When repairing main gas pipelines, it is necessary to comply with the safety rules set out in GOSTs, OSTs of the Occupational Safety Standards System (OSSS) and other regulatory documents.

The main industrial hazards and hazards at the facility are as follows:

* on a relatively narrow strip, in the work zone, work is carried out simultaneously and transport operations are carried out, which leads to the concentration of a large number of mechanisms in certain places and the movement of traffic past moving people in cramped conditions;

* dangerous work associated with lowering strings of pipes, etc. into a trench;

* saturation of the air with harmful gases, gasoline vapors, dusty splashes of insulating mastic during insulation work;

* possibility of defeat electric shock when carrying out welding work;

* work is often carried out in the dark without sufficient lighting of the work area and workplaces.

That's why construction site, work areas, workplaces, passages and approaches to them in the dark must be illuminated accordingly. Illumination should be uniform, without the glare of lighting devices on workers. During assembly and welding work, stationary lamps with a voltage of 220 V, suspended at a height of at least 2.5 m, should be used to illuminate workplaces at night. The voltage of portable lamps should not exceed 12 V.

Processes of increased danger during the construction of pipelines are loading and unloading of pipes and pipe sections using lifting equipment, and their transportation by pipe carriers and pipe carriers.

Harmful effects of harmful substances on the human body

At the operating facility, the main explosive, hazardous and toxic substances are: gas, ethyl mercaptan (odorant), methanol.

Operating personnel working at an operating facility must know the composition and basic properties of gases and its compounds. Action harmful substances used in production on the human body depends on the toxic properties of the substance, its concentration and duration of exposure. Occupational poisoning and illness are only possible if the concentration of a toxic substance in the air of the work area exceeds a certain limit.

Table 6 - Information on hazardous substances at the facilities of Gazprom Transgaz Tchaikovsky LLC

Natural gas is a colorless mixture of light natural gases, lighter than air, without a noticeable odor (an odorant is added to impart an odor). Explosion limits 5.0... 15.0% by volume. MPC in the air production premises 0.7% by volume, in terms of hydrocarbons 300 mg/m 3. Self-ignition temperature 650°C.

At high concentrations (more than 10%), it has a suffocating effect, since oxygen deficiency occurs; as a result of increasing the concentration of gas (methane) to a level of at least 12%, it is tolerated without noticeable effect, up to 14% leads to a mild physiological disorder, up to 16% causes severe physiological effect, up to 20% - already deadly suffocation.

Ethyl mercaptan (odorant) - used to give an odor to gases transported through the main gas pipeline; even in small concentrations they cause headaches and nausea, and in high concentrations they act on the body like hydrogen sulfide; in significant concentrations it is toxic, affects the central nervous system, causing convulsions, paralysis and death.. The maximum permissible concentration of ethyl mercaptan in the air of the working area is 1 mg/m 3.

The odorant evaporates and burns easily. Poisoning is possible by inhaling vapors or absorption through the skin. In its toxicity it resembles hydrogen sulfide.

The concentration of ethyl mercaptan vapor 0.3 mg/m 3 is the limit. Ethyl mercaptan vapor in a certain mixture with air forms an explosive mixture. Explosion limits 2.8 - 18.2%.

Methane in its pure form is not toxic, but when its content in the air is 20% or more, the phenomenon of suffocation, loss of consciousness and death is observed. Saturated hydrocarbons exhibit more toxic properties with increasing molecular weight. So propane causes dizziness after a two-minute stay in an atmosphere containing 10% propane. MPC (maximum permissible concentration) is 300 mg/m3.

Ethyl mercaptan interacts with iron and its oxides, forming iron mercantides (pyrophoric compounds) that are prone to spontaneous combustion.

To provide safe conditions for execution various types construction and installation work and to eliminate injuries, workers and engineering and technical personnel are required to know well and follow the basic safety rules.

In this regard, workers and engineering and technical personnel involved in the construction or repair of pipelines are trained in their specialty and safety regulations. The knowledge test is formalized with appropriate documents in accordance with current industry regulations on the procedure for testing knowledge of rules, regulations and instructions on labor protection.

Before starting work on repairing gas pipelines, the organization operating the gas pipeline is obliged to:

* give written permission to carry out work on repairing the gas pipeline;

* clean the gas pipeline cavity from condensate and deposits;

* identify and mark gas leaks;

* disconnect the gas pipeline from the existing main;

* identify and mark gas pipeline locations at a depth of less than 40 cm;

* provide communication between repair and construction areas with the control room, the nearest compressor station, the nearest lineman’s house and other necessary points;

* provide technical and fire safety during repair work.

After shutting down and removing the pressure in the gas pipeline, grading and stripping work is carried out.

The gas pipeline is opened with an overburden excavator in compliance with the following safety conditions:

* opening of the gas pipeline must be carried out 15-20 cm below the lower generatrix, which facilitates slinging the pipe when lifting it from the trench;

* it is prohibited to carry out other work and keep people in the operating area of ​​the working body of an overburden excavator.

The location of mechanisms and other machines near the trench should be behind the prism of soil collapse.

Hot work on the gas pipeline should be carried out in accordance with the requirements Standard instructions on the safe conduct of hot work at gas facilities of the USSR Ministry of Gas Industry, 1988.

Electric welders who have passed the established certification and having the appropriate certificates. When working with a cleaning machine, make sure that a foam or carbon dioxide fire extinguisher is installed on it.

Turbine oils are lubricating oils with a wide range of applications - in addition to being used as a lubricant for bearings and gearboxes in steam turbines and hydraulic turbines, as a working oil for brake systems, they are also used in compressors, fans and other mechanisms. Typically, turbine oils consist of highly refined paraffinic base oils to which various combinations of additives are added to give the oils the required performance characteristics.

There are 2 types of turbine oils - with additives and without additives, classified by the Japanese industrial standards system according to the K 2213 standard.

9-1 Necessary properties that turbine oils must have

Turbine oils have a fairly broad purpose, and since they must act as a lubricant for bearings, gears, compressors and other mechanisms under various conditions, they are subject to the following requirements:

(1) Have a degree of viscosity corresponding (suitable) to operating temperature conditions

(2) Possess antioxidant properties and thermal oxidation stability

(3)Have high anti-corrosion properties

(4)Have high demulsifying ability and provide good water separating ability

(5) Possess high anti-wear properties

(6) Possess high anti-foam properties.

1. 
   Viscosity grade

1. 
   Stability to thermal oxidation and antioxidant properties

1. 
   Anti-corrosion qualities

1. 
   Demulsifying ability

Typically, highly refined base oils have good demulsifying properties, but when adding an anti-corrosion additive, the demulsifying ability is reduced, so it is very important to maintain the right balance.

1. 
   Anti-wear properties

1. 
   Anti-foam properties

Air foam, causing oil oxidation, also harms the lubrication process and leads to excessive oil loss from the oil tank, so it is important and necessary that the oil has anti-foam properties. And usually, as such an additive, a foam damper of silicone origin is added, which quickly extinguishes the resulting foam.

1. 
   Turbine lubrication

1. 
   Bearing lubrication

Since turbines are operated for a long time, this factor increases oil oxidation.

1. 
   Gearbox lubrication

On ships, turbines equipped with gearboxes with gears are predominantly used; the same turbine oil with additives is used to lubricate the main (drive) bearings of the turbine, gearbox, bearings, outer rings of bearings and gears.

Due to the fact that as the power of ship turbines increased and their size decreased, the load on the gearbox increased and became quite high, it became necessary to additionally add an “extreme load” additive to turbine oils, and oils with such additives are designated as “turbine oil for extreme loads.” loads" (EXTREME PRESSURE)

1. 
   Turbine speed regulator

1. 
   Deterioration of turbine oil parameters (oil decomposition) and standards for its replacement

Therefore, the process of oil decomposition occurs gradually, step by step. This process is expressed by a color change from red to red-brown and then to black, and the appearance of an irritating odor. At this stage, the acid number increases, sludge is formed, and anti-foam, anti-corrosion, and demulsifying properties decrease.

Since to some extent it is possible to control the process of oil decomposition by paying attention to those. condition of the lubrication system in normal turbine operating mode, below are several points that need to be paid attention to when periodically checking the condition of the lubrication system.

1. 
   Oil cooler

1. 
   The presence of foreign (foreign) substances in the lubrication system.

Before adding oil, it is necessary to remove foreign substances by flushing or purging, and it is also important to take measures to protect against the penetration of foreign substances from the outside through the air ventilation system.

