Steam Turbine Production Selection - Diploma

Contents

1. Purpose and description of the designed plant

1.1. Purpose of turbine P 6 - 2,2/0,

1.2. Process Description

1.3. Technical characteristics of steam turbine P 6-2.2/0,

1.4. Deficiencies and recommendations for modernization

1.5. Selection of Structural Materials

2. Process calculation

2.1. Source Data

2.2. Determination of steam flow to turbine

2.3. Turbine Flow Calculation

2.4. Turbine Thermal Calculation

3. Mechanical calculation

3.1. Strength analysis of double-crown impeller

speed stages

3.2. Calculation for strength of belt band of JN rotor blades

3.3. Calculation of rotor blades of the control stage for bending and stretching at the mode of the first fully open valve

3.4. Calculation of tail attachment of JN blades

3.5. Tail calculation

3.6. Calculation of disk rim

3.7. Calculation of critical rotor speed

3.8. Calculation of shaft journal for short-circuit twisting

3.9. Turbine casing calculation in exhaust area

3.10. Calculation of flange and stud in the area of control stage

3.11. Calculation of the diaphragm of the first non-adjustable stage in the mode of maximum steam transmission

4. Pump Process Calculation

4.1 . Source Data

4.2. Select Pipe Diameter

4.3. Head loss

4.4. Pump selection

5. Mechanical calculation of the pump

5.1. Source Data

5.2. Bending Shaft Calculation

5.3. Results of calculation of shaft for critical rotation speed

6. 0. Process calculation of IPA

6.1. Thermal calculation of low pressure heater

6.2. Constructive calculation

6.3. Hydraulic calculation of low pressure heater

6.4. Strength calculation of heater elements

7.0. Economic part

Specification

Introduction

A steam turbine (French turbine from lat. Turbo whirl, rotation) is a continuous thermal engine in which the potential energy of compressed and heated water vapor is converted into kinetic, which in turn performs mechanical work on the shaft.

Flow of water steam is supplied through guide vanes to curvilinear vanes fixed along circumference of rotor and, acting on them, drives rotor into rotation.

The steam turbine is one of the elements of the steam turbine plant (STP). Certain types of steam turbines are also designed to provide heat energy to consumers.

Steam turbine and electric generator make up turbine unit.

Steam turbine power plants, generating one type of energy - electric, are equipped with condensation-type turbines and are called condensation power plants (CES). [1]

Condensation steam turbines are used to convert the maximum possible part of the heat of steam into mechanical work. They work with the release (exhaust) of spent steam to the condenser, in which the vacuum is maintained (hence the name).

Stationary turbines are manufactured on the same shaft as AC generators. Such units are called turbogenerators. Thermal power plants where condensing turbines are installed are called condensing electric stations (CES). The main final product of such power plants is electricity.

Only a small part of the thermal energy is used for its own needs of the power plant and, sometimes, to supply heat to a nearby settlement. Usually this is a village of power engineers. It is proved that the greater the power of the turbine generator, the more economical it is, and the lower the cost of 1 kW of installed power. Therefore, high-power turbogenerators are installed at condensing power plants.

Rotor speed of stationary turbine generator is connected with electric current frequency of 50 Hertz. That is, at bipolar generators, 3000 revolutions per minute, at four-pole, respectively, 1,500 revolutions per minute. The frequency of the electric current of the generated energy is one of the main indicators of the quality of the produced electricity. Modern technologies allow you to maintain the speed with an accuracy of three revolutions. A sharp drop in electrical frequency entails a disconnection from the network and an emergency shutdown of the power unit, in which a similar failure is observed.

Depending on the purpose, steam turbines of power plants can be basic, bearing a constant main load; peak, short-term operation to cover load peaks; auxiliary turbines ensuring the power plant power demand. The basic ones require high efficiency at loads close to full (about 80%), from peak ones - the possibility of quick start-up and inclusion in operation, from auxiliary turbines - special reliability in operation. All steam turbines for power plants are designed for 100 thousand hours of work (before overhaul).

Transport steam turbines are used as main and auxiliary engines on ships and ships. Attempts were repeatedly made to use steam turbines on locomotives, but steam turbines were not widespread. Gear gears are used to connect high-speed turbines with propellers that require a small (from 100 to 500 rpm) speed. Unlike stationary turbines (except for turbo-air ducts), ships operate at a variable speed determined by the required speed of the ship.

