Fittings and instrumentation of auxiliary boilers. Boiler equipment

The development of a boiler house automation project is carried out on the basis of a task drawn up during the implementation of the heat engineering part of the project. The general tasks of monitoring and managing the operation of any power plant are to ensure:

Works at every moment required amount heat at certain pressure and temperature parameters;

fuel economy, rational use electricity for the installation's own needs and minimizing heat losses;

Reliability and safety, i.e. establishing and maintaining normal operating conditions for each unit, excluding the possibility of malfunctions and accidents of both the unit itself and auxiliary equipment.

Based on the tasks and instructions listed above, all control devices can be divided into five groups intended for measurement:

1. Consumption of water, fuel, air and flue gases.

2. Water pressure, air gas, vacuum measurement in the elements and gas ducts of the boiler and auxiliary equipment.

3. Water, air and flue gas temperatures

4. Water level in tanks, deaerators and other containers.

5. Qualitative composition gases and water.

Secondary devices can be indicating, registering and summing. To reduce the number of secondary devices on the heat shield, some of the values ​​\u200b\u200bare collected on one device using switches; for critical values ​​on the secondary device, they mark with a red line the maximum permissible values ​​​​they are measured continuously.

In addition to the devices displayed in the control panel, local installation of control and measuring instruments: thermometers for measuring water temperatures; manometers for measuring pressure; various draft meters and gas analyzers.

The regulation of the combustion process in the KV-TS-20 boiler is carried out by three regulators: a heat load regulator, an air regulator and a vacuum regulator.

The heat load controller receives a command pulse from the main corrective controller, as well as water flow pulses. The heat load regulator acts on the body that regulates the supply of fuel to the furnace.

The common air regulator maintains the fuel-to-air ratio by receiving fuel flow rate pulses from the sensor and pressure drop across the air heater.

A constant vacuum in the furnace is maintained by means of a regulator in the boiler furnace and a smoke exhauster acting on the guide vane. There is a dynamic connection between the air regulator and the vacuum regulator, the task of which is to supply an additional impulse in transient modes, which makes it possible to maintain the correct draft mode during the operation of the air and vacuum regulator.

The dynamic coupling device has a direction of action, i.e. only the vacuum regulator can be a slave regulator.

Monitoring network consumption and feed water power regulators are installed.

Mercury expansion thermometer:

Industrial mercury thermometers are made with an embedded scale and, according to the shape of the lower part with the tank, there are straight types A and corner type B, bent at an angle of 90º in the direction opposite to the scale. When measuring temperature Bottom part thermometer is completely lowered into the measured medium, i.e. their immersion depth is constant.

Expansion thermometers are indicating instruments located at the place of measurement. Their principle of operation is based on the thermal expansion of liquid in a glass tank depending on the measured temperature.

Thermoelectric thermometer:

For measuring high temperatures with remote transmission of readings, thermoelectric thermometers are used, the operation of which is based on the principle of the thermoelectric effect. Chromel - kopel thermoelectric thermometers develop thermo - emf, significantly exceeding the thermo - emf of other standard thermoelectric thermometers. The range of application of chromel - kopel thermoelectric thermometers is from - 50º to + 600º C. The diameter of the electrodes is from 0.7 to 3.2 mm.

Tubular - spring manometer:

The most widely used for measuring the excess pressure of liquid, gas and steam are manometers that have a simple and robust design, clarity of indications and small size. The main advantages of these devices are also large range measurements, the possibility of automatic recording and remote transmission of readings.

The principle of operation of a deformation manometer is based on the use of deformation of an elastic sensitive element that occurs under the influence of the measured pressure.

A very common type of deformation devices used to determine excess pressure are tubular - spring pressure gauges, which play an extremely important role in technical measurements. These devices are made with a single-turn tubular spring, which is a metal elastic tube of oval section bent around the circumference.

One end of the helical spring is connected to the gear, and the other end is fixed to the rack supporting the transmission mechanism.

Under the action of the measured pressure, the tubular spring partially unwinds and pulls the leash behind it, setting in motion the gear-sector mechanism and the pressure gauge needle moving along the scale. The manometer has a uniform circular scale with a central angle of 270 - 300º.

