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In the process of heating the coolant, accumulations of hazardous gases are formed, therefore, constant monitoring of the level of gas contamination in the boiler room is necessary. Installing sensors is not enough, it is desirable to combine gas alarms in the boiler room with the output of light and sound alarms to the control room. We offer development, installation gas pollution systems in the boiler room, which determines the degree of gas contamination and shutting off the gas supply.
Control of gas contamination in the boiler room
At work gas equipment CO and CH4 are released. Violations in the technological process lead to the accumulation of harmful and dangerous gases, leading to poisoning of people or to an explosion or fire. Therefore, it is necessary to constantly monitor the gas content in the boiler room.
According to RD 12-341-00, it is necessary to install carbon monoxide gas analyzers in it. If gas is used to heat the coolant, then it is additionally necessary to control the content of methane and natural gas.
When the level is exceeded, the signaling device gives a light and sound signal. The CH4 alarm is placed at least one meter away from the gas equipment in places where gases are expected to accumulate. In this case, the distance to the ceiling is from ten to thirty centimeters. The number of signaling devices is determined by the number of potential places of gas accumulation, but not less than one signaling device per two hundred meters of area or per room.
The installation height of carbon monoxide sensors is recommended at a height of 150-180 centimeters from the floor in the area of permanent stay of personnel. At the same time, the distance to open vents and windows should be at least two meters.
Gas analyzers
Sensors used in boiler rooms must meet the following requirements:
- ensure continuous uninterrupted operation;
- selective sensitivity;
- display of the measured value on the display;
- light signaling when the threshold value is exceeded.
Alarms from several sensors are sent to the control panel. The control system provides for the activation of emergency ventilation upon a signal that the upper alarm threshold is exceeded. When the indications of the signaling devices decrease to normal values, emergency ventilation is automatically turned off.
Limits of control
Gas content rateCO in gas boiler rooms determined normative documents. Gas control must be carried out continuously and selectively to carbon monoxide and methane.
Two limits are set boiler room gas alarm:
- The lower limit is 20±5 mg/m3. When it is reached, an intermittent type light signal is given.
- The upper control limit is 100 ± 25 mg/m3. Reaching the upper limit is accompanied by continuous light and sound signals.
The lower alarm limit for methane is 10% LEL (lower concentration limit of flame propagation), the upper threshold is 20% LEL.
Information from the sensors about exceeding the threshold should be sent to the dispatcher console.
Boiler room gas control system includes:
- automation shield;
- power unit;
- carbon monoxide and methane sensors;
- control (closing/opening) of the shut-off valve at the gas pipeline inlet when the upper alarm threshold is exceeded.
The valve on the gas pipeline closes automatically in the following cases:
- room gas alarms (exceeding the upper limit for CO and/or CH4);
- when triggered fire alarm;
- loss of voltage.
Actions in case of gas contamination of the boiler room
Gas contamination of the premises occurs when the operation of individual elements of the equipment is disrupted. This may be a malfunction in the operation of a smoke exhauster or a blower fan. Destruction of the chimney or violation of the tightness of pipelines, boiler equipment also lead to the flow harmful substances to the air.
If the boiler room is equipped modern system control of gas contamination, then when the dangerous value is exceeded automatically:
- the gas pipeline is blocked;
- the operating equipment is de-energized, except for fans;
- non-working fans turn on;
- the emergency signal is sent to the control room and to the emergency service.
With absence automatic system control of gas contamination, measures to prevent explosion, fire and death of people are taken by the operator on duty. Not only his life depends on his actions, but also the life and health of other employees. In this case, the operator is obliged to immediately notify the dispatcher and management of the incident.
Operator action in case of gas contamination of the boiler room depends on what kind of gas has accumulated in the room.
Carbon monoxide contamination
Carbon monoxide does not cause an explosion, but is dangerous to people. Inhalation of CO for a short time leads to loss of consciousness, so at the first sign of accumulation carbon monoxide, the operation of signaling devices in the boiler room, all personnel must immediately leave the premises. The operator must put on personal protective equipment (gas mask), inspect the premises to identify persons who did not have time to leave the premises. He must take out (take out) people, call for help, call for emergency help. Prior to the arrival of doctors, provide primary care.
Gas contamination natural gas
Accumulation of natural gas (CH) that occurs when gas contamination of the gas boiler may cause an explosion or fire. Therefore, when gas is detected, the operator must perform the following actions:
- wear personal protective equipment;
- turn off the burners;
- ensure ventilation of the room;
- try to independently detect the cause of the leak by examining the devices, valves;
- if the cause is not found, it is necessary to turn off the burners, stop the boilers;
- inform the dispatcher and management about the emergency.