Purpose and description of the designed plant

1.1. Purpose of turbine P 6 - 2.2/0.6.

The turbine generator plant is designed to generate electricity to supply production units of OJSC Nizhnekamsktekhcarbon.

1.2. Process description.

From the main steam line, superheated steam with a temperature of 390-440 0C and a pressure of 18-22 kgf/cm2 enters the turbine flow section on the control stage wheel, where there is a uniform distribution of steam flow along the turbine section. Then, receiving the direction in the nozzle apparatuses of the stator grates of the turbine, steam enters the rotor impeller blades. The stream of steam creates pressure on rotor blades of the rotor and extending consistently on steps up to the pressure of 0.03÷0.04 kgfs/cm2 abs. comes to the condenser (poses.22/2 see the technological scheme). The kinetic energy of the steam flow drives the turbine rotor, the torque of the turbine rotor is transmitted to the generator rotor through a rigid clutch. In the generator (item 20/2), the mechanical energy of the rotor rotation is converted into electric energy and its supply to the consumers of the plant.

Steam spent in the turbine enters the condenser (item 22/2) and passes through the annulus, condenses due to heat exchange with circulating water flowing through the tubes. The non-condensable gas-air mixture is sucked from the condenser by the main ejector (pos.33/2). Condensate collected in condensate collector is supplied to condensate pumps suction (item 23/2). After condensate pumps, part of condensate with pressure of 4-5 kgf/cm2 is sent to coolers of the main ejector (pos.33/2), and ejector of the system of suction from seals (pos.35/2), and the second part of condensate is sent to the level regulator .

The condensate directed to the level controller is automatically distributed in two directions: part of the condensate equal to the load on

condenser (item 22/2), heated in IPA (item 37/2) and supplied to deaerator (item 6/1, 2.3), and the difference between the capacity of the condensate pump and the load on the condenser is discharged through the recirculation line to the condenser (item 22/2).

To prevent steaming through the turbine front seal (pos.19/2), stop and control valve rods, suction cups through

rear seal of turbine, part of steam from main steam line is directed to seal regulator, where it is throttled and supplied to seal header. Steam suction from seals is performed by seal ejector (item 35/2).

The start-up ejector (item 34/2) is activated when the turbine generator is started, when it is necessary to create a primary vacuum in the condenser.

The oil supply system is designed to provide lubrication and heat removal of turbine and generator bearings and oil supply to the hydrodynamic control and protection system.

In the oil supply system, four oil circulation circuits connected to each other can be conditionally distinguished:

The suction circuit of the main oil pump (MMN) located on the turbine shaft, in which oil from the MMN delivery line is supplied to the injector, where it, leaving at a high speed of 63 l/s from the nozzle, sucks oil from the tank to the diffuser in an amount that compensates for all drains from the system to the tank.

The contour of a lubricant system in which oil passes through an injector, oil coolers, (poses.28/1ab, 2ab) where it is cooled up to the temperature of 40÷45 °C, an adjustable throttle and an oil filter (poses.27/2) and with pressure not less than 0.7 kgfs/cm2 arrives on cooling and lubricant of bearings.

Circuit of protection system, in which oil with pressure of not less than 0.8 kgf/cm2 from MCP delivery line through automatic gate, hydraulic pressure switch in lubrication system and turbine remote switch is supplied to quick shut-off device of stop valve, hydraulic drive of check valve and to control closing relay

valves.

Control system circuit, in which oil from the MCP delivery line with pressure not less than 0.8 kgf/cm2 is supplied to the control unit and returned to the MCP suction.

PMN (item 24/2) is used during start-up and shutdown operations on the turbine when it is necessary to maintain pressure in the control systems and

protection 8 kgf/cm2 g. and pressure in lubrication system 0.7 kgf/cm2 g.

At pressure drop in lubrication system to 0.25 kgf/cm2, oil supply starts from LCS (pos.25/2), or AMN (pos.26/2) with DC motor (if for some reason LCS is not activated). Actuation of LCS and AMN is performed automatically by action of pressure switch sensor in lubrication system. (RDS)

Oil intake for the operation of all indicated circuits comes from an oil tank (pos.24/2) with a capacity of 3.6 m ³; drain from circuits is carried out there

All leaks in the oil supply system are drained to the drain oil tank (pos.31/2) and pumped to the main oil tank (pos.30/2) using the transfer pump (pos. 32/2), which is switched on and off automatically by the level relay.

Cooling of the condenser (item 22/2), oil coolers of the turbine (item 28/2ab) and air coolers of the generator (item 21/2) of the turbine unit is carried out by cooling water .

