2017-06-23 Evgeniy Fomenko
Causes of boiler overheating
There are many various reasons, due to which this can happen, let’s try to consider them using examples of boilers with different ways work.
Gas
The first reason why a gas boiler overheats and the liquid in it boils is the lack of circulation in the heating circuit. The reason for this lies in clogged filters, or the heating circuit has become airy. It is necessary to inspect all filters, wash them, and, if necessary, replace them with new ones. If the problem lies in airing, it is necessary to remove the air. Very often this situation arises in old gas devices Navien company.
The next reason could be a simple blockage with scale, that is, plaque particles have peeled off and clogged the duct. At the same time, during operation there may be clicks or sounds as if it is knocking. The solution is quite simple - you need to clean the device using special chemicals, or using acids.
It is also possible that there was a long period of non-use of the system, and then its start-up without preliminary testing ventilation system. When starting up, there may be some noise and the device will show an error about insufficient circulation. This may be due to sticking in the pump due to inactivity. You need to disassemble the pump and wash it, then start it again.
A poor-quality gas-air mixture can cause an explosion; there are lower and upper limits at which an explosion occurs.
Another reason is non-compliance with recommendations for the installation location of the equipment. If the room has high humidity air or low temperature, the metal from which the boiler is made will deteriorate. Corrosion may occur if sulfur fuel is used.
After all, there are areas that cannot be completely cleaned by blowing, for example, gaps in pipes and partitions. If the boiler is constantly in working condition, moisture cannot damage it, but when it is turned off, the ash, as well as the surface of the lining, absorb moisture, which then leads to corrosion, and this in turn can lead to gas leakage and explosion.
Users often wonder why water gurgles; there may be several reasons. The first is that the pump has failed or is jamming, the coolant is boiling and similar sounds are heard. Second, the battery is clogged.
If your device overheats, you must follow these steps to resolve it:
Flushing the heat exchanger Solid fuel
Very often, the abnormal operation of a solid fuel heating boiler is associated with wrong choice models. That is, when choosing a wood-burning boiler, the user gives preference to a device that has a large firebox, which is designed to heat an area of over 150 m2.
However, if you have a heated room of only 70 m2, this will lead to the device overheating. And also to an increase in pressure in the boiler, which can ultimately lead to an explosion. Another reason could be incorrect installation, because often such a responsible task is entrusted not to qualified specialists, but to people from the street.
The next situation that can increase blood pressure is if the electricity suddenly goes out and, as a consequence, the circulation pump. The coolant stops circulating through heating system, the pressure rises sharply and the liquid begins to boil quickly, all this can lead to an accident.
Circulation pump in the heating system
What to do if this happens? Shut off the fuel supply to the combustion chamber; it is strictly forbidden to extinguish the flame with water, as this can lead to thermal burns to the skin and an explosion of the boiler. To safely extinguish the flame, you can use sand and ash.
Steam
Let's consider what are the main reasons why a boiler can explode. If the liquid level in the steam boiler is sharply reduced. This reason is the most common; due to a decrease in liquid, the walls overheat above the maximum permissible value. The chemical structure of the metal changes, its resistance decreases, and when pressure is applied to the walls, they can be blown out, which ultimately leads to an explosion.
If the water level drops, under no circumstances should it be filled. cold water, this will lead to a coma, the metal will lose its ductility, its fragility will increase and cracks will form. If a decrease in water is detected, it is necessary to gradually turn off the device and stop the fuel supply. After it has cooled, fill it with liquid until established norm, then run again.
To prevent the liquid level from decreasing to a critical value, it must be equipped with a device that monitors the upper and lower boundaries of the liquid level, and if a discrepancy between the values is detected, the fuel supply must be stopped.
Liquid of inadequate quality. Occurs due to change chemical composition water, and most often, an increase in its hardness, as scale deposits increase. If the water that flows in your pipeline does not meet the specifications stated in the instructions, you need to clean it.
For this, a soda-lime solution, sodium, phosphate precipitation is used, it can also be purified by cationization, this method involves filtering water through a special cation material.
