EP0354924B1 - Corrosion prevention for braces - Google Patents

Abstract

Process for quickly arresting all corrosive processes taking place at any point within a cable, in a simple and controllable manner, without any material destruction, while avoiding the need for revarnishing. Constant ''drying'' is carried out, and the ''annular gap'' (3), insulated from the exterior by a prolonged-resistance special steel plate (4) and in which circulates pressurized N2? gas, ensures a reliable insulation from the atmosphere.

Description

• ― daß der Ringspaltraum mit einer Korrosionsschutzflüssigkeit, die ein niedrigeres spezifisches Gewicht als Wasser und dazu eine besonders niedrige Viskosität aufweist, gefüllt ist und in der gegen Korrosion schützenden Additiva gelöst sind;
• ― daß die Korrosionsschutzflüssigkeit feuchtigkeitsunterwandernde und korrosionshindernde Beimischungen in Form von Gasphaseninhibitoren erhält, so daß die Restsauerstoffmengen durch Reaktionsmittel neutralisiert werden und die Feuchtigkeit auf den Stahlflächen unterwandert, gelöst und im Ringspalt zum Absinken gebracht wird;
• ― daß der Ringspaltraum an beiden Enden des Zuggliedes gegen dieses abgedichtet wird;
• ― daß sich am oberen Ende des Zuggliedes ein Ausgleichsgefäß befindet, das mit dem Ringspalt in Verbindung steht, und
• ― daß oberhalb des Ausgleichsgefäßes eine aus der eintretenden Luft Feuchtigkeit herausziehende Silikatgelschleuse oder eine ähnlich wirkende Vorrichtung, die von der Feuchtigkeit in der Atmosphäre abtrennt, angeordnet ist.

In the patent DE-C-3629704, the corrosion protection for tension members, in the form of steel ropes, parallel wire and strand bundles, for absorbing large loads for cable-spanned bridges, for bracing towers and masts and for reactor construction was claimed, the tension member Surrounded with a sheet steel sheath is characterized in that the sheath is held by spacers at such a distance from the tension member that an annular gap surrounding the tension member results, this sheathing being tightly folded over the entire length of the tension member between the ends, soldered or is welded and a compensating stretching device is arranged at the upper end of the casing,

• - That the annular gap is filled with a corrosion protection liquid, which has a lower specific weight than water and also a particularly low viscosity, and are dissolved in the anti-corrosion additives;
• - That the anticorrosive fluid receives moisture-infiltrating and corrosion-preventing admixtures in the form of gas phase inhibitors, so that the residual amounts of oxygen are neutralized by reactants and the moisture on the steel surfaces is infiltrated, dissolved and brought to a decrease in the annular gap;
• - That the annular gap space is sealed at both ends of the tension member against this;
• - That there is a compensation vessel at the upper end of the tension member, which is connected to the annular gap, and
• - That a silica gel lock or a similarly acting device, which separates from the moisture in the atmosphere, is arranged above the compensating vessel.

DE-A-3532204 also discloses a similar method for corrosion protection according to the preamble of patent claim 1.

Further considerations led to developments with which the main objective, which continues to be aimed at, to quickly and reliably end the corrosion process in the tension members, wire bundles or rope packages of various types already affected by corrosion, and thus to maintain the respective stock without further damage, can be achieved even better and more reliably. There are various ways to protect such tension members from the ingress of other pollutants from the surrounding atmosphere with more or less success and for a long time.

However, in the current state of the art, it is obviously not possible to call a reliably effective method by which it can be made possible in the short term to render the pollutants that have already penetrated inside a cable harmless, for which purpose it is necessary to have oxygen or even moisture that has already flowed in are present in the cable at an unknown location and in an unknown quantity - the most unfavorable location, which alone determines the load-bearing capacity, can hardly ever be determined by spot checks - to physically take it out and to make any remaining small residues chemically harmless.

Thus, the engineer entrusted with bridge maintenance must make the difficult decision as to whether the load-bearing behavior of the cables can still be sufficient if the corrosion process which continues for a certain time has gradually consumed the moisture present by forming Fe 2 O 3. Because of the lack of knowledge of the pollutants that nourish the corrosion process and the amount of moisture present that forms the electrolyte, such a decision is difficult and very risky. In addition, no one could propose a control option for the respective condition without material-damaging interventions if a covering was placed around the cable to protect it from the effects of the atmosphere and a decision was made to destroy this sheath at some point after a certain time for control purposes. by no means will the crucially important most unfavorable point be found with a cable length of several 1000 m. This makes it imperative to provide larger safety reserves.

