CH529628A - Welding plastic pipe sleeve - joint in two stages with cooling between to improve surface contact - Google Patents
Welding plastic pipe sleeve - joint in two stages with cooling between to improve surface contactInfo
- Publication number
- CH529628A CH529628A CH68372A CH68372A CH529628A CH 529628 A CH529628 A CH 529628A CH 68372 A CH68372 A CH 68372A CH 68372 A CH68372 A CH 68372A CH 529628 A CH529628 A CH 529628A
- Authority
- CH
- Switzerland
- Prior art keywords
- stage
- welding
- stages
- socket
- electrical energy
- Prior art date
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
- B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
- B29C65/3472—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint
- B29C65/3476—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
- B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
- B29C65/3404—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint
- B29C65/342—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint comprising at least a single wire, e.g. in the form of a winding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/66—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by liberation of internal stresses, e.g. shrinking of one of the parts to be joined
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/01—General aspects dealing with the joint area or with the area to be joined
- B29C66/05—Particular design of joint configurations
- B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
- B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
- B29C66/112—Single lapped joints
- B29C66/1122—Single lap to lap joints, i.e. overlap joints
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
- B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
- B29C66/52—Joining tubular articles, bars or profiled elements
- B29C66/522—Joining tubular articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
- B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
- B29C66/52—Joining tubular articles, bars or profiled elements
- B29C66/522—Joining tubular articles
- B29C66/5229—Joining tubular articles involving the use of a socket
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
- B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
- B29C66/9141—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature
- B29C66/91441—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature the temperature being non-constant over time
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
- B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
- B29C66/9141—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature
- B29C66/91441—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature the temperature being non-constant over time
- B29C66/91443—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature the temperature being non-constant over time following a temperature-time profile
- B29C66/91445—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature the temperature being non-constant over time following a temperature-time profile by steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
- B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
- B29C66/9161—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux
- B29C66/91641—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux the heat or the thermal flux being non-constant over time
- B29C66/91643—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux the heat or the thermal flux being non-constant over time following a heat-time profile
- B29C66/91645—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux the heat or the thermal flux being non-constant over time following a heat-time profile by steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
- B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
- B29C66/9161—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux
- B29C66/91651—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L47/00—Connecting arrangements or other fittings specially adapted to be made of plastics or to be used with pipes made of plastics
- F16L47/02—Welded joints; Adhesive joints
- F16L47/03—Welded joints with an electrical resistance incorporated in the joint
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/90—Measuring or controlling the joining process
- B29C66/94—Measuring or controlling the joining process by measuring or controlling the time
- B29C66/949—Measuring or controlling the joining process by measuring or controlling the time characterised by specific time values or ranges
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
Abstract
A method of welding plastic sleeve connections on pipes uses resistance wire between the pipes and sleeve, and dosing equipment for the energy supplied; the energy is supplied in two stages. The intervening period is pref. long enough to allow cooling after the first stage.
Description
Verfahren zum Schweissen von Kunststoffrohr-Muffenverbindungen unter Verwendung elektrischer Energiedosiergeräte
Aus Praxis und Patentliteratur sind verschiedene elektrisch schweissbare Systeme für das Verbinden thermoplastischer Rohrleitungsteile bekannt. Dabei besteht das Verbindungselement stets aus einem muffenartigen Körper mit innen eingelegtem metallischem Widerstandsdraht, in welchem während des Schweissvorganges elektrische Energie in Widerstandswärme umgewandelt wird. Der Muffenkörper kann ein unabhängiges Rohrbauelement oder mit Rohrformstücken verbunden sein. Die Dosierung der in Form von elektrischer Energie den Schweissmuffen zuzuführenden Schweisswärme erfolgt mit Hilfe eines zwischen Stromquelle und Muffenanschluss liegenden elektrischen Energiedosiergerätes.