The formation of scale on internal elements, which is formed as a result of the accumulation of salts contained in the feed liquid. This can be avoided by using cleaning filters that are installed before entering the device. If it has already accumulated, it is necessary to clean the boiler in order to avoid overheating. The scale layer should not exceed 0.5 mm for proper operation of the device.
Accumulation of explosive gas in the combustion chamber, resulting from improper operation of the ventilation system or fuel supply.
Device explosions are often caused by defects or malfunction of the main components, a decrease in their safety margin due to improper operation, breakdown of control sensors, as well as measuring devices.
Increase in working pressure. The main reason for such a malfunction is the failure of safety elements, as well as non-compliance with the established regime.
Heating boiler safety group
In order to identify a malfunction in a timely manner, it is necessary to periodically subject them to technical inspection (once a year), as well as tests; for greater safety, carry them out not only according to plan.
Electrical
Causes of overheating in electric boilers:
Preventative measures and prevention of overheating
Measures to prevent and prevent emergency situations include the following:
- Install an additional circuit for cooling a boiler that runs on solid fuel. IN double-circuit boiler when the coolant increases, the liquid can be cooled due to the water supply system.
- Installing a buffer tank, it will prevent the boiler from boiling, take on excess temperature, and can also store heat for the heating circuit.
- Need to install the source uninterruptible power supply . If there is a power outage, the uninterruptible power supply will automatically turn on, energy will come from the battery, and the system will continue to operate.
- Periodically clean the ventilation system.
Operating principle of the heating system
To describe it very briefly, then the principle of the heating system in a private home is that a certain liquid, be it water or frequently used antifreeze, is heated in the boiler to a temperature specified by the user.
Heating system diagram
Then it flows through the heating main (pipe) to the radiators, where it gives off its heat, then circulates back using a return circuit to heating device. There it warms up again, it is essentially a closed circuit.
There are two types of system:
- Single-pipe. It is the most economical and easiest to implement. It has the form of a ring into which the heating radiators. The coolant circulates in a circle, while the warmest liquid flows to the first radiator, which shares heat with it and at the same time loses several degrees, while the coolant, which has already cooled down considerably, reaches the fifth or sixth radiator.
The way out of this situation, so that the batteries do not become cold, is to increase the number of sections with each subsequent radiator, so that heat losses are not so noticeable. Or increase the temperature of the coolant in the boiler, and this will entail significant costs.
However, you can install a circulation pump, which will artificially increase the speed of movement of the coolant and, accordingly, reduce heat loss, and this will also slightly shorten the heating interval. However, there is a drawback here, namely, energy costs.
- Double-pipe, many times superior in energy performance. It involves branching the coolant into two outlets, as a result of which heat losses are halved. They have a common return circuit.
However, to build such a system you will need twice as many pipes, shut-off valves, and sensors. Most often used in gasified rooms.
Explosion of a homemade heating boiler
At first glance, the working process of solid fuel boilers (SFC) does not present any difficulties: fill in the coolant, add fuel, light it and bask to your health. However, with the onset of cold weather, we increasingly learn from the media about boiler explosions in different areas Russia, and not only. The TTK itself is massive, assembled from cast iron sections, and during explosions it sometimes destroys boiler rooms and, unfortunately, takes human lives. Therefore, the safety of solid fuel boilers is not an empty phrase, but necessary condition during their operation. Let's consider several reasons that lead to explosions, ruptures of pipelines, and failure of the TTC security group. So:
Incorrect installation of a solid fuel boiler
If you decide to install a solid fuel boiler for yourself, it is best to involve real specialists who have proven themselves positively in this matter. But it happens that this is impossible: either they don’t exist, or they need to pay a lot and have to install the TTK themselves. Since this happened and in order to avoid incorrect installation of a solid fuel boiler, pay attention to the following requirements for the safe installation of a solid fuel boiler:
- The area of the room where the boiler is supposed to be located (boiler room) must be at least 7 m².
- Mandatory presence in the boiler room supply ventilation, the cross section of which is determined at the rate of 85 mm per 1 kW of solid fuel boiler power. Ventilation is ensured by the presence of a vent in the window and a gap under the door.
- There must be a distance of at least 0.5 m between the boiler body and the wall.