Of course, it is impossible to completely avoid the entry of foreign substances into the lubrication system, so it is important to regularly remove test samples from the lubrication system, or carry out regular maintenance of filters and washing equipment, and it is also important to clean the system.

1. 
   Ventilation

1. 
   Technical factors

For example, if air enters the internal pumping part of the system, the oil begins to foam; if the seals are not tightly sealed, a connection with water and steam occurs; if the oil pipeline comes into contact with areas with high temperatures, then the oil temperature will increase if the ends of the pipes through which it returns When the oil is located above the oil level, air is mixed in, and any of these factors accelerate the deterioration of the performance parameters of turbine oils, so sufficient attention must be paid to the location of the pipeline and the design of the turbine.

1. 
   Timing for replacing turbine oils

Ecology/4. Industrial ecology and occupational medicine

Ermolaeva N.V., Doctor of Technical Sciences Golubkov Yu.V., aspirant Aung Khaing Pyu

Moscow State University of Technology"Stankin"

Minimizing the impact of oil-based cutting fluids on human health

The threat to human health and well-being associated with environmental pollution is currently one of the most pressing problems. According to the World Health Organization, environmental pollution is responsible for approximately 25% of all diseases worldwide, with children accounting for more than 60% of the diseases caused by this cause.

Lubricating and cooling technological agents (LCTS), the vast majority of which are cutting fluids (LCFs), are an integral element of the technological processes of modern metalworking industries. There are a number of requirements for oil-based coolants. In particular, they should not cause a pronounced biological effect on the skin and respiratory organs of the worker, have a minimal irritating effect when exposed to mucous membranes, have a low ability to form oil mist, and not contain 3,4-benzpyrene and some other hazardous substances.

The main health risk factor for workers working with oil-based cutting fluids is the entry into the respiratory tract of aerosols of oil, formaldehyde, acrolein and other products of thermal-oxidative destruction. It has been established that even if the maximum permissible concentrations in the working area for acrolein, benzene, formaldehyde, 3,4-benzpyrene, acetaldehyde are observed, the individual lifetime carcinogenic risk with twenty years of production experience can reach 9* 10 -3 , and with thirty years of experience – 1.3* 10 -2 , which is significantly higher than acceptable (1* 10 -3 ) for professional groups. Despite the fact that for almost all components that make up cutting fluids and the products of their thermal-oxidative destruction, there are maximum permissible concentrations, cutting fluids, being complex mixtures, can have an adverse effect on human health. Since it is difficult to reliably predict this effect on the basis of theoretical analysis, a mandatory step in determining the degree of danger of cutting fluids is their toxicological assessment, which determinesLD 50 , L.C. 50 , ability to irritate skin and mucous membranes, sensitizing and mutagenic properties, hazard class.

Most often, oil coolants are made on the basis of industrialny oils. Therefore pIt is of significant interest to determine the molecular composition of industrial oils in order to identify individual compounds - potential environmental pollutants. Such data is necessary for the development and adoption of measures to implement active methods for protecting personnel and the environment from harmful components of oil coolants.

In this work, we used the chromatography-mass spectrometric method to study the molecular composition of some brands of oil coolants (MR-3, MR-3K, SP-4) and industrial oil (I-40A). As a result of the studies, it was established that the most harmful substances in MP-3 coolant for humans and the environment are benzene homologues - ethylbenzene and m-xylene, present in amounts from 2.4 to 3.3 ng/g. It has also been established that polycyclic aromatic hydrocarbons are present in MP-3K brand coolant: 3-methylphenanthrene, 9- and 2-methylanthracene in amounts from 6.0 to 21.2 ng/g. It has been shown that the most harmful substances in SP- brand coolant 4 are halogen-containing organic compounds contained in amounts from 0.3 to 1.0 μg/g.

Almost all organic substances are hazardous to the environment. The most powerful carcinogens in petroleum oils are aromatic hydrocarbons (MPC 0.01...100 mg/m³), olefins (1...10 mg/m³), as well as sulfur, nitrogen and oxygen compounds. Currently, it is difficult to identify the substances that are most harmful to the environment, since many of them, including alkylphenols, have a structure similar to sex hormones and affect people’s reproductive health and cause an increase in cancer. For example, the carcinogenic effect of nonylphenol, which accelerates the development of cancer cells, was accidentally discovered.

One of the principles of the scientific and educational complex “Environmental Engineering, Labor and Life Safety” of MSTU “Stankin” is the priority of minimizing the impact on the environment and humans before managing this impact. The implementation of this principle lies in the fact that it is necessary to reduce the impact on the environment and humans directly at the source, and not then take measures to manage this impact through the construction of treatment facilities of various types, waste disposal, their neutralization, etc.

Let us list possible methods for purifying industrial oil I-40A and the mentioned oil coolants from harmful components. Hydrotreating– the most effective method for removing sulfur compounds of all types from petroleum products. Adsorption on natural clays and other adsorbents - universal cleaning method. This work, in our opinion, should be carried out at the coolant manufacturer.

Literature:

1. Onishchenko G.G., Zaitseva N.V., Ulanova T.S. Control of the content of chemical compounds and elements in biological media: Guide. – Perm: Book format, 2011. – 520 p.

2. Lubricating and cooling technological means and their use in cutting: Directory / Under the general. ed. L.V. Khudobina. - M.: Mechanical Engineering, 2006. - 544 p.

3. Maistrenko V.N., Klyuev N.A. Ecological and analytical monitoring of persistent organic pollutants. – M.: BINOM. Laboratory of Knowledge, 2004. – 323 p.

Turbine oil is a high-quality distillate oil obtained during the distillation process of petroleum. The lubrication and control system uses turbine oils (GOST 32-53) of the following brands: turbine 22p (turbine with VTI-1 additive), turbine 22 (turbine L), turbine 30 (turbine UT), turbine 46 (turbine T) and turbine 57 (turbo - gearbox). The first four grades of oil are distillate products, and the latter is obtained by mixing turbine oil with aviation oil.

In addition to oils produced in accordance with GOST 32-53, turbine oils produced in accordance with Inter-Republican Technical Specifications (MRTU) are widely used. These are primarily sulfur oils with various additives, as well as low-sulfur oils from the Fergana plant.

Currently, digital marking of oils is used: the number characterizing the type of oil represents the kinematic viscosity of this oil at a temperature of 50°C, expressed in centi-Stokes. The index “p” means that the oil is used with an antioxidant additive.

The cost of oil is directly dependent on its brand, and the higher the viscosity. oil, the cheaper it is. Each type of oil must be used strictly for its intended purpose, and replacing one with another is not allowed. This especially applies to the main energy equipment of power plants.

Application areas are different. oils are defined as follows.

Turbine oil 22 and 22p is used for bearings and control systems of small, medium and large turbogenerators. power with a rotor speed of 3000 rpm. Turbine oil 22 is also used for sliding bearings of centrifugal pumps with circulation and ring lubrication systems. Turbine 30 is used for turbogenerators with a rotor speed of 1500 rpm and for ship turbine installations. Turbine oils 46 and 57 are used for units with gearboxes. between the turbine and the drive.

Physico-chemical properties of turbine oils. are given in table. 5-2.

Turbine oil must meet the standards of GOST 32-53 (Table 5-2) and be highly stable in its properties. Of the main properties of oil that characterize its performance qualities, the most important are the following:

Viscosity. Viscosity, or coefficient of internal friction, characterizes friction losses in the oil layer. Viscosity is the most important characteristic of turbine oil, according to which it is labeled.

The viscosity value determines such operationally important values ​​as the coefficient of heat transfer from the oil to the wall, power loss due to friction in bearings, as well as oil flow through oil lines, spools, and metering washers.

Viscosity can be expressed in units of dynamic, kinematic and conditional viscosity.

Dynamic viscosity, or internal friction coefficient, is a value equal to the ratio of the internal friction force acting on the surface of a liquid layer with a velocity gradient equal to unity to the area of ​​this layer.

Where Di/DI is the velocity gradient; AS is the surface area of ​​the layer on which the internal friction force acts.

In the CGS system, the unit of dynamic viscosity is the poise. Poise dimension: dn-s/cm2 nli g/(cm-s). In technical system units, dynamic viscosity has the dimension kgf-s/m2.

There is the following relationship between dynamic viscosity, expressed in the GHS system, and technical:

1 poise = 0.0102 kgf-s/m2.

In the SI system, the unit of dynamic viscosity is taken to be 1 N s/img, or 1 Pa s.