Automatic potentiometer:

The main feature of the potentiometer is that it develops thermo-e. d.s. is balanced (compensated) by a voltage equal to it in magnitude, but opposite in sign, from a current source located in the device, which is then measured with great accuracy.

Automatic compact potentiometer type KSP2 is an indicating and self-recording device with a linear scale length and a chart tape width of 160 mm. The main error of the instrument readings is ±0.5 and the recording error is ±0.1%.

The variation of readings does not exceed half of the basic error. The chart tape speed can be 20, 40, 60, 120, 240 or 600, 1200, 2400 mm/h.

The potentiometer is mains powered alternating current voltage 220 V, frequency 50 Hz. The power consumed by the device is 30 V A. Changing the supply voltage by ±10% of the nominal does not affect the readings of the device. Permissible value ambient temperature 5 - 50ºС and relative humidity 30 - 80%. The dimensions of the potentiometer are 240 x 320 x 450 mm. and weight 17 kg.

Deformation electric pressure gauges are recommended to be installed near the pressure tap, fixed vertically with the nipple down. For pressure gauges, the ambient air may have a temperature of 5 - 60ºC and a relative humidity of 30 - 95%. They must be removed from powerful sources of alternating magnetic fields (electric motors, transformers, etc.)

The pressure gauge contains a tubular spring 1, fixed in the holder 2 with the help of a sleeve 3. To the free end of the spring, a magnetic plunger 5 is suspended on the lever 4, located in the magnetic modulation converter 6 sitting on the holder. Amplifying device 7 is fixed next to the latter on a folding bracket.

The device is enclosed in a steel case 8 with a protective casing 9 adapted for flush mounting. The connection of the pressure gauge with the measured pressure is carried out using the holder fitting, and the connecting wires are connected through the terminal box 10. The pressure gauge is equipped with a zero corrector 11. The dimensions of the device are 212 x 240 x 190 mm. and weight 4.5 kg.

MPE type pressure gauges can be used with one or more secondary DC devices: automatic electronic indicating and self-recording milliammeters of types KSU4, KSU3,

KSU2, KSU1, KPU1 and KVU1, calibrated in units of pressure, magnetoelectric indicating and self-recording milliammeters of types H340 and H349, central control machines, etc. Automatic electronic DC milliammeters differ from the corresponding automatic potentiometers only by a calibrated load resistor connected in parallel to the input, the voltage drop across which from the flowing current of the pressure gauge is the measured value.

Magnetoelectric milliammeters of types H340 and H349 have a scale and chart width of 100 mm. instrument accuracy class 1.5. The chart tape is set in motion at a speed of 20 - 5400 mm / h from a synchronous micromotor powered by an alternating current mains with a voltage of 127 or 220 V, a frequency of 50 Hz.

Dimensions of the device 160 x 160 x 245 mm. and weight 5 kg.

Direct Acting Regulator:

An example of a direct acting regulator is a control valve.

The valve consists of a cast-iron body 1 closed from the bottom with a flange cover 2, which closes the hole for draining the medium filling the valve and for cleaning the valve. Seats 3 of of stainless steel. The plunger 4 sits on the saddle. The working surfaces of the plunger are lapped to the seats 3. The plunger is connected to the stem 6, which can raise and lower the plunger. The rod runs in a stuffing box. The stuffing box seals cover 7, which is attached to the valve body. To lubricate the rubbing surfaces of the rod, oil is supplied to the stuffing box from the oiler 5. The valve is controlled by a membrane-lever device, consisting of a yoke 8, a membrane head 13, a lever 1 and weights 16.17. In the membrane head, between the upper and lower cups, a rubber membrane 15 is clamped, resting on a plate 14, planted on the rod 9 of the yoke. A rod 6 is fixed in the rod 9. The rod of the yoke has a prism 12, on which the lever 11 rests, rotating on the prismatic support 10, fixed in the yoke 8.

In the upper bowl of the membrane head there is a hole in which is fixed impulse tube, supplying a pressure pulse to the membrane. Under the action of increased pressure, the membrane bends and drags the plate 14 and the rod of the yoke 9 down. The force developed by the membrane is balanced by the weights 16 and 17 suspended on the lever. Weights 17 serve for coarse adjustment set pressure. With the help of load 16 moving along the lever, a more precise adjustment of the valve is made.

