shops.

Professional oil compressors with direct transmission (coaxial type). The lack of lubrication in Hobby compressors negatively affects the resource of the devices, therefore, oil compressors with direct transmission are used to increase it.

In this type of compressors, as well as in other types of piston oil compressors, the lubrication of the connecting rod-piston group is organized in the same way. The oil in the crankcase is supplied to the rubbing parts by spraying. The "sprinkler" is a special needle-like tide on the lower head of the connecting rod, which, when the compressor shaft rotates, is periodically immersed in an oil bath and sprays oil particles on the cylinder walls, preventing dry friction.

The use of lubrication reduces the coefficient of friction and thereby reduces the operating temperature of the head, and, therefore, increases the intensity of the coaxial oil compressor, so its application is much wider than that of the Hobby class compressors.

The productivity of compressors of this type ranges from 170 l/min to 400 l/min at 2850 rpm. The correction factor for real productivity is 0.60.65.

A direct-transmission oil compressor is the most common type of compressor. The word "professional" is not present in the name of this class by chance. The optimal price-quality ratio was used by him in a wide variety of small business areas, where there is no such burden as in serial and small-scale mass production. These compressors are suitable for use in small car service enterprises, but they are poorly adapted for round-the-clock work and should not be used for more than 40 minutes per hour.

At relatively low cost, high-performance versions of coaxial lubricated compressors are attractive for use in bus assembly areas. But this class of compressors also found the most widespread use in the field of personal consumption - for the garage, house, cottage. It, like the Hobby compressor, is indispensable for minor repairs of a personal car (blowing of a radiator, carburetor, painting, tire pumping, etc.).

This class uses compressors with single-cylinder single-stage and double-cylinder single-stage compressor groups.

The single-stage compressor has one stage of air compression, i.e. when the piston cylinder moves downwards, air is sucked from the atmosphere, and when it moves upwards, it is pumped to the receiver .

The theoretical performance of the compressor is equal to the product of the volume of the compression chamber by the number of compression cycles per unit time. This defines the main ways to increase productivity, an important characteristic for a professional compressor. An increase in the volume of the chamber, achieved by an increase in the diameter of the cylinder, piston or its stroke, leading to an increase in the mass of moving parts, from a certain moment becomes unprofitable.

In this case, a two-cylinder circuit is used, which allows, at a constant rotation speed of the motor, to double the number of compression cycles or reduce the rotation speed, winning in the resource of the drive mechanism. In a two-cylinder compressor group, unlike a single-cylinder one, two pistons operate simultaneously, but in antiphase, when one sucks air, the other is in the discharge mode.

In coaxial two-cylinder compressors, the cylinder arrangement may be in-line or V-shaped. The V-shaped arrangement of the cylinders is the most successful from the point of view of compensation for inertial forces arising from the movement of the pistons. The capacity of V-shaped coaxial compressors reaches 400550 l/min.

When purchasing two-cylinder compressors, preference should be given to those models in which increased performance is combined with a low (1450 rpm) motor speed. They are more reliable, as confirmed by the longer warranty period of the manufacturer, usually increasing by 30%.

Professional belt-driven piston compressors. This class includes oil compressors having a different design than coaxial compressors. These are compressors with V-belt transmission from the motor to the compressor head. The advantages of such a scheme are obvious. The absence of a rigid connection between the electric drive and the compressor head in case of failure of one of the units minimizes the possible consequences. In addition, the belt transmission allows designers to flexibly select the optimum compressor shaft speed to ensure the desired performance of a particular model.

This compressor drive scheme improves the cooling efficiency of the head, since the fan-cooled motor heated during operation is arranged separately. Head is blown by pulley of drive shaft whose spokes are made in the form of blades.

The use of the forced air cooling system, thanks to the special design of the guide air flow from the pulley - fan, allows to further reduce the compressor temperature. The reduction of the speed of the compressor group and the special measures taken for more efficient cooling at the same capacity as the compressors with direct transmission make it possible to increase the resource and use this type of compressor for a more intensive mode of operation.

The thermal mode of the head is critical to the compressor operating mode. Therefore, V-belt compressors operate in a longer mode. The life of such compressors is 5000 hours or more.

V-belt compressors may be single-cylinder or double-cylinder. Single-cylinder compressors are produced in a mobile version, two-cylinder compressors can be both mobile and stationary.

The range of single-cylinder compressors is limited to 500 l/min, and two-cylinder compressors with V-belt transmission begin with a capacity of 250 l/min and reach a capacity of 1000 l/min.

In two-cylinder compressor heads, the in-line arrangement of cylinders is used. The use of a belt drive in this class made it possible, using a two-cylinder single-stage compressor group, to reduce the speed of the compressor shaft by almost half compared to the engine speed. Unlike direct-transmission compressors of the same capacity, in which the speed of the engine and the crankshaft are equal, in belt-transmission compressors, the RPM is reduced due to a change in the gear ratio between the engine and the compressor head.

Thanks to good technical characteristics and relatively low cost, compressors of this class have been widely used both at large STOs and at small car service enterprises.

Industrial piston compressors with belt drive. Belt-driven compressors of this class are divided by design and layout into two groups - devices with one compressor head and with two compressor heads, the so-called tandem compressors.

In the class of industrial compressors with belt drive, a two-cylinder two-stage compressor group is used. Such a scheme allows at the constant speed of the motor to double the number of compression cycles or reduce the rotation speed, further facilitate the temperature mode of operation of the compressor, which gives a significant benefit in the resource of the mechanism. Compressors can operate in a longer mode. Their resource is over 5000 hours. Two-stage compressors with V-belt transmission are oriented to work in difficult conditions.