The relationship between old and new viscosity units is as follows:

1 poise = 0.1 N s/mg = 0.1 Pa-s;

1 kgf s/m2 = 9.80665 N s/m2 = 9.80665 Pa-s.

Kinematic viscosity is a value equal to the ratio of the dynamic viscosity of a fluid to its density.

The unit of kinematic viscosity in the CGS system is st o k s. Stokes dimension - cm2/s. One hundredth of a Stokes is called a centistokes. In the technical and SI systems, kinematic viscosity has the dimension m2/s.

Conditional viscosity, or viscosity in degrees Engler, is defined as the ratio of the time of flow of 200 ml of the test liquid from a VU or Engler type viscometer at the test temperature to the time of flow of the same amount of distilled water at a temperature of 20°C. The magnitude of this ratio is expressed as the number of conventional degrees.

If a VU type viscometer is used to test oil, then the viscosity is expressed in conventional units; when using an Engler viscometer, the viscosity is expressed in Engler degrees. To characterize the viscosity properties of turbine oil, both units of kinematic viscosity and units of conditional viscosity (Engler) are used. To convert degrees of conditional viscosity (Engler) to kinematic, you can use the formula

V/=0.073193< - -, (5-2)

Where Vf is the kinematic viscosity in centi-Stokes at a temperature t 3t is the viscosity in degrees Engler at a temperature t E is the viscosity in degrees Engler at 20°C.

Oil viscosity depends very strongly on temperature (Fig. 5-ii3), and this dependence is more pronounced

Rns. 5-13. Dependence of turbine oil viscosity on temperature.

22, 30, 46 - oil grades.

Expressed in heavy oils. This means that in order to maintain the viscosity properties of turbine oil, it is necessary to operate it in a fairly narrow temperature range. Technical operation rules set this range within 35-70°C. Operation of turbo units at lower or higher oil temperatures is not permitted.

Experiments have established that the specific load that a sliding bearing can withstand will melt with increasing oil viscosity. As the temperature rises, the viscosity of the grease decreases and, consequently, the load-bearing capacity of the bearing, which can ultimately cause the lubrication layer to cease to function and the babbitt filling of the bearing to melt. In addition, at high temperatures, the oil oxidizes and ages faster. At low temperatures, due to an increase in viscosity, oil consumption through the metering washers of the oil lines is reduced. Under such conditions, the amount of oil supplied to the bearing is reduced, and the bearing will operate with increased oil heating.

The dependence of viscosity on pressure can be more accurately calculated using the formula

Where v, - kinematic viscosity at pressure p Vo - kinematic viscosity at atmospheric pressure; p - pressure, kgf/cm2; a is a constant, the value of which for mineral oils is 1.002-1.004.

As can be seen from the table, the dependence of viscosity on pressure is less pronounced than the dependence of viscosity on temperature, and when the pressure changes by several atmospheres, this dependence can be neglected.

The acid number is an indicator of the acid content in the oil. The acid number is the number of milligrams of potassium hydroxide required to neutralize 1 g of oil.

Lubricating oils of mineral origin contain mainly naphthenic acids. Naphthenic acids, despite their mild acidic properties, when in contact with metals, especially non-ferrous ones, cause corrosion of the latter, forming metallic soaps that can precipitate. The corrosive effect of oil containing organic acids depends on their concentration and molecular weight: the lower the molecular weight of organic acids, the more aggressive they are. This also applies to acids of inorganic origin.

The stability of an oil characterizes the preservation of its basic properties during long-term operation.

To determine stability, the oil is subjected to artificial aging by heating it while simultaneously blowing air, after which the percentage of sediment, acid number and content of water-soluble acids are determined. The deterioration of the quality of artificially aged oil should not exceed the standards specified in table. 5-2.

Ash content of oil is the amount of inorganic impurities remaining after burning a sample of oil in a crucible, expressed as a percentage of the oil taken for combustion. The ash content of pure oil should be minimal. High ash content indicates poor oil purification, i.e. the presence of various salts and mechanical impurities in the oil. The increased salt content makes the oil less resistant to oxidation. Increased ash content is allowed in oils containing antioxidant additives.

The demulsification rate is the most important performance characteristic of turbine oil.

The demulsification speed refers to the time in. minutes, during which the emulsion formed when steam is passed through the oil under test conditions is completely destroyed.

Fresh and well-refined oil does not mix well with water. Water quickly separates from such oil and settles at the bottom of the tank even if the oil remains in it for a short time. If the quality of the oil is poor, the water is not completely separated in the oil tank, but forms a fairly stable emulsion with the oil, which continues to circulate in the oil system. The presence of a water-oil emulsion in the oil changes the viscosity. oil and all its basic characteristics, causes corrosion of oil system elements and leads to the formation of sludge. The lubricating properties of the oil deteriorate sharply, which can lead to damage to the bearings. The aging process of oil in the presence of emulsions is even more accelerated.

The most favorable conditions for the formation of emulsions are created in the oil systems of steam turbines, therefore turbine oils. there are requirements for high demulsifying ability, i.e. the ability of oil to quickly and completely separate from water.

The flash point of an oil is the temperature to which the oil must be heated so that its vapors form a mixture with air that can ignite when an open flame is brought to it. (

The flash point characterizes the presence of light volatile hydrocarbons in the oil and the evaporation of the oil when it is heated. The flash point depends on the type and chemical composition of the oil, and as the viscosity of the oil increases, the flash point usually increases.

During turbine oil operation, its flash point decreases. This is due to evaporation. low-boiling fractions and oil decomposition phenomena. A sharp decrease in flash point indicates intensive decomposition of the oil caused by local overheating. The flash point also determines the fire hazard of the oil, although a more characteristic value in this regard is the auto-ignition temperature of the oil.

The auto-ignition temperature of an oil is the temperature at which the oil ignites without bringing an open flame to it. This temperature for turbine oils is approximately twice the flash point and depends largely on the same characteristics as the flash point.

Mechanical impurities are various solid substances found in oil in the form of sediment or in suspension.

Oil. may become contaminated with mechanical impurities during storage and transportation, as well as during operation. Particularly severe oil contamination is observed due to poor cleaning. oil lines and oil tank after installation and repairs. Being suspended in the oil, mechanical impurities cause increased wear of rubbing parts. According to GOST. There should be no mechanical impurities in turbine oil.

The pour point of the oil is a very important indicator of oil quality, allowing one to determine the ability of the oil to operate at low temperatures. ‘The loss of oil mobility with a decrease in its temperature occurs due to the release and crystallization of solid hydrocarbons dissolved in the oil.

Pour point. oil is the temperature at which the test oil thickens so much under experimental conditions that when the test tube with oil is tilted at an angle of 45°, the oil level remains motionless for 1 minute.

Transparency characterizes the absence of foreign inclusions in the oil: mechanical impurities, water, sludge. The transparency of the oil is checked by cooling the oil sample. Oil cooled to 0 °C should remain transparent.

B) Operating conditions of turbine oil. Oil aging

The operating conditions of the oil in the oil system of a turbogenerator are considered difficult due to the constant action of a number of factors unfavorable to the oil. These include:

1. Exposure to high temperature

Heating the oil in the presence of air contributes greatly. due to its oxidation. Other operational characteristics of the oil also change. Due to the evaporation of low-boiling fractions, viscosity increases, flash point decreases, de-emulsion ability worsens, etc. The main heating of the oil occurs in the turbine bearings, where the oil is heated from 35-40 to 50-55 ° C. The oil is heated mainly by friction in the bearing oil layer and partly by heat transfer along the shaft from the hotter parts of the rotor.

The temperature of the oil leaving the bearing is measured in the return line, which gives an approximate idea of ​​the temperature conditions of the bearing. However, the relatively low temperature of the oil at the drain does not exclude the possibility of local overheating of the oil due to imperfections in the bearing design, poor quality manufacturing or improper assembly. This is especially true for thrust bearings, where different segments can be loaded differently. Such local overheating contributes to increased aging of the oil, since with an increase in temperature* above 75-80°C, the oxidation of the oil increases sharply.

The oil can also heat up in the bearing housings themselves from contact with hot walls heated externally by steam or due to heat transfer from the turbine housing. Oil heating also occurs in the control system - servomotors and oil pipelines passing near the hot surfaces of the turbine and steam pipelines.

2. Spraying oil by rotating parts of the turbine unit

All rotating parts - couplings, gears, ridges on the shaft, ledges and sharpening of the shaft, centrifugal speed regulator, etc. - create oil splashing in the bearing housings and columns of centrifugal speed regulators. The atomized oil acquires a very large surface area of ​​contact with the air, which is always in the crankcase, and mixes with it. As a result, the oil is exposed to intense oxygen from the air and oxidizes. This is also facilitated by the high speed acquired by the oil particles relative to the air.

