Physicist and astronomer Stefan Feeney of University College London, one of the...
Dielectric insert(or - one-piece connection that prevents the spread of leakage currents. The dielectric insert also protects the electronic components (for example, control units) and electrical circuits (for example, the electric ignition system, lighting) of gas-consuming equipment from the harmful effects of stray currents. The insert is installed between the gas cock and the gas supply. Of course, a gas meter can also suffer from stray currents. And, importantly, the insulating insert eliminates the possible heating and even sparking of the metal gas supply as a result of the accumulation of electric potential on it.
There are several reasons for the occurrence of stray currents, or leakage currents. The main ones are:
- Damage to the insulator on the gas line. On the steel pipes main gas pipelines to prevent corrosion, a small electric potential is specially supplied, which must be quenched at the entrance to the apartment house or at the exit from the gas distribution unit in the immediate vicinity of the outlet to the individual house. For these purposes, a special main dielectric insert is used. In the event of its destruction or absence, the electric potential freely penetrates into the intra-house and intra-apartment gas pipelines.
- Lack of electrical grounding, faulty wiring and 
local electrical circuits. Modern gas consuming appliances ( gas boilers and water heaters, stoves, ovens etc.) are often crammed with electronics and local electrical circuits. These are electronic control modules, and electric ignition, and timers, and lighting systems, etc. In the absence of the necessary electrical grounding, as well as when electricity hits the metal body equipment due to a malfunction of local electrical circuits (the so-called breakdown to ground), such equipment itself becomes a source of harmful currents.
-Illegal grounding electrical appliances on gas steel pipes. Often your neighbors, who entrusted the work of connecting certain electrical appliances to "craftsmen", are happily unaware of the fact that their (neighbor's) electrical appliances are grounded on a gas pipe.
SPECIFICATIONS:
Mounting dimensions insulating inserts: 1/2", 3/4";
Execution option: fitting-fitting;
Material metal parts: brass CW614N according to EN12165, analogue of sanitary brass LS59-1 according to GOST 15527;
Dielectric: Polyamide according to GOST 14202-69 with fire resistance category PV-0 according to GOST 28157-89;
Nominal pressure PN=6 Bar (or about 6 atm). For reference: according to SNIP 2.04.08-87, in intra-house and intra-apartment gas pipelines, gas pressure up to 0.03 atm is considered normal;
A conversion table for pressure units is available on our website.
Electrical resistance: more than 5 MΩ at U=1000V;
Operating temperature range: from -60 to +100 degrees. Celsius.
The use of an insulating insert is regulated by the Letter of MOSGAZ No. 01-21 / 425 of December 26, 2008: "... When connecting gas stoves to flexible eyeliner provide for a dielectric insert.
Dielectric insert:
A dielectric coupling is a shut-off fitting that protects the "brains" of gas-consuming devices from the damaging effects of stray currents. That is, we have a very useful node, the effectiveness of which is proven by the definition itself. However, many owners of gas stoves, columns and boilers, as well as employees gas services are unaware of the existence of such an insert. And in this material we will try to eliminate this gap in knowledge by talking about the benefits of a dielectric fitting, its varieties and installation methods.
Stray current - where does it come from in the gas pipeline
Such currents appear in the ground due to an accidental breakdown of a household or industrial power line. The source of stray voltage can be both a ground loop and an electrified Railway or tram line. Such a current enters the gas pipeline due to the difference between the resistivity of the earth and the metal parts of the gas supply line. In fact, all the electricity discharged into the ground does not go into the ground (it has too much resistance), but into bare cables or metal structures. And since most of main and household gas pipelines is made of metal, then the appearance of a stray current in the system is only a matter of time.
The main pipe can become a source of stray voltage in a household gas pipeline. To protect the gas supply pipeline from corrosion, the line is loaded with an electric potential of insignificant strength, which suppresses the natural process of electrochemical splitting in the structural material. And if in the common insulator separating the main from the household branch, a breakdown of the dielectric insert for gas occurs, then the useful protective potential will turn into an unwanted stray current.
