DK9600169U3

DK9600169U3 - System for defining a fluid and its use.

Info

Publication number: DK9600169U3
Application number: DK9600169U
Authority: DK
Inventors: Kim Kirkegaard
Original assignee: Loegstoer Roer A S
Priority date: 1996-05-15
Filing date: 1996-05-15
Publication date: 1997-09-12
Also published as: WO1997043575A1; AU2887597A

Description

DK 96 00169 U3DK 96 00169 U3

TEKNIKKENS STANDPUNKTBACKGROUND OF THE ART

Frembringelsen angår et system til afgrænsning af et fluidum, fortrinsvis flydende nitrogen, på overfladen af et medietransporterende kappebeklaedt rør, hvilken medietransport fortrinsvis omfatter væsker, og hvilket rør i en rørsektion har demonteret et kappestykke. Frembringelsen angår tillige anvendelse af systemet.The invention relates to a system for defining a fluid, preferably liquid nitrogen, on the surface of a media transporting sheath-coated tube, which media transport preferably comprises liquids and which tube in a pipe section has dismantled a sheath. The generation also relates to the use of the system.

I forbindelse med reparation af rørsystemer, specielt fjernvarmereparationer, er det et problem at foretage en afgrænsning af det område, der skal repareres, uden at dette medfører større ulemper for forbrugerne. Ved reparation eller påmontering af en studs til et fjernvarmerør er det i dag almindeligt at foretage en aflukning af rørstykket, dernæst foretage en aftapning af vand i det område, som er involveret, og dernæst en oplukning af det implicerede område. Herved sker der en forholdsvis stor iltning af rørene, som siden kan medføre korrosion, ligesom vandspildet er betydeligt. Desforuden giver disse aflukninger anledning til problemer hos forbrugerne, idet der tit og ofte ses afbrændte cirkulationspumper efter sådanne reparationer.In connection with the repair of pipe systems, especially district heating repairs, it is a problem to delimit the area to be repaired without causing major disadvantages to consumers. When repairing or installing a studs for a district heating pipe, it is nowadays customary to shut off the pipe piece, then to drain water in the area involved, and then to open the implicated area. This results in a relatively large amount of oxygenation of the pipes, which can subsequently cause corrosion, as is the considerable waste of water. In addition, these closures cause problems for consumers, as often and often burnt circulation pumps are seen after such repairs.

Det er derfor forsøgt at foretage en isolering af området, der ønskes repareret eller renoveret ved at fryse området omkring det område, der ønskes behandlet ved hjælp af nitrogen. Herved dannes der propper på hver sin side af det implicerede område. Det har dog ikke hidtil været muligt at foretage en styring af denne metode, ligesom metoden har givet anledning til et forholdsmæssigt stort forbrug af den meget dyrebare flydende nitrogen.Therefore, an attempt has been made to isolate the area that is desired to be repaired or refurbished by freezing the area around the area that is desired to be treated by nitrogen. Hereby, plugs are formed on each side of the implicated area. However, it has not yet been possible to control this method so far, and the method has given rise to a relatively high consumption of the very precious liquid nitrogen.

FORKLARING AF FREMBRINGELSENEXPLANATION OF PRODUCTION

Det er således frembringelsens formål at anvise en væsketæt membran, således at det muliggøres at fremstille et fry- 2 DK 96 00169 U3 seaggregat, der har til opgave at danne ispropper i fortrinsvis fjernvarmerør, så der kan foretages forskellige indgreb uden at aftappe fjernvarmevandet samtidig med, at denne frysning foregår på en simpel arbejdsbesparende måde 5 uden det store forbrug af nitrogen.It is thus the object of the invention to provide a liquid-tight membrane so that it is possible to produce a freezing unit which is tasked with forming ice plugs in preferably district heating pipes, so that various interventions can be made without draining the district heating water at the same time. that this freezing takes place in a simple labor-saving manner 5 without the large consumption of nitrogen.

Målet er, at tætheden omkring kapperøret skal være optimal, for at tabet af nitrogen kan begrænses. Literprisen for nitrogen er p.t. 11-12 kr. pr. liter, og der skal bruges 10 betydelige mængder for at nedkøle medierør af stål. Hvis væsken løber ud af området, går køleeffekten tabt, idet det er fordampningen, der giver nedkølingen. Det betyder med andre ord, at væsken er virkningsløs, når der er utætheder.The goal is for the density around the casing to be optimal in order to limit the loss of nitrogen. The liter price of nitrogen is p.t. 11-12 kr. 10 significant volumes and 10 significant volumes must be used to cool steel pipes. If the liquid runs out of the area, the cooling effect is lost as it is the evaporation that causes the cooling. In other words, it means that the liquid is ineffective when there are leaks.