Während der Beschickung der Schweissmuffen mit elektrischem Strom erwärmen sich die Muffeninnenfläche und die Aussenfläche der in die Muffen eingesteckten Rohrleitungsteile über den Schmelzpunkt des Werkstoffes hinaus. Nach dem Erkalten so geschweisster Verbindungen bilden Muffen und Rohrleitungsteile eine Einheit. Der metallische Widerstandsdraht verbleibt im Material, ohne weitere Funktionen erfüllen zu müssen. Bei zu grosser Energiezufuhr knicken infolge Erweichung die in die Muffen eingesteckten Rohrleitungsteile ein, während eine zu geringe Energiedosierung eine unvollständige Schweissung zur Folge hat. Zwischen diesen beiden Extremen liegt der für die Schweissung nutzbare Arbeitsbereich.
Die Praxis zeigt jedoch, dass der zur Verfügung stehende Spielraum zu schmal ist, um in jedem Fall mit einer einheitlichen Energiedosierung pro Rohrleitungsdimension auszukommen. Dies gilt vor allem dann, wenn zwecks Ausschliessung von Bedienungsfehlern Dosiergeräte verwendet werden, welche das Schweissen verschiedener Rohrleitungsgrössen ohne individuelle Geräteeinstellung erlauben. Solche Geräte arbeiten meistens innerhalb ihres Verwendungsbereiches mit einheitlicher Schweisszeit und einheitlichem Schweissstrom. Das bedingt aber Kompromisse bei der Festlegung dieser Daten, indem der Arbeitspunkt nicht für alle Rohrleitungsgrössen in die Mitte des schweisstechnisch verfügbaren Spielraumes gelegt werden kann. Es genügen dann unter Umständen bereits kleinere Abweichungen von den üblichen Schweissbedingungen, um eine der beiden Spielraumsgrenzen zu überschreiten.
Als praktisch bedeutungsvolle Ursachen für Abweichungen von den idealen Schweissbedingungen sind zu nennen: - extremes Spiel zwischen Muffen und Rohrleitungsteilen, - Schweissen bei tiefer Umgebungstemperatur, - Verwendung von Rohrleitungsteilen mit gegenüber Stand ardelementen verdickter Wand.
Im erstgenannten Fall kann die Wärmeübertragung auf die Aussenfläche der in die Muffen eingesteckten Rohrleitungsteile ungenügend sein, so dass nur muffenseitig über den ganzen Umfang ein schweissbarer Zustand entsteht. Im zweitgenannten Fall beanspruchen die zu verschweissenden Rohrleitungsteile und Muffen einen Teil der zugeführten Energie, um jenes thermische Energiepotential zu erreichen, das unter idealen Schweissbedingungen die Ausgangslage für den Schweissvorgang darstellt. Der drittgenannte Fall bietet seltener Probleme, indem der erforderliche Aufwand an Schweissenergie nur in bescheidenem Umfang mit der Wanddicke der Rohrleitungsteile wächst.
Die Erfahrung zeigt, dass die für eine einwandfreie Verbindung erforderliche Schweissenergie erheblich reduziert werden könnte, wenn stets ein guter Kontakt zwischen Muffen und Rohrleitungsteilen gewährleistet wäre. Diese Voraussetzung ist aber in der Praxis nicht erfüllt, weil eine wirtschaftliche Fertigung von Muffen und Rohrleitungsteilen ohne masslichen Toleranzbereieh nicht möglich ist. Tiefe Umgebungstemperaturen verschärfen das Kontaktproblem, weil die Rohrleitungsteile einer Materialkontraktion unterworfen sind, während die Muffen infolge des eingelegten Widerstandsdrahtes diese Kontraktion nur im Ausmass des gegenüber Kunststoffen wesentlich kleineren metallischen Schrumpfens mitmachen können.
Ein vollständiger Kontakt zwischen Muffen und Rohrleitungsteilen ergibt sich in den meisten Fällen erst während des Schweissvorganges, indem die Muffen - ein diesbezüglich geeignetes Muffenherstellverfahren vorausgesetzt - Schrumpfneigung aufweisen, welche aber erst zur Auswirkung kommen kann, nachdem die Stützwirkung des Widerstandsdrahtes infolge Erweichung des benachbarten thermoplastischen Muffenmaterials entfällt.