In addition, stray voltage may appear in the internal gas supply line due to poor grounding. circulation pump or other electrical appliances that come into contact with the heating system wiring or the domestic branch of the gas pipeline. Another reason for the appearance of such currents may be an error when installing the boiler, column or gas stove connected to the mains. As you can see, stray current is not a myth, but real. existing problem. And the metal structure that fell under its action turns into a serious threat to the safety of all residents of the house connected to the gas pipeline.
What happens if there is no shut-off fitting in the system
To cut off stray currents in pipelines, a special dielectric insert is used. It cuts into the area between the tap and the connection to the gas-consuming device. Or in the area between the gearbox and the gas meter. What happens if there is no such insertion? Believe me, no good. Firstly, your or a neighbor's stove, column or boiler may suffer from a stray current or turn into a source of one. As a result, there is a risk of losing their performance, due to the defeat of the "smart" filling, assembled on the basis of capricious chips, reacting even to minor power surges.
Secondly, a spark can occur in the pipeline - a source of fire. Moreover, cases of spontaneous combustion of the eyeliner are not so rare. And if this fact is not discovered in time, the case may end in a big catastrophe. The detonation of the gas-air mixture can destroy even an apartment building. Thirdly, the user may be electrocuted. If the potential of the stray charge is significant, and this happens during a thunderstorm or a power failure, then we can not talk about an unpleasant "bite", but about a full-fledged injury with difficult to predict consequences.
Therefore, in the set of rules SP 42-101-2003, regulating the construction of gas distribution systems, there is a special clause (6.4), stipulating the mandatory presence of a dielectric insert, used even in polyethylene pipelines. A modern industry produces several types of such cutters.
Varieties of dielectric cut-offs - couplings and bushings
The product range of stray current cutters for gas distribution systems is usually divided into two groups, which include:
- Dielectric couplings (MD) are special fittings with threaded ends, mounted between the gas pipeline and the device consuming blue fuel.
- Dielectric bushings (VD) - non-conductive liners installed at the place of collapsible interface of gas pipeline elements.
In turn, the nomenclature of couplings is divided into four sizes, based on the diameters of the threaded part: ½, ¾, 1, 1 ¼. Such a set allows you to cover all varieties pipe fittings used in gas pipelines, since diameters less than ½ inch and more than an inch and a quarter are not used in such systems. In addition, the range of couplings can be divided according to the design features of this fitting, distinguishing three groups: MD thread/thread, MD thread/nut, MD nut/nut. After all, the thread of this fitting can be cut both outside and inside the end part.
The nomenclature of dielectric bushings is divided only on the basis of their geometric dimensions- according to the diameter of the liner. In this case, we are dealing with 11 standard sizes and diameters from 8 to 27 millimeters. At the same time, both couplings and bushings have the same margin of safety. The working pressure of both types of cut-offs is 0.6 MPa (about 6 atmospheres), and the limit is 50 MPa (493 atmospheres). As a dielectric in both cases, a practically non-combustible polymer is used - polyamide, which has an enormous resistance (about 5 million ohms).
How to install the clutch - act carefully
Item 6. 4 of the set of rules SP 42-101-2003 indicates that MD and HP must be mounted between the gas distribution valve and the consumer device, therefore, when installing dielectric cut-offs, the following sequence of actions is used:
- We close the valve on the metal pipe supplying gas to the stove, boiler or column. At the same time, it is better to leave the burners of the devices open so that the gas in the supply burns out.
- Holding the valve body with the first wrench, carefully twist the supply nut with the second wrench - a flexible pipeline (hose) connecting the shut-off assembly with the gas inlet pipe of the boiler, stove or column. The use of a key pair in this case it is necessary, since the supply nut can “stick” to the fitting or valve nozzle and transfer torque to it, after which gas will pour into the room, and it will be possible to shut off its supply only with a street reducer valve.
- We screw the FUM coupling (polymer sealant) onto the free ends and screw it into the gas pipeline valve with our hands. Next, we take the same two keys and, holding the valve body, screw in the coupling until it stops. Try not to overdo it at this stage, as excessive force will deform the valve body and leak gas.