15 Dette formål opnås med et system af den i indledningen angivne type, ocj hvor systemet omfatter et tætningssvøb omfattende en laminatfolie af alufolie og mindst et plastlag, hvilket tætningssvøb i samspil med rørsektionen medomkran-ser et hulrum, hvilket tætningssvøbs plastlag vender mod 20 røret og rørsektionen i tættende anlæg mod rørsektionens tilstødende kappe.This object is achieved with a system of the type set forth in the preamble, wherein the system comprises a sealing wrap comprising a laminate foil of aluminum foil and at least one plastic layer, which sealing wrap in cooperation with the pipe section surrounds a cavity which seals the plastic wrap against the tube and the pipe section in sealing plant against the adjacent casing of the pipe section.

Systemet virker på følgende måde. Flowet i det rør, hvor indgrebet skal foretages, standses ved at lukke de nærmeste 25 ventiler. Der etableres dernæst to frysesteder på det ene af rørene med en afstand afhængig af indgrebets omfang. Et frysested etableres ved, at der fjernes et stykke af rørets kappe i en passende længde, fortrinsvis 300 mm. Dernæst svøbes tætningssvøbet omkring området, idet plasten, der er 30 beliggende på mindst den ene side af alufolien og vender mod røret, tilsikrer, at der er tilstrækkelig tæthed mellem kapperør og folien, idet plastfolien sørger for at følge de ujævnheder, der måtte være i kappens overflade. Ved at bruge et laminat bestående af alu samt plast sikres, at denne 35 er diffusionstæt uanset temperaturforhold, samt at der opnås tæthed mellem kappen og den diffusionstætte aluminiumsfolie. Når tætningssvøbet er placeret, igangsættes nedfrys- 3 DK 96 00169 U3 ningen, idet der ledes flydende nitrogen ned i det opståede hulrum. Der dannes således en isprop i røret, der har til formål at spærre for vandet, når indgrebet skal foretages. Rørene kan nu skæres over, og man kan efter behov enten på-5 svejse et nyt rørstykke, endebund eller aflukke rørenderne med afspærringspropper. Efterfølgende kan de nærmeste ventiler, der blev lukket for at standse vandflowet, åbnes, så forbrugerne igen kan få tilført energi. Nedfrysningen kan standses, og det fjernede kappestykke erstattes nu med et 10 nyt kappestykke af passende størrelse.The system works as follows. The flow in the pipe where the intervention is to be made is stopped by closing the nearest 25 valves. Two freezing points are then established on one of the pipes at a distance depending on the extent of the engagement. A freezing point is established by removing a piece of the casing of a suitable length, preferably 300 mm. Next, the sealing wrap is wrapped around the area, the plastic being located on at least one side of the aluminum foil and facing the tube ensuring that there is sufficient tightness between the cap tube and the foil, the plastic foil ensuring to follow the bumps that may be present. the surface of the jacket. By using an aluminum and plastic laminate it is ensured that this 35 is diffusion-proof regardless of temperature conditions, and that a density is obtained between the casing and the diffusion-tight aluminum foil. When the sealing sleeve is located, the freezing is initiated, liquid nitrogen being discharged into the cavity that arises. Thus, an ice plug is formed in the pipe, which is intended to block the water when the intervention is to be made. The pipes can now be cut and, if necessary, you can either weld a new pipe piece, end bottom or seal the pipe ends with shut-off plugs. Subsequently, the nearest valves that were closed to stop the flow of water can be opened, so that consumers can again be supplied with energy. The freezing can be stopped and the removed sheath is now replaced with a new sheath of suitable size.

Ved at tildanne et system ifølge opfindelsen som angivet i krav 2 opnås, at tætningssvøbets afstivning i forbindelse med, at alufolien strammes omkring kapperøret, sikres.By forming a system according to the invention as claimed in claim 2, it is achieved that the stiffening of the sealing wrap in connection with the tightening of the aluminum foil around the casing pipe is ensured.

