The need to install insulating connections (IS) for the gas pipeline.
A high danger to equipment, personnel and the gas pipeline itself are stray currents. The main problem is that the section of the gas pipeline exposed to stray currents is impossible or extremely difficult to calculate in advance. Such impacts create the preconditions for the occurrence of destructive processes and disrupt the operation of control and measuring instruments.
Divide the areas between each other and eliminate the appearance electrochemical corrosion allows an insulating connection (IC) for a gas pipeline. It ensures breaks in the galvanic connection of gas pipeline sections and eliminates the possibility of initiating corrosion processes. ICs cut off grounded areas from the common branch that are in contact with adjacent equipment or structural elements. The gas pipeline IC increases the resistance between sections to values that prevent further propagation of currents along the length of the gas pipeline. It is allowed to use only units manufactured at specialized enterprises and having the appropriate certificates. Each product must have a passport. The use of an insulating connection is a mandatory point of the technical regulations.
Insulating connection (IS, IFS, ISSG, ISM) - a product intended for dielectric separation (sectioning) of a gas pipeline into adjacent sections in order to exclude (limit) the flow of electric current between them.
ICs are an additional means of protecting underground gas pipelines from electrochemical corrosion in addition to passive and active protection and are recommended for:
Electrical separation of underground gas pipelines into separate sections, which increases the efficiency of their electrochemical protection;
Electrical isolation of sections of underground gas pipelines from poorly insulated or grounded areas;
Preventing the formation and action of macrogalvanic corrosive couples that occur at the contact areas of gas pipelines and structures made of various metals;
Elimination of protective current flow into sections of gas pipelines where electrochemical protection is impossible for safety reasons;
Increasing the longitudinal resistance of underground gas pipelines, along which stray currents are likely to spread;
Saving energy costs.
Using IS allows you to:
Reduce the current density of electrochemical protection by 1.5 - 2 times;
Increase the coverage area of the protective installation while simultaneously reducing its power.
It is advisable to install the IS:
On newly constructed gas pipelines, if necessary, their cathodic polarization in accordance with the standards;
On existing gas pipelines, if their cathodic protection is ineffective or they are subject to major repairs.
The IS should not have a harmful effect on adjacent underground structures or on “cut-off” sections of the gas pipeline:
Reduce or increase in absolute value the minimum and maximum values of protective potentials on adjacent metal structures that have cathodic polarization;
Cause electrochemical corrosion on adjacent underground metal structures that previously did not require protection.
Installation of the IC is required in the ECP coverage area:
The entry and exit of the gas pipeline from the ground;
The entrance and exit of the underground gas pipeline from the hydraulic fracturing station (SRP);
Introducing gas pipelines into a building where the gas pipeline can come into contact with the ground through grounded metal structures, building utilities and neutral conductors of the building's electrical wiring; entering a gas pipeline to an industrial enterprise;
Introducing a gas pipeline to an object that is a source of stray currents.
IC is also installed for sectioning gas pipelines and electrically isolating individual sections of the gas pipeline from the rest of the gas pipeline. If the spreading resistance of the ground loop of hydraulic fracturing or underground LPG tanks is more than five (5) Ohms, IS may not be installed on gas pipelines. When transitioning an underground gas pipeline to an above-ground one, it is allowed, instead of installing an IS, to use electrical insulation of gas pipelines from supports and structures with insulating gaskets.
IS is prohibited from being installed on sections of gas pipelines laid under doorways and balconies. When laying gas pipeline inlets along the outer walls of brick buildings, ICs are installed on branches to individual consumers (risers of the entrances of residential buildings). When laying gas supply pipelines along the outer walls of reinforced concrete buildings or when laying gas pipelines along supports, bridges or overpasses, ICs are installed at the entrances and exits of the gas pipeline from the ground.
Installation of the IS should be provided on above-ground sections of gas pipelines (at inputs to industrial and utility enterprises, buildings, as well as on supports, bridges and overpasses). ICs can be installed on underground inputs in special wells. The well must have reliable waterproofing and be dry.
When placed in wells, the IC must be bridged with a permanent detachable electrical jumper. The jumper contact connections should be provided outside the well. Magnesium and (or) zinc protectors can be used as a current conductor, which, in addition, protect the gas pipeline in the anodic zones at the insulating connections and protect them from breakdown in the event of high voltage entering the pipeline.
Installation of IC
ICs are installed in areas specified in electrical protection projects. The main installation requirements are as follows:
The cross-section of the pipes should be in the range of 20-1400 mm.
Excessive pressure of liquid or gas inside the system is up to 7 MPa. In cases where the purpose of the pipeline is not industrial, but domestic, insulating and small-sized flange connections are used that can withstand operating pressure up to 1.6 MPa.
