Technical characteristics and scope of reinforced pipe insulation

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Pipelines are laid for more than a dozen years. Their repair, replace­ment of indi­vid­ual sec­tions is an ener­gy-inten­sive and cost­ly under­tak­ing. Pipe man­u­fac­tur­ers are improv­ing meth­ods of pro­tect­ing pipes from the action of aggres­sive envi­ron­men­tal fac­tors. A new word is rein­forced and very rein­forced pipe insu­la­tion based on extrud­ed poly­eth­yl­ene. It increas­es not only the peri­od of trou­ble-free ser­vice, but the mechan­i­cal strength of pipe prod­ucts.

Heav­i­ly insu­lat­ed pipes

What is meant by VUS and US

Any type of insu­la­tion is under­stood as a mul­ti­lay­er struc­ture of a coat­ing of pro­tec­tive mate­ri­als.

US — rein­forced insu­la­tion is used in soils with resis­tiv­i­ty from 10 to 20 Ohm * m.

VUS insu­la­tion has a decod­ing — very rein­forced, it is nec­es­sary where the soil resis­tiv­i­ty is less than 10 Ohm * m, which is typ­i­cal for an increased cor­ro­siv­i­ty of the envi­ron­ment.

The main dif­fer­ence between these types of insu­la­tion is the thick­ness of the insu­lat­ing lay­er.

Types of protective coating

The pro­tec­tive coat­ing is divid­ed into four types:

  1. Polyurethane foam. Pipes with insu­la­tion of this type form the basis of heat­ing mains. They are designed to trans­port liq­uids with tem­per­a­tures up to 140 0С, as they have ther­mal con­duc­tiv­i­ty up to 33 mW/m0C and with­stand a pres­sure of not more than 1.5 MPa. Pro­tec­tion is cre­at­ed by form­ing a shell of poly­eth­yl­ene gal­va­nized coat­ing. Ser­vice life up to 30 years. It is applied to ordi­nary and gal­va­nized steel. Are made in accor­dance with GOST 30732–2006.
  2. Foam poly­mer min­er­al. It is used for insu­la­tion of heat­ing mains with a coolant tem­per­a­ture of up to 150 0C and work­ing pres­sure 2.5 MPa. Three-lay­er pro­tec­tion: anti-cor­ro­sion mate­r­i­al, porous heat insu­la­tor, water­proof­ing. The thick­ness of the insu­la­tion can be increased due to the heat-insu­lat­ing mate­r­i­al and depends on the region where the heat­ing main is laid. The water­proof­ing mate­r­i­al can also serve as pro­tec­tion against impact dam­age. Pipes are pro­duced accord­ing to GOST 17177–94 and TU577768-001–70440350.
  3. Rub­ber-bitu­men mas­tic. Such pro­tec­tion does not improve the tech­ni­cal char­ac­ter­is­tics of the pipes, but increas­es the resis­tance to cor­ro­sion and is a water­proof­ing. Accord­ing to GOST 51164–98, the base of the pipe is primed, mas­tic is applied, cov­ered with a rein­forc­ing non-woven fab­ric and an out­er wrap. Water­proof­ing, mechan­i­cal pro­tec­tion indi­ca­tors can be increased by apply­ing sev­er­al lay­ers of mas­tic. Such pipes are not used for heat­ing mains: at tem­per­a­tures below ‑100C and above + 400With iso­la­tion is destroyed. The VSL with this method of pro­tec­tion is achieved by the num­ber of coat­ing lay­ers.
  4. extrud­ed poly­eth­yl­ene. An effec­tive way to insu­late pipelines with a work­ing mix­ture tem­per­a­ture of not more than 800C. Increas­es the ser­vice life of pipes up to 50 years, enhances resis­tance to mechan­i­cal stress. Refers to a very enhanced pro­tec­tion. The qual­i­ty of the pipe in VUS insu­la­tion and the process of apply­ing insu­la­tion is reg­u­lat­ed by GOST 9.602‑2005.

 

In addi­tion, steel cas­es can be used for increased pro­tec­tion against mechan­i­cal impact, for exam­ple, in those places where pipes are laid under a high­way.

Advantages and scope of VUS

The advan­tages of using pipes with VUS relate to improv­ing their oper­a­tional and tech­ni­cal char­ac­ter­is­tics:

  • guar­an­teed trou­ble-free use of the pipeline for more than 40 years;
  • a high lev­el of water­proof­ing allows you to lay pipes under water or in heav­i­ly flood­ed places;
  • a wide range of oper­at­ing tem­per­a­tures from 500From to — 600FROM;
  • ener­gy-sav­ing effect up to 30% due to an increase in ther­mal insu­la­tion prop­er­ties;
  • full pro­tec­tion against all types of cor­ro­sion, bio­log­i­cal pol­lu­tion.