 = 150 N/mm² bei Seilen und △

 = 150 bzw. 200 N/mm² bei Paralleldrahtbündeln noch eine tatsächliche Bruchkraft von 75% bzw. 80% der rechnerischen vollen Bruchkraft nachgewiesen werden. Liegt in einem Ballungsgebiet ein nahezu dichter Schnellbahnverkehr auf der Brücke, so können in 20-22 Jahren die 2 Mio. Lastwechsel erreicht werden. Es muß allerdings nach der neueren DIN-Fassung nur noch eine Verkehrsbelastung von 50% der rechnerischen Größe angesetzt werden. So konnte in einem praktischen Fall mit sehr aufwendigen Versuchen bei allerdings Berücksichtigung von 60% der möglichen Verkehrslasten (also um 20% zu hoch gegenüber der jetztigen DIN) nur eine hauchdünne Bestätigung erreicht werden, was erkennen läßt, daß die praktisch vorhandenen Sicherheitsreserven gegenüber der vorhandenen Dauerschwingfestigkeit nur gering sind. Aus diesem Grunde muß der durch eingefressene Rostnarben verursachten Abnahme der Dauerfestigkeit infolge der hier zu fürchtenden Lochfraß- und Spannungsrißkorrosion durchaus eine beträchtliche Bedeutung beigemessen werden. Deshalb kann ein einfaches Erneuern der Kabelumhüllung, ohne daß der Korrosionsprozeß nachweisbar in kontrollierbarer Weise unterbrochen wird, bereits ein unverantwortbares Risiko bedeuten. Es stellt sich somit die Aufgabe: 1. das angerostete Kabel gegen das Eindringen weiterer Schadstoffe zuverlässig und zeitlich langandauernd zu schützen. Kontrolliergelegenheiten des jeweiligen Zustandes sollten ohne Materialzerstörungen jederzeit möglich sein, damit sie bei der Größe des bestehenden Risikos häufig genutzt werden. 2. der bereits im Lauf befindliche Korrosionsprozeß ist, um ein Fortschreiten der Schädigung zu verhindern, möglichst schnell und effektiv abzubrechen, was mit der Maßnahme zu 1. allein nicht möglich ist.Compared to static loads, the safety values of r = 2.22 or 2.38, which are usual for the cross-sectional dimensioning, will hardly be a greater risk at first, if one accepts an ongoing corrosion process uncontrollably. All however, the situation is different when it comes to the permanent use of bridge cables. It is known in specialist circles in bridge construction that the fatigue strength specified in the relevant DIN 1073 and possibly taken into account in a rail traffic by means of arithmetical fatigue strength analysis or the results of tests to be proven has been set extremely high, so that this value is hardly ever fully achieved in practice can be. After 2 million load changes with a swing width of △

= 150 N / mm² for ropes and △

= 150 or 200 N / mm² for parallel wire bundles, an actual breaking strength of 75% or 80% of the calculated full breaking strength can be proven. If there is an almost dense express train traffic on the bridge in a conurbation, the 2 million load changes can be achieved in 20-22 years. However, according to the newer DIN version, only a traffic load of 50% of the calculated size has to be applied. In a practical case with very complex tests, but taking into account 60% of the possible traffic loads (i.e. 20% too high compared to the current DIN), only a wafer-thin confirmation could be achieved, which shows that the practically existing safety reserves compared to the existing one Fatigue strength is only low. For this reason, the decrease in fatigue strength caused by rust scars that have been eaten up due to the pitting and stress corrosion cracking to be feared here must certainly be given considerable importance. Therefore, simply replacing the cable sheathing without demonstrably interrupting the corrosion process in a controllable manner can already be an irresponsible risk. The task thus arises: 1. To reliably protect the rusted cable against the ingress of further pollutants and for a long time. Checks of the respective condition should be possible at any time without material destruction, so that they are used frequently given the size of the existing risk. 2. The corrosion process that is already in progress is to be stopped as quickly and effectively as possible in order to prevent the progression of the damage, which is not possible with the measure for 1. alone.

With the measures described in DE-C-3629704 or DE-A-3532204, this goal is sought. However, the research laboratories of the major oil processing companies were unable to confirm without any doubt whether the low-viscosity oil penetrating into the cable is able to bind the moisture there sufficiently and flush it into the annular gap. On the contrary, it was recommended to use the dewatering fluid to drain the inside of the cable. The effect should probably be achieved. However, the risk associated with the use of this highly flammable drainage liquid and the fact that partial quantities could remain inside the cable make it absolutely advisable to refrain from using these fluids.