Water is supplied from the cooling water supply station with temperature of 20 0С and pressure of 3-4 kgf/cm2. Main water flow is directed for condenser cooling, while part of water flow is directed through mechanical filter for cooling of turbine oil coolers and generator air coolers. After passing the above heat exchangers, circulating water is supplied through the return pipeline for cooling to the cooling tower of the cooling water supply station.

For uniform heating and cooling of the rotor, the turbine is equipped with a shaft-turning device rotating the turbine rotor at a rotation frequency of 1/2 rpm. It is driven by an electric motor

30 kW power.

Remote control of the turning gear from the local shield is provided.

1.3. Technical characteristics of steam turbine P 62.2/0.6.

Steam stationary condensing turbine P 62.2/0.6 is designed to directly drive a generator with a capacity of 6 MW.

Generator Terminal Power:

nominal - 6 MW

maximum - 6.6 MW

Rated rotor speed - 50 1/s (3000 rpm)

Direction of turbine rotor rotation - counterclockwise (see from turbine side to generator)

Nominal parameters of fresh steam:

absolute pressure, MPa (kgf/cm2) - 2.2 (22)

temperature, ° С - 425

Absolute steam pressure downstream turbine at rated power:

in the heating mode (at nominal steam parameters and steam flow rate to controlled extraction, nominal temperature and cooling water flow rate with HPH, IPA and pure condenser tubes on) - 4.22 kPa (0.0422 kgf/cm2);

At condensation mode (at nominal parameters of fresh steam, nominal temperature and cooling water flow rate, with HPH, IPA and clean condenser tubes on) - 5.2 kPa (0.052 kgf/cm2).

Specific steam flow at heating operation mode at nominal values of basic parameters - 7.43 kg/kWh

Specific heat flow at condensation mode at nominal values of basic parameters - 12523 kJ/kWh, 2991 kcal/kWh

Fresh steam flow rate with nominal parameters through stop valve at nominal values of main parameters, rated power,

Nominal temperature and cooling water flow rate:

at condensation mode, t/h - 24.6

at heating mode (steam flow rate

in nominal selection 15 t/h) - 39.6

Limits of control of absolute pressure of production steam by means of pressure regulator - 0.50.7 MPa (5.07.0 kgf/cm2), which will correspond to limits of steam temperature variation from 270 to 350 ° С.

Long-term operation of the turbine is allowed, without time limitation, at the following changes of fresh steam parameters:

absolute pressure of fresh steam, MPa (kgf/cm2) - 1.8 - 2.2 (from 18 to 22)

fresh steam temperatures, 0С - 390-440

Design absolute steam pressure in the turbine control stage chamber at nominal values of main parameters and rated power:

at heating mode (at nominal steam parameters and steam flow rate to controlled extraction, nominal temperature and cooling water flow rate) - 1.54 MPa (15.4 kgf/cm2);

at condensation mode (at nominal parameters of fresh steam, nominal temperature and cooling water flow rate) - 1.36 MPa (13.6 kgf/cm2).

The designed turbine has 19 stages (see sheet 1 of the graphic part). One production selection is provided. Turbine flow section consists of one two-stage control stage and eighteen single-stage stages. Turbomachine is divided into two parts of LPC and HPH by controlled bleed chamber.

The HPH includes a valve steam distribution made in the form of five single-seat control valves with diffuser seats with a lever drive, and a flow part consisting of one control

two-crown stage (see sheet 3 of the graphic part) and seven active stages. Control stage consists of welded segment of nozzles with partial steam supply (see sheet 2 of graphic part), double-rim impeller and guide vane. The remaining seven stages consist of steel diaphragms of welded structure with full basement

a steam house and a one-time wheel.

The LPC consists of a steam distribution made in the form of a steel axial flat unloaded rotary diaphragm with a hydraulic drive (see sheet 2 of the graphic part) and ten active single-stage stages, five of which have a partial steam supply. All stages consist of welded steel diaphragms and a single wheel.

Single-stage disks of active stages are autofreted and fitted on shaft with tension. The working blade apparatus, with the exception of the last stage (see sheet 4 of the graphic part), is made with a profile of constant cross section and has a band.

The turbine casing is cast and consists of a lower part and two upper parts, which are tightened by means of studs. The valve box is welded to the top of the housing.

The front part of the turbine rests freely with two legs on the housing of the front bearing and is fixed by two remote bolts (see sheet 1 of the graphic part), which keep the legs from vertical movement. The machine housing is fixed relative to the front bearing housing with vertical keys located below the bearing housing and two keys under the housing legs, which movably fix the turbine housing with the bearing and provide their alignment during expansion of the turbine housing in radial direction.

