EP3566816B1 - Method for tightening a bolt system - Google Patents

Description

The invention relates to a method for screwing a bolt system with a flange connection and a use of a bolt tensioning device for carrying out such a method.

Hydraulic pretensioning devices and their tightening methods are generally known from the state of the art.

DE 10 2009 043 907 A1 describes a hydraulic threaded bolt tensioning device for tightening and loosening highly loaded bolts.

EP 2 942 156 A2 describes a clamping device for stretching a threaded bolt by pulling on its threaded end section.

The methods known from the state of the art all have the disadvantage that reliable documentation of the screw connection cannot be guaranteed.

The object of the invention is to provide a method and a use of a bolt clamping device by means of which a secure clamping of flanges is ensured, which in particular is verifiable or determinable and/or documentable.

The object is achieved according to the invention by the subject matter of the independent claims.

1. a) Ermitteln eines bolzensystemtypischen Dehnverhaltens und Ermitteln eines bolzenspannvorrichtungstypischen Kompressionsverhaltens,
2. b) Ausrichten der ersten Flanschausnehmung zur zweiten Flanschausnehmung,
3. c) Einbringen eines Bolzensystems in die erste Flanschausnehmung und die zweite Flanschausnehmung,
4. d) Montieren einer Bolzenspannvorrichtung an den Bolzen auf einer Mutterseite der Flanschverbindung,
5. e) Aufbringen einer Zugkraft (Fb) auf den Bolzen, bis eine bestimmte Maximalkraft erreicht ist, und Ermitteln, bevorzugt kontinuierlich während der Aufbringung der Zugkraft (Fb), eines Längungswertes, der mit einer Bolzenlängung, einer Bolzenspannvorrichtungskompression und einer Flanschkompression der Flanschverbindung korreliert,
6. f) Nachdrehen der Mutter mit einem bestimmten Drehmoment,
7. g) Ablassen der Zugkraft, bevorzugt auf eine Rückstellkraft (Fbrück),
8. h) mindestens einmalige Wiederholung der Schritte e) bis g), und
9. i) Auswerten der ermittelten Werte für Zugkraft und Längungswert, Bestimmen der Flanschkompression und daraus Bestimmen der Flanschkompressionskraft, bevorzugt für jeden Zeitpunkt der Druckbeaufschlagung und des Druckablassens.

According to a first aspect, the invention proposes a method for screwing a bolt system to a flange connection, wherein the bolt system has at least one bolt, one nut and one abutment, wherein the flange connection has at least one first flange with at least one first flange recess and a second flange with at least one second flange recess, comprising the steps

1. a) Determination of a bolt system-typical expansion behaviour and determination of a bolt clamping device-typical compression behaviour,
2. b) aligning the first flange recess with the second flange recess,
3. c) inserting a bolt system into the first flange recess and the second flange recess,
4. d) Mounting a bolt tensioning device to the bolts on one nut side of the flange connection,
5. e) applying a tensile force (Fb) to the bolt until a certain maximum force is reached and determining, preferably continuously during the application of the tensile force (Fb), an elongation value which correlates with a bolt elongation, a bolt tensioning device compression and a flange compression of the flange connection,
6. f) Re-tightening the nut with a certain torque,
7. g) Release of the tensile force, preferably to a restoring force (Fbrück),
8. h) repeating steps e) to g) at least once, and
9. i) Evaluating the determined values for tensile force and elongation value, determining the flange compression and from this determining the flange compression force, preferably for each point in time of pressurisation and depressurisation.

A bolt system for carrying out the method mentioned comprises at least one bolt, an abutment and a nut, wherein the bolt has a bolt system-typical expansion behavior, which is determined by means of at least one identical bolt. The bolt system-typical expansion behavior of the identical bolt is preferably determined using a measuring system described below.