The task is solved by the characterizing features of claim 1. The solution is planned in stages

1. Removal of moisture by vacuum drying

(Evaporation when the cables are heated and a corresponding negative pressure is created)

With the help of an electrical current of about 14-30 volts and about 4000 to 6000 amps introduced into the wires of the cables usually via the anchor body encapsulation (usually zinc alloy) into the wires of the cables, the cables are heated by measuring devices by about 40 ° to Max. 60 ° C. With regard to the heating-up time, a test is required, as this depends on the heat loss on the cladding sheet.

At the same time, a negative pressure of up to 60 mbar may be generated even briefly in the annular gap space by means of a "pump" specially designed for vacuum technology (preferably a two-stage rotary vane vacuum pump in a performance range between about 65-200 m³ / h suction capacity). Theoretically, the moisture in the cavities between wires, strands and ropes can be reduced to about 1/24000 by such an evaporation and pumping process.

The pump conveys the steam to the outside, whereby the amount of liquid delivered can be measured and recorded in absolute terms and in relation to the time unit by means of partial pressure measurement on the downstream mass spectrometer. The duration of this first drying stage naturally depends on the amount of moisture actually inside the cable and the temperatures present during evacuation. If a steady state can be recognized by means of the measuring device, this process is to be regarded as finished. Specialist companies and certain departments of local government have particular experience in this area from the frequent evacuation of district heating pipes.

At the same time, this process reveals the amount of moisture inside the cable except for the residues mentioned. By observing an increase in pressure in relation to time, the leak rate of the system (i.e. the amount of leak per unit of time) can be determined relatively easily before the drying process. This affects the tightness of the welded sheaths as well as the function of the stuffing boxes. This provides a good opportunity to determine the practically given but not known values.

2. Overlay the cables in the annular gap using a nitrogen cushion

By a certain, even if only slight overpressure of the injected dry gaseous medium - preferably completely dry air or N₂ gas - of about 50 mbar in the annular gap - the tightness is guaranteed by the stuffing box construction - penetration of water, oxygen or other Prevents pollutants. The low loss due to leakage rates has to be compensated for by cold nitrogen gasifiers, which have to be replenished by the specialist companies in industrialized countries every several months (eg from Messer, Griesheim).

The nitrogen supply is automatically checked via a pressure cell. This process may be connected to an alarm signal line. Otherwise there is no risk of environmental damage due to leaks if they should actually occur. The medium-sized cold carburettor can almost accommodate the annual demand that arises with normal European bridges on the Rhine and Danube, with one or two refills per year. The costs for the annual requirement - cold gasifier rental and the required nitrogen material - would be less than the annual interest amount of the funds that would be needed to fill up with the anti-corruption oil previously used. The use of nitrogen is therefore cheaper, and there are also the technical advantages: When using dry air or N₂ gas, it is possible at any time to use the mass spectrometer to examine the gas escaping from the glands for moisture and thus very easily provide reliable control over the processes exercise in the annular gap and in the cable. The welding of any leaks in the sheet metal shell is completely unproblematic with a nitrogen filling in the ring hole.

The most important advantage to be achieved with the use of nitrogen for the annular gap filling is the subsequent drying in the interior of the cable.

In practice, the constantly renewed N₂ gases sweep away the last remnants of moisture from the inside of the cable into the annular gap when they pass by and at the same time penetrate them and carry them out from there, since physically the effort to equalize the partial pressure between the two media is effective. 1 kg = 800 l of N₂ gas are able to bind and remove 280 times the residual moisture remaining after the evaporation process, when it penetrates through fine channels and gaps between the wires and into the interior of the cable where there is material contact Partial pressure equalization can perform. This effect could exist where there are pressure differences between the cable edge and the middle and hinder the close media connection and only through the detour of the diffusion necessary close contact can be slowed down. The amount of moisture still present after the evaporation process, the leak rate and thus the size of the N₂ gas renewal and the nitrogen flushing process, the temperature inside the cable especially but the ways available in the cable interior to achieve the partial pressure compensation determine the speed of the after-drying effect. Only a few of these factors can be calculated theoretically in advance, which is why a trial on a short distance is first necessary to determine the basics.

