Accidents of steam and hot water boilers. Analysis of the causes of damage to steam water-tube boilers. Mechanical damage to pipes

To prevent accidents in steam boilers due to excess pressure, the Boiler Rules provide for the installation of safety valves.

: The purpose of safety valves is to prevent pressure increases in steam boilers and pipelines above established limits.

Exceeding the operating pressure in the boiler can lead to rupture of the boiler screen and economizer pipes and drum walls.

The reasons for increased pressure in the boiler are a sudden decrease or cessation of steam flow (switching off consumers) and excessive boost of the furnace,

Especially when working with heavy oil or gaseous fuels.

Therefore, to prevent the pressure in the boiler from rising above the permissible limit, the operation of boilers with faulty or unregulated valves is strictly prohibited.

Measures to prevent an increase in pressure in a steam boiler are: regular checks of serviceability of safety valves and pressure gauges, alarm systems from steam consumers to obtain information about upcoming steam consumption, trained personnel and good knowledge and compliance with production instructions and emergency circulars. -

To check the serviceability of the safety valves of the boiler, superheater and economizer, they are purged by forcefully opening them manually:

At operating pressure in the boiler up to 2.4 MPa inclusive, each valve must be used at least once a day;

At an operating pressure from 2.4 to 3.9 MPa inclusive, one valve at a time for each boiler, superheater and economizer at least once a day, as well as at each boiler start-up, and at a pressure above 3.9 MPa, within a period of time established by the instructions.

In the practice of operating boilers, accidents still occur when the pressure in the boiler exceeds the permissible limit. The main cause of these accidents is the operation of boilers with faulty or unregulated safety valves and faulty pressure gauges. In some cases, accidents occur due to the fact that boilers are put into operation with safety valves turned off using plugs or jammed, or they allow arbitrary changes in valve adjustment, placing additional load on the valve levers in the event of a malfunction or absence of automation and safety equipment.

In the boiler room, an accident occurred with the E-1/9-1T steam boiler due to excess pressure, as a result of which the boiler room was partially destroyed. The E-1/9-IT boiler was manufactured by the Taganrog House-Building Plant to operate on solid fuel. In agreement with the manufacturer, the boiler was converted to liquid fuel, an AR-90 burner device was installed and automatic devices were installed to shut off the fuel supply to the boiler in two cases - when the water level drops below the permissible level and the pressure rises above the set one. Before putting the boiler into operation, the ND-1600/10 feed pump with a flow rate of 1.6 m3/h and a discharge pressure of 0.98 MPa, which turned out to be faulty, was replaced with a centrifugal vortex pump with a flow rate of 14.4 m3/h and a discharge pressure 0.82 MPa. The high power of the engine of this pump did not allow it to be included in the electrical circuit for automatically regulating the water supply to the boiler, so it was carried out manually. The automatic protection against low water level was disabled, and the automatic protection against overpressure did not work due to a sensor malfunction. The operator, having detected a loss of water, turned on the feed pump. The hatch cover of the upper drum was immediately torn out and the lower left manifold was destroyed at the place where the grate beam was welded to it. The accident occurred due to a sharp increase in pressure in the boiler due to a deep release of water and its subsequent replenishment. Calculations showed that the pressure in the boiler in this case could increase to 2.94 MPa.

The thickness of the hatch cover in a number of places was less than 8 mm, and the cover was deformed.

In connection with this accident, the USSR Gosgortekhnadzor suggested that owners operating steam boilers: do not allow the operation of boilers in the absence or malfunction of automatic safety equipment and instrumentation; ensure maintenance, adjustment and repair of security automation equipment by qualified specialists.

In accordance with the letter of the USSR State Mining and Technical Supervision No. 06-1-40/98 dated May 14, 1987 “On ensuring reliable operation of steam boilers E-1.0-9”, owners of boilers of this type are required to reduce the pressure allowed for operation for boilers that have a cover thickness 8 mm hatch with fastening the hatch cover with studs up to 0.6 MPa, since the plants of the Ministry of Energy of Mash produced E-1.0-9 boiler drums with a steam capacity of 1 t/h with hatch covers 8 mm thick and the thickness of the hatch cover was increased to 10 mm.

An accident occurred in the boiler room with the E-1/9T boiler due to excess pressure.

As a result of the bottom of the lower drum being torn off, the boiler was thrown from the installation site towards another boiler and, upon impact, tore off the casing, destroyed the lining, deformed 9 pipes of the side screen. Safety valves were torn out of their seats upon impact. When tested on a pressure bench 1 .1 MPa valves did not work. When disassembling the valves, it was established that its moving parts of the valve were stuck.

The investigation established that the bottom of the boiler 0 600X8 mm was made in a handicraft manner from steel that did not have a certificate.

After welding the bottom, the boiler room workers carried out a hydraulic test with a pressure of 0.6 MPa, and the bottom became deformed. After a few days of boiler operation, cracks appeared in the weld, which were welded.