Preferably, the nut has an internal thread with a geometry that essentially corresponds to a geometry of the bolt that is stretched or elongated by means of a certain maximum force, which can also be referred to as a certain preload force. Preferably, the bolt is elongated up to a yield point. If the term "geometry" is used in the context of the invention in relation to internal and/or external threads, this is preferably understood to mean at least the thread pitch, the thread angle and/or the thread diameter.

Preferably, the abutment has a screw head or a lock nut. More preferably, the abutment is directly connected to the bolt material and is preferably designed as a lock nut with a polygon, preferably a hexagon. Particularly Preferably, the bolt has been stretched or elongated at least once to its yield point.

According to a second aspect, the invention proposes a use of a bolt tensioning device for carrying out a method which is designed according to the first aspect, wherein the bolt tensioning device has a housing, a tension unit, an elongation value measuring device, a tensile force determination device and a computing unit, wherein an elongation value can be measured by means of the elongation value measuring device, wherein a flange compression can be calculated from the determined elongation value by means of the computing unit.

A method for screwing a bolt system to a flange connection is proposed. The bolt system comprises at least one bolt, a nut and an abutment. In one embodiment, the abutment has a screw head that is directly connected to the bolt material. In a further, particularly preferred embodiment, the abutment has at least one lock nut. Furthermore, in one embodiment, the bolt system can have at least one, preferably two washers. It is particularly preferred that the nut has an internal nut thread that corresponds to the external thread of a pre-stressed bolt. Further preferably, a support surface of the nut is designed in such a way that no washer has to be used with it. In particular, the nut has a flat support surface that is further preferably designed at right angles to a thread axis of the nut. If the abutment is designed as a lock nut, the above statements on the nut also apply to the lock nut of the abutment. The bolt is in particular a threaded bolt whose external thread corresponds to the internal thread of the nut and, if applicable, the lock nut or whose geometry of the external thread, in particular when a maximum force is applied to the bolt, corresponds to the internal thread of the nut and, if applicable, the internal thread of the lock nut.

The flange connection has at least a first flange with at least one first flange recess and a second flange with at least one second flange recess. In particular, the flange has a plurality of flange recesses into which a plurality of bolt systems can be introduced.

For the bolt system-typical expansion behaviour to be determined in step a) and the bolt clamping device-typical A measuring system for compression behavior is shown below.

The measuring system according to the invention, which is preferably used at least for determining a typical bolt system expansion behavior, comprises a receiving device, a bolt tensioning device and a bolt elongation measuring device, wherein the receiving device has a nut side, an abutment side opposite the nut side and at least one flange recess, wherein the bolt of the bolt system can be arranged in the flange recess, wherein the bolt tensioning device can be arranged on the nut side of the receiving device and wherein a tensile force (Fb) can be applied to the bolt by means of the bolt tensioning device and wherein a bolt elongation Δb can be measured with the bolt elongation measuring device. If the term "measuring system" is used in the context of the invention, this is preferably understood to mean a test bench, field test and/or laboratory setup, etc.

The bolt system preferably has at least one bolt, one nut and one abutment. The nut of the bolt system is preferably assigned to the nut side of the receiving device and the abutment of the bolt system is assigned to the abutment side of the receiving device. In a preferred embodiment, the abutment has a further nut or a counter nut. In an alternative embodiment, the abutment is connected directly or in one piece to the bolt material and preferably has a bolt head and more preferably a screw head. The bolt preferably has a longitudinal extension with a first end region and an opposite second end region. The first end region is preferably assigned to the nut side of the receiving device and the second end region is assigned to the abutment side of the receiving device. The bolt preferably has a first contact element, preferably in the middle, on a first end face that is assigned to the first end region. More preferably, the bolt or the abutment has a second contact element, preferably in the middle, on a second end face that is assigned to the second end region. The first and/or the second contact element preferably has a tip that extends away from the bolt. More preferably, the first and/or second contact element extends away from the bolt in a dome shape. Particularly preferably, the contact element is embedded in the first and/or second end face and protrudes essentially in a dome shape from the end face. out of here.