1515

Ved at tildanne et system ifølge opfindelsen som angivet i krav 3 opnås en beskyttelse af alufolien imod smuds, som kan punktere alufolien. Dugen er så robust, at indersvøbet kan anvendes flere gange. Dugen kan enten sys fast eller 20 leveres separat, alt efter behov, til alufolien.By forming a system according to the invention as claimed in claim 3, a protection of the alu foil is obtained against dirt which can puncture the alu foil. The tablecloth is so sturdy that the inner cover can be used several times. The tablecloth can either be stitched or supplied separately, as needed, to the aluminum foil.

Ved at tildanne et system ifølge opfindelsen som angivet i krav 4 opnås, at muligheden optimeres for at fastholde temperaturen i det temperaturområde, der har interesse, nemlig 25 -196°C til 220°C. Isoleringssystemet består af en dug, der er specielt udviklet til at fungere i dette store temperaturområde, og som indeslutter selve isoleringsmaterialet, som kan være fremstillet af et hvilket som helst isoleringsmateriale som f.eks. rockwool, glasuld eller andre 30 isoleringsmaterialer.By forming a system according to the invention as claimed in claim 4, it is achieved that the possibility is optimized to maintain the temperature in the temperature range of interest, namely 25 -196 ° C to 220 ° C. The insulation system consists of a tablecloth specially designed to function in this large temperature range, which encloses the insulating material itself, which may be made of any insulating material such as e.g. rockwool, glass wool or other 30 insulation materials.

Ved at tildanne et system ifølge opfindelsen som angivet i krav 5 opnås et tæt anlæg af tætningssvøbet til kappen og dermed tildannelse af et hulrum, fra hvilket der foregår et 35 minimum af spild og udslip af nitrogen. Løber væsken ud af det dannede hulrum, går køleeffekten tabt, idet det er fordampningen, der giver nedkølingen. Det betyder således, at 4 DK 96 00169 U3 væsken er virkningsløs, hvis hulrummet/proppen er utæt.By forming a system according to the invention as claimed in claim 5, a dense abutment of the sealing envelope for the sheath is obtained and thus the formation of a cavity from which there is a minimum of waste and discharge of nitrogen. If the liquid runs out of the formed cavity, the cooling effect is lost as it is the evaporation that gives the cooling. This means that the fluid is ineffective if the cavity / plug is leaking.

Ved at tildanne et system ifølge opfindelsen som angivet i krav 6 opnås, at dugen påmonteret alufolien er så robust, at denne kan anvendes flere gange, samt at materialet desuden udviser stor fleksibilitet også ved -196°, således at materialet ved lave temperaturer ikke krakelerer eller revner og mister sine vandtætte egenskaber. Ved brug af materiale til selve isoleringsmåtten fordeles det isolerende materiale ved at sy dugen i sektioner. Isoleringssystemet kan genanvendes, og det forventes, at mindst 50 frysninger kan gennemføres, hvorefter isoleringsmåtten må inspiceres for skader, og hvorefter nye 50 frysninger kan gennemføres.By forming a system according to the invention as claimed in claim 6, it is achieved that the cloth mounted on the alu foil is so robust that it can be used several times, and that the material also exhibits great flexibility even at -196 °, so that the material does not crack at low temperatures. or cracks and loses its waterproof properties. When using material for the insulation mat itself, the insulating material is distributed by sewing the tablecloth in sections. The insulation system can be reused and at least 50 chills are expected to be completed, after which the insulation mat must be inspected for damage, and new 50 chills can be completed.

Ved at tildanne et system ifølge opfindelsen som angivet i krav 7 opnås, at kuldetab minimeres som følge af konvektionstab, idet isoleringsmåtten løbende kan ligge tæt an, idet denne efterspændes i takt med, at rørets dimensioner ændres som følge af frysningen. Røret fremstilles fortrinsvis i stål, hvorfor den termiske udvidelseskvotient for dette materiale er bestemmende for rørets dimensionsændringer.By forming a system according to the invention as claimed in claim 7, it is achieved that cold losses are minimized as a result of convection losses, since the insulating mat can be kept close together, being tensioned as the dimensions of the pipe change as a result of the freezing. The tube is preferably made of steel, so the thermal expansion ratio for this material determines the dimensional changes of the tube.

Systemet tænkes primært som angivet i krav 8 anvendt til fjernvarmerør.The system is primarily intended as set forth in claim 8 used for district heating pipes.