In the bearing housings, there is a constant exchange of air due to its suction into the gap along the shaft due to the slightly reduced pressure in the crankcase. The decrease in crankcase pressure can be explained by the ejecting effect of the oil drain lines. Movable couplings with forced lubrication spray oil especially intensively. Therefore, to reduce oil oxidation, these couplings are surrounded by metal casings that reduce oil splashing and air ventilation. Protective covers are also installed on rigid couplings in order to reduce air circulation in the crankcase and limit the rate of oxidation of the oil in the bearing crankcase.

To prevent oil from leaking out of the bearing housing in the axial direction, oil squeegee rings and grooves machined in babbitt at the ends of the bearing at the shaft exit points are very effective. The use of vintokan - UralVTI seals - has a particularly great effect.

3. Exposure to air contained in oil

Air in oil is contained in the form of bubbles of various diameters and in dissolved form. Air entrapment in oil. occurs in places where oil and air are most intensively mixed, as well as in oil drain lines, where oil does not fill the entire cross-section of the pipe and sucks in air.

The passage of oil containing air through the main oil pump is accompanied by rapid compression of air bubbles. At the same time, the air temperature in large bubbles increases sharply. Due to the speed of the compression process, the air does not have time to give off heat environment, and therefore the compression process should be considered adiabatic. The generated heat, despite its negligible absolute value and short duration of exposure, significantly catalyzes the process of oil oxidation. After passing through the air, the compressed bubbles gradually dissolve, and the impurities contained in the air (dust, ash, water vapor, etc.) pass into the oil and, thus, pollute and water it.

Oil aging due to the air contained in it is especially noticeable in large turbines, where the oil pressure after the main oil pump is high, and this leads to a significant increase in the air temperature in the air bubbles with all the ensuing consequences.

4. Exposure to water and condensing steam

The main source of oil watering in turbines of old designs (without steam suction, from labyrinth seals) is steam.

Knocked out of the labyrinth seals and sucked into the bearing housing. The intensity of watering in this case largely depends on the state of the labyrinth seal of the turbine shaft and on the distance between the bearing and turbine housings. Another source of watering is a malfunction of the steam shut-off valve of the auxiliary turbo oil pump. Water also enters the oil from the air due to vapor condensation and through small coolers.

In feed turbopumps with central lubrication, the oil may become waterlogged due to water leakage from the pump seals.

Particularly dangerous is watering of the oil, which occurs due to contact of the oil with hot steam. In this case, the oil not only gets watered, but also heats up, which accelerates the aging of the oil. In this case, the resulting low-molecular acids pass into an aqueous solution and actively act on metal surfaces in contact with the oil. The presence of water in the oil contributes to the formation of sludge, which settles on the surface of the oil tank and oil lines. If sludge gets into the bearing lubrication line, it can clog the holes in the metering washers installed on the discharge lines and cause overheating or even melting of the bearing. Sludge entering the control system. may disrupt the normal operation of spool valves, axle boxes and other elements of this system.

The penetration of hot steam into the oil also leads to the formation of an oil-water emulsion. In this case, the surface of contact between oil and water increases sharply, which facilitates the dissolution of non-ecomolecular acids in water. An oil-water emulsion can enter the turbine lubrication and control system and significantly worsen its operating conditions.

5. Exposure to metal surfaces

While circulating in the oil system, the oil is constantly in contact with metals: cast iron, steel, bronze, babbitt, which contributes to the oxidation of the oil. Due to the impact of metal. On the surface of acids, corrosion products are formed and enter. oil. Some metals have a catalytic effect on the oxidation processes of turbine oil.

All these constant unfavorable conditions cause oil aging.

By aging we mean a change in physico-chemical

Properties of turbine oil in the direction of deterioration of its performance.

Signs of oil aging are:

1) increase in oil viscosity;

2) increase in acid number;

3) lowering the flash point;

4) the appearance of an acidic reaction in the aqueous extract;

5) the appearance of sludge and mechanical impurities;

6) decrease in transparency.

Oil aging intensity

Depends on the quality of the filled oil, the level of operation of the oil facilities and the design features of the turbine unit and oil system.

Oil that shows signs of aging is still considered suitable according to standards. for use if:

1) the acid number does not exceed 0.5 mg KOH per 1 g of oil;

2) the viscosity of the oil does not differ from the original by more than 25%;

3) the flash point has decreased by no more than 10°C from. original;

4) the reaction of the aqueous extract is neutral;

5) The oil is transparent and free of water and sludge.

If one of the listed oil characteristics deviates from the norms and it is impossible to restore its quality on a running turbine, the oil in the shortest possible time to be replaced.

The most important condition for high-quality operation of the turbine shop oil facilities is careful and systematic control of oil quality.

For oil in service, two types of control are provided: shop control and abbreviated analysis. The scope and frequency of these types of control are illustrated in Table. 5-4.

If there is an abnormally rapid deterioration in the quality of the oil in use, the testing period may be reduced. In this case, tests are carried out according to a special schedule.

Oil supplied to the power plant is subjected to laboratory testing for all indicators. If one or more indicators do not meet the established standards for fresh oil, the resulting batch of fresh oil must be sent back. Oil analysis is also carried out before filling it into steam turbine tanks. Oil in reserve is analyzed at least once every 3 years.

The aging process of oil in continuous operation leads to the fact that the oil loses its original properties and becomes unsuitable for use. Further operation of such oil is impossible, and its replacement is required. However, given the high cost of turbine oil, as well as the quantities in which it is used in power plants, it is impossible to count on a complete oil change. It is necessary to regenerate used oil for further use.

Oil regeneration is the restoration of the original physical chemical properties used oils.

Collection and recovery of used oils is one of the effective ways their economic

Mia. The norms for collection and regeneration of turbine oil are given in table. 5-5.

Existing methods for regenerating used oils are divided into physical, physicochemical and chemical.

TO physical methods These include methods in which the chemical properties of the regenerated oil do not change during the regeneration process. The main ones of these methods are sedimentation, filtration and separa- tion. Using these methods, oils are purified from impurities and water undissolved in the oil.

Physico-chemical regeneration methods include methods in which the chemical composition of the processed oil is partially changed. The most common physical and chemical methods are oil purification with adsorbents, as well as oil washing with hot condensate.

Chemical regeneration methods include cleaning oils with various chemical reagents (sulfuric acid, alkali, etc.). These methods are used to restore oils that have undergone significant chemical changes during operation.

The choice of regeneration method is determined by the nature of oil aging, the degree of change in its performance qualities, as well as the requirements for the quality of oil regeneration. When choosing a regeneration method, you must also take into account the cost indicators of this process, giving preference to the simplest and cheapest methods possible.

Some regeneration methods allow oil to be cleaned while the equipment is running, as opposed to methods that require completely draining the oil from the oil system. From an operational point of view, continuous regeneration methods are more preferable, since they allow you to extend the service life of the oil without refilling and do not allow deep deviations in oil performance from the norm. However, continuous oil regeneration on an operating turbine can only be carried out using small-sized equipment that does not clutter the room and allows for easy installation and dismantling. Such equipment includes separators, filters, adsorbers.

If there is more complex and bulky equipment, the latter is placed in a separate room, and the cleaning process in this case is carried out with the oil drained. It is irrational to use the most expensive equipment for oil regeneration for one station, given the frequency of its operation. Therefore, such installations are often made mobile. For large block stations with a significant volume of oil in operation, stationary regenerative plants of any type are also justified.

Let's consider the main methods of cleaning and regenerating turbine oil.

Sucks. The simplest and cheapest method of separating water, sludge and mechanical impurities from oil is to settle the oil in special settling tanks with conical bottoms. In these tanks, over time, stratification of media with different specific gravity occurs. Pure oil having less specific gravity, moves to the upper part of the tank, and water and mechanical impurities accumulate at the bottom, from where they are removed through a special valve installed at the lowest point of the tank.

The oil tank also plays the role of a sump. Oil tanks also have conical or sloping bottoms to collect water and sludge for subsequent disposal. However, oil tanks do not have the proper conditions for the oil-water emulsion to separate. The oil in the tank is in constant motion, which causes mixing of the upper and lower layers. The unreleased air in the oil smoothes out the difference between the densities of the individual components of the oil-water mixture and makes it difficult for them to separate. In addition, the residence time of the oil in the oil tank does not exceed 8-10 minutes, which is clearly not enough for high-quality settling of the oil.