The temperature regime of the internal environment is -60 to +180 °C.
Humidity - up to 100%, subject to an average temperature of 25 °C.
Electrical resistance - from 5 mOhm.
After installation, before switching on the electrical protection, the IC is checked for the absence of a short circuit between the metal ends of the pipes on both sides of the IC, and the electrical insulating flanges are additionally checked between the coupling bolts and the metal flanges.
ICs must be protected from the external environment (aprons, boxes, etc.).
IP operation
Operation, incl. periodic technical inspection of the IS is carried out by specialized offices "Podzemmetallzaschita" or protection services (groups), laboratories and departments of gas industry enterprises, which have the necessary staff of specialists trained and approved for these types of work. Information systems on gas pipelines owned by enterprises and organizations must be serviced by the forces and resources of these enterprises (departments) or specialized organizations under contracts for work.
When operating an IS, it is necessary to systematically, at least once a year:
Check the serviceability (efficiency) of the IS operation;
Measure and, if necessary, adjust the current in the shunt jumpers;
Determine the spreading resistance of down conductors.
Types of insulating connections
There are IPs flanged(IFS) And wafer (IC-welded, ISSG-surges, ISM couplings). The most popular are flanged models, the design of which includes insulating gaskets (rings, bushings), pipes, flanges, studs, nuts and washers. Wafer types have threads for connection with mating parts or elements for the possibility of welding the IC to the pipeline. ICs of the second type also have a number of advantages for which they do not lose their relevance: resistance to deformation, stability of the dielectric background for up to 30 years, low price. ICs are distinguished by installation method permanent And detachable type.
Stray currents pose a high danger to equipment, personnel and the gas pipeline itself. The main problem is that the section of the gas pipeline exposed to stray currents is impossible or extremely difficult to calculate in advance. Such impacts create the preconditions for the occurrence of destructive processes and disrupt the operation of control and measuring instruments.
Why are insulating connections used on a gas pipeline?
An insulating connection (IC) for a gas pipeline allows you to separate sections from each other and prevent the occurrence of electrochemical corrosion. It ensures breaks in the galvanic connection of gas pipeline sections and eliminates the possibility of initiating corrosion processes.
ICs cut off grounded areas from the common branch that are in contact with adjacent equipment or structural elements. The gas pipeline IC increases the resistance between sections to values that prevent further propagation of currents along the length of the gas pipeline.
Most often, the protective device takes the form of flange connections equipped with a dielectric gasket. It is allowed to use only units manufactured at specialized enterprises and having the appropriate certificates. It should be taken into account that the use of an insulating connection is a mandatory clause of the technical regulations, the violation of which entails various consequences, including criminal prosecution.
What are the types of insulating connections?
The most commonly used types of insulation are:
- flanged;
- one-piece;
- insulating rings made of paronite.
The most common type is the insulating flange connection. The design of such a unit is quite simple and reliable. It does not consist of 2 flanges, as usual, but of three - there is an average intermediate flange 16-20 mm thick.
Insulating rings made of paronite are installed between the flanges, which, in order to avoid impregnation with water and loss of dielectric properties, are coated with a special bakelite varnish. The tie is made with steel pins installed in fluoroplastic dielectric split bushings. A more modern insulation option is permanent connections, such as an insulating coupling. They are presented in various design options, different sizes, but have common specific qualities.
The most important of them should be considered the high durability of such ICs. They do not require maintenance and do not change their properties over time, while the insulating flange connection gradually loses its dielectric properties and requires restoration work.
All types of connections must have appropriate certificates and are produced at specialized enterprises. The use of homemade or uncertified devices is strictly prohibited.
Gas pipeline ICs are used in accordance with the electrical protection plan and are installed in compliance with all safety measures. At the same time, the protection should not have a harmful effect on adjacent structures: it is necessary to exclude the formation of electrochemical corrosion on adjacent elements of the system that previously did not require protection.
The optimal points for installing the gas pipeline IC are: 
- Entry or exit from the ground.
- Entrance or exit from a gas distribution point.
- Entry into an industrial facility (enterprise).
- Entry into the building with the possibility of contact with grounded elements.
- Inserting a gas pipeline into an object that is a source of stray currents.
- At gas pipeline branches, an IS is installed for each branch.
The use of IS is prohibited on open sections installed under balconies or doorways. In wells, the protection is bridged with a detachable electrical jumper. On above-ground sections of gas pipelines, it is necessary to install insulating connections at the entrances to buildings, on supports, overpasses or bridges. The use of insulation makes it possible to reduce the current density of electrochemical protection by 1.5–2 times.
Installation rules
The assembly of protection units is carried out in the factory. When installing a unit on an existing gas pipeline, all safety requirements and technical rules for working with gas installations must be observed.