- We screw on the free end of the coupling the nut for supplying to the device that consumes gas, controlling our effort and holding the fitting with one of the adjustable wrenches.
- Next, you need to check the tightness of the resulting connection. To do this, you need to purchase a shaving brush and, after carefully lathering it, process all the joints of the valve, coupling and supply. After that, you open the valve and observe the foam at the joints. If you don't see any bubbles, the joints are hermetically sealed and your gas pipeline is ready for safe operation.
In case of detection soap bubbles at the joints, turn off the gas supply valve and carefully tighten the coupling or supply nut. If this does not help, you will have to disassemble the entire connection and add a few turns of the FUM to the ends of the coupling.
Attention: the use of matches or lighters instead of soap suds when testing the tightness of the joints is strictly prohibited. You may not have time to react and turn off the gas, causing a serious fire. And with a strong leak, panic can seize you - the sight of a flaming valve unbalances even the most cold-blooded masters. Therefore, the best leak tester is soap suds.
Dielectric gas coupling provides safety in residential areas, and saves people's lives.
Equipment running on natural gas connected to power sources. To prevent an accident when hit electric current on the gas supply network, a protective insert must be mounted on gas appliances.
The purpose of the dielectric coupling for gas
For water heating heating system use boilers and boilers. The kitchen is equipped with stoves, ovens and hobs. In the listed devices there is a system of control sensors, electric ignition, oven lighting. So gas type The appliance requires an electrical connection.
So that the current does not flow through the gas pipe inside the room, polyamide insulators are used - couplings. For the dielectric coupling for gas, yellow polyamide is used due to the low content of conductive impurities.
Dielectric insulating inserts, when current enters the gas network, will remain operational gas devices and gas meters.
How does a breakdown occur in the gas network
Natural gas is supplied to homes and other premises by metal pipes, laid underground in urban areas or above its surface in the private sector. Metal corrodes when exposed to moisture. Applying a positive electrical potential helps to reduce the degree of corrosion.
According to the safety regulations, a dielectric coupling is installed on the pipe at the entrance to the house. In this way, the indoor gas riser is protected, provided that the coupling is installed correctly and in good condition. But the deaf grounding of the pipe in the basement of the house can break due to corrosion.
Further, in a house or apartment, suppose the stove is connected to the riser through a rubber hose with a metal braid. If suddenly the insulation of the electrical wire in the plate is broken, the current will go through the hose braid. Depending on the strength of the current, the time for heating up and breakdown of the hose will be short or long, but a breakdown will definitely occur.
Sometimes residents of the house arrange grounding on the gas pipe.
Possible fire due to a gas leak in the apartment. Everything can do without victims, but with material losses. After such an event, the question of why a dielectric coupling for gas is needed will no longer be hypothetical for residents.
How the clutch works
Details of the gas network are produced in several types according to the type of fastening: "fitting - fitting", "nut - fitting". The product is one-piece, non-separable, and therefore safe to use. Any excess connection is a source of gas leakage.
High-quality couplings are made of brass, the thickness of the tube is not less than 4.5 millimeters. The insulating part is made of yellow polyamide, which includes a "flame retardant".
The choice of eyeliner and coupling
It is better to choose a bellows eyeliner coated with a yellow insulator. It is easier for housewives to wash such an eyeliner from dust and kitchen soot. At the same time, the insulator will protect against the flow of current when touching the bare terminals of live devices or the conductive body of the device.
Of course, an inexpensive rubber hose could be supplied. But rubber tends to age, lose elasticity, microcracks appear on the rubber hose - places of gas leakage.
Dielectric couplings for gas will protect against the flow of current through any hose. These parts are tested for breakdown with a current of 50 Hertz and a voltage of 3.75 kV for 6 seconds or more. When a voltage of one kilovolt is applied, the electrical resistance is 5 megaohms. Inserts withstand temperature differences from -60 to +100 degrees. Insulator manufacturers guarantee a service life of at least 20 years.
By installing a dielectric coupling for gas, leaving the house on business or taking a bath, the reader will be confident in the safety of home, loved ones and neighbors. Dielectric insulator - protection against burning of the eyeliner, subsequent gas leakage and inevitable explosion.