In the settling tank, the oil is in more favorable conditions, since the settling time is not limited in any way. The disadvantage of this method is low productivity with significant settling time. Such settling tanks take up a lot of space and increase the fire hazard of the room.

Separation. A more productive method of purifying oil from water and impurities is oil separation, which consists in separating suspended particles and water from the oil due to centrifugal forces occurring in the separator drum rotating at high frequency.

According to the principle of operation, oil purifier separators are divided into two types: low-speed with a rotation speed of 4500 to 8,000 rpm and high-speed with a rotation speed of about 18,000-20,000 rpm. Low-speed separators, having a drum equipped with plates, are most widespread in domestic practice. In Fig. 5-14 and 5-15 show a diagram of the device and overall dimensions of disc separators.

Separators are also divided into vacuum separators, which ensure removal from the oil, in addition to mechanical impurities and suspended moisture, also partially dissolved moisture and air, and separators
open type tori. iB depending on the nature of the contaminants, oil purification using separators can be carried out by the clarification method (clarification) and the purification method i (lurification).

Oil purification by clarification is used to separate solid mechanical impurities, sludge, and also to separate water contained in oil in such small quantities that its direct removal is not required. In this case, the impurities separated from the oil remain in the drum sump, from where they are periodically removed. Removing contaminants from oil by cleaning is used in cases where the oil is significantly watered and is essentially a mixture of two liquids with different densities. In this case, both water and oil are removed from the separator continuously.

Turbine oil contaminated with mechanical impurities and a small amount of moisture (up to 0.3%) is purified using the clarification method. For more significant watering - according to the cleaning method. In Fig. 5-114 the left side of the drum is shown assembled for work according to the clarification method, and the right side - according to the cleaning method. The arrows indicate the flow of oil and separated water.

The transition from one method of separator operation to another requires reassembly of the drum and oil outlet pipes.

The productivity of a drum assembled using the clarification method is 20-30% higher than when assembled using the cleaning method. To increase the productivity of the separator, the oil is preheated to 60-65°C in an electric heater. This heater is supplied with a separator and has a limiting thermostat. oil heating temperature.

Using a separator, oil purification can be carried out while the turbine is running. This need usually arises when there is significant water content in the oil. In this case, the suction pipe of the separator is connected to the lowest point of the dirty compartment of the oil tank, and the purified oil is directed to the clean compartment. If there are two separators at the station, they can be connected in series, and the first separator should be assembled according to the cleaning circuit, and the second - according to the clarification circuit. This significantly improves the quality of oil purification.

Filtration. Oil filtration is the separation of oil-insoluble impurities by passing (pressing) through a porous filter medium. Filter paper, cardboard, felt, burlap, belting, etc. are used as filter materials. Frame filter presses are widely used for filtering turbine oils. The frame filter press has its own pump, a rotary or vortex type, which, under a pressure of 0.294-0.49 MPa (3-5 kgf/cm2), passes oil through the filter material sandwiched between special frames. Contaminated filter material is systematically replaced with new one. The general view of the filter press is shown in Fig. 5-16. Oil filtration using a filter press is usually combined with its cleaning in a separator. It is irrational to pass heavily watered oil through a filter-press, since the filter material quickly becomes dirty, and cardboard and paper lose their mechanical strength. A more reasonable scheme is to pass the oil first through a separator and then through a filter press. In this case, oil purification can be done with the turbine running. If there are two separators operating in series, the filter press can be turned on after the second separator along the oil flow, assembled according to the clarification scheme. This will allow you to achieve a particularly high degree of oil purification.

LMZ uses a special “filter-belting” type fabric in the filter press, organizing the filtration process under a low differential. This method is very effective when the oil is heavily clogged with adsorbent, and the filter itself does not require systematic maintenance.

‘VTI has developed a cotton filter, which is also successfully used.

To ensure the normal functioning of the oil system of a turbine unit, it is necessary not only to continuously clean the oil, but also to periodically (after repairs) clean the entire system.

Accepted laminar mode oil flow in the system pipelines at a speed not exceeding 2 m/s contributes to the deposition of sludge and dirt on internal and especially cold surfaces.

The Glavenergoremoit Central Design Bureau has developed and tested in practice a hydrodynamic method for cleaning oil systems. It is as follows: the entire oil system, excluding bearings, is cleaned by pumping oil at a speed 2 times or more higher than the operating speed at a temperature of 60-bb^C. This method is based on the organization of a turbulent flow in the near-wall region, in which sludge and corrosion products, due to the mechanical action of the oil flow, are washed off from the internal surfaces and carried into the filters.

The hydrodynamic cleaning method has the following advantages:

1) the passivating film formed as a result of prolonged contact of the metal with the operating oil is not damaged;

2) eliminates the formation of corrosion on babbitt and nitrided surfaces;

3) does not require chemical solutions to wash away deposits;

4) eliminates disassembly of the oil system (except for places where jumpers are installed);

5) reduces the labor intensity of cleaning by 20-40% and makes it possible to reduce the duration of a major overhaul of a turbine unit by 2-3 days.

The operation of the oil used to clean the systems has shown that its physical and chemical properties do not deteriorate; therefore, oil systems can be cleaned using operating oil.

Adsorption. This method of cleaning turbine oils is based on the phenomenon of absorption of substances dissolved in the oil by solid, highly porous materials (adsorbents). Through adsorption, organic and low molecular weight acids, resins and other impurities dissolved in it are removed from the oil.

Used as adsorbents various materials: silica gel (SIg), aluminum oxide and various bleaching earths, chemical composition which is mainly characterized by the content of BiOg and Al2O3 (bauxite, diatomite, shales, bleaching clays). Adsorbents have a highly branched system of capillaries running through them. As a result, they have a very large specific absorption surface per 1 g of substance. So, for example, the specific surface of activated carbon reaches 1000 m2/g, si - lycagel and aluminum oxide 300-400 m2/g, bleaching earths ilOO-300 m2/g.

In addition to the total surface area, the efficiency of adsorption depends on the pore size and the size of the absorbed molecules. The diameter of the holes - (pores) in the absorbers is on the order of several tens of angstroms. This value is commensurate with the size of the absorbed molecules, as a result of which some high-molecular compounds will not be absorbed by particularly finely porous adsorbents. For example, activated carbon cannot be used for oil purification due to its finely porous structure. Materials with pore sizes of 20-60 angstroms can be used as adsorbents for turbine oil, which allows the absorption of high-molecular compounds such as resins and organic acids.

Silica gel, which has become widespread, absorbs resinous substances well and, somewhat worse, organic acids. Aluminum oxide, on the contrary, extracts organic, especially low-molecular, acids from oils well and absorbs resinous substances worse.

These two absorbents are artificial adsorbents and are expensive, especially aluminum oxide. Natural adsorbents (clays, bauxites, diatomites) are cheaper, although their efficiency is much lower.

Cleaning with adsorbents can be carried out in two ways. methods: contact and percolation.

The contact method of oil processing involves mixing the oil with finely ground adsorbent powder. Before cleaning. the oil must be heated. Cleaning from the adsorbent is done by passing the oil through a press filter. In this case, the adsorbent is lost.

The process of percolation filtration consists of passing oil heated to 60-80 °C through a layer of granular adsorbent loaded into special devices (adsorbers). In this case, the adsorbent has the form of granules with grain sizes of 0.5 mm and above. With the percolation method of oil recovery, in contrast to the contact method, the recovery and reuse of adsorbents is possible. This reduces the cost of the cleaning process and, in addition, allows the use of more effective, expensive adsorbents for oil processing.

The degree of use of the adsorbent, as well as the quality of oil purification with the percolation method, is usually higher than with the contact method. In addition, the percolation method allows you to restore oil without draining it from the oil tank, while the equipment is running. All these circumstances. brought. Moreover, this method has found widespread use in domestic practice.

The mobile type adsorber is shown in Fig. 5-17. It is a welded cylinder filled with granular adsorbent. The lid and bottom of the adsorber are removable. A filter is installed in the upper part of the adsorber to retain small adsorbent particles. Oil filtration occurs from bottom to top. This ensures the most complete air displacement and reduces filter clogging. For the convenience of removing spent adsorbent, the device can be rotated around its axis by 180°.

The adsorbent has the ability to absorb not only oil aging products, but also water. That's why,

Before being treated with an adsorbent, the oil must be thoroughly cleaned of water and liquid. Without this condition, the adsorbent will quickly lose its absorbing properties and oil purification will be of poor quality. In the general scheme of oil processing, adsorption should come after oil purification through separators and filter presses. If there are ■two separators at the station, the role of a filter press can be performed by one of the separators operating in the clarification mode.