3. Creation of a molecular protective layer on the surfaces of the wires by vapor phase inhibitors thus by means of chemical action

To accelerate the extinction of corrosion processes in the interior of the cable, the use of gas phase inhibitors (VPI = vapor phase inhibitors, an agent that has been used in the USA for decades to preserve sensitive weapon parts and for a long time also by the German exporting industry) is used as an additional step for post-drying. proposed for this purpose here, for which protection has already been claimed in DE-C-3629704. According to the Institute for Export Packaging, Hamburg University of Applied Sciences, it is recommended that the N₂ gas be saturated right up to the point of saturation, i.e. Add discyclohexylammonium nitrite immediately after the evaporation process (approx. 40 g per 1000 l) because then the heating inside the cable continues and the negative pressure in the capillaries inside the cable is largely vented, which facilitates quick penetration.

As an inexpensive fine chemical, this substance is manufactured by international large oil refineries, including Shell, under the name VPI 260-350 with certain variations in properties depending on the application. The chemical is split under the influence of water vapor. Free forms Amine and nitrous acid. The latter oxidizes the iron to iron oxides on the metal surface. In addition, the surface is covered with a thin layer of amine. The nitrogen oxide produced during the oxidation of iron in turn forms nitrous acid with the moisture and oxygen present, which is able to passivate further parts of the surface. The protective layers are of molecular strength and therefore of limited duration. The material VPI 300 dissolves with 55.6 parts by weight in 100 parts by weight of water, the liquid that is still present being rendered ineffective in corrosion. The expediently mixed VPI chemical is able to penetrate and infiltrate the moist rust material at corrosion points and thereby make the moisture present in the electrolyte ineffective against corrosion. The VPI material can exert an accelerating effect on the corrosion process in the interior of the cable until these liquid parts are bound and transported away by the constant drying process in the partial pressure equalization with the flushing nitrogen. If this residual moisture is removed, which can be reliably determined by investigations using a mass spectrometer, it is no longer necessary to add this chemical.

It can only be determined in practice whether it is necessary in addition to the evaporation and post-drying by rinsing with moisture using the N₂ gas. Since the replenishment of pollutants is prevented in a controllable manner and the constantly flowing nitrogen maintains the drying process, the 3 described steps stop the corrosion process inside the cable in a short time and prevent it from flaring up again.

Fig.

1

Querschnitt des Schrägkabels; als Beispiel ein Paralleldrahtbündel mit Abstandhalterkranz gewählt. Bei Seilpaketen bedarf es abgewandelter Lösungen, wobei das Heraustreiben der Feuchtigkeit aus dem Innern und Auslöschen der Korrosionsprozesse dadurch erleichtert wird, daß im allgemeinen die Hohlräume zwischen den Seilen und Litzen nicht kunststoffverfüllt sind. Der Verdampfungsprozeß und das Spülen mit N₂-Gas, gegebenenfalls mit VPI-Beigabe, sind somit einfacher und auch sehr schnell wirksam.

Ziff.

1

Schrägkabel als Paralleldrahtbündel, bei dem die Holräume vor der Montage im Tauchverfahren oder durch Injektion mit Kunststoff aufgefüllt sind.

2

Reste dieses Kunststoffes am Kabelrand, welche mit Hilfe eines rotierenden Rundschälgerätes oder in ähnlicher Weise so abgefräst werden, daß sich eine weitgehend runde Oberfläche als Grundlage für die Abstandhalterkränze ergibt.

3

Durchgehender Ringspaltraum, von dem aus die vorgesehene Behandlung und auch Kontrolle des Kabelzustandes erfolgen kann. Abschließend wird dieser Ringspalt bei leichtem Überdruck mit trockenem Stickstoff angefüllt. Der geringe Verlust an den Stopfbuchsen wird laufend ersetzt, so daß sich praktisch eine andauernde Nachtrocknung ergibt.

4

Verschweißte Blechhülle aus einem Edelstahlmaterial, welches bei nur gelegentlicher Oberflächenreinigung zumindest die Brückenlebensdauer erreicht. Z.B. ist von dem Werkstoff 1.4439 eine solche Beständigkeit aufgrund intensiver positiver Teste mit großer Sicherheit zu erwarten, d etwa von 0,9-2 mm.

5

Abstandhalter aus Spritz-Polyethylen.
a) Kranz senkrecht zur Kabelrichtung aufgeklebt ― e = 1,00 - 2,00 m bstand
b) längs gerichtete Abstandhalter etwa 0,30-0,40 m lang; am Ende jeden Montagestückes von hinten eingepreßt, um das mit leichtem Spiel über die Abstandhalterkränze hinweggeführte Hohlrohr auf die Abstandhalter vor der Anschlußverschweißung herunterzudrücken. Dieser Arbeitsgang findet im Schutze der allseits gegen die Witterung abgeschlossenen Arbeitsbühne Fig. 14, Ziff. 49.b der DE-C-3629704 statt.

Fig.