Housing of rear bearing is made integral with welded exhaust part of turbine and serves simultaneously as housing of front bearing of generator and coupling coupling, which is connected by means of gear engagement to shaft-turning device, which is also located on housing of rear bearing.

Steam distribution control unit of HPH is arranged on front bearing housing. The rotary diaphragm is driven by two levers, each of which has a separate hydraulic drive, which is mounted directly on the lower part of the turbomachine by means of a flange connection.

1.4. Deficiencies and recommendations for modernization.

Production output increased at OJSC Nizhnekamsktekhcarbon from 104 thousand tons per year to 115 thousand tons over the past 3 years. This is due to the modernization of equipment as part of the investment program. Old equipment is replaced with more modern. New equipment is more powerful, consumes more electricity. In the period from 2010 to 2013, electricity consumption for own needs increased from 8 MW/h to 9.2 MW/h .

In this regard, there was a problem of lack of steam for power generation, since cats recyclers PKK75/45 No. 1.2. in which steam is produced and operated on exhaust gas, which is obtained as a by-product in the production of carbon black.

The PCC team of the power plant put forward a proposal to modernize the production extraction unit of the steam turbine P 62.2/0.6. Production extraction of turbines serves to supply spent steam from intermediate stages of the turbine with certain parameters to the consumer.

But since the steam consumption by the plant is insignificant (mainly for steaming railway tanks at the raw material drain site, pipeline steam satellites in winter) it was not involved. Needs of the plant are provided by ROU1 (reduktsionno - the cooling installation) on which steam from the collector of high pressure from package boilers No. 1.2; with the parameters of P =22 kgfs/cm2 and with the temperature of t=440 0C about P =1,01,5kgs/cm2 and with the temperature of t=180200 0C are reduced. Consumption is extremely not stable.

Heating of chemically demineralized water from the chemist to feed boilers in preheaters PKHOV1,2; IPA-1; HPH 1,2,3; DB-1,2,3; steam is produced from RCP3 on which steam from the high-pressure header from boilers No. 1,2; with the parameters of P =22 kgfs/cm2 and with the temperature of t=440 0C about P =5.0 kgfs/cm2 and with the temperature of t=230250 0C are reduced.

Modernization consists in the fact that the production extraction pipeline was brought to the output of RCP3, as a result the steam to the boilers does not go to RCP3, but comes to the head of the turbine and the exhaust after the 7th stage of the HPV is not condensed later in the turbine condenser, and with parameters P =5.0 of kgf/cm2 and with the temperature of t=230250 0C goes for heating of khimobessoleny water and feedwater of coppers in regenerative PHOV1.2 heaters; IPA-1; HPH 1,2,3; DB-1,2,3;.

As a result of modernization, the efficiency of the plant as a whole increased by 6.2%, it was no longer necessary to supply feed water to the RCP3 injection, the turbine condenser was unloaded (since the supply of steam from the last stages of the turbine decreased and the vacuum in the condenser increased less than the steam-air mixture), and the operation of regenerative heaters was stabilized because the pressure fluctuation of the production extraction steam is not more than 0.1 MPa.

1.5. Select structural materials.

For modern turbine installations characterized by high steam temperature, the first requirement for metal is proper corrosion resistance. It is only after this requirement has been met that the choice of metal based on mechanical strength can be made.

Gas corrosion - chemical corrosion of metals in oxidizing gases at high temperatures. In steam turbine plants at high temperatures, oxidation processes can occur not only due to free oxygen, but also due to water vapor.

The rate and progression of steel oxidation depends on the temperature, velocity and pressure of the steam, time, chemical composition of the steel, composition and physical properties of the resulting scale.

The properties of the metal coating oxide film exert an exceptional influence on the heat resistance of steel. The film of oxides formed on the metal can serve as a protective layer if there are no fusible oxides or oxides inside it that can give their oxygen to the constituent elements of the alloy, and due to the tight fit to the metal, it is gas-tight and is heat resistant.

The main elements contributing to the formation of protective films are chromium, silicon and aluminum. Of these, chromium is most important, the oxides of which are closer to oxides of iron, nickel, cobalt.

In modern complex alloyed alloys on iron, nickel and cobalt bases, the content of chromium ranges from 12-25%. Chromium and chromomolybdenum steels with 5-6% chromium in terms of resistance to scale formation can be used up to 600-650 ° C; stainless steels based on 12% chromium can also be used to this temperature.