The pressure on the diaphragm head is transmitted directly by the regulated medium.

Actuating mechanism:

Regulators are used to regulate the flow of liquid, gas or steam in the process. The movement of regulatory bodies is carried out by executive mechanisms.

Regulators and actuators can be in the form of two separate units interconnected by means of lever rods or cables, or in the form of a complete device, where the regulator is rigidly connected to the actuator and forms a monoblock.

The actuator, receiving a command from the regulator or from a command apparatus controlled by a person, converts this command into a mechanical movement of the regulatory body.

The mechanism is electric, single-turn, designed to move control elements in relay control systems and remote control. The mechanism perceives an electrical command, which is a three-phase mains voltage of 220 or 380 V. The command can be given using a magnetic contact starter.

The actuator consists of an electric motor part

I - servo drives and control columns, II servo drive unit. The servo drive consists of a three-phase asynchronous reversible motor 3 with a squirrel-cage rotor. From the motor shaft, the torque is transmitted to gearbox 4, which consists of two stages of a worm gear. On the input shaft lever 2 is mounted on the gearbox, which is articulated with the regulating body with the help of a rod.

By turning the handwheel 1, with manual control, it is possible to turn the output shaft of the gearbox without the help of an electric motor. When manually operating the flywheel, the mechanical transmission from the electric motor to the flywheel is disconnected.

The regulatory body is designed to change the flow rate of the regulated medium, energy or any other quantities in accordance with the requirements of the technology.

In poppet valves, the closing and throttling surface is flat. For a valve with smooth working surfaces of the plug type, the characteristic is linear, i.e. throughput valve is directly proportional to the stroke of the plunger.

The regulation is carried out by changing the flow area by translational movement of the spindle during the rotation of the flywheel using a lever articulated through a rod with an electric actuator.

Valves cannot serve as shut-off devices.

Control starter:

Starters PMTR - 69 are made on the basis of magnetic reversing contacts, each of which has three normally open power contacts included in the power supply circuit of the electric motor. In addition, the starting device has a braking device made on the basis of electrical capacitor and connected through breaking contacts to one of the stator windings of the electric motor. When any group of power contacts is closed, the auxiliary contacts open and the capacitor is disconnected from the electric motor, moving by inertia, interacts with the residual magnetic field stator and induces emf in its windings.

Auxiliary contacts, closing the circuit of the stator winding of the capacitor, create their own magnetic field in the stator of the rotor and the stator causes a braking effect that counteracts rotation, which prevents the actuator from running out. The main disadvantage of starters is low reliability (burning of contacts, short circuit).

The block has three current and one voltage inputs. Block R - 12 consists of the main components: input circuits of VkhTs, DC amplifiers UPT 1 and UPT 2, MO limiting unit, while UPT 2 allows you to receive one current signal and an additional voltage signal at the output. Block R - 12 receives power from the power supply unit, which receives an additional signal from the control unit CU.

The signal from the sensor is fed to the node of the input circuits, where the signal of the setting device I z is also supplied. Further, the error signal y goes to the DC amplifier UPT 1, passing through the adder, where the error signals are generated from the input circuits and feedback. The OM signal limiter provides its further transformation, limiting the signal to the minimum and maximum. The UPT 2 amplifier is the final amplification unit. The feedback block MD receives a signal from the output of the UPT 2 amplifier and provides smooth switching of circuits with manual control to automatic. The feedback block MD ensures the formation of a control signal in accordance with the P -, PI - or PID control laws.

Technological protection.

In order to avoid emergency modes of equipment control systems in case of excessive deviations of parameters and to ensure the safety of work, they are equipped with technological protection devices.

Depending on the results of the impact on the protection equipment, they are divided into: those that stop or turn off the units; transferring equipment to reduced load mode; performing local operations and switching; preventing emergencies.

Protection devices must be reliable in pre-emergency and emergency situations, i.e., there should be no failures or false positives in the actions of the protections. Failures in protection actions lead to untimely shutdown of the equipment and further development of the accident, and false alarms take the equipment out of the normal technological cycle, which reduces its efficiency. To meet these requirements, highly reliable instruments and devices are used, as well as appropriate construction of protection circuits.