The use of a two-cylinder two-stage compressor group allowed to increase its life. Compressors with two-stage compression have a capacity of 500 l/min and higher.

Compressors with one compressor head and two-stage air compression are produced with horizontal and vertical receivers. In most cases, such compressors are stationary. With a vertical receiver, compressors are more compact and occupy a smaller production area.

Higher performance requirements can be met with two-head compressors. This is the so-called tandem. His work has no fundamental differences. In fact, these are two compressors, but using the same receiver. Both heads, working on a common receiver, have independent drives and independent pressostats (pressure adjustment devices). The pressostat of one of the heads is adjusted by 50 kPa (0.5 bar) of lower actuation pressure than that of the other. At the same time, both heads can work simultaneously and in parallel, or one of the heads acts as the main one, the other is connected in the case of peak air discharge, when the first one does not provide the required performance. One compressor group is switched on first, and then, after a set time, a second one. Electronic control device is used in tandems.

Tandem compressor capacity up to 2000 l/min. The reliability of such devices is doubled, and the danger of remaining without compressed air at all is minimized. If one of the heads fails, the second will be able to temporarily meet production needs. From time to time, adjustments of the pressostats are reversed in order to equalize the operating time of both heads.

Rotary (screw) compressors

With a large STR with a compressed air consumption of 1000 to 5000 l/min and above, rotor (screw) compressors are more suitable, providing pressure on the exhaust line up to 1.5 MPa 1 (15 bar). In this sector, they are more economical and promising. Rotary machines are a completely different level of technology, quality and reliability. They are more expensive than professional pistons, but with intensive use and taking into account all operating costs, the price difference pays off very quickly. Rotary compressors are quite simple in design, equipped with an automatic control and serviceability control system, and therefore are safe, do not need control, have great reliability, are able to work for a long time without maintenance. They have a number of advantages: they have a low level of noise and vibration, small dimensions and weight, practically do not consume oil (2-3 mg per 1m3 of air flow.). The quality of compressed air from screw compressors is an order of magnitude higher than that obtained using piston compressors.

Compressors of this type are produced in a housing installed on the receiver, or without a receiver. In the latter case, the receiver is installed separately and connected to the compressor by high-pressure air hoses.

4.3 Installation, maintenance and repair of BALMA NS 59 S/500 FT 10 compressor

4.3.1 BALMA NS 59 S/500 FT 10 compressor installation

When selecting the mounting position of the device, consider the following points:

- Access to oil filling/level measurement holes and drain plugs.

- Sufficient space for circulation of cooling air around the device.

- Sufficient distance from heat sources, such as the exhaust system of the vehicle or hot pipes, which may in any case affect the compressor temperature.

- Air discharge by bypass/control valve shall be unobstructed and directly to atmosphere.

- The bypass and/or safety and adjustment valve shall be located as close to the outlet as possible.

- The exhaust valves shall be so arranged that no hot air enters the operator or compressor.

- The silencers shall be placed as close to the outlet as possible.

- For information on the recommended layout of the device and auxiliary systems.

The mass of a standard compressor without auxiliary systems is 295 kg. The mounting surface on which the standard article is installed shall be even to avoid skew/stress, the mounting bolts/locking nuts shall be of size M16, class 8.8 or higher. The standard compressor is supplied with an installed rymbolt designed for lifting operations. After installation of the device, remove the eye-bolt and close this place with an insulating washer (attached in the package). Any equipment used for lifting operations shall comply with the requirements of the regulations.

4.3.2 Compressor Maintenance and Repair

Timely high-quality maintenance and repair are the key to trouble-free and trouble-free operation of the compressor .

It is not allowed to exceed the operating pressure in the receiver.

Maintenance of piston compressors is divided into:

- daily maintenance (ES) performed during the working shift;

- scheduled maintenance depending on the operation mode of the head is performed (approximately) after development of the compressor head:

- 175... 200 hours - TO-1 ;

- 500.. 750 hours - TO-2 .

In EO:

- check the oil level in the compressor head crankcase before starting the pistons into operation and, if necessary, add to the top mark of the probe;

- check the condition and tension of the drive belts transmitting rotation from the motor to the crankshaft of the compressor head;

- check the safety valve operation;

- check tightness of connections;

- if air or oil leak is detected, eliminate the fault cause;

- check the operation of the dehydrator. After 2... 3 hours of operation, after depressurizing the receiver, condensate must automatically drain through the moisture removal device ;

- constantly clean both compressor head and compressor as a whole from dust and dirt.

At TO1:

- replace oil in compressor head crankcase, wash crankcase and magnetic plug;

- check the filter element of the air filter made of ultra-thin glass fiber, if necessary - replace the filter element;

- remove the drain plug from the low pressure header on the compressor head and drain the condensate; wash the water removal valve;

- check tightening of connecting rod bolts; check tightening of connections and, if necessary, tighten: nut of flywheel attachment, nuts of cylinder block attachment to housing, nuts of cylinder head attachment, nuts of colletors and pipes attachment, nuts of crankcase covers attachment

At TO2:

- remove cylinder block head, cylinder block - clean pistons, piston rings, valves, internal walls of cylinders and covers from oil coke; - clean compressor cooling surfaces; after cleaning the external surfaces of the cooler of piston compressors and pipelines from dust, dirt, oil deposit, it is necessary to wash them with water and blow them with compressed air; blow the receiver with compressed air;

- replace gaskets ensuring tightness of connections; Replace individual parts from the spare parts set.