Carbon steels are sufficiently resistant to oxidation at temperatures only up to 535 ° C, above which their intensive oxidation and scale formation begin.

Low and medium alloy heat-resistant pearlite steels

(molybdenum, chromomolybdenum, molybdenovanadioic, chromo- molybdenovanadioic) in their heat resistance in air and steam media do not differ much from carbonaceous steels. The corrosion resistance of these steels at high temperatures is determined by the content of chromium and silicon, which is higher, the higher the content of alloying elements allowed for reasons of heat resistance.

Molybdenum - the most important component of pearlite steels - does not affect the heat resistance in the air, but the oxidation resistance in the steam medium is slightly increased.

Highly alloyed austenitic steels can be used up to a temperature of 750 ° C, and some of them up to higher temperatures.

Intergranular corrosion of austenite steels. Highly alloyed austenitic steels - chromonikel, chromonikelevolfram, den chromonikelmolib, etc. - are used in turbo construction at temperatures above 580 ° C. They have high heat resistance, but some of them show a tendency to a special type of corrosion destruction, developing mainly along the boundaries of metal grains. This type of corrosion is called intercrystallite or intercrystalline corrosion and is inherent, for example, in chromium steels of grades 0XM18H9, 1X18H9, 2X18H9.

Intercrystalline corrosion, destroying grain boundaries, quickly destroys the metal, as a result of which it is considered the most dangerous type of corrosion of turbine materials.

The causes of intercrystalline corrosion are associated with the decay of a carbon supersaturated solid solution in (austenite), since the solubility of carbon in austenite in the above-mentioned steels is small and therefore carbon in them is unstable.

When steel is heated to a temperature of 500 ° C and higher, carbides rich in chromium of the CgC6 type are isolated from the solid solution.

First, fine carbides are isolated along the grain boundaries. Then there is enlargement and coagulation of carbides falling along the grain boundaries. This phenomenon causes depletion of nearby metal regions with chromium and carbon, and therefore contributes to the formation of ferrite, whereby narrow layers or zones of chromium-poor solid solution are created along the boundaries of austenite grains, which have sharply reduced corrosion resistance.

The solubility of nickel in austenite is greater than in ferrite, as a result of which these areas are also poor with respect to nickel. As a result, a large heterogeneity of structural elements (austenite, ferrite, carbides) is created along the grain boundaries, between which there is a potential difference, which, if there is an electrolyte, leads to the formation of galvanic pairs.

The destruction of less persistent chromium-depleted interlayers located along the grain boundaries occurs under the influence of galvanic pairs. Due to the high degree of initial grinding of carbides, an especially large number of galvanic pairs are formed that destroy carbides.

Intercrystalline corrosion, gradually spreading into the depths of the metal, weakens the bond between its grains, and then leads even to their complete isolation from each other.

The metal affected by intercrystalline corrosion loses its inherent monolithicity, strength and elasticity, while the electrical conductivity and sound emitted by the metal sample when falling on a stone slab also change. A typical voiced metal sound produced by a sample when falling is replaced by a deaf sound similar to a falling wooden plate.

Intercrystalline corrosion of steels poses a serious danger to their service at temperatures of 500 ° C and higher under conditions of sufficiently aggressive corrosive media. This is further aggravated by the fact that intercrystalline corrosion can lead to sudden destruction of the part without manifesting itself noticeably until the moment of destruction. In

after welding, austenitic steels can develop intercrystalline corrosion, especially in weld areas where the temperature during welding reached 550-750 "C.

To prevent intercrystalline corrosion, titanium, niobium, tantalum are introduced into the composition of austenitic steels, which are stronger carbide-forming than chromium. These elements are combined into carbides with the released carbon, and chromium remains in the solid solution. The introduction of titanium into austenitic steel in an amount of 5-6 times, and niobium 10-12 times higher than the carbon content in steel, significantly reduces, and in some cases completely eliminates the tendency to intercrystalline corrosion. For example, 1X18N9T (EYA1T) steel contains C < 0.12%; Si < 0,8%; Mp < 2.0%; Sg = 17520%; No. = 8-5-11%; Ti = = (% C - 0.03) X 5 to 0.8% (design GOST 5632 - 61).

Thus, the reduction of carbon content is also a factor reducing the tendency of austenite steels to intercrystalline corrosion.