- Particular attention should be paid to the material with which the floor around the boiler is paved. Typically, a sheet of metal or other non-combustible material is used for these purposes.
- The requirements for the chimney must be the following: avoid sharp turns of the chimney whenever possible, a chimney consisting of several pipes must be reliably sealed at the joints and the cross-section of the pipes must correspond to the cross-section at the outlet of the boiler.
- The cross-section of the electrical wiring to the circulation pump must comply with fire safety requirements.
Installation of a solid fuel boiler
This is what concerns the installation of a solid fuel boiler, but you need to pay attention to some more nuances that, to one degree or another, affect safe operation TTK:
- When loading and unloading the boiler, care must be taken;
- before purchasing a boiler, correctly set its power corresponding to the area of the heated room;
- after installing the boiler, check all connections for leaks;
- Before starting the boiler, carefully read the operating instructions for the device.
The pressure in the boiler exceeds the permissible
It is necessary to constantly monitor the pressure in the boiler
The most common cause of explosion of solid fuel boilers is excess pressure, which occurs due to boiling of the coolant. This is especially true for heating systems with closed heating systems. At open type expansion barrels, excess pressure is released into the tank and in most cases it is possible to avoid a boiler explosion or damage to the coolant tubes. In turn, there are several reasons for increasing coolant pressure:
- Stopping the circulation pump.
- The boiler automation is not adjusted correctly.
- Heat exchanger leakage, which occurs when microcracks form in the heat exchanger. In this case, it is difficult to detect the leak as it evaporates quickly.
- Water seeping through the make-up tap. Occurs when it is faulty or open.
- Problems with three way valve. The functionality of the valve is impaired due to its blockage.
- Lack of coolant in the heating system
If eliminating the above reasons does not give the desired result, call a gas technician.
The heating system circulation pump does not work
Before starting, you need to remove air from the circulation pump
The circulation pump may not work for several reasons. One of them, although banal, but everything exists - they just forgot to turn it on and left home. Again, let's pay attention to the type of expansion barrel. If the barrel closed type, great misfortune can happen if the pressure relief valve malfunctions. The problem is not so dire with consequences if the tank system is open and there is a discharge of excess coolant through the tank drain pipe.
The pump may still stop if there are power outages and, again, if the pressure relief valve malfunctions, the pressure in the boiler may increase with all the ensuing consequences. In the safety system of some boilers, an additional battery is installed in this case, which feeds the circulation pump during a lack of electricity.
When installing the circulation pump, the impeller axis must be installed strictly horizontally!
The boiler safety group is faulty
Boiler safety group
Installing a safety group for solid fuel boilers is mandatory as it helps to avoid exceeding permissible pressure in the heating system, keeps it (pressure) at the proper level, and also ventilates the system in a timely manner. Please remember that the operating pressure in the heating system should be between 1 and 2 bar.
Structurally, a security group consists of three elements: pressure gauge ,safety valve And air vent A. Failure of one of these elements can lead to an increase in pressure in the boiler. And yet, it is strictly prohibited to install shut-off valves between the boiler and the safety group.
Heating boiler chimneys not cleaned
Chimney clogged with soot
No matter how high-quality the chimney cleaning is, otherwise the boiler will fail. The chimney pipes become clogged with soot deposits, which, if a spark hits it, can simply explode. Of course, the explosion will not be as strong as the rupture of boiler sections, but it can cause a lot of trouble. In addition, soot deposits on the chimney pipe will impair the extraction of combustion products, which can break into the boiler room, poisoning the air. And the worse the draft, the lower the efficiency of the boiler, which means you need to use more fuel and money will literally go down the drain.
The first sign of a clogged chimney is the appearance of dark smoke and sparks at the outlet of the chimney. The second sign can be considered the absence of a hum when burning wood, as well as a yellowish tint to the flame. All this suggests that it’s time to clean the chimney.
Uncleaned boiler ash pan
Soot deposits in the ash pan can also cause a soot explosion. Therefore, this place in the boiler must be constantly monitored and soot removed in a timely manner. It is necessary to take into account the fact that the amount of soot in the ash pan (as in the chimney) depends on the quality of the fuel burned. Wet and resinous firewood will produce more soot than dry and clean firewood. Burning any kind of plastic in a firebox also leads to increased soot formation.