Diese thermisch auslösbare Muffenschrumpfung bildet die Basis für vorliegendes Patent. Letzteres betrifft ein Verfahren zum Schweissen von Kunststoffrohr-Muffenverbindungen unter Verwendung von elektrischen Energiedosiergeräten, das dadurch gekennzeichnet ist, dass der zwischen Muffe und eingesteckten Rohrleitungsteilen liegende Widerstandsdraht in zwei Etappen mit Heizstrom beschickt wird. Dabei genügt es, in erster Etappe nur so viel Heizenergie zuzuführen, damit ein für guten Kontakt ausreichender Muffenschrumpf ausgelöst wird. Diese Energiemenge liegt unter der für reguläre Schweissvorgänge üblichen Dosis, so dass eine Anpassung durch vorzeitigen Abbruch eines regulären Schweissvorganges bewerkstelligt werden kann.
Es kann aber auch in der ersten Etappe mit der für reguläre Schweissvorgänge üblichen Energiemenge gearbeitet werden, so dass lediglich das elektrische Energiedosiergerät zweimal in Aktion gesetzt werden muss. Die vor der zweiten Etappe einzulegende Pause ist hiebei länger oder mindestens ungefähr gleich der Abkühlzeit für die in erster Etappe erwärmte Verbindung zu wählen.
Die erste Erwärmungsetappe dient lediglich der Gewährleistung eines guten Kontaktes zwischen Muffen und eingesteckten Rohrleitungsteilen im Hinblick auf die zweite Etappe, die als eigentlicher Schweissvorgang zu betrachten ist.
Damit sind bereits zu Beginn derselben Bedingungen geschaffen, die einem spielfreien Zusammenpassen von Muffen und eingesteckten Rohrleitungsteilen entsprechen. Ein Einknicken der letzteren ist trotz dieser schweisstechnischen Begünstigung nicht zu befürchten, weil die Einstellung der für das betreffende System üblichen elektrischen Stromdosiergeräte der Möglichkeit einer spielfreien Paarung von Muffen und Rohrleitungsteilen ohnehin Rechnung tragen muss.
Ausserdem vermindern der gleichmässige Wärmeübergang auf die eingesteckten Rohrleitungsteile und ihre in erster Etappe mindestens teilweise erfolgte Bindung an die Muffeninnenfläche die Gefahr des Einknickens. In zweiter Etappe steht somit eine beträchtliche Energiemenge, die sonst der Gewährleistung eines guten Kontaktes zwischen Muffen und eingesteckten Rohrleitungsteilen hätte dienen müssen, zur Deckung zusätzlichen Wärmebedarfes infolge anderweitiger Abweichungen von den idealen Schweissbedingungen zur Verfügung. Die zwischen den beiden Etappen einzulegende Pause soll vermeiden, dass die zweite Etappe, d. h. der eigentliche Schweissvorgang, von einem erhöhten thermischen Energiepotential der Verbindung ausgeht und somit trotz der erwähnten reduzierten Knickfreudigkeit der eingesteckten Rohrleitungsteile Einknickungen vorkommen können.
Die notwendige Pausenlänge liegt je nach Rohrleitungsdimension und Schweisssystem praktisch etwa zwischen 15 und 60 Minuten. In der Praxis können die Pausen nutzbringend überbrückt werden, indem ein grösserer Abschnitt vorverlegter Rohrleitungen in erster Etappe geschweisst und hierauf in gleicher Reihenfolge die zweite Etappe durchexerziert wird.
Aufgrund der vorliegenden Erfindung ist es möglich, den Einsatzbereich von Standard-Stromdosiergeräten erheblich zu erweitern.
Method for welding plastic pipe socket connections using electrical energy metering devices
Various electrically weldable systems for connecting thermoplastic pipeline parts are known from practice and patent literature. The connecting element always consists of a sleeve-like body with a metallic resistance wire inserted inside, in which electrical energy is converted into resistance heat during the welding process. The socket body can be an independent pipe component or connected to pipe fittings. The welding heat to be supplied to the welding sleeves in the form of electrical energy is metered with the aid of an electrical energy metering device located between the power source and the sleeve connection.