One of the main parts of the turbine stator is its housing, or cylinder. In the housing there are steam supply and steam discharge channels, nozzle devices, diaphragms installed directly in the cylinder or in the holders are fixed; there are also branch pipes for steam extraction. The outlet pipe in powerful condensing turbines is a complex structure.

Thus, the housing has a complex shape with varying lengthwise sections and flanges with horizontal or vertical connectors. In the course of steam, the difference in temperature and pressure of steam acts on the housing, which also changes dramatically when the turbine operation modes change.

The main active forces on the housing are excess steam pressure, representing the difference in steam pressure inside it and outside (atmosphere) or the difference between the external pressure of the atmosphere and the steam pressure below atmospheric - vacuum in the outlet parts of the condensing turbines.

Temperature difference between walls and flanges of turbine housings, created in different sections and at different distances from surfaces washed by steam, as well as sharp temperature fluctuations during starts, stops or changes of modes, in turbine housings cause temperature stresses. In addition, the active forces of the housing are its mass together with the mass of insulation, pipe valves and other parts located inside it.

Thus, the design of the housing is determined by many factors, the main of which are the purpose and type of the turbine, operating conditions, initial and final steam parameters, intermediate steam overheats, the dimensions of the flow part, the capabilities of its manufacturing technology, etc. Depending on the steam parameters, there is a conditional division into ultra-high, high, medium and low pressure housings.

In this steam turbine, the body is made of 15CM stainless dry steel.

All-forged rotors are widely used in modern active turbines with increased steam parameters for operation in the temperature area above 350400 ° C. For active turbines operating in the high steam temperature area, the construction of all-forged rotors is the only acceptable. In all-forged rotors, the disks with the shaft are pulled out of one whole forging, therefore, the weakening of the disks due to relaxation of voltages during operation of turbines in variable thermal modes is excluded.

All-forged rotors are made of large forgings (several tens of tons), while the uniformity of the metal and the symmetric distribution of its structure relative to the shaft axis must be ensured. Even a slight difference in the coefficients of linear expansion depending on the state of the structure can lead to a noticeable difference in the expansion of fibers on opposite sides of the rotor, which can cause deflection and unbalance of the rotor during heating.

Check of thermal stability of rotor is performed before its clouding. To this end, the rotor is placed in an electric furnace and when it rotates 2 rpm, indicators indicate the occurrence of even a slight eccentricity, which can appear during bending as a result of thermal expansion.

If the rotor is designed to operate under sharply different temperature conditions along its length, then the test of the thermal stability of the rotor is carried out in an electric furnace having separate compartments with different temperatures.

In all-forged rotors, a central drill is usually made to examine its surface using an optical device.

The use of all-forged rotors is limited to a disk diameter of up to 1 m, exceeding this size sharply complicates the production of high-quality forgings.

. The material for forging the rotor is selected based on the operating conditions of the first stages at high steam parameters, although subsequent stages could be made of weakly alloyed steels.

Thus, an excessive amount of expensive alloyed steel is used to manufacture all-forged rotors. In addition, when processing such a rotor, a large percentage of metal (the volume of metal between the discs) of the forging goes into chips to obtain the desired configuration of the discs.

In an all-forged rotor, there are no disk hubs, so the length of its flow part will be determined only by the width of the diaphragms and the width of the disk web, and not by their hubs, which sometimes leads to a reduction in the length of the all-forged rotor compared to a rotor having set disks.

The absence of disk hubs reduces the diameters of the diaphragm seals, which in turn reduces the leakage of steam through them and increases the flow point of the turbine.

A significant drawback of all-forged rotors is

necessity of replacement of the entire rotor in case it is impossible to correct improperly manufactured or damaged at least one of impeller discs during operation. The rotor of the turbine P 6 - 2.2/0.6 is manufactured of GOST 105088 steel 20H3MVF.

Discs of steam turbines are the most stressed parts after rotor blades. Disruption of the disk is a serious accident, causing an accident of the entire turbine.

The material of the working discs, drums and forged rotors shall satisfy the following basic conditions:

1) have high and stable mechanical properties at the temperatures at which this part operates;

2) purity, homogeneity of composition and absence of internal defects of metal;

3) minimum values of internal stresses;

4) good mechanical workability.

The discs are susceptible to the corrosive effects of the vapor environment, which is relatively small in the bond of 6 to the considerable thickness of the discs and the relatively slow development of corrosion. Therefore, steels that are weakly resistant to corrosion are used for the manufacture of discs.