You should not clean the ash pan when the stove has not cooled down, because hot soot is a fire hazard. For the same reasons, you do not need to rake it out with your hands, but use a special shovel for this.
NOTE: It is strictly prohibited to go into the workshop until the damaged steam pipeline is disconnected and steamed. If fistulas or leaks and steam are detected in the fittings, the workshop shift manager must immediately identify the dangerous area and fence it off to prevent people from entering this area. In a hazardous area, stop all work, constantly monitor the damaged area, monitor the level in the drum and the pressure in the steam line. The shutdown time of the unit is determined by the chief engineer of the station.
15. EXPLOSION IN FIRES OR BOILER GAS FLUES
A) SIGNS of this a.s. is:
A characteristic sound in the area of the accident, destruction of the lining of the boiler.
Poor ventilation of the furnace and boiler flues before lighting or after shutdown;
Extinguishing of the torch in the boiler furnace;
Leakage of fuel fittings in front of the burners;
Violation of the combustion regime (incomplete combustion of fuel due to insufficient air, poor mixing of fuel and air).
C) PERSONNEL ACTIONS:
Emergency shutdown of the boiler and unit;
Check the execution of operations to stop the unit according to point 3;
Ventilate the furnace and boiler flues for 10 minutes. in the absence of combustion sources in the furnace and gas ducts;
Find out the cause of the explosion;
Inspect the boiler in order to determine the magnitude and nature of the destruction, close the peek-a-boo hatches and manholes that could have opened during the explosion, inspect the condition of the boiler lining and the lining of the gas ducts.
You can start lighting the boiler only after identifying and eliminating the cause of the explosion and eliminating the consequences of the explosion with the permission of the chief engineer.
16. IGNITION OF TAIL HEATING SURFACES OF BOILERS
If there are signs of a sharp increase in the temperature of the flue gases or the temperature difference between gas and air, operating personnel are obliged to:
Immediately turn off the boiler;
Turn off the draft machines by closing their guide vanes, excluding ventilation of the firebox and flue ducts;
A conclusion about the cessation of combustion can only be made after a thorough internal inspection of the heating surfaces and flues;
Enable all types of internal fire extinguishing and washing of TVP;
Ensure abundant external irrigation of the gas duct (air duct) and water supply through hatches directly onto burning surfaces using fire nozzles using our own operational and maintenance personnel, as well as with the involvement of fire departments;
Pump water through the economizer and create the necessary flow of accumulated steam through the superheater by opening the purge into the atmosphere to prevent their damage.
17. FIRE IN THE SHOP
A) SIGNS of a fire are:
Heavy smoke in the workshop;
Flame within the workshop.
B) CAUSES of a fire can be:
Explosion or bang in the firebox;
Short circuit in electric cable or electric motor;
Breaking the rules fire safety in the workshop.
C) PERSONNEL ACTIONS:
If a fire is detected, act in accordance with the general facility instructions for preventing and extinguishing fires and the operational fire extinguishing plan;
In the event of a fire that threatens the lives of personnel or equipment, as well as circuits remote control shut-off valves included in the protection circuit, immediately turn off the boiler and unit. Check the execution of operations to stop the unit according to step 3.
18. INCREASING LIVE STEAM PRESSURE AFTER THE BOILER
A) Signs of this AS, determined from the readings of panel devices, may be:
Operation of PS ROU at a steam pressure in front of the turbine of 143 kgf/cm 2 ;
Opening of control pulse safety valves when the pressure behind the boiler increases to 155 kgf/cm 2 ;
Opening working pulse safety devices when the pressure in the boiler drum increases to 172 kgf/cm2.
B) THE REASONS for this a.s. can be:
A sharp increase in frequency in the system (load shedding);
Poor performance of the turbine control system;
Malfunction of thermal load regulators or fuel regulators.
, for a boiler and boiler in Minsk
“My home is my fortress” - the expression has become popular. This is exactly how we imagine our home; we are sure that while we are in it, we are completely protected from any external troubles, and especially domestic troubles. But what about internal dangers? We will talk about the danger that can lead not only to the destruction of your “fortress”, but also to injury or even death. This is an explosion. Most often, it is solid fuel boilers that explode. less prone to such force majeure events. So why do we see news about heating boiler explosions in media reports every winter? Why does a seemingly small and safe heating device cause the destruction of a house or the death of a person? let's consider possible reasons
such an incident.