Preferably, the flange recess completely penetrates the receiving device. More preferably, the flange recess penetrates the receiving device from the nut side to the abutment side. Preferably, the receiving device has a longitudinal extension that extends approximately at right angles to a height and a depth of the receiving device. In one embodiment, the receiving device is designed as a rectangular block. In a preferred embodiment, the receiving device has two blocks arranged on top of one another. Preferably, the two blocks arranged on top of one another are a first flange and a second flange and form a flange connection.

If the term "approximately" or "substantially" is used in relation to values or value ranges within the scope of the present invention, including the measuring system according to the invention, this is to be understood as what the person skilled in the art will regard as usual in the given context. In particular, deviations from the stated values of ±10%, preferably ±5%, more preferably ±2%, are included in the terms "approximately" and "substantially".

The longitudinal extent of the receiving device of the measuring system is preferably in a ratio of length to height and/or depth in a range from about 2 to 1 to about 10 to 1. More preferably, the length of the longitudinal extent in relation to height and/or depth is in a range from about 4 to 1 to about 8 to 1. Particularly preferably, the length of the longitudinal extent in relation to height and/or depth is about 6 to 1.

Preferably, the bolt clamping device is arranged on the receiving device after the bolt of the bolt system is arranged in the flange recess. Further preferably, the bolt clamping device can be assigned to the flange recess. Preferably, the bolt clamping device at least partially and preferably substantially completely encloses the flange recess on the nut side.

Preferably, the bolt tensioning device comprises a housing and a pulling unit. Preferably, the housing encloses the pulling unit. Further preferably, the pulling unit has a pulling unit internal thread on a gripping area. Preferably, the bolt of the bolt system is not completely arranged in the flange recess. Preferably, the bolt protrudes partially from the flange recess on the nut side and the abutment side of the receiving device. The internal thread of the traction unit is preferably designed to engage with an external thread of the bolt. Particularly preferably, the traction unit engages with the internal thread of the traction unit in the external thread of the bolt in order to lengthen it in one process step. In a subsequent process step, at least one nut is connected to the elongated threaded bolt. Particularly preferably, the nut has an internal thread, the geometry of which is preferably almost or completely designed to match the elongated external thread of the bolt.

In a preferred embodiment of the measuring system, the bolt elongation measuring device comprises a tripod and a frame, wherein the tripod has at least one bearing that supports the frame in a translational manner on the frame. In one embodiment, the tripod is designed as part of a wall. In an alternative embodiment, the tripod is arranged self-supporting on a base.

The frame of the bolt elongation measuring device preferably has a bolt elongation measuring rod and a bolt probe, the bolt elongation measuring rod being assigned to the nut side of the receiving device and the bolt probe being assigned to the abutment side of the receiving device. In a preferred embodiment in which the bolt is arranged in the flange recess, the frame of the bolt elongation measuring device with the bolt elongation measuring rod has a contact with the first end region of the bolt. More preferably, the bolt elongation measuring rod has a contact with the first end face of the bolt. Particularly preferably, the bolt elongation measuring rod has a contact with the first contact element of the bolt. Preferably, the frame of the bolt elongation measuring device with the bolt probe has a contact with the second end region of the bolt. More preferably, the bolt probe has a contact with the second end face of the bolt. Particularly preferably, the bolt probe has a contact with the second contact element of the bolt.

In an advantageous embodiment, the frame of the bolt elongation measuring device rests on the stand via a spring element. The at least one spring element serves to press the frame against the bolt. The spring element is preferably supported by the support of the frame is prestressed to a certain extent. Preferably, the frame of the bolt elongation measuring device has a constant, two-sided contact with the bolt by means of the spring element. Further preferably, at least the bolt sensor has a constant contact with the bolt by means of the spring element.