Due to changes in the design of the lower drum hatch cover (without the approval of the manufacturer) and unsatisfactory repairs, an accident with serious consequences became possible.

Safety valve malfunctions

To prevent accidents of steam and hot water boilers due to excess pressure in them, the State Rules

The USSR Gortechnadzor provides for the installation of at least two safety valves for each boiler with a steam capacity of more than 100 kg/h.

On steam boilers with pressures above 3.9 MPa, only pulse safety valves are installed.

Due to improper operation of safety valves or their defects, accidents occurred in boiler rooms of industrial enterprises and power plants. Thus, at one power plant, during a sharp load shed due to a malfunction of the safety valves, the steam pressure in the boiler increased from 11.0 to 16.0 MPa. This disrupted the circulation and the screen pipe ruptured.

At another power plant, under the same operating conditions, the pressure increased from 11.0 to 14.0 MPa, as a result of which two screen pipes ruptured.

The investigation found that some safety valves did not work because the impulse lines were blocked by the valves, and the remaining valves did not provide the necessary steam release due to the use of uncalibrated springs in the impulse safety valves and, as a result, some of them broke.

The destruction of springs was observed in pulse valves after each opening. This occurred as a result of large dynamic forces from the jet of escaping steam at the moment of opening of the valve, which has a seat cross-sectional diameter of 70 mm.

The main malfunctions in the operation of lever-load and spring safety valves are given in table. 2.4.

Safety valves must protect boilers and superheaters from exceeding their pressure by more than 10% of the design pressure. An excess of pressure when the safety valves are fully opened by more than 10% of the calculated value can only be allowed if this possible increase in pressure is taken into account when calculating the strength of the boiler and superheater.

Accidents and malfunctions in the operation of the boiler installation and measures to eliminate them.

Boiler and compressor installations.

Boilers operate on liquid, solid and gaseous fuel. The rules prohibit the installation of boilers in schools, clubs, bathhouses, etc., as well as in buildings adjacent to a combustible materials warehouse.

Technical inspection of a steam boiler consists of an internal inspection carried out at least once every 4 years. And hydraulic testing. Conducted at least once every 8 years. When inspecting a boiler or compressor, the strength of the walls, seams, pipes (inside the boiler), and the operability of the devices are checked.

Steam boilers and hot water boilers are subjected to hydraulic tests: at an operating pressure of 1.5 P slave (but not less than 200 kPa); at Р slave > 500 kPa – 1.25 Р slave (but not less than 300 kPa). The pressure is increased to the maximum (then reduced to the working pressure) slowly and gradually. The maximum pressure is maintained for 5 minutes.

An explosion of a steam boiler occurs as a result of a decrease in pressure in it to atmospheric pressure. The temperature in a steam boiler, in which the pressure is greater than atmospheric, exceeds 100 0 C. When communicating with the atmosphere, the water pressure drops to atmospheric pressure, and its temperature drops accordingly to 100 0 C. As a result, a huge amount of heat is released in the water mass, which is used for instantaneous vaporization . A huge volumetric amount of steam is formed, because When water turns into steam at atmospheric pressure, its volume increases approximately 1700 times. In this case, the pressure in the boiler instantly increases, and destruction of large sizes and consequences occurs. The source of danger is water; The more water in a steam boiler, the more heat is released, and, consequently, the more steam is produced. So the effect of water weighing 60 kg with an initial pressure of 0.5 MPa during a boiler explosion is equivalent to the effect of gunpowder weighing 1 kᴦ.

Causes of boiler explosions:

1) low quality of the boiler metal or poor processing;

2) general wear and tear of the boiler (over time, the walls of the boiler lose their metallic properties);

3) incorrect boiler design or incorrect installation;

4) drainage of water (one of the basic reasons) - a decrease in the water level in

5) a steam boiler may occur due to untimely and insufficient

6) precise water supply to the boiler unit;

7) excessive increase in pressure in the boiler unit, especially when working with faulty pressure gauges and safety valves, when hanging additional weights on the safety valves or jamming the valve levers, as well as in the event that when the pressure gauge needle reaches the red line and the corresponding opening of the safety valve , the fireman does not take immediate measures to lower the pressure.

8) collapse of the boiler masonry above the fire line, when gaseous combustion products begin to heat the walls of the steam boiler, which are not cooled on the other side by boiler water, as a result of which they overheat;

9) deposition of scale and sludge on the heating surface of the boiler;

10) internal and external corrosion of the walls of the boiler unit;

Accidents and malfunctions in the operation of boiler units, sometimes accompanied by great destruction, pose a danger to the health and life of people. In this regard, the operation and regulation of boiler units must be carried out by specially trained stokers who have received the rights to care for them.