2

Paralleldrahtbündel; Querschnitt zwischen den Abstandhalterkränzen.

Ziff.

6

Mittels eines elektrisch geheizten, der Rundung des Schrägkabels angepaßtem Schneidegerätes wird eine Fensteröffnung in die verbliebene Hülle geschnitten und danach unter Befestigung eines Ziehgerätes an das abgetrennte Kunststoffasernetz, mit dem das Kabel umwickelt worden war oder auf ähnliche Weise abgezogen. Es werden 2 längs versetzte Öffnungen, möglichst großen Querschnitts, etwa 60 bis 100 × 300 mm² hergestellt, um den "Verdampfungsprozeß" und das "Nachtrocknen" zu erleichtern und zu beschleunigen.

Fig.

3-7

Widerstandserwärmung durch konduktive elektrische Einwirkung auf die einzelnen Schrägkabel mit Strom hoher Stärke und niedriger Spannung.

Fig.

3

Schrägkabel als Paralleldrahtbündel im Pylonenkopf unterbrochen und einzeln verankert.

Ziff.

7

Ankerhülse und Stopfbüchsenpackung auf Isolierplatten und Röhrchen von der Brückenkonstruktion galvanisch getrennt.
Zuleitung des niedrig gespannten Stromes vom Trafo:
1. PDB führt Strom hinein
2. PDB führt Strom zurück

8

zwischen 2 PDB eine Cu-Kabel-Einleiter-Kabelbrücke

9

Transformator, Bauart wie für Schweißstromumformung

Fig.

4

wie bei Fig. 3 jedoch erfolgt unmittelbare Stromrückführung vom Punkt C zum Trafo 9 durch besondere Leitung

Ziff.

10

8 bis 10 Einleiter-Kabel; Cu-Querschnitt je Leiter etwa 120 mm²

Fig.

5

Kabel am Polyonenkopf C durchlaufend, galvanische Verbindung kann bei C erhalten bleiden, wenn diese bei A und B unterbrochen wird

Ziff.

7

galvanische Verbindung bei den Punkten A und B der Brückenkon-

11

struktion beseitigt (Details Fig. 3)

10

wie bei Fig. 4, jedoch zwischen 11 und 9

Fig.

6

Endverankerung der Paralleldrahtbündel
Isolierung der galvanischen Verbindung im Detail wie beim Beispiel Rheinbrücke Mannheim-Ludwigshafen, wobei die Ankerhülsen mittels Pressen (Z_max. = 5400 KN) eine geringe Strecke angezogen werden müssen, um im Bereich der Druckverteilungsplatte eine etwa 3-4 mm starke Isolierplatte einzuwechseln; vorgeschlagen werden hochfeste Zirkon-OxidKeramik-Platten der Friedrichsfelder Steinzeugfabrik, durch Glasfaser verstärkte Kunstharzplatten von Ciba Geigy oder ähnliche druckfeste, galvanisch isolierende Platten.

Ziff.

12

Die Zuleitung des Heizstromes von etwa I = 4000 - 6000 Amp. Stärke, mit dem das Drahtkabel oder Seilpaket auf 60°C gebracht werden soll, ist so anzulegen, daß die Einzeldrähte möglichst gleichmäßig beaufschlagt werden. Irgendwelche Lichtbogenbildung ist zu verhindern beispielsweise:
es sind auf die Längsseiten der Stahlgußankerhülse diametral gegenüber zwei ca. 140 mm lange Kupferschienen aufgeschraubt bzw. gelötet, an denen jeweils 5 Einleiterkabel ∅ 120 mm², zusammen also 10, angeklemmt oder geschraubt werden. Der Stromfluß über die gewöhnliche Zinklegierungs-Vergußmasse im Ankerkonus kann gleichmäßig in die Drähte des Paralleldrahtbündels oder der aufgespreizten Seile eines Kabelpaketes erfolgen. An Stellen, wo ein Kugelkunststoffverguß ausgeführt wurde, muß der Strom von der Rückfront des Ankerkörpers über die blank gesäuberten, ehemals aufgestauchten Drahtköpfe und die KöpfchenLochplatte zugeleitet werden.

13

abstützende Stahlkonstruktion, in der Mitte das PDB Ziff. 1

14

Ankerbarren

15

Druckverteilungsplatten

16

Futterplatten variable Anzahl

17

Knagge, welche den Längsschub am unteren Abschluß der Blechhülse auf die Stahlkonstruktion 13 überträgt.

18

Stopfbuchsenhülse

19

galvanisch isolierende Röhrchen ― 2 Halbschalen aus Kunstharz

20

hochdruckfeste isolierende Druckplatten

Fig.