The finished assembly is tested for resistance and tightness in the laboratory, about which a corresponding record is made. Installation is carried out by welding, after which the quality of electrical separation of the sections is checked. The evaluation criterion is the value of electrical resistance, which must be at least 5 ohms and provide a voltage drop of at least 5 mV when measured at different ends of the flanges.
The finished connection is isolated from possible contact with the ground or structural elements using aprons, boxes or similar means.
Acceptance of an insulating connection into operation is documented by a corresponding entry in the journal and a certificate.
An insulating flange connection (IFJ) is an element of a pipeline system that is used to protect pipelines from electrochemical corrosion.
Insulating flange connections (IFJ) provide electrical isolation of one section of the pipeline from another. This is necessary to combat electrochemical corrosion, a process that leads to accelerated destruction of metal parts. In most cases, IFS is installed at pipeline transitions from an underground or underwater section to an above-ground section. This is due to the fact that it is the underground part of the pipeline that is affected by stray currents, leading to electrochemical corrosion. The working medium transported through insulating flange connections is dielectric liquids and gases with an excess pressure of no more than 7.0 MPa (70 kgf/cm2).
These connections consist of two or three flanges separated by dielectric spacers and dielectric bushings for electrical insulation of the studs.
Insulating flange connections consisting of two flanges:
IFS uses flat flanges in accordance with GOST 12820-80, or butt welded flanges in accordance with GOST 12821-80, with sealing surface designs 2 (with a projection) and 3 (with a depression). Very common in Russia are IFS in accordance with GOST 25660-83, used for electrochemical protection against corrosion of underwater, underground and onshore pipelines at a pressure of 10.0 MPa (100 kgf/m 2).
LLC "Hermes" offers insulating flange connections of standard size: DN 25-219.
The composition of insulating flange connections includes:
- flanges;
- insulating rings (paronite gaskets) between the flanges;
- insulating bushings (installed in mounting holes);
- hairpins;
- nuts;
- washers.
The production of IFS is regulated by GOST 25660-83 “Insulating flanges for underwater pipelines for Ru 10 MPa”.
Insulating rings (paronite gaskets) are coated with electrically insulating bakelite varnish to protect them from moisture saturation. Also, vinyl plastic or fluoroplastic can be used for the manufacture of electrical insulating gaskets.
Hermes LLC offers a wide selection of insulating flange connections.
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Insulating flange connections (IFS) |
Insulating flange connections (IFS) P<=1,6 МПа |
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IFS 25 |
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IFS 25 |
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Welded insulating connections IS (Gas) P<=1,6 МПа |
Insulating connections - clamps |
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IS 25 |
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IS-SG Du 15 |
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Small-sized insulating connections ISM |
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ISM Du 15 |
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An insulating flange connection is installed in the following cases:
- on pipelines near objects that may be sources of stray currents (tram depots, power substations, repair depots, etc.);
- on pipeline branches from the main pipeline;
- for electrical disconnection of an insulated pipeline from non-insulated grounded structures (gas pumping, oil pumping, water pumping stations, field communications, pipelines, tanks, etc.);
- when connecting pipelines made of different metals;
- for electrical disconnection of pipelines from explosive underground structures of enterprises;
- at the exit of the pipeline from the supplier’s territory and the entrance to the consumer’s territory;
- at the input of the heating network to objects that may be sources of stray currents;
- on above-ground vertical sections of inputs and outputs of GRP (gas distribution points) and GDS (gas distribution stations);
- for electrical disconnection of pipelines from underground structures of enterprises where protection is not provided or is prohibited due to explosion hazard.
Insulating flange connections are assembled at the factory. When assembling insulating flange connections, a clear sequence must be followed:
1. Before assembly, the sealing surfaces of the flanges are coated with insulating varnish or special spraying (IFS according to GOST 25660-83);
2. IFS fasteners are isolated from the flanges with bushings (GOST 25660-83) or insulating gaskets;
3. To avoid distortion, the flanges are connected by sequentially tightening diametrically opposed studs.
According to the “Rules for the Construction and Safe Operation of Process Pipelines,” the assembled IFS must undergo electrical and hydraulic tests. The assembled insulating flange connection is tested in a dry room with a megger at a voltage of 1000 V.
During electrical tests, insulating flanges are checked both in wet and dry states with a special device - a megger. For hydraulic testing of the strength and tightness of the joint, the water pressure test method is used on a special stand. Pressure testing is carried out using a hydraulic hand pump.
In addition to IFS, Hermes LLC sells welded shaped products made of low-density polyethylene, base inlets, permanent polyethylene steel connections and other necessary products for gasification and water supply.
Check prices with managers
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