The used adsorbent can be easily restored by blowing hot air through it at a temperature of about 200°C. In Fig. 5-18 shows an installation for the recovery of adsorbents, which includes a fan for pumping air, an electric heater for heating it, and a reactivator tank into which the recovered adsorbent is loaded.

Adsorption purification cannot be used for oils containing additives, since the latter (except ionol) are completely removed by adsorbents.

Flushing with condensate. This type of oil treatment is used when the acid number of the oil increases and low molecular weight water-soluble acids appear in it.

As practice has shown, as a result of oil washing, its other indicators also improve: demulsibility increases, the amount of sludge and mechanical impurities decreases. To improve the solubility of acids, the oil and condensate should be heated to a temperature of 70-809C. The amount of condensate required for flushing is 50-100% of the amount of oil being washed. Necessary conditions for high-quality flushing are good mixing of the oil with condensate and the creation of the largest possible surface of their contact. To ensure these conditions, it is convenient to use

Vestya separator, where the water and. the oil is in a finely dispersed state and mixes well with each other. Low molecular weight acids pass from the oil into water, with which they are removed from the separator. Sludge and impurities present. in oil, are moistened, their density increases, as a result of which the conditions for their separation improve.

Oil flushing with condensate can also be done in a separate tank, where the circulation of water and oil is carried out using steam or a special pump. Such flushing can be carried out during turbine repair. In this case, the oil is taken from the oil tank and, after washing, enters the reserve tank.

Treatment with alkalis is used when the oil is deeply worn, when all previous methods of restoring the operational properties of the oil are insufficient.

Alkali is used for. neutralization of organic acids and free sulfuric acid residues in oils (when oil is treated with acid), removal of esters and other compounds that, when interacting with alkali, form salts that pass into an aqueous solution and are removed by subsequent processing of the oil.

To regenerate used oils, 2.5-4% sodium hydroxide or 5-14% trisodium phosphate is most often used.

Oil can be treated with alkalis in a separator in the same way as when washing oil with condensate. The process is carried out at a temperature of 40-90°C. To reduce alkali consumption and improve the quality of cleaning, the oil must first be dehydrated in a separator. ‘Subsequent treatment of the oil after its reduction with alkali consists of washing it with hot condensate and treating it with adsorbents.

Since the use of chemical reagents requires preliminary and subsequent oil treatment, combined installations for deep oil regeneration have appeared, where all stages of oil processing are combined into a single technological process. These installations, depending on the oil regeneration scheme used, have quite complex equipment and are either stationary or mobile.

Each scheme includes equipment specific to a given processing method: pumps, mixing tanks, settling tanks, filter presses, etc. There are also universal installations that allow the oil regeneration process to be carried out using any method.

The use of additives is the most modern and effective method of preserving the physical and chemical properties of oil during long-term operation.

Additives are highly active chemical compounds added to oil in small quantities to maintain the basic performance characteristics of the oil at the required level over a long period of operation. Additives added to turbine oils must meet a number of requirements. These compounds must be fairly cheap, used in small quantities, readily soluble in oil at operating temperature, not produce sediments and suspensions, not washed out with water and not removed by adsorbents. The action of additives should give the same effect for oils of different origins and varying degrees of wear. In addition, while stabilizing some indicators, additives should not worsen other performance indicators of the oil.

It should be noted that there are no additives that satisfy all these requirements yet. In addition, there is no compound capable of stabilizing all oil performance characteristics at once. For this purpose, there are compositions of various additives, each of which affects one or another indicator.

A variety of additives have been developed for oils of petroleum origin, of which the most important for turbine oil are antioxidant, anti-corrosion and demulsifying.

The main value is the antioxidant additive, which stabilizes the acid number of the oil. It is for this indicator that under unfavorable operating conditions the oil ages the fastest. For a long time, the main type of domestically produced antioxidant additive was the VTI-1 additive. This additive is quite active, dissolves well in oil, and is used in small quantities (0.01% by weight of the oil). The disadvantage of this additive is that it is only suitable for stabilizing fresh oils. For oils that have been in use and are partially oxidized, it can no longer delay the process of further oxidation.

In this regard, the VTI-8 additive has the best characteristics. It is more active and, in addition, is suitable for both fresh and used oils. As a disadvantage, it should be noted that this compound can release a suspension after some time, causing cloudiness in the oil. To eliminate this phenomenon, the oil must be passed through a filter press at the initial stage of operation. The VTI-8 additive is added in an amount of 0.02-0.025% of the oil weight.

The most effective antioxidant, which is widely used both here and abroad, is 2,6-ditertiary butyl-4-methylphenol, called DBC (ionol) in the USSR. This additive easily dissolves in oil, does not produce precipitation, is not removed from the oil by adsorbents, and is not destroyed when the oil is treated with alkali and sodium metal. The additive is removed only when the oil is cleaned with sulfuric acid. The use of the DBK additive extends the service life of well-refined oil by 2-5 times. The only drawback of this antioxidant is its increased consumption compared to other additives (0.2-0.5%). There are also reasons to increase this norm.

Anti-corrosion additives are used to protect the metal from the action of acids contained in fresh oil, as well as oil oxidation products. The anti-corrosion effect is reduced to the formation of protective film, protecting it from corrosion. One of the most effective anti-corrosion additives is additive B-15/41, which is an ester of alkenyl-succinic acid. Anti-corrosion additives can to some extent increase the acid number of oils and reduce their stability. Therefore, anti-corrosion additives are used in the minimum required concentration together with antioxidant additives.

Demulsifying additives (demulsifiers) are substances used to break down petroleum and oil emulsions. Demulsifiers are aqueous solutions of neutralized acid sludge or highly purified mineral oil emulsion with an aqueous solution of sodium salts of petroleum and sulfo-petroleum acids. Recently, new compounds have been proposed as demulsifiers - di-proxamines. The most effective of them is Diproxa - min-157 [DPK-157], developed by VNIINP.

18.09.2012
Turbine oils: classification and application

1. Introduction

Steam turbines have been around for over 90 years. They are engines with rotating elements that convert steam energy into mechanical work in one or more stages. The steam turbine is usually connected to a driving machine, most often through a gearbox.

The steam temperature can reach 560 °C, and the pressure ranges from 130 to 240 atm. Increasing efficiency by increasing steam temperature and pressure is a fundamental factor in improving steam turbines. However, high temperatures and pressures increase the requirements for lubricants used to lubricate turbines. Initially, turbine oils were manufactured without additives and could not meet these requirements. Therefore, oils with additives have been used in steam turbines for about 50 years. These turbine oils contain oxidation inhibitors and anti-corrosion agents and, provided certain specific rules are followed, provide high reliability. Modern turbine oils also contain no a large number of extreme pressure and anti-wear additives that protect lubricated components from wear. Steam turbines are used in power plants to drive electric generators. In conventional power plants, their output power is 700-1000 MW, while in nuclear power plants this figure is about 1300 MW.

2. Requirements for turbine oils - characteristics

Requirements for turbine oils are determined by the turbines themselves and their specific operating conditions. Oil in lubrication and control systems of steam and gas turbines must perform the following functions:
. hydrodynamic lubrication of all bearings and gearboxes;
. heat dissipation;
. functional fluid for control and safety circuits;
. preventing the occurrence of friction and wear of the teeth of the teeth in turbine gearboxes during shock rhythms of turbine operation.
Along with these mechanical and dynamic requirements, turbine oils must have the following physical and chemical characteristics:
. resistance to aging during long-term use;
. hydrolytic stability (especially if additives are used);
. anti-corrosion properties even in the presence of water/steam, condensate;
. reliable water separation (vapor and condensed water release);
. fast deaeration - low foaming;
. good filterability and high degree of purity.

Only carefully selected base oils containing special additives can meet these stringent requirements for lubricants for steam and gas turbines.