It is forbidden to turn on electrical equipment, as a spark can provoke an explosion!
The process of formation of carbon monoxide OC in the air in a concentration that can harm the health of working personnel. The likelihood of such a situation exists regardless of the type of fuel on which it operates. boiler plant.
There is a special directive that establishes the rules for controlling the gas content of the boiler room: this RD 12-341-00 "Instruction for monitoring the content of carbon monoxide in boiler rooms". She defines the terms general provisions, names the reasons for the occurrence of an excessive level of CO in the room, and also indicates the requirements that apply to boiler room gas control devices.
Often the cause of gas pollution in the boiler room becomes a violation in the operation of boiler or other thermal equipment. In particular, one of the reasons could be:
- too little draft for installations with natural draft;
- inconsistent operation of the smoke exhauster and fan;
- breakage of the chimney, its destruction, water ingress;
- the formation of a leak in one of the boiler plants;
- violation in the operation of ventilation, leading to the gas contamination of the boiler room;
- soot ignition in solid/liquid fuel boilers;
- switching to a type of fuel, the density of which differs significantly from that provided for by the project;
- influence on each other of boilers with a single chimney.
These are just some of the reasons why gas pollution can occur. boiler room: in fact, there are many more. Only a specialist is able to identify and fix the problem - otherwise the boiler room will be potentially dangerous for all employees.
The following requirements are imposed on devices that monitor the level of gas contamination in a room:
- they must operate continuously and immediately signal in case of exceeding the permissible level of CO in the air;
- alarm on control devices should be two-stage: at the first stage, an intermittent light signal is switched on when the gas content level is 20 ± 5 mg/m3, at the second stage, a solid light and sound signal is switched on when the gas content level is 100 ± 25 mg/m3;
- devices must respond to a specific type of gas (in this case, carbon monoxide), "ignoring" all the others;
- gas control devices should be connected to emergency ventilation and other emergency systems in order to turn them on or off in case of a dangerous situation;
- devices must have a common control panel, which will receive data from all sensors;
- devices must be sufficiently resistant to cold, heat and temperature extremes, and work effectively at temperatures from -5 to + 50 ° C;
- and of course, all devices must comply with state standards and have the necessary certificates.
As a rule, boiler room gas sensors are installed at a level of 1.5–1.8 m from the floor level in those rooms where the presence of personnel is likely. One sensor is needed for every 200 m2, or one sensor per room, while the floor without overlap is considered as a single room.
Gas supply has firmly entered our lives. Gas is used to heat houses and entire residential complexes, not to mention industrial applications. The gases used - methane, hydrogen, oxygen, carbon monoxide, formed during the combustion of solid fuels, are explosive, some of them are toxic, so it is very important to control the condition of gas networks. For these purposes serve gas control sensors premises.
Device types
Through gas sensor it is possible to register an excess of the norm of the content of one or another gaseous component in the air or its presence. The device includes a gas sensor (gas analyzer). It converts the measured concentration of a substance into an electrical signal (or another type of signal), which allows you to register and visualize this signal. The main characteristics of the gas sensor are:
- the degree of selectivity (selectivity) for a particular substance;
- the rate of reaction (response) to fluctuations in the concentration of a substance;
- limits for determining the concentration of a substance.
Recording devices are part of special systems - signaling devices, the general tasks of which include:
- Continuous automatic concentration control installed gases in the air;
- Receiving signals about a malfunction or an accident from an external device;
- An alarm is given when the gas content is detected above the norm.
- Emergency termination of the supply of the component.
Measuring tools that are part of the signaling devices differ in the principles of operation. The following types of devices are installed in industrial premises:
- Electrochemical– works on the basis of an electrochemical three-electrode sensor placed in a container with an electrolyte.
- semiconductor- is a silicon substrate with a heating film deposited on it.
- Infrared (optical)- operates on the basis of the principle of absorption of infrared rays.
- Thermochemical– works on the basis of the principle of heat release during gas oxidation.
- photoionization– acts on the basis of ionization of a gas molecule by ultraviolet radiation when passing through the sensor.
- Linear gas sensor measures the gas content and converts it to a linear analog signal, output to the rendering device.
Widely used optical gas sensor on a par with semiconductor and electrochemical.
Gas alarm sensor according to the type of execution can be:
- stationary - fixed motionless;
- portable - powered by a built-in battery.