Personnel directly servicing the boiler unit are obliged to immediately stop its operation and report this to the person in charge of the boiler room in the following cases:

1) the pressure in the boiler has risen above the permitted level and continues to rise despite the measures taken (cutting off the fuel supply, reducing draft and blast, increasing the supply of water to the boiler unit);

2) water has drained from the boiler or its level in the boiler is rapidly decreasing, despite its continued increased supply;

3) all nutritional devices (pumps, injectors) stopped working;

4) the masonry has collapsed or parts of the boiler unit or boiler elements have been exposed from the lining, the distortion and casing of the boiler have become red-hot;

5) all water heating devices or all safety valves have ceased to function;

6) in the basic elements of the boiler (drum, manifold, chamber, flame tube, fire box, furnace casing, tube sheet) bulging (except for water-tube boiler pipes), cracks, leaks in welds, pipe ruptures, breakage of two or more connections located near;

7) the control plug (of special boilers) melted;

8) the water level has risen above the top point of the water indicator glass (or above the top water test valve), and it is not possible to quickly reduce it by blowing the boiler;

9) the steam line or economizer pipes have ruptured;

10) the gas supply suddenly stopped completely (if the regulator fails, if the shut-off safety valve is activated, or if there is an accident in the gas pipeline);

11) the fan stopped and the air supply to the burners with forced air supply stopped;

12) the gas pressure at the burners increased sharply and strongly (due to a malfunction of the regulator or safety shut-off valve);

13) gas burners went out spontaneously;

14) cravings stopped;

15) gas is passed into the boiler room;

16) fire in the boiler room (or the presence of a fire threat);

17) the gas pipeline and gas fittings are damaged;

18) explosion of gases in the furnace or flue of the boiler unit;

19) fuel combustion was detected in the gas ducts of the tail section of the boiler unit.

The reasons for the emergency shutdown of the boiler should be recorded in the logbook. The boiler unit is stopped with the permission of the person in charge of the boiler room in the following cases:

1) leaks are detected in rivet seams or pipe rolling areas;

2) fistulas were found on the pipes of the water boiler;

3) the pressure gauge indicating the pressure in this boiler unit is faulty;

4) strange phenomena were noticed (noise, shocks, knocking in the boiler unit).

When stopping the boiler it is extremely important:

1) quickly stop the operation of gas burners and fuel oil nozzles, tightly close the operating and control valves in front of the burners, open the safety gas pipeline valves and spark plugs, close the pilot valves (in case of an emergency shutdown of the entire boiler room, close the valve at the gas pipeline entrance to the boiler room);

2) disconnect the boiler unit from the main steam line;

3) continue powering the boiler unit if there was no draining of water;

4) gradually release steam through raised safety valves or through an emergency valve (except in cases of increased water level and the cessation of operation of all feeding devices);

Instructions for safe work and labor protection of stokers:

1) the external doors of the boiler room should never be locked with locks or bolts and should always open outwards by hand pressure. Doors from the boiler room to service, household and auxiliary production doors should have springs and open towards the boiler room. To avoid drafts, vestibules are installed in the boiler room;

2) all hot pipelines and tanks must be covered with thermal insulation;

3) to avoid burns when the flame ejects from the firebox and in case of touching the hot parts of the boiler, stokers should use smoky or blue glasses and gloves;

4) when lighting the boiler, you should not stand against the firebox doors, so as not to get damaged in case of pops in the firebox; the same caution must be observed when opening the firebox doors and peepholes;

5) during all work in the boiler installation, you cannot use personal electric lamps with a voltage higher than 12 V, and during cleaning - kerosene lamps in order to avoid electric shock and severe burns. For electric lamps for local and general lighting, suspended at a height below 2.5 m above the floor or working platform, a voltage not exceeding 36V is allowed;

6) turn on electric motors while wearing rubber gloves;

7) during a fire and any accidents outside the boiler room, stokers must remain at their workplaces.

In the event of a fire in the boiler room, stokers must take measures to extinguish it and at the same time raise the alarm. In the event of an immediate threat, robotic boilers must be stopped in an emergency and steam released from them through safety valves.

Stokers can leave the boiler room only after stopping the boilers and extinguishing the fireboxes. In case of accidents, the victim is given first aid and a doctor is called.

Accidents and malfunctions in the operation of the boiler installation and measures to eliminate them. - concept and types. Classification and features of the category "Accidents and malfunctions in the operation of the boiler installation and measures to eliminate them." 2017, 2018.