7

Isolierung der galvanischen Verbindung bei der Verankerung von Seilpaketen, die mittels Spreizschellen, welche verschiedentlich Kontakt mit der Stahlkonstruktion der Brücke haben, den freien Raum für die Unterbringung der Ankerhülsen ermöglichen, als Beispiel Rheinbrücke Leverkusen gewählt.

Ziff.

21

Schnitt durch das Kabel-Paket von 19 vollverschlossenen Seilen, etwa ∅ 59,5 mm, die Schellen werden auf freier Strecke entfernt, um die Längsbewegungen im Ringspalt nicht zu behindern. Es sind ein oberer und unterer Abstandhalterkranz und freie Zwischenräume vorgesehen.

22

Jede Ankerhülse wird geringfügig mittels Pressen vom Ankerbarren abgehoben und wie bei Fig. 6 Ziff. 19 und 20 die isolierenden Rohrhälften und Druckverteilungsplatten eingefügt.

23

Querschnitt durch die Spreizschellen

24

Schnitt im Spreizbereich

25

Schnitt vor dem Spreizbereich

26

mittels 2 Pressen wird diese Schelle von der Stahlkonstruktion der Brücke der Höhe oder auch der Seite nach etwas abgehoben und dabei die eine galvanische Isolation herstellende Zwischenlage eingefügt. Dort, wo von der Spreizschelle kein Kontakt zur Brückenkonstruktion besteht, was häufig der Fall ist, entfällt eine solche Maßnahme.

Fig.

8

Mögliche, gegen Einwirkungen der Öffentlichkeit geschützte Unterbringung der Kaltvergasergefäße und des VPI-Austauschers zum Mischen von N₂-Gas mit Discyclohexylammoniumnitrit-Pulver ― in Brückenlängsrichtung gesehen

Ziff.

1

Schrägkabel

30

untergehängte Decke zwischen den Brückenhohlkastenträgern, von der Treppe im Pylonenpfeiler aus zugänglich

31

Kaltvergaser für N₂-Gas (Zahl und Größe hängen vom Erneuerungsbedarf entsprechend der Leckrate ab).

32

Zylinderförmiges Mischgefäß, in dem von unten eingeführtes N₂-Gas durch das VPI-Pulver bis zur völligen Sättigung (40 g VPI auf 1 kg N₂-Gas) hindurch geleitet wird

33

Rohrleitungen + Armaturen zur Gasweiterleitung

Fig.

9

wie 8 jedoch in Brückenseitenansicht, geschnitten durch Brückenmitte

30-33

wie Fig. 8

29

Strahlrohrrüstung am Pylonenkopf, Zugänglichkeit zu den Kabelverankerungsstellen

34

Schrägkabelverankerung innerhalb des Brückentragwerkes

35

Stopfbüchse als unterer Abschluß des Ringspaltes

36

Kondenswasserabscheider und Wasserpumpe

37

Anschlußstutzen für N₂-Gaszufuhr mit Druckregelungsventilen und Alarmmeldevorrichtung bei Unterschreitung der vorgegebenen Toleranzen

38

Vakuumeinheit zur Evakuierung des Ringspaltraumes und damit zur Verdampfung der im Kabel befindlichen Feuchtigkeit

Fig.

10

Skizzenhafte Darstellung der auf der Pylonenplattform stationierten Pumpenanlage zur Druckabsenkung im Ringspalt mit den wesentlichsten Vorrichtungen, wie sie von der Industrie zum Evakuieren von Fernwärmeleitungen üblicherweise verwandt werden

Ziff.

39

Anschluß an den Ringspalt (Stutzen am Hüllrohr)

28

Ausgleichselemente

40

1. Fernübertragung von Daten zur Meßröhre

41

Kugelhahn zum Abschluß des Ringspaltsystems

42

Staubfilter

43

2. Fernübertragung von Daten zur Meßröhre

44

Magnetventil

45

Reduzierstück

46

Drehschiebervakuumpumpe (Leistungsgröße abhängig von: im Kabel befindlicher Wassermenge, Kabellänge, Ringspalt- und Kabelquerschnitten sowie Temperaturverhältnissen)

47

Schaltschrank mit Meßgeräten und Schreiber

48

u.U. Fernschaltung bzw. Abfragemöglichkeit vom Brückendeck aus

49

elektrische Anschlüsse

50

Automatische Meldung bei Unregelmäßigkeiten zur Arbeitsstelle auf dem Brückendeck

The essential processes are explained with the attached FIGS. 1-10.

Fig.