Design room gas sensors performed in accordance with GOST 12.2.007-75 ( last edition 10/18/2016) “System of labor safety standards. Electrical products. General safety requirements”.
Choice of device mounting locations
Equipped with gas sensors industrial premises should be carried out in coordination with the management of the enterprise on the basis of guidance and methodological documents. For industrial halls placement of gas sensors regulated by the methodology of the Ministry chemical industry VSN 64-86.
According to this method, a list of hazardous, explosive and flammable substances is compiled for each production site or workshop, the leakage of which is possible when performing specific technological processes. Each substance must have a lower flammable limit (LEL) and a maximum allowable concentration (MAC) in the workspace.
Besides, installation of gas sensors is carried out on the basis of the installation manual of the plant, attached to the signaling devices and the standards of the "Rules for Electrical Installations (PUE-76)".
In order to carry out automatic control over the content of flammable components, measuring instruments are fixed at a certain level. The density of the gaseous component relative to air, corrected for the ambient temperature, should also be taken into account:
- If the relative density of the gas is less than unity - measuring device mounted at a level of 50-70 cm relative to the potential source of leakage.
- If the relative density of the gas is in the range from 1.0 to 1.5, the device is mounted at the level of the potential source of leakage or below it, but no further than 70 cm.
- If the relative density of the gas is more than 1.5 - the device is mounted at a level of no more than 50 cm relative to the floor.
To control the concentration of methane in working area concentrated source, measuring instruments are set at a level of 50-70 cm above the source. If the sources of methane emissions in the room are dispersed, installation height of gas sensors depends on the potential location of the highest gas concentration, most often its value is set equal to 50-60 cm below the upper ceiling. The same principles apply when installing hydrogen gas sensor.
In order to control harmful substances, devices are placed at a height of 100-150 cm relative to the floor or production site in areas where it is possible to find working personnel.
If during the technological process the simultaneous release of various hazardous substances is possible, the height of the placement of control devices depends on the density of the substance, for which the proportion of the percentage of the substance in the mixture and the lower concentration limit of flame propagation (LEL) is the largest.
Installation of control devices in the boiler room
The boiler room is Utility room, where special equipment is used to heat the coolant and transfer it to consumers through a network of pipes.
Currently, boiler houses are switching to gaseous fuels, but liquid and solid heat carriers are still used, as a result of which gases are released as a result of heating. In connection with the use of combustible substances in the work, the space of boiler rooms is equipped appropriately for the timely prevention of emergency situations due to gas leakage and the prompt elimination of the consequences of such accidents.
The main components, the leakage of which is observed during the operation of the thermal equipment of boiler houses, are carbon monoxide and methane. Carbon monoxide is very toxic substance, a significant excess of its concentration in the workspace can lead to poisoning of a person and his death. Methane is highly explosive. Exceeding its concentration in the air at the slightest sharp violation of the air environment leads to devastating consequences.
Rules for installing gas sensors in the boiler room are regulated by guidelines for controlling the content of methane and carbon monoxide in the working space of boiler houses.
In order to control the concentration of gases in boiler rooms, measuring control devices. Gas sensors in the boiler room placed at the rate of one unit per 200 sq.m. working area. If the area of the workroom is less than this value, it must contain at least one device.
Methane gas sensor installed at a distance of at least 1 m from the gas appliance and 10 cm from the ceiling. The number of measuring instruments also depends on the number of possible places for gas accumulation. CO gas sensor(carbon monoxide) should be located at a height of 150-180 cm relative to the floor in the personnel access area and at the entrance to the boiler room.
It is allowed to use one device that measures the concentrations of both gases, or two monogas devices for separate control of each component.
In automated boiler rooms, the signal from the measuring device must be output to the control panel in the control room.
The distance from the gas concentration control device to the place of air inflow must be at least 2 m. The devices must be protected from moisture and dust.
Mounting the gas sensor assumes the presence of a shut-off valve, which is located at the inlet of the gas pipeline to the boiler room. Gas contamination sensor in the boiler room and shut-off valve are a system - a highly sensitive sensor built into the device detects changes in the concentration of a substance in the air, and the gas line is shut off by means of a valve. Automatic actuation of the valve occurs in the event of an alarm from the measuring instrument in case of gas leakage and in the event of an increase in pressure in the gas line or a decrease in voltage in the network due to a malfunction of the equipment.