In a particularly preferred embodiment, a tensile force (Fb) can be applied to the bolt by means of the bolt tensioning device and a bolt elongation (Δb) can be measured with the bolt elongation measuring device. The bolt can preferably be lengthened by applying the tensile force (Fb). More preferably, the bolt of the bolt system is arranged in the flange recess and the abutment rests on the abutment side of the receiving device. The bolt is preferably lengthened by applying the tensile force (Fb) and is held on the abutment side by means of the abutment. The bolt can preferably be lengthened essentially in the direction of the longitudinal extent of the bolt. The bolt can preferably be lengthened essentially starting from the abutment up to essentially the first end region. More preferably, the bolt can be lengthened essentially starting from the abutment up to essentially the area in which the bolt tensioning device grips the bolt via the internal thread of the tensile unit. The bolt elongation measuring rod and the bolt probe each preferably have a contact with the bolt. Preferably, the bolt elongation measuring rod and the bolt sensor are in constant contact with the bolt during elongation. Preferably, and depending on factors such as the material and/or gaps of the receiving device, the receiving device is lifted from the abutment side towards the nut side. More preferably, and depending on factors such as the material and/or gaps, the abutment side and the nut side are compressed at least in some areas and thus pushed towards one another. When the abutment side of the receiving device is lifted, the bolt and preferably the bolt system are moved towards the bolt tensioning device. Preferably, the frame of the bolt elongation measuring device rests on the spring element of the tripod. The bolt sensor, which preferably has constant contact with the bolt, is lifted together with the bolt by means of the pre-tensioned spring element and maintains contact with it. The spring element, which releases the pre-tension, preferably lifts the entire frame of the bolt elongation measuring device. The bolt elongation measuring rod, which preferably has a constant contact with the bolt during the elongation thereof, is preferably on the first end region of the bolt, more preferably on the first end face of the bolt and particularly preferably arranged on the first contact element of the bolt. Preferably, a maximum movement of the bolt can be determined by applying the tensile force (Fb) at least on the first end face. The maximum movement of the bolt is caused by the elongation of the bolt and by the flexibility or compression of at least the receiving device. Preferably, the bolt elongation measuring rod moves with the maximum movement of the bolt. Preferably, the frame moves along a path that at least the receiving device yields by applying the tensile force (Fb). The bolt elongation (Δb) or an actual bolt elongation (Δb) can be measured using the bolt elongation measuring rod and the bolt probe of the bolt elongation measuring device. Preferably, the bolt elongation (Δb) is a result of the maximum movement of the bolt. Preferably, in the present invention in all its embodiments, the term compression is to be understood as the yielding of materials, such as that of the bolt tensioning device, the receiving device and possibly gaps that close due to a preferred increase in pressure.

The bolt tensioning device of the measuring system preferably comprises an elongation value measuring device with which an elongation value (ΔI) can be measured. The bolt tensioning device preferably measures a correlating elongation value (ΔI), wherein a distance covered by the tensile unit with the application of the tensile force (Fb) can be measured. The elongation value (ΔI) is in particular the sum of the bolt elongation (Δb) and any compressions in the measuring system. The elongation value (ΔI) is preferably the sum of the bolt elongation (Δb), a bolt tensioning device compression (Δs) and a flange compression (Δf).

Preferably, the bolt tensioning device compression (Δs) is the compression of the bolt tensioning device that occurs when at least the bolt tensioning device lengthens the bolt of the bolt system with the tensile force (Fb). Preferably, when the tensile force (Fb) is applied, the bolt tensioning device is pressed in the direction of the receiving device on its nut side, while the tension rod lengthens the bolt in the opposite direction.

In a particularly preferred embodiment of the measuring system, the receiving device is designed as a flange connection. Preferably, the receiving device or the flange connection comprises at least the first flange and the second flange, wherein the first flange has at least the nut side, a first contact side and at least one first flange recess and wherein the second flange has at least a second Contact side and the abutment side and at least one second flange recess, wherein the first contact side and the second contact side are assigned to one another and wherein the first flange recess and the second flange recess are assigned to one another. Preferably, the bolt of the bolt system can be arranged in the first and the second flange recess.