1

Cross section of the cable; a parallel wire bundle with spacer ring selected as an example. With rope packages it is necessary modified solutions, the expulsion of moisture from the interior and extinguishing the corrosion processes is facilitated by the fact that the cavities between the ropes and strands are generally not filled with plastic. The evaporation process and the purging with N₂ gas, possibly with the addition of VPI, are thus easier and also very quickly effective.

No.

1

Inclined cable as a parallel wire bundle, in which the cavities are filled with plastic before installation by immersion or by injection.

2nd

Remnants of this plastic on the edge of the cable, which are milled with the help of a rotating circular peeling device or in a similar manner so that there is a largely round surface as the basis for the spacer rings.

3rd

Continuous annular space from which the intended treatment and also the control of the cable condition can take place. Finally, this annular gap is filled with dry nitrogen under a slight overpressure. The low loss at the stuffing boxes is constantly being replaced, so that practically an ongoing drying process results.

4th

Welded sheet metal casing made of a stainless steel material, which achieves at least the life of the bridge with occasional surface cleaning. For example, material 1.4439 can be expected with such certainty due to intensive positive tests with a high degree of certainty, d of about 0.9-2 mm.

5

Spacer made of spray polyethylene.
a) Wreath glued on perpendicular to the cable direction - e = 1.00 - 2.00 m spacing
b) longitudinal spacers about 0.30-0.40 m long; at the end of each assembly piece, pressed in from behind to press the hollow tube, which is guided over the spacer rings, with a slight play onto the spacers before the connection welding. This operation takes place under the protection of the working platform, which is closed against the weather on all sides, Fig. 14, no. 49.b of DE-C-3629704 instead.

Fig.

2nd

Parallel wire bundle; Cross section between the spacer rings.

No.

6

By means of an electrically heated cutting device adapted to the curvature of the inclined cable, a window opening is cut into the remaining sheath and then, with the aid of a pulling device, attached to the separated plastic fiber network with which the cable had been wrapped or in a similar manner. There are 2 longitudinally offset openings, the largest possible cross section, about 60 to 100 × 300 mm² made to facilitate and accelerate the "evaporation process" and the "drying".

Fig.

3-7

Resistance heating through conductive electrical action on the individual inclined cables with current of high strength and low voltage.

Fig.

3rd

Inclined cable as parallel wire bundle interrupted in the pylon head and anchored individually.

No.

7

Anchor sleeve and gland packing on insulating plates and tubes galvanically isolated from the bridge construction.
Supply of the low-voltage current from the transformer:
1. PDB feeds electricity into it
2. PDB returns power

8th

a copper cable single-conductor cable bridge between 2 PDBs

9

Transformer, design as for welding current conversion

Fig.

4th

as in Fig. 3, however, there is direct current feedback from point C to transformer 9 through a special line

No.

10th

8 to 10 single-core cables; Cu cross section per conductor about 120 mm²

Fig.

5

Cable running through polyon head C, galvanic connection can be maintained at C if this is interrupted at A and B.

No.

7

galvanic connection at points A and B of the bridge con

11

structure eliminated (details Fig. 3)

10th

as in FIG. 4, but between 11 and 9

Fig.

6

End anchorage of the parallel wire bundle
Isolation of the galvanic connection in detail as in the example of the Rhine bridge Mannheim-Ludwigshafen, whereby the anchor sleeves have to be tightened a short distance using presses (Z _max. = 5400 KN) in order to insert an approximately 3-4 mm thick insulating plate in the area of the pressure distribution plate; High-strength zirconium oxide ceramic plates from the Friedrichsfeld stoneware factory, glass fiber reinforced synthetic resin plates from Ciba Geigy or similar pressure-resistant, galvanically insulating plates are proposed.

No.

12th

The supply of the heating current of about I = 4000 - 6000 Amp. Strength, with which the wire cable or cable package is to be brought to 60 ° C, is to be designed in such a way that the individual wires are applied as evenly as possible. To prevent any arcing, for example:
on the long sides of the cast steel anchor sleeve, they are screwed or soldered diametrically opposite two approximately 140 mm long copper bars, to each of which 5 single-core cables ∅ 120 mm², that is 10 in total, are clamped or screwed. The current flow via the usual zinc alloy casting compound in the anchor cone can take place evenly in the wires of the parallel wire bundle or the spread ropes of a cable package. In places where a spherical plastic encapsulation has been carried out, the current must be supplied from the rear of the anchor body via the brightly cleaned, previously exposed wire heads and the perforated plate.