TEGNINGENDRAWINGS

Et udførelseseksempel for systemet ifølge frembringelsen skal herefter beskrives nærmere under henvisning til tegningen, hvor fig. 1 viser tætningssvøbet med dug på bagsiden, fig. 2 viser et snit langs linien II-II i fig. 1,An embodiment of the system according to the invention will now be described in more detail with reference to the drawing, in which fig. 1 shows the sealing sleeve with tablecloth on the back; FIG. 2 shows a section along line II-II of FIG. 1

5 5 DK 96 00169 U3 fig. 3a viser isoleringsmåtten i sidebillede, fig. 3b viser isoleringsmåtten, og fig. 4 viser et udførelseseksempel for systemet ifølge opfindelsen monteret på et afbarket rør.5 5 DK 96 00169 U3 fig. 3a shows the isolation dimension in side view; FIG. 3b shows the insulation measure, and FIG. 4 shows an exemplary embodiment of the system according to the invention mounted on a barked pipe.

BESKRIVELSE AF UDFØRELSESEKSEMPLETDESCRIPTION OF THE EXAMPLE

1010

Fig. 1 viser et udførelseseksempel for tætningssvøbet 6, på hvilket der er monteret en dug 12. Tætningssvøbet er rektangulært, og dimensionerne er afhængige af det rør, som svøbet skal omslutte. På svøbets langsgående sider og i 15 dets periferi ses midlertidige spændeorganer 14 i form af velcrobånd påmonteret. Herefter anvendes spændeanordninger af anden udformning, eksempelvis a la lastbilspænder, hvilket vil sige remme med påmonterede kamspænder. Disse etablerer tætning mellem svøbet og kappen.FIG. 1 shows an exemplary embodiment of the sealing sleeve 6 on which a tablecloth is mounted 12. The sealing sleeve is rectangular and the dimensions are dependent on the tube to which the sleeve is to enclose. On the longitudinal sides of the sheath and on its periphery, temporary clamping means 14 in the form of Velcro straps are seen. Thereafter, clamping devices of a different design are used, for example a la truck buckles, ie belts with mounted cam buckles. These establish a seal between the shell and the sheath.

20 Tætningssvøbet 6 er et laminat 7, og omfatter et som det fremgår af fig. 2 i midten liggende alufolie 8, som på hver side har påmonteret et plastlag 9,10, fortrinsvis en type af polyethylen, polyester, polypropylen, polyamid eller 25 lignende. På den flade, der vender væk fra røret, er monteret en dug 12, hvilken dug fremstilles i et vævet polyamidfiber, og som tillige er imprægneret med silikone, hvorved der opnås en stærk og væskeuigennemtrængelig flade. Laminatfolien 7 og dugen 12 kan være syet sammen eller limet 30 sammen. Også andre forbindelsesmetoder kan komme i betragtning. Materialet, som dugen er lavet i, er vandtæt og har en ekstrem styrke, og kan ikke beskadiges, uden at der anvendes skærende værktøjer som f.eks. en kniv eller tilsvarende skarpe genstande. Desuden har det den egenskab, at 35 selv ved meget lave temperaturer, helt ned på -196°C, udviser denne specialudviklede dug stadig fleksibilitet, således at materialet ved denne lave temperatur ikke krakelerer 6 DK 96 00169 U3 eller revner og mister ej heller sine vandtætte egenskaber. Laminatfolien har en tykkelse fordelt således, at alufoliens tykkelse udgør 7-25 my, fortrinsvis 9-10 my, mens de på hver sin side af alufolien anbragte plastlag har en tykkelse på omkring 70 my.The sealing wrap 6 is a laminate 7, and comprises one as shown in FIG. 2 in the middle are aluminum foil 8, which has mounted on each side a plastic layer 9,10, preferably a type of polyethylene, polyester, polypropylene, polyamide or the like. On the surface facing away from the tube is mounted a tablecloth 12, which tablecloth is made of a woven polyamide fiber and which is also impregnated with silicone, thereby obtaining a strong and liquid-impermeable surface. The laminate foil 7 and the cloth 12 may be sewn together or glued 30 together. Other connection methods may also be considered. The material in which the tablecloth is made is waterproof and of extreme strength and cannot be damaged without the use of cutting tools such as a knife or similar sharp objects. Furthermore, it has the property that even at very low temperatures, all the way down to -196 ° C, this specially developed tablecloth still exhibits flexibility, so that the material at this low temperature does not crack or crack or lose its waterproof properties. The laminate foil has a thickness distributed such that the thickness of the alu foil is 7-25 microns, preferably 9-10 microns, while the plastic layers disposed on each side of the aluminum foil have a thickness of about 70 microns.