It may be that the first flange and/or the second flange are not completely flat and have a gap. More preferably, the first flange and/or the second flange have unevenness and therefore a gap at least in the area of the first and second contact side. Even under these conditions, an accurate determination of the flange compression force is possible with the method according to the invention and the bolt tensioning device. In one embodiment, the receiving device of the measuring system comprises at least one spacer element, wherein the spacer element is arranged between the first flange and the second flange and the first contact side is spaced from the second contact side. The spacer element preferably simulates the unevenness of the receiving device.

Preferably, at least one flange compression measuring device is arranged in and/or on the receiving device, which comprises a flange compression measuring rod. The flange compression measuring rod is arranged at least partially in a flange compression measuring recess of the receiving device. Preferably, the flange compression recess completely penetrates the receiving device, starting from the abutment side to the nut side. Preferably, the flange compression (Δf) can be measured with the flange compression measuring rod. In one embodiment, the flange compression recess on the nut side of the receiving device borders on an area in which the bolt tensioning device is arranged on the nut side. Preferably, the bolt tensioning device, more preferably with the housing, rests on the flange compression recess on the nut side. More preferably, the bolt tensioning device covers the flange compression recess on the nut side. The flange compression measuring rod, which reaches through the flange compression recess, preferably has a contact with the bolt tensioning device. Preferably, the receiving device has a flange compression as soon as the bolt tensioning device applies the tensile force (Fb). Preferably, the flange compression measuring device is arranged in the flange compression recess on the Abutment side of the receiving device. The flange compression measuring device measures the flange compression (Δf). Preferably, the flange compression measuring device measures the flange compression (Δf) on the abutment side by means of the length of the flange compression measuring rod that emerges from the flange compression recess when the tensile force (Fb) is applied.

In a preferred embodiment, a first and a second flange compression measuring device are provided. Preferably, the first and the second flange compression measuring device are arranged in and/or on the receiving device and comprise a first and a second flange compression measuring rod. Preferably, the first flange compression measuring device comprises the first flange compression measuring rod and the second flange compression measuring device comprises the second flange compression measuring rod. Preferably, a first flange compression (Δf1) can be measured with the first flange compression measuring rod. More preferably, a second flange compression (Δf2) can be measured with the second flange compression measuring rod. Preferably, the first flange compression measuring rod is arranged at least partially in a first flange compression measuring recess of the receiving device. More preferably, the second flange compression measuring rod is arranged at least partially in a second flange compression measuring recess of the receiving device. Particularly preferably, the first flange compression recess is the flange compression recess that borders the bolt tensioning device on the nut side and more preferably the housing. Preferably, the first flange compression gauge, which extends through the first flange compression recess, has a contact with the bolt tensioning device. Preferably, the first flange compression gauge measures a flange compression (Δf1) under the bolt tensioning device.

In an embodiment in which the bolt system has a nut on the nut side, the second flange compression recess is preferably arranged directly or indirectly under the nut. Preferably, the second flange compression recess is the flange compression recess that borders the nut of the bolt system on the nut side. Preferably, the second flange compression measuring rod, which reaches through the second flange compression recess, has direct or indirect contact with the nut of the bolt system. Preferably, the second flange compression measuring rod measures a flange compression (Δf2) under the nut of the bolt system.

Preferably, any measurement variables such as at least the elongation value (ΔI), bolt elongation (Δb), flange compression (Δf) and bolt clamping device compression (Δs) can be measured and/or determined with the measuring system. Particularly preferably, the measurement variables such as the elongation value (ΔI), the bolt elongation (Δb) and the flange compression (Δf) can be measured with the measuring system and the bolt clamping device compression (Δs) can be determined. In particular, the measuring system is designed so that the bolt clamping device compression (Δs) can be determined as follows: Δs = Δl - Δb - Δf. The compression behavior typical of the bolt clamping device can preferably be taken from the documentation of the bolt clamping device compression (Δs) in relation to the increasing tensile force (Fb).