POSSIBLE EMERGENCIES

Emergency situations causing disruption of the normal operating mode of boilers, in which, according to the requirements of the Rules for the Design and Safe Operation of Steam and Hot Water Boilers, they must be immediately stopped by automation or by personnel on duty, include:

Safety valve fault detection;

If the pressure in the boiler drum has risen above the permitted value by 10% and continues to rise;

Reducing the water level below the lowest permissible level, in this case, replenishing the boiler with water is strictly prohibited;

Increasing the water level above the highest permissible level;

Stopping all feed pumps;

Termination of all direct action water level indicators;

If cracks, bulges, and gaps in their welded seams, breakage of an anchor bolt or connection;

Unacceptable increase or decrease in pressure in the direct-flow boiler path up to the built-in valves;

Extinguishing of torches in the furnace during chamber combustion of fuel;

Reducing water flow through the hot water boiler below the minimum permissible value;

Reduction of water pressure in the hot water boiler circuit below the permissible level;

Increasing the water temperature at the outlet of the hot water boiler to a value 20°C below the saturation temperature corresponding to the operating water pressure in the boiler outlet manifold;

Malfunctions of automatic safety or alarm systems, including loss of voltage to these devices;

The occurrence of a fire in the boiler room that threatens operating personnel or the boiler;

The appearance of leaks in the lining, in places where safety-explosion valves are installed and in gas ducts;

Stopping the power supply or disappearing voltage on remote, automatic control devices and measuring instruments;

Malfunctions of instrumentation, automation and alarm systems;

Failure of safety interlocking devices;

Malfunctions of burners, including fire stoppers;

The appearance of gas contamination, detection of gas leaks on gas equipment and internal gas pipelines;

Explosion in the combustion chamber, explosion or combustion of flammable deposits in gas ducts;

Accidents in the gas industry.

CAUSES AND CONSEQUENCES OF ACCIDENTS AND FAILURES IN BOILER STATIONS

The most serious consequences of the accident are explosions when the density of the boiler is violated due to non-compliance with operating modes and operating rules, as well as explosions associated with gas contamination of the furnace due to improper maintenance and combustion of fuel.

In the firebox and flue ducts, pops and explosions occur when the gas concentration in the air is in the range of explosion limits and an explosive gas-air mixture is created.

In a boiler room operating on solid fuel, during layer combustion of fuel in the furnace and flues, combustible gases are released in large quantities from fresh fuel if, during a short shutdown of the boiler, it is thrown onto the remaining unburned fuel and not removed from the furnace.

The reasons for the formation of an explosive gas-air mixture in the furnaces and flues of a gasified boiler room may be incorrect actions of personnel during the operation of boilers, malfunction of shut-off devices in front of the burners and their activation when the automatic flame control system is faulty or disabled, the absence of devices for monitoring the tightness of the shut-off organs of the burners.

When burning liquid fuel, fires and explosions in the furnace and flues occur in the event of poor-quality atomization by nozzles, which leads to fuel oil leaking into the embrasure and onto the walls of the furnace. When fuel oil is poorly mixed with air and its combustion is incomplete, increased soot is carried into the flues. In case of fire of deposits and soot, the temperature of the gases increases, the draft decreases, the casing heats up significantly, and sometimes a flame breaks out.

The cause of the accident may be unsatisfactory water conditions of the boilers. As a result, scale deposits are formed, causing an increase in the temperature of the metal pipes and their burnout. The accumulation of scale and sludge can also cause problems with water circulation. The causes of damage and accidents may be manufacturing defects in the boiler, poor quality of the material from which individual components of the boiler are made, as well as unsatisfactory condition of the equipment due to poor installation or repair.

Table 1 shows typical cases of accidents and malfunctions in boiler rooms and indicates their causes and possible consequences.

Table 1

Typical cases of accidents and failures in boiler rooms, their causes and possible consequences

Malfunction

Possible consequences

Fire in the boiler room

Failure to comply with the requirements of production instructions and fire safety rules. Ignition of flammable materials and substances. Malfunctions in the operation of boiler equipment. Malfunction of the boiler safety automatics. Electrical fault

Accidents and loss of life. Material damage

NOTIFICATION PROCEDURE IN CASES OF EMERGENCY SITUATIONS

Owners of boilers registered with the Gospromnadzor authorities are required to immediately notify the territorial technical supervision body and other government agencies about each accident, fatal, serious or group accident in accordance with the regulations on the procedure for technical investigation of the causes of accidents and incidents at hazardous production facilities.

The personnel on duty servicing boiler installations, in the event of any equipment failure, breakdown, accident and in the event of a fire or threat of fire, is obliged to:

Immediately notify the person responsible for the good condition and safe operation of the boilers (boiler room manager);

Notify all officials according to a pre-compiled list;

Before the arrival of the commission to investigate the circumstances and causes of the accident or incident, ensure the safety of the entire situation of the accident (accident), if this does not pose a danger to the life and health of people and does not cause further development of the accident or emergency situation;

Draw up an explanatory note, which will be the primary document of the preliminary investigation into the causes of the accident.

GENERAL SAFETY MEASURES IN EMERGENCY CONDITIONS OF BOILERS OPERATING WITH SOLID, LIQUID AND GASEOUS FUEL

When eliminating accidents associated with emergency shutdown of boilers, maintenance personnel must be able to quickly assess the current emergency situation, remain calm and act confidently at any stage of the accident.

In case of emergency shutdown of boilers, the following safety precautions must be observed.