While the welding sockets are being charged with electrical current, the inner surface of the socket and the outer surface of the pipeline parts inserted into the socket heat up beyond the melting point of the material. After the joints welded in this way have cooled down, sleeves and pipeline components form a unit. The metallic resistance wire remains in the material without having to fulfill any other functions. If the amount of energy supplied is too great, the pipeline parts inserted into the sleeves buckle due to softening, while too little energy will result in incomplete welding. The working area that can be used for welding lies between these two extremes.
Practice shows, however, that the available leeway is too narrow to be able to manage with a uniform energy dosage for each pipe dimension. This is especially true if, in order to rule out operating errors, dosing devices are used which allow the welding of different pipe sizes without individual device settings. Such devices mostly work within their area of use with a uniform welding time and a uniform welding current. However, this requires compromises in the definition of these data, as the operating point cannot be placed in the middle of the latitude available for welding for all pipe sizes. Under certain circumstances, even minor deviations from the usual welding conditions are then sufficient to exceed one of the two limits.
The following practically significant causes for deviations from the ideal welding conditions are to be mentioned: - extreme play between sockets and pipe parts, - welding at low ambient temperatures, - use of pipe parts with a wall that is thicker than standard elements.
In the first-mentioned case, the heat transfer to the outer surface of the pipeline parts inserted into the sleeves can be insufficient, so that a weldable state is created over the entire circumference only on the sleeve side. In the second case mentioned, the pipeline parts and sleeves to be welded require part of the energy supplied in order to achieve the thermal energy potential which, under ideal welding conditions, represents the starting point for the welding process. The third case seldom poses problems in that the required welding energy expenditure increases only to a modest extent with the wall thickness of the pipeline parts.
Experience shows that the welding energy required for a perfect connection could be reduced considerably if good contact between the sockets and pipeline parts were always guaranteed. However, this requirement is not met in practice, because an economical production of sleeves and pipeline parts without a dimensional tolerance range is not possible. Low ambient temperatures exacerbate the contact problem because the pipeline parts are subject to material contraction, while the sleeves, due to the inserted resistance wire, can only take part in this contraction to the extent of the significantly smaller metallic shrinkage compared to plastics.
In most cases, complete contact between the sockets and pipeline parts is only achieved during the welding process, as the sockets - assuming a suitable socket manufacturing process in this regard - have a tendency to shrink, which can only take effect after the support effect of the resistance wire due to the softening of the adjacent thermoplastic socket material not applicable.
This thermally triggered sleeve shrinkage forms the basis for this patent. The latter relates to a method for welding plastic pipe and socket connections using electrical energy metering devices, which is characterized in that the resistance wire located between the socket and the inserted pipeline parts is fed with heating current in two stages. In the first stage, it is sufficient to only add enough heating energy to trigger a sleeve shrinkage that is sufficient for good contact. This amount of energy is below the usual dose for regular welding processes, so that an adjustment can be made by prematurely terminating a regular welding process.
In the first stage, however, it is also possible to work with the amount of energy that is usual for regular welding processes, so that only the electrical energy metering device has to be activated twice. The break to be taken before the second stage should be longer or at least approximately the same as the cooling time for the connection warmed up in the first stage.
The first heating stage only serves to ensure good contact between the sleeves and the inserted pipeline parts with regard to the second stage, which is to be regarded as the actual welding process.
In this way, the same conditions are created at the beginning that correspond to a backlash-free fitting together of sleeves and inserted pipeline parts. Buckling of the latter is not to be feared despite this welding technology advantage, because the setting of the electrical current metering devices customary for the system in question must take into account the possibility of a play-free pairing of sleeves and pipeline parts anyway.
In addition, the uniform heat transfer to the inserted pipeline parts and their at least partially binding to the inner surface of the socket reduce the risk of buckling. In the second stage, a considerable amount of energy, which otherwise would have had to ensure good contact between the sleeves and the inserted pipeline parts, is available to cover additional heat requirements due to other deviations from the ideal welding conditions. The break between the two stages is intended to avoid the second stage, i.e. H. The actual welding process is based on an increased thermal energy potential of the connection and kinks can therefore occur despite the aforementioned reduced tendency to kink the inserted pipeline parts.