The reasons for the explosion of a solid fuel heating boiler can be different: this is an incorrect selection of equipment, incorrect equipment, neglect of the rules for operating heating boilers, as well as a desire to save money on simple safety systems. It is not enough to just BUY a solid fuel boiler, and just INSTALL a heating boiler! What does “wrong selection of heating boiler” mean? It's simple. Recently, more and more often, when buying a wood-burning boiler, the client prefers to consider models with a deep firebox, which provide for heating a house with an area of 150 and above. But the larger the volume of the furnace in the boiler, the more the buyer likes this boiler. There is a nuance here, for an area of 50 sq.m. the boiler cannot and should not have such power. Otherwise, when adding a larger volume of firewood, you will not be able to avoid overheating and “boiling” of the boiler. And this, in turn, leads to an increase in pressure in the boiler. High blood pressure
there is no explosion in the boiler yet, but it may precede it. You are one step closer to irreparable consequences. The next step may not be solid fuel boiler. In our country there are no strict rules regarding specialists installing household appliances. heating devices. So they are installing wood-burning boilers for Uncle Vanya, Petya, etc. all over the country. Why are they trusted with such important work? The client does not always want to save money (not without this, of course), but we analyzed the objects with solid fuel boilers and realized that the owners of private houses at the time of installation of the boilers did not have information about the installation rules and the specialists who wire the boilers. Good modern solid fuel boilers are boilers with automatic regulation air supply to the combustion chamber and with sensors for controlling heating circuits. Very often the market of recommendations worked, like: - d. Vanya “cooked” my heating 10 years ago and everything still works. D. Vanya advised to take a Cooper or Mozyrselmash boiler.... 
It’s good that it works, it’s good that you advised... but over the past 10 years the fundamental approach to the home heating system, and even more so to solid fuel heating boilers, has changed. Modern system and boilers have become more energy-dependent, but at the same time economical. Installation, management and operation of which require certain knowledge, skills and abilities. And also being constantly “in the know.” After installation, you must be told how to use the system with a heating boiler. And not just quickly explain where to place a match, but how to light a boiler, how to check for draft in the chimney, how to turn on the pumps,
If you have chosen the right boiler and installed it correctly, then this is only half the success. According to statistics, the percentage of errors in operation is much higher than the number of installation errors. So, what should the owner of a solid fuel boiler pay attention to?
These simple rules will help you avoid possible problems with a boiler.
There is also another reason that is independent of the user. This is when, at the moment of heating with wood or other solid fuel electricity disappears, the circulation pump stops and the coolant does not enter the system. In this case, the temperature in the boiler increases, as does the pressure, which can lead to an explosion of the boiler.
But, what should you do if, for some of the above reasons, the boiler began to uncontrollably increase in temperature and the pressure began to increase?
WHAT TO DO IF THE BOILER “BOILED”???
Shut off the fuel supply to the combustion chamber. DO NOT pour water on the flame!!! If you extinguish a boiler with water, you can get burned by the steam or explode the boiler. If possible, throw sand or ash on the flame. If there is a pump in the system and electricity in the network, open all windows, vents, doors to increase heat loss in the system. If everything is really bad - RUN, the further the better.
We would like to give a couple of tips on how to avoid a heating boiler explosion.
Be sure to install emergency valve, A better group boiler safety.
-It is advisable to install the boiler cooling circuit using solid fuel. If the temperature rises, the water jacket of the boiler will begin to receive cold water from the water supply system, which will reduce the temperature in the boiler.
If possible, buy and install it, it will not allow your boiler to “boil” even when exposed to electricity. It will take on excess temperature and retain heat for the heating system. It will also extend the burning time of one bookmark.
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Install for operation of boilers and pumps. Then, if there is a power outage, your equipment will be supplied with electricity from the backup battery. And will help you avoid an explosion of the heating boiler.