When a boiler room operates on solid fuel, burning fuel from the furnace of a stopped boiler must be removed. In exceptional cases, if it is impossible to quickly remove fuel from the firebox, burning fuel can be filled with water. In this case, the driver (stoker) must pay special attention to ensure that the stream of water does not hit the walls of the boiler furnace and the lining. The raked out slag can only be poured using a brassboot from a distance that ensures the safety of personnel during pouring (at least 2-3 m).

It is prohibited not only to “suppress” the flame with fuel, but also to stop the air supply when removing fuel. If this instruction is not followed, this will lead to the flame being thrown out of the firebox by the gases accumulated in it and injury to operating personnel.

The firebox doors must have locks on them to prevent gases and flames from escaping from the firebox and creating smoke in the boiler room.

When the boiler room is operating on liquid fuel, the supply of fuel to the nozzle or air is immediately cut off when installing an air atomization nozzle. If the design allows, the nozzle is removed from the firebox. The valve at the outlet of the pipeline to the nozzle of the emergency boiler, the general valve of the intra-boiler pipeline, is turned off.

When the boiler room is operating on gaseous fuel, the shut-off valve at the gas pipeline inlet in front of the boiler room or the safety shut-off valve and shut-off valve in front of the emergency boiler are closed to disconnect it from the general gas pipeline.

In this case, first the gas supply is quickly shut off, then the air supply, and then the tap on the gas pipeline of the safety plug is opened.

Operation of gas equipment with disconnected control and measuring instruments, interlocks and alarms provided for by the project is prohibited.

DANGEROUS ACTIONS OF BOILER HOUSE OPERATING PERSONNEL THAT RESULT IN THE POSSIBILITY OF EMERGENCIES

In order to avoid possible accidents and failures during the operation of boiler equipment, the operator (stoker) is prohibited from:

Jam the safety valves or place additional load on them;

Carry out repair work on boilers that are under pressure (lubricate bearings, fill and tighten seals, bolts of flange connections);

Open and close fittings using hammers or other objects, as well as using extended levers;

Allow the water level in the steam boiler to fall below the permissible lowest level or rise above the permissible highest level;

Allow the needle to cross the red line indicated on the pressure gauge;

Bleed the boiler if the purge valves are faulty;

Blow soot off the boiler, blow it without using gloves or safety glasses;

Use open fire to find gas leaks;

Turn on and off electrical appliances if there is a smell of gas in the boiler room;

Turn on and off electric motors of pumps and smoke exhausters without electrical protective gloves and in the absence of grounding of electrical equipment;

Use electric lamps with a voltage of more than 12 V in chimneys and boilers;

Clutter the boiler room with foreign objects;

Perform any other duties while on duty that are not provided for in the production instructions;

Leave the boiler without constant supervision both during operation of the boiler and after it is stopped until the pressure in it decreases to atmospheric pressure;

Allow unauthorized persons not related to the operation of boilers and boiler room equipment.

Great attention is paid to the safe operation of steam boilers.

As a result of the replacement of obsolete structures (vertical-cylindrical, heat-turbine, etc.), the accident rate of steam boilers has recently decreased sharply. However, accidents have not yet been completely eliminated, especially due to loss of water. In some cases, the loss of water led to explosions of steam boilers with the destruction of the boiler room and human casualties.

In recent years, due to the equipping of steam boilers with a nominal steam output of 0.7 t/h or more with automatically operating sound alarms for the upper and lower limit positions of water levels, water loss accidents on such boilers have sharply decreased. Water leaks occurred only on boilers that did not have alarms or, due to poor maintenance, were faulty and inactive at the time of the accident.

In some cases, the consequences of the accident were aggravated by the incorrect actions of the maintenance personnel who recharged the boiler after detecting a water leak in violation of the requirements of the “Standard Instructions for Boiler House Personnel” approved by the USSR State Mining and Technical Supervision on July 12, 1979.

An analysis of accidents of steam boilers that do not have automatic power regulators installed shows that accidents due to water loss occur mainly as a result of weakened personnel attention, mainly in the evening and at night. Thus, in the period from 0 to 8 a.m. the number of accidents reaches 50%, from 8 to 16 a.m. - up to 20%, and from 4 to 24 p.m. - up to 30%.

As a result of violations of personnel's production discipline, about 80% of accidents occur due to loss of water.

Loss of water in a steam boiler can occur not only due to the fault of personnel who did not refuel the boiler in a timely manner, but also due to technical malfunctions of water indicating devices, purge and feed fittings, feed devices, insufficient productivity and pressure of feed devices, rupture of the screen, boiler or economizer pipe. Let's give a few examples.

At the thermal power plant, due to a deep loss of water, an accident occurred in the TGME-454 boiler with a capacity of 500 t/h (pressure in the drum "16.2 MPa). In this case, four screen pipes ruptured, fistulas appeared in two pipes, the entire screen system was deformed with amplitude up to 250 mm (gas-tight firebox).