The necessary pause length is practically between 15 and 60 minutes, depending on the pipe dimension and welding system. In practice, the breaks can be bridged usefully by welding a larger section of pipelines laid in advance in the first stage and then practicing the second stage in the same order.
Due to the present invention, it is possible to considerably expand the range of use of standard current metering devices.
Claims (1)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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CH68372A CH529628A (en) | 1972-01-18 | 1972-01-18 | Welding plastic pipe sleeve - joint in two stages with cooling between to improve surface contact |
CA187,359A CA986960A (en) | 1972-01-18 | 1973-12-04 | Ski brake |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CH68372A CH529628A (en) | 1972-01-18 | 1972-01-18 | Welding plastic pipe sleeve - joint in two stages with cooling between to improve surface contact |
Publications (1)
Publication Number | Publication Date |
---|---|
CH529628A true CH529628A (en) | 1972-10-31 |
Family
ID=4192719
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CH68372A CH529628A (en) | 1972-01-18 | 1972-01-18 | Welding plastic pipe sleeve - joint in two stages with cooling between to improve surface contact |
Country Status (1)
Country | Link |
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CH (1) | CH529628A (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1979001000A1 (en) * | 1978-04-28 | 1979-11-29 | W Sturm | Method and apparatus for connecting thermoplastic conductor elements |
EP0036963A1 (en) * | 1980-03-31 | 1981-10-07 | Georg Fischer Aktiengesellschaft | Welding socket for thermoplastic materials, method and apparatus for its manufacture |
FR2516439A1 (en) * | 1981-11-13 | 1983-05-20 | Armosig | Electrically fusible liners for thermoplastic pipework joints - pre-assembled by partial fusion for satisfactory alignment |
EP0297185A1 (en) * | 1985-11-08 | 1989-01-04 | R.W. LYALL & COMPANY, INC. | Method and apparatus for making fused connections |
US4943706A (en) * | 1988-04-18 | 1990-07-24 | R. W. Lyall & Company, Inc. | Method and apparatus for fusing thermoplastic materials |
WO1995016557A2 (en) * | 1993-12-15 | 1995-06-22 | Tokushu, Kogyo Kabushikigaisha | Electrofusion fastening apparatus |
WO1997020682A1 (en) * | 1995-12-05 | 1997-06-12 | Hürner Gmbh | Method and arc welding device for automatically welding heater coil fittings |
-
1972
- 1972-01-18 CH CH68372A patent/CH529628A/en not_active IP Right Cessation
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1979001000A1 (en) * | 1978-04-28 | 1979-11-29 | W Sturm | Method and apparatus for connecting thermoplastic conductor elements |
EP0036963A1 (en) * | 1980-03-31 | 1981-10-07 | Georg Fischer Aktiengesellschaft | Welding socket for thermoplastic materials, method and apparatus for its manufacture |
FR2516439A1 (en) * | 1981-11-13 | 1983-05-20 | Armosig | Electrically fusible liners for thermoplastic pipework joints - pre-assembled by partial fusion for satisfactory alignment |
EP0297185A1 (en) * | 1985-11-08 | 1989-01-04 | R.W. LYALL & COMPANY, INC. | Method and apparatus for making fused connections |
US4943706A (en) * | 1988-04-18 | 1990-07-24 | R. W. Lyall & Company, Inc. | Method and apparatus for fusing thermoplastic materials |
WO1995016557A2 (en) * | 1993-12-15 | 1995-06-22 | Tokushu, Kogyo Kabushikigaisha | Electrofusion fastening apparatus |
WO1995016557A3 (en) * | 1993-12-15 | 1996-02-29 | Tokushu Kogyo Kabushikigaisha | Electrofusion fastening apparatus |
WO1997020682A1 (en) * | 1995-12-05 | 1997-06-12 | Hürner Gmbh | Method and arc welding device for automatically welding heater coil fittings |
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