The protection includes sources of discrete information - sensors, contact devices, auxiliary contacts, logic elements and a relay control circuit. The activation of the protections should ensure the unambiguity of the action, while the transfer of equipment to the operating mode after its protection is carried out after checking and eliminating the causes that caused the operation.

When designing thermal protection of boilers, turbines and other thermal equipment provide for the so-called priority of the action of protections, i.e., the execution of operations in the first place for one of the protections that causes a greater degree of unloading. All protections have independent power sources and the ability to fix the causes of operation, as well as light and sound alarms.

Technological signaling.

General information about signaling.

Technological alarm, which is part of the control system, is designed to alert the operating personnel about unacceptable deviations in the parameters and operation mode of the equipment.

Depending on the requirements for the alarm, it can be conditionally divided into several types: alarm, ensuring the reliability and safety of the equipment; signaling, fixing the operation of the equipment protection and the reasons for the operation; alarm signaling of unacceptable deviations of the main parameters and requiring an immediate shutdown of the equipment; signaling of power failure of various equipment and equipment.

All signals are sent to the light and sound devices of the block control panel. Sound alarm There are two types: warning (bell) and emergency (siren).

Light alarms are made in two-color versions (red or green bulbs) or with the help of luminous displays, which indicate the reason for the alarm.

Newly received signals against the background of those already controlled by the operator may go unnoticed, so the signaling circuits are built so that the new signal is highlighted by flashing.

Functional diagram of the alarm device.

The signaling circuit is powered by a DC power supply, which increases their reliability. The signal for switching on the alarm CB is fed to the block of the relay signal interruption of the BRP signal, and then in parallel to the light panel ST and the sound device of the memory. At the same time, the circuit in the PDU is designed in such a way that it provides an intermittent glow on the display and a constant sound signal.

After receiving a signal and removing the sound, the circuit must be ready to receive the next signal, regardless of whether the signaling parameter has returned to its nominal value.

Each light signal must be accompanied by a sound signal to attract the attention of service personnel.

Signaling means.

Electronic contact manometer.

To measure and signal pressure, a manometer of the EKM type with a tubular spring is used. The manometer has a case with a diameter of 160 mm. with rear flange and radial fitting. The device contains an arrow 1, which sets the signal arrows 2 and 3 (minimum and maximum), set to the specified pressure values ​​using a key. Box 4 with clamps for connecting the alarm circuit to the device. The pressure gauge mechanism is enclosed in a housing 5. The device communicates with the medium being measured through the fitting 6.

When any of the specified marginal pressures is reached, the contact associated with the index arrow comes into contact with the contact located on the corresponding signal arrow and closes the alarm circuit. The contact device is powered by a DC or AC network, 220 V.

Reliable, economical and safe work boiler room with a minimum number of staff can only be carried out with thermal control, automatic regulation and process control, signaling and equipment protection.

The volume of automation is accepted in accordance with SNiP II - 35 - 76 and the requirements of manufacturers of thermal mechanical equipment. Mass-produced instrumentation and regulators are used for automation. The development of a boiler house automation project is carried out on the basis of a task drawn up during the implementation of the heat engineering part of the project. The general tasks of monitoring and managing the operation of any power plant, including a boiler, are to ensure:

• production in each this moment the required amount of heat; (steam, hot water) at certain parameters - pressure and temperature;
• efficiency of fuel combustion, rational use of electricity for the plant's own needs and minimization of heat losses;
• reliability and safety, i.e., the establishment and maintenance of normal operating conditions for each unit, excluding the possibility of malfunctions and accidents of both the unit itself and auxiliary equipment.

The personnel servicing this unit must constantly have an idea of ​​​​the operating mode, which is provided by the readings of control and measuring instruments, which the boiler and other units must be equipped with. As you know, all boiler units can have steady and unsteady modes; in the first case, the parameters characterizing the process are constant, in the second they are variable due to changing external or internal disturbances, for example, load, fuel combustion heat, etc.

The unit or device in which it is necessary to regulate the process is called the object of regulation, the parameter maintained at a certain set value is called the regulated value. The object of regulation together with automatic regulator form an automatic control system (ACS). Systems can be stabilizing, software, tracking, connected and unconnected, stable and unstable.