Always choose time-tested sales companies heating equipment, which can also be installed “with one hand”. The heating system of a private home requires constant attention not only from the user of the heating equipment, but also from the service technician, who will come once a year and check the functionality of the installed system, check the condition of filters, expansion tanks, threaded connections, automatic air vents...
Good luck with your home heating system, and may your guests be happy and your home warm.
Here on the website of our online store House of Boilers Minsk you can choose and buy heating boilers gas, solid fuel or electric, as well as various heating equipment - boiler, water heater, heat accumulator, buffer capacity, heating radiators, chimneys, pipes, combs and heated floors - see our online store in Belarus "Boilers and home heating" price and availability. We will fulfill according to your order necessary work- see Heating installation, boiler piping, installation of heating equipment in Minsk and throughout Belarus, including turnkey.
Do you need “holes, not a drill” - the ultimate quality solution for home heating systems?
With us, our clients comfortably implement the wisdom of “trust and verify” – without “buts”. Those executors of your plan who share your concerns and worries in such a global issue of home heating create conditions for you to comfortably control all the steps and details, so that you do not have to trust in everything, and trust grows with each stage.
You can entrust your home heating to us - we have experience and recommendations from our clients. And we are already with you – now – at the moment of searching for information. After all, it was for this step of yours that we made this site and wrote these articles for you from our experience.
Take the next step in heating installation with us - call or write to us.
The operation of gaseous fuel boilers requires great skill and attention from drivers (operators). Inattention or error when maintaining the combustion mode can lead to serious consequences. The driver must know and take into account dangerous properties flammable gases, i.e. they are explosive.
Most common reasons The formation of an explosive concentration of a gas-air mixture can be caused by: insufficient ventilation of the firebox and flues; supplying gas to the burner before the introduction or formation of a pilot flame; failure of the flame of a portable ignition device in the firebox when the burners are turned on; an attempt to ignite an adjacent burner from a working one without using a pilot torch; restarting the burners after the pilot or main flame fails without preliminary ventilation of the firebox and flues; incorrect or premature opening of taps in front of the burners; improper purging of gas pipelines before putting the boiler into operation.
The causes of explosions and gas contamination when burner devices are turned on are also: a malfunction of the igniter or its incorrect installation; errors by maintenance personnel in fixing the position of the gas shut-off valves and their leakage; turning on burner devices when automatic flame control is disabled or faulty; incorrect assessment of instrument readings or their malfunction.
During operation of the boiler, the reasons for the extinguishing of the torch, gas contamination of the furnace and an explosion from the hot surfaces of the lining can be: a short-term interruption of the gas supply; flame failure as a result of a sharp increase in vacuum in the furnace; extinguishing of the torch in cases of malfunction of the gas pressure regulator or gas-air valve, clogging of gas outlets, stopping of the smoke exhauster or fan, as well as incorrect actions of personnel when regulating the thermal power of the burners.
Even minor gas leaks in a poorly ventilated area can create explosive mixtures.
The lack of odor in gases that do not contain mercaptan sulfur, as well as the lack of color in all hydrocarbons, creates difficulties in the timely detection and elimination of possible gas leaks.
Therefore, gas is given an odor by adding sharp substances, in particular ethyl mercaptan C2H5SH, in order to detect leaks. This process is called gas odorization. The smell of odorized gas should be felt when its content in the air is approximately 7b of the lower explosive limit of the gas.
Due to the fact that the air density is 1.293 kg/m3, and natural gas depending on the content of components - about 0.8 kg/m3, in case of leaks, gases to the outside. particles will accumulate in the upper parts of the room (since they are lighter than air), making them difficult to detect.
Gas fuel is burned in boiler furnaces using burner devices.
The quality of operation of gas burner devices is assessed by the completeness of gas combustion. To determine the completeness of gas combustion, various instruments are currently used: gas analyzers (VTI, GKhP-100), chromatographs (GSTL, Gazokhrom-3101), etc.
Gas fuel various types to ensure reliable and safe work burner devices must comply with state standards and meet the following basic requirements: contain as little as possible the amount of harmful and ballast (non-burning) impurities; have a constant composition of components and, accordingly, have a constant calorific value; contain a minimum amount of oxygen and air, which contribute to corrosion of the internal surface of gas pipelines.