Each disc is made by individual forging by settling metal to achieve high quality forging. The forging axis of the disc must be approximately the same as the axis of the ingot, and its bushing hole is pierced during forging. Forging of disks is subjected to thermal treatment according to the modes set for each disk depending on chemical composition of its metal, size of forging and required mechanical properties.

In order to improve hardenability and uniformity of forging structure of discs, heat treatment is carried out after preliminary machining with minimum required allowance of finishing dimensions. When determining these allowances, the possibility of warpage (leash) during heat treatment should be taken into account.

For carbon steel forgings, a typical metal structure is perlite in a ferrite grid. For discs of alloyed steels, the structure after heat treatment is sorbitol, and in a number of forgings sorbitol is observed with a martensite orientation.

Residual stresses must be minimal, as they can lead to unacceptable values that cause the part to collapse when combined with operating voltages.

The specifications for impeller discs allow residual stresses of not more than 39.2 Mn/m2 (4 kG/mm?) at the final diameter of the disc D = 600 - 1000 mm and 49 Mn/m2 (5 kG/mm2) at D > 1000 mm,

Cracks and flocks are not allowed in discs forging. Flokens are porosities detected on the treated metal surface in the form of very thin tortuous cracks, and on the fractures of samples or articles - in the form of sharply emitted silver spots of a rounded shape and crystalline structure. The dimensions of the flockens vary in length from fractions of a millimeter to 20 mm or more. Flokens affect forged steel products of various compositions and are almost not found in cast steel. In areas of forging with a low degree of ducks, flocks are more common than in dense well-forged areas. For example, in forging disks, flocks are more often found in massive, less forged hubs than in a canvas or rim.

Flokens are a very dangerous phenomenon, since in them, like sharp slots in the metal thickness that have a significant extent, stresses are concentrated that reduce the plastic and strength characteristics of steels, and under alternating loads they can develop into fatigue cracks.

If at least one flocken is found on the forging surface, it can be stated that there are many of them in the forging body. In this case, all forgings of this smelting, forged and heat treated according to the same process as the sample, are checked for flocks.

One of many hypotheses for the formation of phloquenes is the very common hydrogen theory, which explains that hydrogen dissolved in liquid steel is released under certain conditions into micropores, always available in steel, and can create very significant stresses in the metal, leading to its local breaks - phloquenes.

Various methods are used to identify phloquenes:

1. Macronitration of the ground surface with 15% ammonium persulfate in water for 10 minutes, and then etching with a nitric acid solution for 5-10 minutes.

2. Magnetic kerosene sample.

3. Hardening of sample cut off from forging and its fracture during bending. In the fracture, flockens are found in the form of shiny white spots.

4. Ultrasonic flaw detection, which allows to detect flocks on the surface and in the forging body.

You cannot remove flocks by cutting, grinding, or any other similar method.

Residues of near-shrinkage looseness, large single non-metallic inclusions or significant clusters of small inclusions are not allowed in forging of turbine impellers.

Single defects, the same cracks, plains, hairs, etc., are removed by grinding or gentle cutting, provided that their depth does not exceed 2/3 of the allowance for machining.

Each of the discs passes a sulfur sample on the inner surface of the hub and its ends. It is also recommended to take prints from part of the canvas in order to detect segregation "mustache."

Typically, for forging discs, steel is smelted in acidic open-hearth or main electric furnaces. For weakly loaded discs, carbon steel smelting in main open-hearth furnaces is allowed.

According to the mechanical properties of the steel used for disks up to a temperature of 480 ° C, they are divided into six categories depending on the stresses arising during operation.

The chemical composition of steels for forging discs shall be established at the discretion of the manufacturer in agreement with the contracting authority.

Recommended steel grades: 34KHN1M, 34KHN2M, 34XH3M.

High-chromium heat resisting steel of martensitnoferritny class 12Х13 (GOST 18968-73) is provided for production of a diaphragm shovel. Selection of this steel is carried out from the operating conditions of the product. Blades are the most loaded parts of steam turbines .

Blades of steam turbines are divided into guides (diaphragm) fixed in the stator and working blades - on the rotor. The diaphragm blades are mainly operated only by aerodynamic forces, which are not stationary, but variable. The exposure medium, which is guided by the diaphragm blades, reaches a temperature of 400 0C.

At that there is non-uniform heating of blades. Due to the mutual influence of the applied forces, the blade material experiences varying in value, but always high stresses, which leads to the occurrence of vibration of the fatigue of the material.