3. Turbine oil compositions

Modern lubricants for turbines contain special paraffinic oils with good viscosity-temperature characteristics, as well as antioxidants and corrosion inhibitors. If turbines with gear transmissions require a high degree of load-bearing capacity (for example: failure stage when testing on a gear bench FZG not lower than 8 DIN 51 354-2, then extreme pressure additives are added to the oil.
Currently, turbine base oils are produced exclusively by extraction and hydrogenation. Operations such as refining and subsequent high-pressure hydrotreating significantly determine and influence characteristics such as oxidative stability, water separation, deaeration and pricing. This is especially true for water release and deaeration, since these properties cannot be significantly improved by additives. Turbine oils are usually obtained from special paraffinic fractions of base oils.
To improve their oxidative stability, phenolic antioxidants are introduced into turbine oils in combination with amine antioxidants. To improve the anti-corrosion properties, non-emulsifiable anti-corrosion agents and passivators of non-ferrous metals are used. Contamination with water or water vapor does not have a harmful effect, since these substances remain suspended. When using standard turbine oils in turbines with gearboxes, small concentrations of thermally stable and oxidation-stable long-life extreme pressure/antiwear additives (organophosphorus and/or sulfur compounds) are added to the oils. In addition, silicone-free antifoam and depressant additives are used in turbine oils.
Careful attention should be paid to the complete exclusion of silicones in the antifoam additive. In addition, these additives should not adversely affect the release characteristics of the (very sensitive) oil. Additives must be ash-free (eg zinc-free). Cleanliness of turbine oil in tanks in accordance with ISO 4406 should be within 15/12. It is necessary to completely eliminate contact between turbine oil and various circuits, wires, cables, and insulating materials containing silicones (strictly observed during production and use).

4. Turbine lubricants

For gas and steam turbines, special paraffinic mineral oils are usually used as lubricants. They serve to protect turbine and generator shaft bearings, as well as gearboxes in corresponding designs. These oils can also be used as hydraulic fluid in control and safety systems. In hydraulic systems operating under pressures of approximately 40 atm (if there are separate circuits for lubricating oil and control oil, so-called spiral circuit systems), fire-resistant synthetic fluids such as HDF-R. Revised in 2001 DIN 51 515 entitled “Lubricants and control fluids for turbines” (part 1 -L-TD official service, specifications), and the new so-called high-temperature turbine oils are described in DIN 1515, part 2 (part 2- L-TG lubricants and control fluids for turbines - for high-temperature operating conditions, specifications). The next standard is ISO 6743, part 5, family T(turbines), classification of turbine oils; last option standard DIN 51 515, published in 2001/2004, contains a classification of turbine oils, which is given in table. 1.

The requirements put forward in DIN 51 515-1 - oils for steam turbines and DIN 51 515-2 - high-temperature turbine oils, listed in table. 2 and 3.

Atmospheric air enters the air intake 1 through a filter system and is supplied to the input of a multi-stage axial compressor 2. The compressor compresses the atmospheric air and supplies it under high pressure to the combustion chamber 3, where it is supplied through nozzles a certain amount of gas fuel. Air and fuel mix and ignite. The fuel-air mixture burns, releasing a large amount of energy. The energy of gaseous combustion products is converted into mechanical work due to the rotation of turbine 4 blades by jets of hot gas. Part of the resulting energy is spent on air compression in compressor 2 of the turbine. The rest of the work is transmitted to the electric generator through the drive axis 7. This work is the useful work of the gas turbine. Combustion products, which have a temperature of about 500-550 °C, are discharged through the exhaust tract 5 and the turbine diffuser 6, and can be further used, for example, in a heat exchanger, to obtain thermal energy.

ISO 6743-5 classifies turbine oils by their intended purpose (for steam or gas turbines) and by the content of extreme pressure agents (Table 4).

Specification according to ISO 6743-5 and in accordance with ISO CD 8086 “Lubricants. Industrial oils and related products (class L)—Family T(turbine oils), ISO-L-T still under consideration" (2003).
Synthetic fluids such as PAO and phosphoric acid esters are also described in ISO CD 8068 2003 (see Table 5).

5. Turbine oil circulation circuits

Oil circuits play a particularly important role in the lubrication of turbines in power plants. Steam turbines are typically equipped with oil pressure and control circuits, as well as separate tanks for the lube oil and control oil circuits.
Under normal operating conditions, the main oil pump, driven by the turbine shaft, draws oil from the reservoir and pumps it into the control and bearing lubrication circuits. The pressure and control circuits are usually under pressure in the range of 10-40 atm (the pressure of the main turbine shaft can reach 100-200 atm). The temperature in the oil container ranges from 40 to 60 °C. The oil supply speed to the supply circuits ranges from 1.5 to 4.5 m/s (about 0.5 m/s in the return circuit). The oil, cooled and passed through the pressure reducing valves, enters the bearings of the turbine, generator and, possibly, gearbox under a pressure of 1-3 atm. Individual oils return to the oil tank under pressure equal to atmospheric pressure. In most cases, turbine and generator shaft bearings have white metal liners. Axial loads are usually absorbed by bearings. The lube oil circuit of a gas turbine is basically similar to that of a steam turbine. However, rolling bearings and plain bearings are sometimes used in gas turbines.
Large oil circuits are equipped with centrifugal filtration systems. These systems ensure the removal of the smallest particles of pollutants along with aging products and sludge. Depending on the size of the turbine in transfer systems, oil is passed through filters every five hours using special pumps. The oil is removed from the lowest point of the oil tank and is filtered immediately before being returned back. If oil is taken from the main flow, then the flow rate should be reduced to 2-3% of the main pump capacity. The following types of equipment are often used: oil centrifuges, paper filters, fine cellulose cartridge filters and filter units with separators. The use of a magnetic filter is also recommended. Sometimes bypass and main flow filters are equipped with cooling devices to reduce the temperature of the filtered oil. If there is a possibility of water, steam or other contaminants entering the system, it must be possible to remove the oil from the container using a mobile filter or centrifuge. To do this, it is necessary to provide a special connecting pipe at the bottom of the container, which can also be used for taking oil samples.
Oil aging also depends on how and at what speed the oil is pumped through the circuit. If the oil is pumped too quickly, the excess air is dispersed or dissolved (problem: cavitation in bearings, premature aging, etc.). Foaming of the oil in the oil container may also occur, but this foam usually breaks down quickly. Deaeration and foaming in the oil tank can be positively influenced by various engineering measures. These measures include oil tanks with a larger surface area and return circuits with larger cross-section pipes. Simple measures, such as returning the oil to the container through an inverted U-shaped pipe, also have a positive effect on the deaeration ability of the oil and have a good effect. Installing a choke in a tank also gives positive results. These measures extend the amount of time during which water and solid contaminants can be removed from the oil.

6. Turbine flushing oil circuits

All oil lines must be mechanically cleaned and flushed before commissioning. Even contaminants such as cleaning agents and anti-corrosion agents (oils/greases) should be removed from the system. Then you need to introduce oil for flushing purposes. About 60-70% of the total oil volume is required for flushing. The flushing pump must be running at full capacity. It is recommended to remove the bearing and temporarily replace it with a clean one (to prevent contaminants from getting into the gap between the shaft and the bearing shells). The oil should be repeatedly heated to a temperature of 70 °C and then cooled to 30 °C. Expansion and contraction in the pipeline and fittings are designed to remove dirt from the circuit. Shaft bearing shells must be washed consistently to maintain high operating speeds. After 24 hours of rinsing, the oil filters, oil sieves and bearing oil sieves can be installed. Mobile filter units, which can also be used, must have a cell size of no more than 5 microns. All parts of the oil supply chain, including spare equipment, must be thoroughly flushed. All components and parts of the system must be cleaned from the outside. The flushing oil is then drained from the oil tank and coolers. It is also possible to reuse it, but only after very fine filtration (bypass filtration). In addition, the oil must first be thoroughly analyzed to ensure it meets specification requirements. DIN 51 515 or special equipment specifications. Flushing should be continued until no solid contaminants are detected on the filter and/or a measurable increase in bypass filter pressure is recorded after 24 hours. It is recommended that flushing be carried out over a period of several days, as well as oil analysis after any modifications or repairs. .

7. Monitoring and maintenance of turbine oils

Under normal conditions, it is quite sufficient to monitor the oil at intervals of 1 year. As a rule, this procedure is carried out in the manufacturer's laboratories. In addition, a weekly visual inspection is necessary to ensure timely detection and removal of oil contaminants. The most reliable method is to filter the oil using a centrifuge in the bypass circuit. When operating a turbine, one should take into account the contamination of the air surrounding the turbine with gases and other particles. A method such as replenishing lost oil (refreshing additive levels) is worth considering. Filters, sieves, as well as parameters such as temperature and oil level should be checked regularly. In case of prolonged downtime (more than two months), the oil should be recirculated daily and the water content of the oil should be checked regularly. Control of waste:
. fire-resistant liquids in turbines;
. waste lubricating oils in turbines;
. waste oils in turbines.
carried out in the laboratory of the oil supplier. IN VGB Kraftwerktechnic Merkbl tter, Germany ( VGB- Association of German Power Plants) describes the analysis as well as the required values ​​of the various properties.

