- What is a gas alarm
- Types of signaling devices. Which to choose
- What does the signaling device react to?
- What functions can a gas detector perform?
- What is a solenoid shut-off valve. Its types
- Installation and connection of the gas alarm
- Shut-off valve connection
- Service of the signaling device. Periodic verification costs
What is a gas alarm, what functions does it perform and how does it ensure safety? How does the signaling device work with additional devices, what is their cost and can you install them yourself? You will learn about this and much more from this article..
What is a gas alarm
Gas alarms are devices that provide continuous monitoring of the content of combustible gases and carbon monoxide in the air of premises where gas equipment is installed. Signaling devices have been used in industry for a long time to ensure the safety of facilities, but they have been used relatively recently for gasification of residential buildings.
Types of signaling devices. Which to choose
There are two types of alarms: industrial and household.
More stringent requirements are applied to industrial ones and they often work in conjunction with a control panel, which receives signals from several gas sensors and which provides control over the concentration of the measured parameter in the air. The requirements for a household sensor are not so stringent. Its main task is not to measure and display the concentration, but to trigger if the value of the controlled parameter exceeds the set value. Also, a household sensor should provide a number of reactions to gas contamination.
Gas alarms differ in the monitored parameter; for household sensors, three main types can be distinguished:
- methane (CH4);
- propane (C3H8);
- carbon monoxide (carbon monoxide, CO).
There are also combined sensors that simultaneously monitor the concentrations of combustible and carbon monoxide.
For a room in which gas-fired heating equipment is installed, a combined sensor (CH4 + CO or C3H8 + CO). For a room with stove heating – a carbon monoxide sensor will be enough.
When choosing a signaling device, it is necessary to take into account the power supply of the sensor and the devices with which it will interact in case of triggering, the best option is 220 V. The same power supply should be chosen for the related equipment, which will be discussed below..
Gas alarm price table:
Sensor type Controlled parameter Switching of external electrical networks Shut-off valve control Cost, rub. SGB-1-2 CH4 – 0.1%, CO – 0.01% – – 1269,00 SGB-1-7 CH4 – 1%, CO – 0.005% – – 1724,00 Guardian UM CH4 – 0.5%, CO – 0.01% – – 1282,00 Guardian 110UM CH4 – 0.5%, CO – 0.01% + + 1638,00 Guard UM-005 CH4 – 0.5%, CO – 0.005% – – 1387,00 Guard 110UM-005 CH4 – 0.5%, CO – 0.005% + + 1684,00 SGB-1-2B CH4 – 0.1%, CO 0.01% + + 1545,00 SGB-1-7B CH4 – 1%, CO – 0.005% + + 2073,00 Warta 2-03 CH4 – 1%, CO – 0.005% + + 2252,00 Warta 2-03B CH4 – 1%, CO – 0.005% – – 1850,00 UKZ-RU-CH4-SO CH4 – 0.5%, CO – 0.002-0.01% – + 5664,00 SGB-1-4.01 CO – 0.01% – – 1159,00 SGB-1-4,01B CO – 0.01% + + 1393,00 UKZ-RU-SO CO – 0.002-0.01% – + 3658,00 SGB-1-6 FROM3H8 – 0.46% – – 1270,00 SGB-1-6B FROM3H8 – 0.46% + + 1504,00 Maxi / C CH4 – 1%, C3H8 – 0.4%, CO – 0.005% – – 1112,00 Maxi / K CH4 – 1%, C3H8 – 0.4%, CO – 0.005% – + 1421,00
What does the signaling device react to?
The value of the monitored parameter in the air, at which the signaling device will work, is the same for most household sensors and amounts to:
- Methane – 0.1-1%.
- Propane – 0.46-0.05%.
- Carbon monoxide – 0.005-0.01%.
The percentages of methane and propane are about five times less than the lower concentration limit of flame propagation for these gases. This means that the alarm will be triggered much earlier than the gas content in the air reaches an explosive concentration..
What functions can a gas detector perform?
Household gas alarms, due to their design, are multifunctional devices. The list of capabilities of each signaling device is individual. These are the main ones present in most sensors:
- light and sound notification. In case of gas contamination, the indicator light comes on and a loud sound signal appears;
- the ability to connect an electromagnetic gas cut-off valve;
- relay output, through which it is possible to connect electrical devices (exhaust fan, separate annunciator, signal to the fire or dispatch panel, etc.);
- power outputs for direct connection of additional equipment from the sensor;
- some sensors have the ability to operate from an independent power source.