Automation of the boiler room can be complete, in which the equipment is controlled remotely using instruments, apparatus and other devices, without human intervention, from the central panel by telemechanization. Integrated automation provides for the ATS of the main equipment and the presence of permanent service personnel. Sometimes partial automation is used, when ACS is used only for certain types of equipment. The degree of automation of the boiler house is determined by technical and economic calculations. When implementing any degree of automation, it is imperative to comply with the requirements of Gosgortekhnadzor for boilers of different capacities, pressures and temperatures. According to these requirements, a number of devices are mandatory, some of them must be duplicated.

Based on the tasks and instructions listed above, all instrumentation can be divided into five groups intended for measurement:

1. consumption of steam, water, fuel, sometimes air, flue gases;
2. pressures of steam, water, gas, fuel oil, air and for measuring vacuum in the elements and gas ducts of the boiler and auxiliary equipment;
3. temperatures of steam, water, fuel, air and flue gases;
4. water level in the boiler drum, cyclones, tanks, deaerators, fuel level in bunkers and other containers;
5. qualitative composition of flue gases, steam and water.

Rice. 10.1. circuit diagram thermal control of the operation of the boiler with a layered furnace.

When burning high-sulfur fuels, the fuel regulator maintains a constant water temperature at the outlet of the boiler (150 °C). The signal from the resistance thermometer (pos. 16) installed on the water pipeline in front of the boiler is eliminated by setting the sensitivity knob of this regulator channel to zero position. When burning low-sulphur fuels, it is necessary to maintain such water temperatures at the outlet of the boiler (according to the regime map), which provide the temperature of the water at the inlet to the boiler equal to 70°C. The degree of communication through the channel of influence from the resistance thermometer (pos. 16) was determined during commissioning.

For a hot water boiler KV - TSV - 10 in the circuit shown in fig. 10.15, as for the boiler KV - GM - 10, fuel, air and vacuum regulators are provided.

Rice. 10.14. Scheme of automatic protection and signaling of the boiler KV - GM - 10.

In this circuit, the fuel regulator changes the flow solid fuel impact on the plunger of pneumatic casters. The air regulator receives an impulse from the pressure drop in the air heater and from the position of the regulating body of the fuel regulator and acts on the blower fan guide vane, bringing the fuel-to-air ratio into conformity. The vacuum regulator is similar to the vacuum regulator of the boiler KV - GM - 10.

Thermal protection for the boiler KV - TSV - 10 is carried out in a smaller volume than for the boiler KV - GM - 10, and is activated when the water pressure behind the boiler deviates, the water flow through the boiler decreases, and the temperature of the water behind the boiler rises. When the thermal protection is triggered, the engines of the pneumatic casters and the smoke exhauster stop, after which the blocking automatically turns off all the mechanisms of the boiler unit. The thermal control of the boiler KV - TSV - 10 is basically similar to the thermal control of the boiler KV - GM - 10, but takes into account differences in the technology of their work.

As regulators for both steam and hot water boilers, it is recommended to use regulators of the R - 25 type of the "Kontur" system, manufactured by the MZTA plant (Moscow Thermal Automation Plant). For boilers KV - GM - 10 and KV - TSV - 10, the diagrams show a variant of the R - 25 devices with built-in setpoints, control units and indicators, and for a steam boiler GM - 50 - 14 - with external setters, control units and indicators.

In addition, in the future, control kits 1KSU - GM and 1KSU - T can be recommended for the automation of hot water boilers. In automation schemes conventions correspond to OST 36 - 27 - 77, where it is accepted: A - signaling; C - regulation, management; F - consumption; H - manual impact; L - level; P - pressure, vacuum; Q - a value characterizing the quality, composition, concentration, etc., as well as integration, summation over time; R - registration; T is temperature.

In completely automated installations with protections and locks.

Rice. 10.15. Scheme of automatic regulation and thermal control of the operation of a hot water boiler type KV - TSV - 10.

Telemechanization is used, i.e. the process of automatic start-up, regulation and shutdown of an object, carried out remotely using instruments, apparatus or other devices without human intervention. When telemechanization central point control, from where the operation of heat supply installations located at a considerable distance is controlled, the main instruments are taken out, by which it is possible to check the operation of the main equipment, and control keys.