Factory Installation Rules
Rules for installing gas sensors indoors industrial production suggest the placement of gas analyzers in the most possible places of leakage or accumulation of gas. First of all, these are pumping and compressor rooms, warehouses for combustible materials (one device is installed for each individual pump or compressor (group of pumps or compressors).
Levels of multi-storey industrial buildings with non-continuous floors are considered as separate rooms. The number of control devices in each of them is calculated according to the same principle as for boiler rooms - at least 1 unit per 200 sq.m. area or one room of a smaller area.
If a large volume of combustible or explosive materials can enter the room, at the discretion of the developers, the system emergency equipment turns on:
- warning alarm;
- emergency ventilation;
- manual or automatic (full or partial) shutdown of equipment upon reaching gas concentrations of more than 50% LEL.
Gas analyzer devices for sampling in order to control the MPC of harmful and dangerous gaseous components in the air of working premises are installed no higher than 2 m from the floor level. The installation height of analyzers that collect information on the concentration of several substances is calculated according to the density of the component that has the highest value of the proportion of its concentration in the mixture and LEL.
The construction materials of the devices must have anti-corrosion resistance. Gas supply structures should not change the composition of the analyzed substances passing through them. Also, gas analyzers must comply with explosion-proof requirements to prevent ignition of air both outside the device and inside the supply pipes.
The emergency signaling should be sound and light. In automated halls with periodic maintenance, it is installed at the entrance, in other cases - in the visibility zone of the working personnel. Alarm equipment is also installed in control rooms and operator stations.
The alarm should be well visible in the working lighting that usually accompanies processes. It is forbidden to install devices for extinguishing alarms in the access zone of service personnel.
Rules for installation in a residential building
Accommodation household gas detector in a residential building - an independent decision of the owner. Normative and technical documentation does not provide for mandatory equipment of residential premises with gas analyzers.
AT residential buildings mounted home gas sensors for natural gas. Devices are attached to utility rooms, outbuildings, basements or basement floors. The power of the system must exceed 60 kW.
If gas meters, pressure regulating devices are located in the room, there are detachable connections, access to them is limited in order to exclude the entry of unauthorized persons.
If the removal of combustion products is supposed to be carried out directly into the room, it additionally has:
- carbon monoxide control device;
- light and sound alarm;
- equipment for automatic termination of gas supply devices.
Household control devices are designed to only record the excess of harmful components in the air and report it. If gas equipment is used for home heating, it is advisable to install combined control devices that measure the concentrations of several substances at the same time.
Using the information from the device passport, you can install natural gas sensor on one's own. Mounting locations are indicated in project documentation on house. General rule is that the device is mounted on a vertical wall at a horizontal distance of no more than 4 m from the gas equipment in places of the highest possible concentration of gases. Connecting gas sensors according to the scheme indicated in his passport.
During installation, it is necessary to minimize the ingress of dust, moisture, soot, grease, and flowing air onto the instrument case.
Methane concentration control devices are mounted at a height of 50 cm from the ceiling and less, propane - no higher than 50 cm from the floor, carbon monoxide - above 1.8 m from the floor and below 30 cm from the ceiling, combined - at a height of 30-50 cm from the ceiling .
Gas sensors for the home can be installed in a system with shut-off (solenoid shut-off) valves. Installation Requirements gas sensor and shut-off valve differ - if the device itself can be installed independently, to mount the valve, you must contact a service licensed in this area.
Maintenance
Maintenance of gas analyzing systems operating in industrial premises is carried out by specialized organizations. Personnel involved in the service must be certified in accordance with regulatory documentation(FZ No. 116 of 06/22/2007 and PB 12-529-03 p. 5.7.10, p. 5.7.11).
In the course of maintenance work, the serviceability of the operation of measuring instruments, shut-off valves is checked, the connections of the valve structure are checked for tightness. At the end of the service, an act of work performed is drawn up, which indicates the results of the check.
Maintenance of gas sensors includes mandatory metrological verification. Verification periods and frequency are specified by the manufacturer in technical documentation to the device. If such data are not available, verification is carried out every six months or a year, depending on the profile of production, in the premises of which gas analyzers are installed.
It is forbidden to put into operation the device if they have:
- verification period has expired;
- there are damages;
- there is no stamp (seal).
After the expiration of the service life of the gas analyzer, its diagnostics are carried out in order to determine the possibility of its further use.
Thus, gas concentration monitoring devices are a solution to the issue of safety not only in production, but also in residential premises. Their timely maintenance and verification will make it possible to foresee the occurrence of emergencies as much as possible.