Surfaces of blades are subject to chemical influence of medium. The chemical aggressiveness of water vapor on the vane material is particularly pronounced with an increase in the initial temperature, which leads to the gradual destruction of the material caused by its erosion. The surfaces of the blades (both on the rotor and in the diaphragm) of the last stages of steam turbines at the same time are corroded from the side of the leading edge with wet steam water particles.

Therefore, high-quality materials are used for blades. Such materials require high temperature strength, high ductility, creep resistance, corrosion resistance, high fatigue strength, and high damping decrement.

The requirements for the material of the labyrinth seal ridges arise from the conditions of their operation in the steam medium at various temperatures, depending on the place of their installation in the turbine and on the initial and final steam parameters.

Non-ferrous metals and their alloys are used for sealing ridges pressed into segments and segments with coiled ridges, which are stable for operation under conditions of prolonged corrosion in a medium of superheated and wet steam because the ridges, having a small thickness, must have adequate strength, maintain their dimensions, which ensures good performance of labyrinth seals.

The strength and ductility of these alloys must correspond to operating temperatures at which the thin seal ridges retain their shape and dimensions in service without breaking or bending under the influence of steam flow.

Of particular importance are the properties of the seal material, which determine its behavior in emergency operating conditions. The most severe emergency state of the seal is local friction of the rotor surfaces (shaft, bushings, shrouds of rotor blades) when its shaft bends.

Thus, the third major requirement for a sealing metal is that it may be minimally prone to heat and damage the convex side of the curved shaft by the sealing ridges that penetrate it without adhering their metal to the rotor shaft. Thus, it follows that the metal of the sealing ridges, in the event of their friction against the shaft, should have the property of possible rapid wear.

Recently, the behavior of sealing ridges in emergency modes is studied in CIPI, CKTI, etc., however, the justification for the selection of materials for the manufacture of ridges is not yet enough. The material for ridges operating at steam temperatures above 500 ° C remains an unresolved issue. Usually, austenitic steel EYA1T (1X18H9T) is used at these temperatures.

It follows from the operating conditions of the support bearings that their material should be sufficiently soft and ductile, have good antifriction qualities (wear resistance, insert workability to the shaft neck, low coefficients of semi-fluid and dry friction, resist pouring of the pouring alloy onto the surface of the shaft neck). At the same time, antifriction alloys of bearings must be strong and hard enough to withstand the load exerted by the rotor. To obtain high-quality pouring of the insert, the alloy must have ease of melting, high fluid flow and strong adhesion to the metal of the insert.

In domestic turbine engineering, the high-tin babbit B83 is used to pour support bearings. Sometimes, due to saving the deficient babbit B83, babbit B16 is used to fill only the upper halves of the inserts.

Babbit B83 is an alloy based on tin Sn with additives of antimony Sb and copper C, and babbit B16 is an alloy based on lead RP. The main soft mass of B83 babbit, characterized by high ductility and viscosity, is a solution of antimony and a small amount of copper in the tin. It is very close in properties to tin, but harder and stronger than it.

Babbit B83 is an alloy based on tin Sn with additives of antimony Sb and copper C, and babbit B16 is an alloy based on lead RP. The main soft mass of B83 babbit, characterized by high ductility and viscosity, is a solution of antimony and a small amount of copper in the tin. It is very close in properties to tin, but harder and stronger than it.

Copper with tin forms solid crystals of high specific gravity in the form of sprockets and needles.

Process calculation

2.1. Source data.

N = 6000 kW - electric power of the turbine generator;

p0 = 2.2 MPa - steam pressure at turbine inlet;

t0 = 435 C0 - steam temperature at turbine inlet;

pp = 0.45 MPa - pressure required by the consumer;

Gp = 4.2 kg/s - steam consumption for industrial extraction needs;

Rk =4.5 kPa - vapor pressure at the exit from the turbine.

Mechanical calculation of the pump

5.1 Initial data.

Pump type - centrifugal

Capacity Q = 70 m3/h

Head H = 75 m

Efficiency? = 70%

Speed n = 3000 rpm

Power N = 60.0 kW

Packing type - gland

Pumped Medium - Water

The pump is made of 40X steel GOST 217667;

The shaft is made of 40X steel GOST 105088.

Impeller is made of 40HL steel GOST 97788.

40X steel is used to manufacture the pump. Steel has improved strength properties, in a heat-treated state they are highly ductile. Steels are technological in processing. They deform well in hot and cold conditions. Stamping is good. Steels are well welded by all types of welding. Steels are highly corrosion resistant in many aggressive environments.