13

supporting steel construction, in the middle the PDB number 1

14

Anchor bars

15

Pressure distribution plates

16

Lining plates variable number

17th

Knagge, which transmits the longitudinal thrust at the lower end of the sheet metal sleeve on the steel structure 13.

18th

Stuffing box sleeve

19th

galvanically insulating tubes - 2 half shells made of synthetic resin

20th

high pressure resistant insulating pressure plates

Fig.

7

Isolation of the galvanic connection during the anchoring of rope packages, which are different by means of spreading clamps Have chosen to have contact with the steel structure of the bridge, allow the free space for the accommodation of the anchor sleeves, for example the Rhine bridge Leverkusen.

No.

21st

Cut through the cable package of 19 fully closed ropes, approx. ∅ 59.5 mm, the clamps are removed on the free path in order not to hinder the longitudinal movements in the annular gap. There are upper and lower spacer rings and free spaces.

22

Each anchor sleeve is slightly lifted from the anchor bar by pressing and as in Fig. 6 no. 19 and 20 inserted the insulating pipe halves and pressure distribution plates.

23

Cross section through the expansion clamps

24th

Cut in the spreading area

25th

Cut in front of the spreading area

26

by means of 2 presses, this clamp is lifted slightly from the steel structure of the bridge, either vertically or laterally, and the intermediate layer, which provides galvanic insulation, is inserted. Where there is no contact from the expansion clamp to the bridge structure, which is often the case, no such measure is necessary.

Fig.

8th

Possible, against the influence of the public, sheltering the cold gasification vessels and the VPI exchanger for mixing N₂ gas with discyclohexylammonium nitrite powder - seen in the longitudinal direction of the bridge

No.

1

Inclined cable

30th

suspended ceiling between the hollow box girders, accessible from the stairs in the pylon pillar

31

Cold gasifier for N₂ gas (number and size depend on the need for renewal according to the leak rate).

32

Cylindrical mixing vessel in which N₂ gas introduced from below is passed through the VPI powder until it is completely saturated (40 g VPI per 1 kg N₂ gas)

33

Pipelines + fittings for gas transmission

Fig.

9

like 8 but in a side view of the bridge, cut through the middle of the bridge

30-33

like Fig. 8

29

Beam armor on the pylon head, access to the cable anchor points

34

Inclined cable anchoring within the bridge structure

35

Stuffing box as the lower end of the annular gap

36

Condensate separator and water pump

37

Connection piece for N₂ gas supply with pressure control valves and alarm device if the specified tolerances are undershot

38

Vacuum unit for evacuating the annular gap and thus for evaporating the moisture in the cable

Fig.

10th

Sketchy representation of the pump system stationed on the pylon platform for reducing the pressure in the annular gap with the most important devices, as are usually used by the industry for evacuating district heating pipes

No.

39

Connection to the annular gap (socket on the cladding tube)

28

Compensating elements

40

1. Remote transmission of data to the measuring tube

41

Ball valve to complete the annular gap system

42

dust filter

43

2. Remote transmission of data to the measuring tube

44

magnetic valve

45

Reducer

46

Rotary vane vacuum pump (capacity depends on: amount of water in the cable, cable length, annular gap and cable cross-sections as well as temperature conditions)

47

Control cabinet with measuring devices and recorders

48

May be remote control or query from the bridge deck

49

electrical connections

50

Automatic notification of irregularities to the job on the bridge deck

Claims (4)

1. Corrosion protection for tension members (1) in the form of steel cables, parallel bundles of wires or parallel bundles of strands for absorbing heavy loads for cable-braced bridges, for guying towers and masts, and also for reactor construction, wherein the tension member is surrounded by a sheathing (4) of sheet steel, which by means of spacers (5) is maintained at a distance from the tension member (1) so as to provide an annular clearance surrounding the tension member (1), characterised

― in that at both ends of the tension member (1) the annular clearance is sealed therefrom,

― in that the tension member (1) is heated and/or an underpressure is created in the annular clearance chamber (3) by pumping, so that any moisture present in the tension member (1) vaporises,

― in that, subsequently, the annular clearance is permanently filled with nitrogen which is at a pressure above atmospheric pressure and the overpressure is monitored by an automatic alarm and warning system.

2. Corrosion protection according to Claim 1, characterised in that to remove any residual moisture the annular clearance is flushed with nitrogen.

3. Corrosion protection for tension members according to Claims 1 and 2, characterised in that the tension member (1) is heated by electric conductivity to about 40-60°C.

4. Corrosion protection for tension members according to Claims 1 to 3, characterised in that vapour phase inhibitors are mixed with the nitrogen.

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