1. a) Einbringen des Bolzensystems in zumindest eine Flanschausnehmung der Aufnahmevorrichtung,
2. b) Aufbringen einer zunehmenden Zugkraft (Fb) mit einer Bolzenspannvorrichtung auf den Bolzen,
3. c) Messen einer Bolzenlängung (Δb), bevorzugt kontinuierlich während der Aufbringung einer Zugkraft, und
4. d) in Relation setzten der Zugkraft (Fb) zur Bolzenlängung (Δb) und Ermitteln eines bolzensystemtypischen Dehnverhaltens.

A preferred measuring method at least for determining a bolt system-typical expansion behavior of a bolt system, with a measuring system as described above, wherein the bolt system has at least one bolt, one nut and one abutment, comprises the steps

1. a) Inserting the bolt system into at least one flange recess of the receiving device,
2. b) applying an increasing tensile force (Fb) to the bolt using a bolt tensioning device,
3. c) measuring a bolt elongation (Δb), preferably continuously during the application of a tensile force, and
4. d) relating the tensile force (Fb) to the bolt elongation (Δb) and determining a bolt system-typical elongation behavior.

The bolt tensioning device, which is preferably arranged on a nut side of the receiving device, engages an external thread of the bolt via an internal thread of a pulling unit. The increasing tensile force (Fb) preferably does not have a jerky force on the bolt. The bolt is preferably stressed and elongated with a continuously increasing tensile force (Fb).

In order to measure the bolt elongation (Δb), as described in step c), the measuring system preferably comprises a bolt elongation measuring device. The bolt elongation measuring device preferably has a bolt elongation measuring rod and a bolt probe, which contact the bolt at one end area each. The bolt elongation (Δb) describes a difference length of an elongated bolt to an unstretched bolt. Preferably, the bolt elongation (Δb) is measured continuously during the increase of the tensile force (Fb).

To determine the bolt system-typical elongation behavior mentioned in step d), the tensile force (Fb) is related to the bolt elongation (Δb). Preferably, the increasing tensile force (Fb) and the bolt elongation (Δb) are measured continuously. Preferably, the determined values are shown in a stress-strain diagram. Preferably, the values in relation to one another have a gradient that particularly preferably corresponds to the Hooke's straight line. In order to be able to determine a maximum force (Fmax) and thus a preferred yield point (RE), the area and more preferably the point at which the gradient no longer follows or corresponds to the Hooke's straight line is preferably important. Particularly preferably, a 0.2% yield point (Rp0.2) is used to determine the yield point (RE) and the maximum force (Fmax). Preferably, the 0.2% yield point represents the stress at which a permanent elongation of 0.2% is achieved.

In an exemplary embodiment where the bolt system comprises an M48 bolt and an M48 nut, the maximum force (Fmax) is approximately 1326 kN, which corresponds to approximately 1306 bar for the bolt tensioning system used.

• e) Anziehen der Mutter des Bolzensystems mit einem bestimmten Drehmoment und
• f) Ablassen der Zugkraft (Fb).

More preferably, the measuring method comprises the steps

• e) Tightening the nut of the bolt system with a certain torque and
• f) Releasing the pulling force (Fb).

This creates a residual force (Fbrück) in the bolt system. The nut is preferably tightened onto the bolt of the bolt system. Preferably, the bolt has been elongated before the nut is tightened onto the bolt and the tensile force (Fb) continues to act on the bolt. The nut is preferably tightened on the nut side of the receiving device. In one embodiment, the nut is an HV nut and in an alternative embodiment, the nut is a TTG (TTG=Tension Thread Geometry) nut, which has an internal nut thread that essentially corresponds to the external thread of the elongated bolt. The nut is preferably tightened using a torque with a value in a range of about 20 Nm to about 100 Nm, more preferably with a value in a range of about 30 Nm to about 70 Nm and particularly preferably with a value of about 50 Nm.

