Insulating flange connections GOST. Insulating connections

Is a combination of two or three flanges, between which are set insulating gaskets... In addition to gaskets, additional insulating sleeves... The insulating material can be paronite, graphite and fluoroplastic. Insulating flange connections (abbreviated as IFS) are used to protect the pipeline or any section of the pipeline from electrochemical corrosion. Electrochemical corrosion appears on the pipeline as a result of the influence on the pipeline of electric, or so-called "stray" earth currents. As a result of the influence of such corrosion on the pipeline, cracks form in the pipeline and leakage of the conveyed medium may occur. Stray earth currents appear on those areas of the earth where the earth is used as a conductive medium. These are areas located near tram or railway depots and tracks, as well as near any power plants. (IFS) isolate the pipeline section from stray currents by interrupting the metal structure of the pipeline with an insulating material, thereby preventing the occurrence of electrochemical corrosion. In the figure below, you can see how they schematically look like :

As you can see from the schematic image above, represents a With insulating gasket between flanges and also with insulating sleeves in the holes for the fasteners. This kind it is used in most cases of pipeline laying, but in the gas industry, where the transported medium is gases with an excess pressure of not more than 7.0 MPa, another type is used insulating flange connections are compounds consisting of three flanges... In the figure below, you can see how they schematically look like insulating flange connections (IFS) consisting of three flanges:

As you can see from the schematic image above, this insulating flange connection (IFS) represents a connection of two collar flanges welded to the pipeline through the third flange that is in between. Between flanges also available insulating gaskets, and in the holes for fasteners installed insulating sleeves... In the role of the third flange usually favors flat flange, the thickness of which does not exceed 20mm. Everything gaskets at IFS covered with a special insulating bakelite varnish, this is done to protect the gaskets from moisture saturation.

Insulating flange connections are of the following types

• - insulating flange connections
• - insulating flangeless connections
• - insulating flange connections detachable
• - non-detachable insulating flange connections

Usually, insulating flange connections (IFS) used in pipelines in the following cases:

• near objects that are sources of stray currents;
• on branches of the pipeline from the main line;
• in order to disconnect the electrically insulated pipeline from any non-insulated earthed structure;
• at the junction of pipelines that are made of different metals;
• in order to disconnect an electrically insulated pipeline from any explosive underground structure;
• when entering a heating network to objects that are sources of stray currents;
• at gas distribution points and gas distribution stations, etc.

Insulating flange connections are manufactured according to two main regulatory documents: GOST 25660-83 and TU 3799. IFS according to GOST 25660-83 can be made in one design. In the figure below, you can see how this design looks schematically:

Insulating flange connections in accordance with GOST 25660-83 are used to protect subsea, underground and surface pipelines from electrochemical corrosion at a pressure of 10.0 MPa and an ambient temperature of no higher than 80 ° C.

IFS according to GOST 25660-83 are manufactured and assembled exclusively in the factory as when assembling, a certain clear sequence must be observed, namely:

1. Before assembling IFS, flange sealing surface covered with a special insulating varnish.
2. Hardware with which insulating flange connection connects, isolated with bushings or insulating gaskets from flanges.
3. Flanges are connected by sequential tightening of diametrically opposed studs in order to avoid skewing.
4. After insulating flange connection assembled, ends insulating gaskets and washers, as well as the inner surface of pipes and flanges covered with insulating varnish, and flanges dried at temperatures up to 200 ° C.

After assembly, insulating flange connections according to GOST 25660-83 pass certain electrical and hydraulic tests provided for by the documentation developed by the manufacturer IFS and also checked for compliance general requirements, which are set out in the "Rules for the device and safe operation technological pipelines ". IFS according to GOST 25660-83 tested in a dry room, using a megohmmeter, at a voltage of 1000V, and insulating flanges tested both wet and dry.

Insulating flange connections in accordance with GOST 25660-83 can withstand pressure up to 10.0 MPa, and their diameter varies from 200mm to 500mm. The table below shows all types IFS according to GOST 25660-83 supplied by our company, as well as the characteristics of the data IFS:

Insulating flange connections in accordance with GOST 25660-83:

Below is an example symbol insulating flange connections

On risers, inputs and outputs of hydraulic fracturing, GRPSh, insulating connections (IC) are installed to protect against stray currents and currents of protective installations. The IC must also be installed in front of the GRU - at the entrance to the gasified building.

Currently obsolete, but the most common IC design is the Isolating Flange Connection (IFS). In IFS (Fig. 1.25), except for the two main flanges 2 and 7 welded to the ends of the gas pipeline, there is a third special flange 1 with a thickness of 16-20 mm (depending on the diameter of the gas pipeline). For electrical isolation of the flanges from each other, gaskets are installed between them 4 made of PMB paronite with a thickness of 4 mm, which are covered with electrical insulating bakelite varnish to protect moisture saturation. Electrical insulating gaskets can also be made of vinyl plastic or fluoroplastic.