Automation of the operation of boiler units makes it possible to obtain, in addition to increasing reliability and facilitating labor, a certain fuel economy, which, when automating the regulation of the combustion process and power supply of the unit, is about 1-2%, when regulating the operation of auxiliary boiler equipment 0.2-0.3% and when regulating steam superheat temperature 0.4-0.6%. However total costs for automation should not exceed a few percent of the installation cost.

Control and measuring devices (KIP)- devices for measuring pressure, temperature, flow rate of various media, liquid levels and gas composition, as well as safety devices installed in the boiler room.

Measuring device— technical means measurement, which provides the generation of a signal of measurement information in a form convenient for the observer.

Distinguish between indicating and self-recording indicator devices. Instruments are characterized by range, sensitivity and measurement error.

Instruments for measuring pressure. Pressure is measured by manometers, thrust meters (low pressure and vacuum), barometers and aneroids (atmospheric pressure). Measurements are made using the phenomenon of deformation of elastic elements, changes in the levels of the liquid, which is affected by pressure, etc.

Deformation-type pressure gauges and thrust gauges contain an elastic element (bent hollow springs or flat membranes or membrane boxes) moving under the action of medium pressure transmitted from the measuring probe into the internal cavity of the element through a fitting. The movement of the elastic element is transmitted through a system of rods, levers and gears to the pointer, which fixes the measured value on the scale. Manometers are connected to water pipelines by means of a straight fitting, and to steam pipelines by means of a curved siphon tube (condenser). Between the siphon tube and the manometer, install three-way valve, which allows you to communicate the pressure gauge with the atmosphere (the arrow will show zero) and blow out the siphon tube.

Liquid manometers are made in the form of transparent (glass) tubes partially filled with liquid (tinted alcohol) and connected to pressure sources (vessel-atmosphere). Tubes can be mounted vertically (U-gauge) or obliquely (micromanometer). The magnitude of pressure is judged by the movement of liquid levels in the tubes.

Instruments for measuring temperature. Temperature measurement is carried out using liquid, thermoelectric thermometers, optical pyrometers, resistance thermometers, etc.

In liquid thermometers under the action heat flow there is an expansion (compression) of the heated (cooled) liquid inside the sealed glass tube. Most often, mercury from -35 to +600 0 С and alcohol from -80 to +60 0 С are used as a filling liquid. Thermoelectric thermometers (thermocouples) are made in the form of electrodes (wires) welded together at one end from dissimilar materials placed in a metal case and isolated from it. When heated (cooled) at the junction of thermoelectrodes (in the junction), an electromotive force (EMF) arises and a potential difference appears at the free ends - a voltage that is measured by a secondary device. Depending on the level of measured temperatures, thermocouples are used: platinum-rhodium - platinum (PP) - from -20 to +1300 0 C, chromel-alumel (XA) - from -50 to +1000 0 C, chromel-copel (XK) - from - 50 to +600 0 С and copper - constantan (MK) - from -200 to +200 0 С.

The principle of operation of optical pyrometers is based on comparing the luminosity of the measured object (for example, a torch of burning fuel) with the luminosity of a filament heated from a current source. They are used to measure high temperatures (up to 6000 0 C).

The resistance thermometer works on the principle of measuring the electrical resistance of a sensitive element (a thin wire wound on a frame or a semiconductor rod) under the action of a heat flux. As wire resistance thermometers, platinum (from -200 to +75 0 С) and copper (from -50 to +180 0 С) are used; in semiconductor thermometers (thermistors), copper-manganese (from -70 to +120 0 C) and cobalt-manganese (from -70 to +180 0 C) sensitive elements are used.

Instruments for measuring flow. The measurement of the flow rate of liquid or gas in the boiler room is carried out either by throttling or summing devices.

A throttle flow meter with a variable pressure drop consists of a diaphragm, which is a thin disk (washer) with a cylindrical hole, the center of which coincides with the center of the pipeline section, a pressure drop measuring device and connecting pipes.

The summing device determines the flow rate of the medium by the rotational speed of the impeller or rotor installed in the housing.

Instruments for measuring the level of liquid. Water-indicating devices (glasses) are designed for continuous monitoring of the position of the water level in the upper drum of the boiler unit.