The restoring force (Fbrück) is lower than the tensile force (Fb). It describes the force that remains in the screw connection of the bolt system with a flange connection after the bolt has been elongated or stretched, if no tensile force (Fb) acts on the screw connection.

Preferably, steps b) to f) are repeated at least once. Preferably, steps b) to f) are repeated once. More preferably, steps b) to f) are repeated twice. More preferably, steps b) to f) are repeated three times. More preferably, steps b) to f) are repeated four times. Particularly preferably, steps b) to f) are repeated five times. However, more frequent repetition is also possible.

For example, in an embodiment with an M48 HV nut and a flange thickness of 200 mm, a flange compression force (Ff) under the nut after performing steps b) to f) once (without repetition) is approximately 48% of the previously applied maximum force (Fmax) of 1326 kN. Furthermore, the flange compression force (Ff) under the nut after performing steps b) to f) six times (repeating five times) is approximately 55% of the previously applied maximum force (Fmax) of 1326 kN.

In another embodiment with a HV screw and a TTG nut, for example, the flange compression force (Ff) under the nut after performing steps b) to f) once (without repeating them) is approximately 79% of the previously applied maximum force (Fmax) of 1326 kN. Furthermore, the flange compression force (Ff) under the nut after performing steps b) to f) six times (repeating them five times) is approximately 88% of the previously applied maximum force (Fmax) of 1326 kN.

Preferably, the bolt tensioning device of the measuring system comprises an elongation value measuring device with which an elongation value (ΔI) is measured that correlates with at least the bolt elongation (Δb), a flange compression (Δf) and a bolt tensioning device compression (Δs). Preferably, the elongation value (ΔI) is the sum of the bolt elongation (Δb), the bolt tensioning device compression (Δs) and the flange compression (Δf).

The measuring system preferably comprises at least one flange compression measuring device. The flange compression (Δf) is preferably measured using the flange compression measuring device.

The flange compression measuring device preferably comprises a flange compression measuring rod. The flange compression measuring rod is arranged at least partially in a flange compression measuring recess of the receiving device and has a contact with the bolt tensioning device and/or the nut. Preferably, a compression force can be determined at least via the flange compression (Δf).

The measuring system further preferably comprises at least a first flange compression measuring device and a second flange compression measuring device. Preferably, the first flange compression measuring device is used to measure a first flange compression (Δf1) of the receiving device under the bolt tensioning device and the second flange compression measuring device is used to measure a second flange compression (Δf2) of the receiving device under the nut of the bolt system. Preferably, a compression force under the bolt tensioning device (Fs) can be determined at least via the first flange compression (Δf1). Further preferably, a compression force under the nut (Fm) can be determined at least via the second flange compression (Δf2).

Preferably, the bolt tensioning device compression (Δs) of a bolt tensioning device is determined using the bolt elongation (Δb), the flange compression (Δf) and the elongation value (ΔI). Preferably, the compression behavior typical of the bolt tensioning device can be determined from the documentation of the bolt tensioning device compression (Δs) in relation to the increasing tensile force (Fb).

1. a) Ermitteln eines bolzensystemtypischen Dehnverhaltens und Ermitteln eines bolzenspannvorrichtungstypischen Kompressionsverhaltens,
2. b) Ausrichten der ersten Flanschausnehmung zur zweiten Flanschausnehmung,
3. c) Einbringung des Bolzensystems in die erste Flanschausnehmung und die zweite
4. d) Flanschausnehmung,
5. e) Montieren einer Bolzenspannvorrichtung an den Bolzen auf einer Mutterseite der Flanschverbindung,
6. f) Aufbringen einer Zugkraft auf den Bolzen, bis eine bestimmte Maximalkraft erreicht ist, und Ermitteln eines Längungswertes, der mit einer Bolzenlängung einer Bolzenspannvorrichtungskompression und einer Flanschkompression der Flanschverbindung korreliert,
7. g) Nachdrehen der Mutter mit einem bestimmten Drehmoment,
8. h) Ablassen der Zugkraft (Fb),
9. i) mindestens einmalige Wiederholung der Schritte e) bis g), und