8. Service life of steam turbine oils

The typical service life of steam turbines is 100,000 hours. However, the antioxidant level is reduced to 20-40% of the level in fresh oil (oxidation, aging). Turbine life is largely dependent on the quality of the turbine base oil, operating conditions such as temperature and pressure, oil flow rate, filtration and maintenance, and finally the amount of fresh oil fed (this helps maintain adequate additive levels). The oil temperature in the turbine depends on the load on the bearings, the size of the bearings and the oil flow rate. Radiative heat may also be an important parameter. The oil circulation factor, i.e. the ratio between the flow volume h -1 and the volume of the container with oil, should be in the range from 8 to 12 h -1. This relatively low oil circulation factor ensures efficient separation of gaseous, liquid and solid contaminants, while air and other gases can be released to the atmosphere. In addition, low circulation factors reduce thermal stress on the oil (in mineral oils, the oxidation rate doubles with a temperature increase of 8-10 K). During operation, turbine oils are significantly enriched with oxygen. Turbine lubricants are exposed to air at a number of points around the turbine. Bearing temperatures can be controlled using thermocouples. They are very high and can reach 100 °C, and even higher in the lubrication gap. Bearing temperatures can reach 200 °C with local overheating. Such conditions can only occur in large volumes of oil and at high circulation rates. The temperature of the oil drained from the sliding bearings is usually in the range of 70-75 °C, and the temperature of the oil in the tank can reach 60-65 °C depending on the oil circulation factor. The oil remains in the tank for 5-8 minutes. During this time, the air entrained by the oil flow is deaerated, solid pollutants precipitate and are released. If the tank temperature is higher, additive components with higher vapor pressure may evaporate. The evaporation problem becomes more complex when vapor extraction devices are installed. The maximum temperature of plain bearings is limited by the threshold temperatures of white metal bearing shells. These temperatures are around 120°C. Currently, bearing shells are being developed from metals that are less sensitive to high temperatures.

9. Oils for gas turbines - application and requirements

Gas turbine oils are used in stationary turbines used to generate electricity or thermal energy. Compressor blowers increase the gas pressure, which is supplied to the combustion chambers, to 30 atm. Combustion temperatures depend on the type of turbine and can reach 1000 °C (usually 800-900 °C). Exhaust gas temperatures usually range around 400–500 °C. Gas turbines with a power of up to 250 MW are used in urban and suburban steam heating systems, in the paper and chemical industries. The advantages of gas turbines are their compactness, speed of start-up (<10 минут), атакже в малом расходе масла и воды. Масла для паровых турбин на базе минеральных масел применяются для обычных газовых турбин. Однако следует помнить о том, что температура некоторых подшипников в газовых турбинах выше, чем в паровых турбинах, поэтому возможно преждевременное старение масла. Кроме того, вокруг некоторых подшипников могут образовываться «горячие участки», где локальные температуры достигают 200—280 °С, при этом температура масла в баке сохраняется на уровне порядка 70—90 °С (горячий воздух и горячие газы могут ускорить процесс старения масла). Температура масла, поступающего в подшипник, чаще всего бывает в пределах 50— 55 °С, а температура на выходе из подшипника достигает 70—75 °С. В связи с тем, что объем газотурбинных масел обычно меньше, чем объем масел в паровых турбинах, а скорость циркуляции выше, их срок службы несколько короче. Объем масла для электрогенератора мощностью 40—60 МВт («General Electric") is approximately 600-700 l, and the oil life is 20,000-30,000 hours. For these applications, semi-synthetic turbine oils (specially hydrotreated base oils) - so-called Group III oils - or fully synthetic oils based on synthetic PAOs are recommended. In civil and military aviation, gas turbines are used as traction engines. Since the temperature in these turbines is very high, special low-viscosity ( ISO VG 10, 22) synthetic oils based on saturated esters (for example, oils based on polyol esters). Used for aircraft engine or turbine lubrication, these synthetic esters have a high viscosity index, good thermal stability, oxidative stability and excellent low temperature characteristics. Some of these oils contain additives. Their pour point ranges from -50 to -60 °C. Finally, these oils must meet all military and civilian aircraft engine oil specifications. Aircraft turbine lubricating oils can in some cases also be used to lubricate helicopter, marine, stationary and industrial turbines. Aviation turbine oils containing special naphthenic base oils ( ISO VG 15-32) with good low-temperature characteristics.

10. Fire-resistant liquids that do not contain water, used in power plants

For safety reasons, fire-resistant fluids are used in control and control circuits exposed to fire hazards. For example, in power plants this applies to hydraulic systems in high temperature areas, particularly near superheated steam pipes. Fire-retardant fluids used in power plants generally do not contain water; These are synthetic fluids based on phosphoric acid esters (such as DFD-R By DIN 51 502 or ISO VG 6743-0, ISO VG 32-68). These HFD fluids have the following features. Specifications for turbine fluids based on complex triaryl phosphates are described in ISO/DIS 10 050 - category ISO-L-TCD. According to them, such liquids must have:
. fire resistance;
. spontaneous combustion temperature above 500 "C;
. resistance to auto-oxidation at surface temperatures up to 300 °C;
. good lubricating properties;
. good protection against corrosion and wear;
. good resistance to aging;
. good demulsibility;
. low foaming;
. good deaeration characteristics and low saturated vapor pressure.
To improve oxidative stability, additives (possibly foam inhibitors), as well as rust and corrosion inhibitors, are sometimes used. According to the 7th Luxembourg Report ( The 7th Luxembourg Report) maximum permissible temperature HFD liquids in hydrodynamic systems is 150 °C, and constant temperatures of liquids should not exceed 50 °C. These synthetic phosphoric ester fluids are typically used in control circuits, but in some special cases they are also used to lubricate rolling bearings in turbines (and other hydraulic systems in steam and gas turbines). However, systems must be designed to ensure that these are the fluids that will be used ( HFD- compatible elastomers, paints and coatings). Standard (E)DIN 51 518 lists the minimum fluid requirements for power plant control systems. Additional information can be found in the instructions and specifications associated with fire-retardant liquids, e.g. VDMA sheet 24317 and in SETOR recommendations R 39 N and R 97 H. Information related to replacing one fluid with another is contained in VDMA sheet 24314 and SETOR Rp 86 H.

11. Lubrication of hydraulic turbines and hydroelectric power plants

Hydroelectric power plant personnel must pay special attention to the use of water pollutants such as lubricants. Hydroelectric power plants use oils both with and without additives. They are used to lubricate bearings and gearboxes on main and auxiliary equipment, as well as control and control equipment. When choosing lubricants, the specific operating conditions at hydraulic power stations should be taken into account. Oils must have good water-releasing and deaeration properties, low foaming, good anti-corrosion properties, high anti-wear properties ( FZG load stage in gearboxes), good aging resistance and compatibility with standard elastomers. Due to the fact that there are no established standards for hydraulic turbine oils, the basic requirements for them coincide with the specifications for general turbine oils. The viscosity of oils for hydraulic turbines depends on the type and design of the turbine, as well as on the operating temperature, and can range from 46 to 460 mm 2 /s (at 40 ° C). For such turbines, lubricating oils and oils for control systems of the type T.D. And LTD By DIN 51 515. In most cases, the same oil can be used to lubricate bearings, gearboxes and control systems. Typically, the viscosity of such turbine and bearing oils ranges from 68 to 100 mm 2 /sec. When starting turbines, the temperature of oils used in control systems should not fall below 5 °C, and the temperature of oils for lubricating bearings should not be below 10 °C. If equipment is located in cold environments, the installation of oil heaters is highly recommended. Oils for hydraulic turbines do not experience strong thermal loads, and their volumes in reservoirs are quite high. In this regard, the service life of turbine oils is quite long. In hydroelectric power plants, oil sampling intervals for analysis can be lengthened accordingly. Particular attention should be paid to sealing the circulation circuits of turbine lubricating oils to prevent water from entering the system. In recent years, biodegradable turbine oils based on saturated esters have been successfully used. Compared to mineral oils, these products are more easily biodegradable and fall into a lower category of water pollutants. In addition, hydraulic oils type HLP46 (with zinc-free additives), rapidly biodegradable fluids type HEES 46 and greases NLGI grades 2 and 3 are used in hydroelectric power plants.

Roman Maslov.
Based on materials from foreign publications.