For this purpose, at least two direct-acting water-indicating instruments with flat, smooth or corrugated glasses are installed on the latter. When the height of the boiler unit is more than 6 m, lowered remote water level indicators are also installed.

Safety devices - at devices that automatically stop the supply of fuel to the burners when the water level drops below the permissible level. In addition, steam and water-heating boiler units operating on gaseous fuels, when air is supplied to the burners from draft fans, are equipped with devices that automatically stop the gas supply to the burners when the air pressure drops below the permissible value.

Modern heat power industry cannot be imagined without high-precision measuring instruments. Technological process at energy facilities must be constantly monitored using sensors or transducers, which not only passively collect information, but also allow you to produce automatic adjustment and protective shutdown in case of violation of the normal mode.

Types of instrumentation and automation in the boiler room

From common name and the above, we can conclude that for trouble-free operation gas equipment the following sets are required:

• measuring;
• adjusting;
• protective.

The operation of water heating and power plants without protection devices is prohibited, since when non-standard situations and breakdowns, the threat to human life and the integrity of mechanisms increases many times over. Before kindling, the staff on duty organizes a check of the operation of the protections to stop the boiler. The introduction of this clause in the PTE helped to seriously reduce Negative consequences accidents.

Features of the work of instrumentation and automation of boiler equipment

For network and gas pipelines, both remote digital complexes and mechanical devices in place are provided. This allows maintenance personnel to monitor the state of the environment during a boiler bypass or during a power failure. The action of protections most often extends to the fuel supply, to prevent an explosion in case of violations of the combustion regime in boilers.

Maintenance of instrumentation in boiler rooms

For correct operation control devices at thermal power facilities form a special workshop or division. This service performs the following functions:

• daily monitoring of the correctness of the readings,
• checking protection devices;
• repair and replacement of broken devices;
• periodic verification of measuring devices.

Maintaining the mode of the boiler unit is impossible without constant control by the operator of the boiler room. Several rounds per shift help to keep such measuring equipment in good working order.

Instrumentation and control devices for boiler rooms

The main measuring devices in gas boilers are:

• Pressure gauges. Necessary for pressure control in pipelines, without them operation is often impossible. According to them, the combustion process is regulated in hot water and power boilers, by measuring pressures natural gas and air.
• Thermocouples. The coolant must be released into the city with a certain temperature. To control it, and hence the operating mode of the boiler room, several thermal converters are installed.
• Flowmeters. Economic characteristics production of thermal and electrical energy associated with the costs of the working environment and fuel. To measure them, digital recording devices are used.

Mechanic of instrumentation and control of gas boilers

AT modern production all parameters received from measuring devices are accumulated at the point. Computer systems on it allow you to access this information, up to a certain period. This order is useful for analysis.

Duties of the locksmith on duty include the following general items:

• ensuring the serviceability of control and protection devices;
• periodic check of measuring instruments;
• maintenance of instrumentation in the boiler room;
• accumulation and provision of holistic information on the parameters of the production process.

Operational personnel in shifts ensures the normal operation of measuring systems at power facilities and heating networks. He also controls the information collection system to prevent its failures.

Boiler fittings include: safety devices, water-indicating devices (VUP), shut-off and control devices.

Safety devices.

According to the Rules, each boiler (pressure vessel) must have safety device, which automatically releases steam or water if their pressure exceeds the allowable value. Steam boilers with pressure up to 0.07 MPa are protected by discharge devices in the form of hydraulic gates (Fig. 45).

Rice. 45. Throwaway device:

1 release line; 2, 3 - hydraulic seal pipes; 4 - control valve; 5 - a pipe communicating with the boiler; 6 - holes for returning water to the water seal; 7 - tank; 8 - pipe for ejection of steam into the atmosphere; 9 - plumbing.

When the boiler is running with an excess working pressure of 0.07 MPa, the water level in the inner pipe of the hydraulic seal should be equal to 7 m (more precisely, 1 m higher to avoid frequent shutter releases when steam pressure fluctuates). When the pressure in the boiler rises, the steam displaces water from the inner pipe hydraulic seal into the tank and exits the boiler into the atmosphere. After the pressure in the boiler is reduced, the water fills the valve again, returning from the tank through the holes in the pipe.