Fig. 3 viser isoleringsmåtten 13, hvilken isoleringsmåttes ydre materiale er fremstillet i samme materiale som den ovenfor anførte dug. Inde i isoleringsmåtten 13 er der indlagt isoleringsmateriale, eksempelvis rockwool eller glasuld. Isoleringsmåtten 13 har dimensioner, som sikrer, at denne dækker fuldt ud tætningssvøbet 6, således at tætningssvøbet ikke ligger frit. Tætningssvøbet 6 har således den nøjagtige diameter, der passer til den konkrete kappediameter, og således at der forefindes en lille åbning i toppen. Isoleringsmåtten 13 er tillige udstyret med justerbare spændeancrdninger 15, som sikrer et isolerende anlæg mod det underliggende tætningssvøb. Spændeanordningerne er placeret i måttens periferi, således at disse kan danne et hæfte omkring selve røret og kan være en velcro eller et lastbilspænde eller lignende alt efter behov.FIG. 3 shows the insulating mat 13, which outer material of the insulating mat is made of the same material as the tablecloth mentioned above. Inside the insulation mat 13, insulation material, for example rockwool or glass wool, is inserted. The insulating mat 13 has dimensions which ensure that it fully covers the sealing wrap 6 so that the sealing wrap is not free. Thus, the sealing sleeve 6 has the exact diameter that fits the concrete cutting diameter and so that a small opening is provided at the top. The insulating mat 13 is also equipped with adjustable clamping devices 15 which ensure an insulating system against the underlying sealing envelope. The clamping devices are located at the periphery of the mat so that they can form a booklet around the pipe itself and can be a velcro or a truck clamp or similar as needed.

Fig. 4 viser systemet 1 ifølge opfindelsen monteret på et rør 2, og viser et snit igennem opstillingen, hvor dog for overskuelighedens skyld det nedre hulrum og anlæg af systemet er udeladt. Et rør 2 med isolering 16 og en omgivende kappe 3, hvorfra der er fjernet en del af kappen dannende en rørsektion 5, som er blotlagt, hvilket rør primært er fremstillet i stål, men dog også hvor andre materialer kan komme i anvendelse, og hvor der rundt om denne rørsektion 5 er svøbt et tætningssvøb 6, som er tættende monteret ved hjælp af spændeanordninger 14, som her er lastbilspænder 17 og hvis tilspændingskraft tilpasses forholdene, herunder kapperørets dimensioner, i anlæg mod de tilstødende kappesegmenter 3. Uden om tætningssvøbet 6 er yderligere lagt en isoleringsmåtte 13, som også er fastspændt omkring røret ved hjælp af eksempelvis velcrobånd eller lastbilspænder.FIG. 4 shows the system 1 according to the invention mounted on a pipe 2, and shows a section through the arrangement, however, for the sake of clarity, the lower cavity and abutment of the system is omitted. A pipe 2 with insulation 16 and a surrounding sheath 3 from which a portion of the sheath forming a pipe section 5 has been removed which is exposed, which pipe is primarily made of steel, but also where other materials can be used and where there is wrapped around this pipe section 5 a sealing sleeve 6 which is sealedly mounted by means of clamping means 14, which are here truck tensioner 17 and whose tightening force is adapted to the conditions, including the dimensions of the casing pipe, in abutment against the adjacent sheath segments 3. Without the sealing sleeve 6 is further added an insulation mat 13 which is also clamped around the pipe by means of, for example, Velcro tapes or truck buckles.