If we con­sid­er the coat­ing of extrud­ed poly­eth­yl­ene as VUS, we can talk about the advan­tages of the insu­lat­ing lay­er itself /:

  • increased adhe­sion to met­al;
  • resis­tance to mechan­i­cal dam­age;
  • low lev­el of water absorp­tion;
  • dielec­tric­i­ty. Guar­an­tees high con­tact resis­tance;
  • envi­ron­men­tal­ly friend­ly mate­r­i­al that does not harm the envi­ron­ment.

The dis­ad­van­tages include:

  • high cost;
  • the need for addi­tion­al rein­forc­ing insu­la­tion in regions with con­sis­tent­ly low tem­per­a­tures;
  • impos­si­bil­i­ty to use for trans­porta­tion of high-tem­per­a­ture envi­ron­ments
  • lim­i­ta­tion on work­ing pres­sure 5.5 MPa.

Tak­ing into account the pros and cons of pipes and fit­tings with insu­lat­ed pipelines, it is rec­om­mend­ed to use them in the fol­low­ing areas:

  • all types of oil pipelines;
  • indus­tri­al and domes­tic water sup­ply and san­i­ta­tion;
  • pipelines for var­i­ous pur­pos­es pass­ing through an aggres­sive envi­ron­ment (any water bod­ies, includ­ing indus­tri­al waste, land­fills, indus­tri­al waste);
  • engi­neer­ing gas dis­tri­b­u­tion com­mu­ni­ca­tions with a load of up to 2.5 MPa;
  • places of lay­ing with increased exter­nal influ­ence.

 

How polyethylene insulated pipes are produced

The whole process is mech­a­nized. It con­sists of sev­er­al stages:

  • Sur­face prepa­ra­tion. At this stage, the heat­ed pipe pass­es through the shot blaster and is cleaned of rust. In this case, the shot cre­ates a rough sur­face. The stage of dedust­ing and purifi­ca­tion from the rem­nants of shot pass­es.
  • Sur­face prepa­ra­tion con­trol. Clean­li­ness is checked using adhe­sive tape and a ref­er­ence sam­ple, rough­ness is checked with a spe­cial device. These indi­ca­tors deter­mine the lev­el of adhe­sion.
  • Appli­ca­tion of an anti-cor­ro­sion lay­er. The pipeline is heat­ed with gas, the chromi­um alloy is removed from it, and the tem­per­a­ture is raised to 200 by induc­tion heat­ing. 0C. In this state, the epoxy primer is applied. Primer lay­er thick­ness up to 0.08 mm.
  • Appli­ca­tion of adhe­sive mate­r­i­al. A ther­mo­fusible poly­mer com­pos­ite with a thick­ness of at least 0.3 mm is used as an adhe­sive.
  • For­ma­tion of a pro­tec­tive lay­er. The pipe is insu­lat­ed with poly­eth­yl­ene-based mate­ri­als. A tape base may be used.
Pro­duc­tion

After that, the prod­uct is cooled and dried. Next, the pipes are pre­pared for oper­a­tion: up to 15 cm of insu­la­tion is removed from their ends and a cham­fer is formed.

Production of pipes with bitumen-mastic insulation

*

Prepa­ra­tion for apply­ing pro­tec­tion does not dif­fer from poly­eth­yl­ene. But the super­im­posed lay­ers them­selves have a dif­fer­ent com­po­si­tion:

  • primer;
  • 1st lay­er of bitu­mi­nous mas­tic;
  • 1st rein­forc­ing lay­er;
  • 2nd lay­er of bitu­mi­nous mas­tic;
  • 2nd rein­forc­ing lay­er;
  • out­er cov­er­ing or lay­er wrap.

To achieve VUS, the num­ber of rein­forc­ing, mas­tic lay­ers is increased, but this leads to an increase in the mass of the prod­uct. As bitu­men-mas­tic mate­ri­als, bitu­men-rub­ber, poly­mer-bitu­men films, oth­er mas­tics from hydropho­bic mate­ri­als with var­i­ous types of addi­tives are used. For rein­force­ment, fiber­glass or any non-woven fab­ric is used. The total thick­ness of the insu­la­tion can be up to 10 mm.

High­way

VUS pipes are man­u­fac­tured indus­tri­al­ly, their reli­a­bil­i­ty is ensured by the require­ments of GOST and is con­firmed by a cer­tifi­cate. They com­ply with all mod­ern stan­dards that apply to pipelines oper­at­ing in adverse exter­nal con­di­tions.

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