Material damage from the accident amounted to about 200 thousand rubles. The investigation established that the cause of the accident was: operation of the boiler with the automatic safety system turned off (cutting off the fuel supply to the boiler when the water level drops below the permissible level), incorrect actions of the boiler operator in an emergency situation.

At the thermal power plant, due to a deep loss of water, an accident occurred in the TP-35 steam boiler with a capacity of 45 t/h (pressure in the drum 3.9 MPa). In this case, two screen pipes ruptured, 40% of the screen pipes were deformed. Material damage from the accident amounted to 10 thousand rubles.

Causes of the accident: operation of the boiler with gas supply to the burners through the bypass line, excluding automatic shutdown of fuel when water is lost. The boiler operator intervened in the operation of the automatic regulation by influencing the control key of the supply control valve, and manually closed the valve on the boiler water supply unit when the water level was at an emergency low. The boiler began manual feeding, thereby violating the requirements of the job description and instructions for the prevention and elimination of accidents. Due to changes in the operating mode of the boiler, the shift manager of the thermal power plant did not ensure that his subordinate personnel complied with the requirements of production instructions, and did not take measures to emergency stop the boiler. There was an unsatisfactory state of production discipline among maintenance personnel and engineering personnel, expressed in failure to comply with the requirements of current safety rules and instructions.

In the third case, in the boiler room, due to a deep loss of water, an accident occurred with the steam boiler DKVR-2.5/13. As a result of the accident, the boiler screen and boiler pipes were damaged.

Causes of the accident: the driver left the boiler running without supervision; the boiler was operating with faulty safety automatics; maintenance personnel violated production instructions.

In the boiler room, due to a deep loss of water, an accident occurred with the steam boiler DKVR-10/13. As a result of the accident, the boiler screen and boiler pipes were damaged and the rolling connections were damaged. Damaged pipes have also been completely replaced.

Causes of the accident: incorrect actions of the driver who purged the boiler without proper control over the water level in the upper drum of the boiler; faulty state of automatic safety and alarm systems for water loss from the boiler; acceptance of a shift by a senior driver without checking the status and automatic safety; admission to servicing steam boilers of personnel who have not passed the test of knowledge of current safety rules and production instructions.

To prevent water loss in steam boilers, it is necessary:

Do not allow persons to service boilers who have not completed training in the scope of the relevant program and do not have a certificate from a qualified commission for the right to service the boiler;

Do not allow the operation of boilers with faulty water indicator, purge and feed fittings, as well as automatic safety systems that ensure normal operation of the boiler from the monitoring and control panel;

Check the serviceability of all feed pumps by briefly putting them into operation (for boilers with an operating pressure of up to 2.4 MPa within the time limits established by the production instructions, check water indicators by blowing out for boilers with an operating pressure of up to 2.4 MPa at least once per shift, for boilers with operating pressure from 2.4 to 3.9 MPa - at least once a day, and over 3.9 MPa - within the time limits established by the instructions);

Prohibit leaving the boiler during operation without constant supervision by personnel and prohibit the operator from performing any other duties not provided for in the instructions.

Enterprises in various branches of the alcohol industry used boiler vessels with a capacity of 5.0 and 5.3 m3 with a steam pressure of 0.6 MPa. They were intended for steaming potatoes, beets, grains and other food products. To protect the lower conical part from mechanical wear, the boilers were equipped with a safety sleeve 1600 mm high.

At some factories, proper monitoring of the technical condition of these vessels was not carried out and the wear of their walls was not detected in a timely manner, which led to accidents with serious consequences. Thus, at one of the plants, the destruction of the boiler during operation occurred due to the fact that the walls of the conical part were thinned from 12.0 mm to 2-2.8 mm.

At another plant, a boiler exploded under the following circumstances.

When installing the boiler, the outlet fitting was cut out due to its uselessness, and a patch with a diameter of 240 mm was welded in this place. The patch uses steel with a carbon content of 0.7% instead of the permissible 0.3%

The patch was not completely inserted into the socket, with the mating edges offset by up to 5.5 mm. Welding was carried out with a lack of penetration of the root of the seam along the entire perimeter of the patch with a depth of up to 50%.

The hole for the patch was prepared with a gas cutter without cleaning the edges with an abrasive tool. Welding quality has not been checked. After the completion of the repair, the steam boiler was not presented to the boiler inspection inspector for technical inspection.

Two hours before the rupture, the boiler was disconnected from the steam line and was in working condition, filled with boiled mass. Due to a leak in the shut-off valves, pressure built up in it, and the weld of the patch failed, causing an explosion.

As a result of the explosion, walls were destroyed, technological equipment and communications were damaged, while the boiler broke through the concrete base and went 2.2 m into the ground.