At wrong mode operation of boilers using gas fuel, i.e. in case of disturbance of combustion stability (flame separation or breakthrough during sudden changes in operating modes, malfunction of gas burner, draft and stabilizing devices, damage to gas ducts and air ducts, etc.), in their furnaces, gas ducts and In hogs, under certain conditions, an explosive gas-air mixture may form. If its temperature reaches the ignition temperature, then, regardless of whether this happened in the entire volume or in a limited part of it, an explosion of the mixture is possible.
For most flammable gases, the ignition temperature is the temperature of an open flame of various origins: a match flame, impact or electric spark, lit cigarette. Thus, the ignition temperature of the gas-air mixture of methane is 645 °C, propane is 490 °C, butane is 475 °C.
The accumulation of flammable gases in furnaces and flues and the formation of an explosive mixture most often occur when gas leaks from gas pipelines into the furnace through gas burner devices due to leaks in shut-off valves, violation of the procedure for purging gas pipelines and igniting burners, and other violations of operating instructions.
The most responsible from a safety point of view is igniting a cold one. This especially applies to boilers that do not have smoke exhausters or blower fans. Ventilation of fireboxes and flues in them occurs only with the help of the vacuum created by the chimney. When the boilers are not working, the value of this vacuum is close to zero and for ventilation of the flues and ducts of the boiler room it is required long time. In addition, it is necessary to check these volumes using instruments for the absence of gas contamination.
Examples of accidents associated with the combustion of gas fuel
On the DKVR-6.5/13 boiler, when the boiler was fired up after a five-hour standby period, an explosion of the gas-air mixture occurred in the firebox and flues. As a result of the explosion, the lining was destroyed, the frame, front plate, pipelines in the boiler area, economizer lining, and glazing of the boiler room were deformed.
The cause of the accident was non-compliance with the instructions: the operator brought the lit igniter into the combustion space without ventilating the firebox and flues and without checking the tightness of the shutdown devices. The taps in front of one of the burners were not tightly closed, and gas through them filled the combustion space.
The operator stopped and started the boiler without a written order from the supervisor responsible for the safe operation of the boiler and gas facilities. Earlier, on the same boiler, an explosion of the gas-air mixture occurred due to the disconnection of the remote control of the automatic safety devices of the “Crystal” system. The actuators were deliberately disabled, and when the smoke exhauster and fan were turned off, gas contamination of the firebox occurred.
The failure of the DE-25-14GM boiler in a new boiler house occurred during commissioning works due to an explosion in the firebox and gas duct of the gas-air mixture.
The boiler room staff was led by the foreman of the adjusters group. Due to the lack of water in the deaerator, the operator stopped the boiler. After troubleshooting the line feed water the operator, as instructed by the adjusters, began igniting the boiler. Having previously ventilated the firebox a little, I adjusted the vacuum and began to adjust the gas pressure. The PCV valve (safety valve) was cocked at the hydraulic fracturing high pressure), set the pressure regulator RDUK2 (universal pressure regulator Kazantsev) to a pressure of 0.03 MPa, cocked the PKN valve ( safety valve low pressure), opened the valve at the gas inlet to the valve, then checked that the valve in front gas burner closed.
The operator then opened the valve on the igniter gas line and turned the key on the control panel to apply voltage to the central electrode of the igniter. On the first attempt, the gas in the firebox did not ignite; when the ignition coil of the electric igniter was turned on again, an explosion followed.
As a result of the explosion, the casing of the boiler and economizer was partially damaged, a gas pipeline with a diameter of 150 mm from the collector to the burner was deformed, the frontal lining and about 85% of the window glazing of the boiler room were destroyed.
The investigation established that the valve on the downpipe was open for one revolution of the rotation of the rod, and under the shut-off element of the valve there was a melted piece of metal from electric welding, as a result, gas entered the furnace and gas ducts of the boiler before the start of its kindling, and during kindling, from - due to insufficiency, which led to an explosion of the gas-air mixture after a spark appeared between the electrodes of the electric igniter.
The accident could have been avoided if the duration of pre-start ventilation had been combustion chamber and gas ducts complied with those specified in the instructions.