Rice. 1.25. Insulating flange connection: 1, 2, 7 - flanges; 3, 4 - gaskets; 5 - bushing; 6 - washer; 8 - screw; 9 - hairpin; 10 - nut

Tightening studs 9 enclosed in split sleeves 5 from fluoroplastic. Between the washer 6 and flanges 2 , 7 also provided with insulating gaskets 3 made of paronite covered with bakelite varnish. Along the perimeter of the intermediate flange 1 there are threaded sockets into which the screws are screwed 8 used to check the electrical resistance between each main flange and intermediate flange. IFS are made for DN from 20 mm.

The IFS installation with a steel valve is shown in Fig. 1.26

Rice. 1.26. Installation of IFS with a valve

The assembled IFS is subject to testing for strength and tightness, as well as for the presence of a rupture in electrical network before and after its installation on the gas pipeline. IFS, as a rule, are mounted on above-ground vertical sections of inlets and outlets of hydraulic fracturing, GRPSh. To control the serviceability and repair of the IFS, they must be installed after the shut-off valves along the gas flow at a height of no more than 2.2 m. environment IFS gradually lose their dielectric properties, therefore, during installation, they are covered with aprons, boxes, etc.

Today the industry produces a large number of permanent insulating joints of various designs, some of which are presented in this guide. Since permanent insulating joints do not need to be serviced, and their service life is significant (as a rule, more than 20 years), then in terms of these indicators they are significantly superior to insulating flange joints. Insulating joints of small diameters, including those combined with a shut-off device, are more and more often used for sectioning internal gas pipelines. Their use, in addition to preventing through corrosion of gas pipelines when passing interfloor floors, serves as reliable protection against household electric shock.

An insulating flange joint (IFS) is an element of a pipeline system that is used to protect pipelines from galvanic corrosion.

Insulating flange connections (IFS) provide electrical isolation of one section of the pipeline from another. This is necessary to combat electrochemical corrosion, a process that accelerates the destruction of metal parts. In most cases, the IFS is installed at the crossings of pipelines from an underground or underwater section to an aboveground one. 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 the insulating flange joints are dielectric liquids and gases with an excess pressure of not more than 7.0 MPa (70 kgf / cm 2).

These connections consist of two or three flanges separated by dielectric spacers and dielectric sleeves for electrical insulation of the studs.

Insulating flange connections from two flanges:

In IFS, flat flanges are used in accordance with GOST 12820-80, or butt-welded in accordance with GOST 12821-80, with versions of sealing surfaces 2 (with a ledge) and 3 (with a depression). IFS according to GOST 25660-83 are very common in Russia, used for electrochemical corrosion protection of subsea, underground and surface pipelines at a pressure of 10.0 MPa (100 kgf / m 2).

LLC "Hermes" offers insulating flange connections of standard size: Du 25-219.

Insulating flange connections include:

• flanges;
• insulating rings (paronite gaskets) between the flanges;
• insulating sleeves (installed in the mounting holes);
• hairpins;
• nuts;
• washers.

IFS production is regulated by GOST 25660-83 "Insulating flanges for subsea pipelines for Ru 10 MPa".

Insulating rings (paronite gaskets) are coated with electrical insulating bakelite varnish to protect them from moisture saturation. Also, for the manufacture of electrical insulating gaskets, vinyl plastic or fluoroplastic can be used.

LLC "Hermes" offers a wide range of insulating flange connections.

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 facilities, etc.);
• on branch pipelines from the main line;
• 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 various metals;
• for electrical disconnection of pipelines from explosive underground structures of enterprises;
• at the exit of the pipeline from the supplier's territory and at the entrance to the consumer's territory;
• at the input of the heating network to objects that can be sources of stray currents;
• at above-ground vertical sections of inputs and outputs of hydraulic fracturing stations (gas distribution points) and gas distribution stations (gas distribution stations);
• for electrical disconnection of pipelines from underground facilities of enterprises where protection is not provided or prohibited due to explosion hazard.

Insulating flange connections are factory assembled. When assembling insulating flange connections, a clear sequence must be followed:

1. Before assembly, the sealing surfaces of the flanges are covered with an insulating varnish or a special spray (IFS in accordance with GOST 25660-83);

2. IFS fasteners are insulated from flanges with bushings (GOST 25660-83) or insulating gaskets;

3. To avoid skewing, the flanges are connected by successive tightening of diametrically opposite studs.

According to the "Rules for the Design and Safe Operation of Technological Pipelines", the assembled IFS must undergo electrical and hydraulic tests. The assembled insulating flange joint is tested in a dry room with a megohmmeter at a voltage of 1000 V.

During electrical tests, insulating flanges are checked both wet and dry with a special device - a megohmmeter. For hydraulic tests for strength and tightness of the connection, the method of water pressure testing is used on a special stand. Pressure testing is carried out with a hydraulic hand pump.

In addition to IFS, Hermes LLC sells welded fittings made of low-pressure polyethylene, basement inputs, permanent polyethylene steel joints and other necessary products for gasification and water supply.

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