Due to violations of the water-chemical regime on boilers of the MZK-7G type, ruptures of heating surface pipes occurred during operating hours from 1700 to 3500 hours. The investigation showed that the cause of the pipe rupture was the complete blocking of the open section of the pipes by deposits of scale salts. At enterprises operating these boilers, the following was revealed:

• the boilers were fed partially with raw water or water, the hardness of which was many times higher than the Gosgortekhnadzor standard;
• the boilers were not purged regularly and not in sufficient quantities, and some boilers were not purged at all, and the purge valves were completely clogged with scale and sludge;
• schedules for the regeneration of filters and purging of boilers by specialized (commissioning) organizations were not drawn up individually for the facility, the timing of shutting down the boiler for inspection and cleaning was not established;
• there was no systematic control over the quality of water in feed tanks;
• the requirements for the operation of water treatment units for boilers with a capacity of 1.0-0.4 t/h were grossly violated.

Thus, as the above shows, the main reason for the accelerated deposition of scale salts on the internal heating surfaces of boilers and the formation of sludge in the lower collector is the unsatisfactory water regime, i.e. feeding boilers with high hardness feed water.

During the operation of low-capacity boilers of type E-1/9, accidents with serious consequences occurred.

Thus, at the creamery, as a result of an accident with the steam boiler E 1/9, the boiler room was completely destroyed. During the investigation, it was established that the steam boiler was intended to operate on solid fuel.

In agreement with the manufacturer, the boiler was converted to operate on liquid fuel. At the same time, a burner device was installed, an automatic device was installed to shut off the fuel supply when the water level drops below the permissible level or the pressure rises above the set one, and other work recommended by the manufacturer was performed.

Before putting the boiler into operation, the butter factory workers replaced the faulty feed pump ND-1600/10 with a capacity of 1.6 m3/hour and a pressure of 10 kgf/cm2, with a centrifugal vortex pump with a capacity of 14.4 m3/hour with a pressure of 8.2 kgf/cm2. cm2.

The high electrical power of the engine of this pump did not allow it to be connected to the electrical circuit for automatic control of the boiler power supply. Therefore, the boiler was fed with water manually, and the automatic shutdown of the fuel supply when the level dropped below the permissible level remained inoperative.

Due to a malfunction of the sensor, the automatic shutdown of fuel supply when the pressure increased did not work.

On the day of the accident, the fireman, having lit the boiler, went to the neighboring plant workshop to check the readings of the pressure gauge on the steam line, since there was no telephone connection in the boiler room. During the absence of the fireman (15-20 minutes), the boiler was not supplied with water. Shortly after the fireman returned to the boiler room, a boiler accident occurred, during which the lower drum hatch cover was torn out and the lower left manifold was destroyed at the place where the grate beam was welded to it.

The commission that investigated the accident found that the boiler accident occurred due to a significant excess of pressure above the permissible limit. The reasons for the increase in pressure were the loss of water from the boiler (the boiler was not fed for 15-20 minutes) and the subsequent intensive replenishment of it. The calculations showed that the pressure in the boiler in this case increased to 20-30 kgf/cm2.

A steam boiler exploded in the boiler room of the bath and shower complex

E-1/9-1M, as a result of which the building was completely destroyed. The explosion tore the boiler off its foundation and threw it 20 meters from the boiler room.

A steam boiler, made to operate on liquid fuel, was installed in the boiler room adjacent to the bathhouse, equipped with chemical water treatment and automatic safety systems (automatic replenishment of the boiler, a device for automatic fuel shutoff when the water level in the boiler reaches and the pressure rises above the set one, alarm devices) .

When inspecting the boiler after the accident, it was revealed that the manhole covers of the upper and lower drums were torn out, the manifolds of the side and ceiling screens were torn from the drums, the shut-off valve on the steam line from the boiler was closed, the safety automatics and alarm devices were in the off state (the toggle switch on the panel was fixed in the position manual control).

The commission that investigated the accident found that the boiler explosion occurred due to a significant excess of pressure above the permissible level. The reason for the increase in pressure in the boiler was a deep loss of water followed by intensive water replenishment with a centrifugal pump Ks-10-55/2 with increased productivity (7-19 m3/hour). In violation of the rules, the Ks-10-55/2 pump was installed by the administration of the bath and shower enterprise instead of the PN-1.6-16 pump with a capacity of 1.6 m3/hour provided by the plant, without coordination with the boiler plant manufacturer.

Calculations made by the All-Union Scientific Research Institute of Nuclear Power Engineering (VNIIAM) showed that with intensive supply of a large amount of water to the hot metal of the boiler by a pump, the pressure in the boiler could presumably increase to 61 kgf/cm2. According to the results of research conducted by the institute, the temperature of the metal of the boiler pipes reached 720-840°C.

The accident was also caused by gross violations of safety rules. The enterprise administration did not provide proper technical supervision over the operation of the boiler plant. Untrained personnel were allowed to service the boiler. In the boiler room there was low production discipline of the service personnel. During the vacation of the person responsible for the safe operation of the boiler, an engineer and technical worker was appointed who had not passed the knowledge test on safety rules. Due to a violation of the water regime, there were salt deposits on the heating surfaces of the boiler. Strangers were allowed into the boiler room.