At a pressure of more than 0.07 MPa, lever-load and spring safety valves direct action (Fig. 46).

Rice. 46. ​​Safety valves:

1 - body; 2 - saddle; 3 - plate; 4 - branch pipe for steam removal; 5 - lever; 6 - cargo; 7 - adjusting bolt; 8 - spring.

In the lever-load valve the plate of the locking body is in the saddle if the steam pressure forces are less than the forces created by the load. When exceeding allowable pressure the plate rises and the steam comes out of the boiler into atmosphere through the outlet pipe connected to the valve nozzle.

in spring valve the spring presses the poppet against the valve while the steam pressure is normal. By tightening the spring with a screw, the opening pressure of the valve can be adjusted. lever-cargo and spring valves applied at pressures up to 4 MPa.

At least two safety valves are installed on each boiler. In addition, one safety valve is installed at the inlet and outlet of water from the economizer to be switched off.

The valves are adjusted to open when the pressure is exceeded by 3-10% of the working one.

Water-indicating devices.

The device consists of glass and pipes connected to the steam and water volumes of the boiler. Valves are installed in the pipes and after the glass, which serve to purge the connecting pipes and the glass itself from possible contamination (Fig. 47).

Rice. 47. Water indicating device:

a - scheme of action; b - device with flat corrugated glass:

1 - purge valve; 2 - water tap; 3 - glass; 4 - steam tap; 5 - upper head; 6 - frame; 7 - lower head.

Metal indicators of the highest and lowest permissible water levels in the boiler are attached to the body into which the glass is inserted. At pressures up to 4 MPa, both corrugated and flat glasses (plates) are used. The corrugated surface of the plate refracts light in such a way that the water in the glass appears dark and the vapor appears light.

Each boiler must have at least two direct-acting water-indicating instruments.

AT hot water boilers The water level is controlled by water test valves, the position of which corresponds to the limit values ​​of the water level. A test cock is installed in the upper part of the boiler drum, and in its absence - at the outlet of water from the boiler to main pipeline to the locking device.

Shut-off and control valves for boilers.

Boiler fittings are used to control the operation of boilers, by switching on and off individual elements, changes in flow rates, pressure and temperature of working media.

With passage diameters up to 100-150 mm, valves (shut-off and control devices) are mainly used, and for large diameters, valves (shut-off devices). Check valves are used to pass fluid in one direction.

According to the requirements of the Rules, shut-off and control valves must be clearly marked on the body, which must indicate:

Name or trademark of the organization - manufacturer;

Conditional pass;

Nominal pressure and temperature of the medium;

Direction of medium flow.

Valve handwheels are marked with the direction of rotation when opening and closing the valve.

The fittings are installed on boilers and connecting pipelines.

Safety valves are installed on the upper drum of the boiler. exhaust pipes, water gauges and pressure gauges .

On the steam pipeline connecting the boiler with the steam pipeline of the boiler house, near the boiler drum, the main shut-off device is installed, which in boilers with a steam capacity of more than 4 t / h is equipped with a remote drive with control output to workplace boiler operator.

Fig.48. Gate valve with non-rising stem:

1 - flywheel; 2 - bushing; 3 - stuffing box; 4 - gasket; 5 - cover; 6 - spindle;

7 - sealing gasket; 8 - running nut; 9 - body; 10 - shutter; 11 - saddle.

Rice. 49. Flanged shut-off valve:

1 - flywheel; 2 - running nut; 3 - stuffing box; 4 - cover; 5- spindle; 6 - plate; 7 - saddle; 8 - body; 9 - rack

Rice. 50. Swing check valve:

1 - axis; 2 - lever; 3 - disk; 4 - body; 5 - saddle

The feed pipes are connected to the upper drum of the boiler through a shut-off valve (it is closer to the drum) and check valve. For a water-switched economizer, a non-return valve and a shut-off element are installed before and after the economizer.

For hot water boilers, shut-off devices are installed at the inlet and outlet of water from the boiler.

For boilers with pressure over 0.8 MPa on each pipeline through which boiler water is removed from the boiler, at least two shut-off devices, or one shut-off and one regulating body, are installed.