7 DK 96 00169 U37 DK 96 00169 U3

Spændeanordningerne for det underliggende tætningssvøb omfatter mindst to sæt på hver side af hulrummet 11, og således at den overliggende isoleringsmåtte 13 dækker spændeanordningerne 14 tættest mod hulrummet 11, men lader de y-5 derste spændeanordninger ligge frit. Formålet med dette er at sikre, at en justering af tilspændingen er muliggjort, når røret som følge af den kraftige nedfrysning ændrer dimensioner, det vil sige mindskes. For således at sikre, at der ikke slipper flydende nitrogen ud i en opstået spalte 10 mellem tætningssvøb 6 og kappe 3, foretages en efter- spænding med de yderste spændeanordninger 14 monteret på tætningssvøbet. Selve montagen foregår ved, at tætningssvøbet 6 rulles ud, uden at der kommer smuds på svøbet. Tætningssvøbet har den nøjagtige diameter, der passer til 15 den konkrete kappediameter, således at der forefindes en lille åbning i toppen. Øverst oppe efterlades en åbning, igennem hvilken fyldning af flydende nitrogen foregår. Svøbet inspiceres for utætheder forårsaget af eventuelle punkteringer. Hvis tætningssvøbet er tæt efter et vist tidsrum, 20 fortrinsvis 3 minutter, lægges isolationssystemet rundt om røret, og spænderne strammes således, at en konvektionsfri isolering etableres. Toppen af isoleringssystemet er konstrueret således, at den ene flap af måtten kan vippes op med henblik på at kunne foretage påfyldning i tætningssvø-25 bets åbning. Når væskespejlet når op til åbningens kant, reduceres påfyldningsflowet til det halve, og isoleringssystemets flap vippes over, således at afdampningen kan trænge ud, og at isolering af toppen tilsikres.The clamping devices for the underlying sealing envelope comprise at least two sets on each side of the cavity 11, and so that the overlying insulating mat 13 covers the clamping devices 14 closest to the cavity 11, but leaving the y-5th clamping devices free. The purpose of this is to ensure that an adjustment of the tightening is possible when the pipe, due to the heavy freezing, changes dimensions, that is, decrease. Thus, in order to ensure that liquid nitrogen does not escape into a formed gap 10 between sealing envelope 6 and sheath 3, a post-tensioning with the outermost tensioning devices 14 mounted on the sealing envelope is made. The assembly itself takes place by rolling out the sealing wrapper 6 without getting any dirt on the scoop. The sealing sleeve has the exact diameter to match the concrete cutting diameter so that there is a small opening at the top. At the top, an opening is left through which the filling of liquid nitrogen takes place. The scoop is inspected for leaks caused by any punctures. If the sealing wrap is close after a certain period of time, preferably 3 minutes, the insulation system is laid around the tube and the buckles are tightened so that a convection-free insulation is established. The top of the insulation system is designed so that one flap of the mat can be tilted up to be able to fill in the opening of the sealing swab. When the liquid mirror reaches the edge of the opening, the filling flow is reduced in half and the flap of the insulation system is tilted over so that evaporation can penetrate and insulation of the top is ensured.

30 Efter endt arbejde demonteres systemet, og røret må derefter efterfølgende repareres, idet den del af røret, som er foruden kappe, monteres i et kappestykke, som passer ned i hulrummet 11.After completion of the work, the system is dismantled and the pipe must subsequently be repaired, the part of the pipe, which is besides sheath, mounted in a sheath which fits into the cavity 11.

35 Forsøg har godtgjort, at nitrogenforbruget ved denne metode reduceres 30 - 60%, samt at tidsforbruget er væsentlig lavere.35 Tests have shown that nitrogen consumption by this method is reduced by 30 - 60% and that the time consumption is considerably lower.

Claims

A system for defining a fluid, preferably liquid nitrogen, on the surface of a media-transporting 5 casing-coated tube 2, which preferably comprises liquids, and which tube 2 in a tube section 5 has dismantled a jacket piece 3, which is new in that the system 1, a sealing wrap 6 comprising a laminate foil 7 of aluminum foil 8 and at least one plastic layer 9, which sealing wrap 6 10, in conjunction with the tube section 5, encloses a cavity 11, which sealing wrap plastic layer faces the tube 2 and the tube section 5 in sealing abutment against the adjacent casing of the tube section 5 third

A system according to claim 1, which is new in that the laminate foil 7 of the sealing envelope consists of an aluminum foil 8, and on each side thereof is mounted a plastic foil 9,10.

System according to any one of the preceding claims, which is new in that the sealing wrapper 6 also comprises a tablecloth 12 in a flexible, fluid-tight and strong material and attached to the laminate foil 7.

System according to any one of the preceding claims, which is new in that it also comprises an insulating mat 13 which may surround the sealing sleeve 6.

System according to any one of the preceding claims, which is new in that the sealing sleeve 6 is provided with clamping means 30 14 for clamping the sleeve to the sheath 3.

System according to any one of the preceding claims, which is new in that the tablecloth 12 and the insulating mat 13 are made of a silicone-impregnated polyamide fiber material. 35

System according to claims 4-5, which is new in that the insulating mat 13 comprises at its periphery adjustable clamping devices 15.

Use of a system according to any one of the preceding claims for freezing of district heating pipes, so that a frozen plug is formed in the pipe and using liquid nitrogen.