An E-1/9 type steam boiler exploded in the boiler room of the brewery, as a result of which the boiler room building was destroyed.

During the explosion, the upper and lower drums with the convective bundle of pipes were thrown outside the boiler room, the side screens with collectors were torn off, and the manhole cover of the lower drum was torn out.

The steam boiler ran on solid fuel.

The cause of the explosion was a deep leak of water followed by refilling the boiler. Metallographic studies of metal samples cut from boiler pipes showed that, as a result of the release of water, the temperature of the pipe walls exceeded 720°C, and the pressure in the boiler after make-up rose to 70 kgf/cm2.

During the investigation, gross violations of the Boiler Operating Rules were revealed.

At the plant, in accordance with the staffing table, there are three engineering and technical workers - a director, a technologist and a mechanic. All of them, as well as the stokers and ash workers of the boilers, are trained, certified and received certificates in the established form. Periodic testing of personnel knowledge was carried out in a timely manner and documented with appropriate protocols.

The operational documentation required by the Boiler Inspection Rules (shift log, knowledge testing and training logs, water treatment log, etc.) was available and entries were made regularly.

However, all this was done formally.

A mechanic with a four-year education who had a very vague understanding of the operation of boilers was appointed as the person responsible for the safe operation of the boilers. He did not know and did not fulfill his functional duties, although he signed the shift log daily.

The stokers did not carry out the inspection of equipment, fittings and automation provided for by the Rules, but the same stereotyped entry about the performance of this work was entered into the shift log. Such a recording was made on the day of the accident. The accident occurred an hour after the shift was accepted, and by this time an entry had already been made in the shift log about the work performed during the entire shift and about delivery at 8 a.m. the next day.

In the boiler room there was no thermal diagram of the boiler installation and an electrical circuit of the automation. The instructions compiled for liquid fuel boilers were not revised to suit local conditions, despite the fact that the boilers were converted to solid fuel.

Preventive maintenance of automation was practically not carried out. According to the boiler room workers, if the automation failed, they had to call a specialist from Moscow to set it up or repair it.

Violations of labor and production discipline have repeatedly occurred in the boiler room. On the day of the accident, the fireman and ash worker did not leave after finishing their shift, but stayed to play checkers, which distracted the attention of the working shift. According to the conclusion of the forensic medical examination, all of them were intoxicated. The severe consequences of the accident were facilitated by the fact that the plant administration did not comply with the boiler inspection order to remove from service an additionally installed centrifugal pump, the flow of which was ten times higher than the design one (16.0 m3/hour), and sent a false notification to the boiler inspection department about the alleged fulfillment of this boiler inspection requirement. .

Since 1968, boiler factories have produced E-1/9 boiler drums with manhole covers 8.0 mm thick, and since 1977 the thickness of the cover has been increased to 10.0 mm. In order to prevent accidents with steam boilers of type E-1/9, it was decided to reduce the pressure allowed during operation to 6.0 kgf/cm2 for these boilers, which have a hatch cover thickness of 8.0 mm.

The thickness of the removable drum cover of the E-1/9 boiler should be 10 mm at an operating pressure of 8 kgf/cm2. With a cover thickness of 8 mm, the pressure should be reduced to 6 kgf/cm2. Thinner covers should be replaced with 10mm thick covers.

At the thermal power plant of a chemical plant there was an accident with serious consequences (the plug was torn off) of pipelines of the fourth category (diameter 400 mm, pressure 8 kgf/cm2, temperature 169.6°C).

The pipeline plug was torn off due to a hydraulic shock that occurred when the pipeline was put into operation without first purging it. The pipeline after reconstruction was not subjected to an extraordinary technical inspection; the management and engineering workers of the plant, in violation of the instructions and orders for the plant, did not make entries in the order log about putting the pipeline into operation and did not instruct the mechanic on duty to purge the steam pipeline before putting it into operation.

A similar accident with serious consequences occurred at the Stroyplastmass plant, where a DN-200 mm cast iron valve ruptured due to a hydraulic shock during the launch of a category IV pipeline.

At the TGM-96 TPP boiler, a 133 mm diameter pipeline of the boiler feed line bypass ruptured in a straight section located behind the control valve, causing serious consequences. When inspecting the pipeline, erosive wear of the inner surface of the pipe was discovered in the welding area of ​​the valve body pipe to the pipeline. The pipe was subject to wear along the entire perimeter with a maximum wall thinning of up to 1.2 mm with an initial thickness of 10 mm. Erosive wear was also detected in a similar area at the base of the DN250 mm feed valve. The pipeline was in operation for 40,000 hours with environmental parameters P=230 kgf/cm2 and T=230 °C. An inspection carried out by boiler inspection at other power plants showed that erosive wear of sections of pipelines located behind the control valves occurred not only in the bypasses, but also in the main supply pipelines, as well as on the inner surface of the control valve bodies.