What is a solenoid shut-off valve. Its types
An electromagnetic shut-off valve is a device that is mounted at the inlet of a gas pipeline to a room and is a valve that, when an electric signal is applied to its coil, must shut off the gas supply to gas appliances.
Shut-off valves differ in:
- nominal bore diameter. For domestic needs, valves Dn 15, 20, 25 are often used;
- nutrition. Optimal for household needs – 220 V;
- allowable pressure. For low pressure gas pipelines – up to 500 mbar;
- by valve type: normally open and normally closed.
The valve type is the most significant characteristic for working in conjunction with a gas alarm.
The normally open (pulse) valve is a manually operated valve. During operation, no voltage is supplied to its coil. When the gas alarm is triggered, a short-term electrical impulse is sent to the valve coil from the sensor, which triggers the sensor and gas is cut off. The designation of this type of valve is N.A.
The normally closed valve is also a manually cocked valve. However, in order to cock (open) it, it is necessary to apply voltage to its coil. When the gas alarm is triggered, the voltage on the coil disappears and the valve is cut off. The designation of this type of valve is N.C.
For domestic use, a normally open valve with a 220 V power supply is more suitable. This is due to the fact that a power outage will not cause it to operate. This makes it possible to use non-volatile gas appliances (stove, column). Also, there is no need to waste electricity to keep the valve open..
The only inconvenience with such a valve may arise if it works in conjunction with a gas sensor, which, when the power is turned on, automatically checks the health of its outputs. After turning on the electricity, such a sensor will send a pulse to the valve, as a result of which it will work. When choosing a sensor, you must carefully study the sequence of its operation..
Information on valve type, power supply, allowable pressure and nominal size is indicated on its label..
Cost of a solenoid shut-off valve: type N.A., 220 V, Pmax: 500 mbar:
Nominal diameter Cost, rub. Madas Dn 15 1490,00 Madas Dn 20 1515.00 Gross Dn 20 1360,00 Madas Dn 25 1950.00 Gross Dn 25 1470,00
Installation and connection of the gas alarm
You can install the domestic gas alarm yourself. To do this, it is necessary to correctly place the sensor, guided by the instructions in the passport, and supply power to it. It is also necessary to connect additional devices according to the scheme provided in the product passport.
In modern gasification projects, the installation site of gas alarms and their number is indicated in the design documentation. The gas service can also help in choosing the right place for placing the sensor, guided by regulatory documents.
The signaling device should be placed on a vertical wall, in places where the likelihood of gas leakage is greatest (near a boiler, column, gas meter, stove), at a distance of no more than 4 meters horizontally from the gas appliance.
Where should the annunciator not be placed:
- at a distance closer than 1 meter from gas burners and ovens;
- in places where steam, ash, dust and grease can get on the alarm;
- near ventilation ducts and open windows;
- in places where paint, solvents, gasoline and similar materials are stored;
- in the immediate vicinity of uninsulated chimneys.
It should be borne in mind that for each type of signaling device (CH4, C3H8, CO or combined) the mounting height of the sensor will differ. This is due to the different density of air and gas, the area of its accumulation in the room:
- methane (CH4) – not lower than 0.5 m from the ceiling;
- carbon monoxide (CO) – at a height of 1.8 m from the floor, or higher, but not closer than 0.3 m to the ceiling;
- combined sensor (CH4 + CO) – in the range from 0.3 m to 0.5 m to the ceiling;
- propane (C3H8) – no higher than 0.5 m from the floor. If there are pits, trenches and other depressions in the room where flammable gas can accumulate, an additional warning device must also be installed in them..
Mounting a household alarm on the wall often does not even require opening the case. The sensor is mounted on the dowels by the mounting holes in the housing.
Shut-off valve connection
The installation of the shut-off valve must be carried out exclusively by specialized organizations licensed for this type of work. The connection of the valve to the signaling device is carried out according to the schemes indicated in the certificates of the valve and the signaling device.
Service of the signaling device. Periodic verification costs
A gas alarm installed in a residential building requires little or no maintenance. The only thing that is necessary is to periodically wipe the grille in the sensor housing from dust and cobwebs..
Once a year, the signaling device must undergo metrological verification. This service is paid. In no case is it allowed to independently check the operation of the signaling device by supplying it with a 100% gas mixture, for example, from a gas lighter. This could damage the sensor’s sensing element..
It is advisable to purchase sensors from domestic manufacturers. This will allow, if necessary, to send the sensor for repair, which is much cheaper than buying a new one..
Remember that a gas alarm is an important and relatively inexpensive safety feature that may one day save your life. The choice is yours!