The method according to the invention for screwing a bolt system comprises, as mentioned above, the steps

1. a) Determination of a bolt system-typical expansion behaviour and determination of a bolt clamping device-typical compression behaviour,
2. b) aligning the first flange recess with the second flange recess,
3. c) Insertion of the bolt system into the first flange recess and the second
4. d) flange recess,
5. e) Mounting a bolt tensioning device on the bolts on one nut side of the flange connection,
6. f) Applying a tensile force to the bolt until a certain maximum force is reached and determining an elongation value which corresponds to a bolt elongation of a bolt tensioning device compression and a flange compression of the flange connection,
7. g) re-tightening the nut with a certain torque,
8. h) release of the tensile force (Fb),
9. (i) repeating steps (e) to (g) at least once, and

Evaluating the determined values for tensile force and elongation value, determining the flange compression and therefrom determining the flange compression force, in particular during the execution of the method, preferably for each time of pressurization and pressure release.

In step a), an elongation behavior typical of the bolt system is determined. In particular, the elongation behavior is determined by means of a tensile test, in which a stress-strain diagram and/or an elongation of the bolt is preferably determined as a function of the tensile force applied to it, for example with the measuring system according to the invention described above and the measuring method described there. When determining the elongation behavior typical of the bolt system, the bolt is preferably stretched once or several times, in particular twice, more preferably three times, more preferably four times, more preferably five times or more often with an increasing force up to a maximum force and then relaxed again. In one embodiment, the maximum force corresponds to a force that stretches the bolt to its yield point. The bolt is preferably stretched several times up to its yield point and the elongation of the bolt is determined as a function of the force applied to it. It is assumed that a bolt from a batch of bolts, more preferably a similarly manufactured bolt, in particular with the same dimensions, thread, thread pitch, alloy and length, behaves identically to the tested bolt. In this respect, a bolt with the same dimensions and essentially the same alloy as the tested bolt exhibits the tensile behavior typical of the bolt system.

Furthermore, a compression behavior typical of a bolt clamping device is determined, for example with the measuring system according to the invention described above and the measuring method described therein, whereby a bolt clamping device is tested or used which is essentially the same as the bolt clamping device used. In this case, a bolt is clamped using the bolt clamping device and the Compression behavior is determined. Preferably, the compression behavior typical of a bolt clamping device is determined simultaneously with the expansion behavior typical of a bolt system by introducing a bolt system into a receiving device and/or a flange connection and using the bolt clamping device to tighten it to the maximum force, in particular to the force that brings the bolt to the yield point. As explained above with regard to the measuring system according to the invention and the measuring method that can be carried out with it, both the compression of the bolt clamping device and the elongation of the bolt are determined. If these are known, an identical bolt that has the expansion behavior typical of a bolt system and a bolt clamping device that has the compression behavior typical of a bolt clamping device can be used for the proposed method.

In step b), the first flange recess is aligned with the second flange recess. Preferably, all flange recesses of the first flange are aligned with all flange recesses of the second flange.

In step c), the bolt system is introduced into the first flange recess and the second flange recess, which are preferably aligned with one another. In a design in which the abutment has a screw head that is materially connected to the bolt, the bolt is guided into the flange recess essentially until the abutment rests on the second flange. As a result, the nut is screwed onto the bolt on the side opposite the abutment so that its bearing surface rests on the nut side of the first flange. The nut is then tightened with a certain torque. In particular, it is important to ensure that the nut is screwed onto the bolt in such a way that the bolt protrudes between a nut-side end of the bolt and the nut to a minimum length that is necessary for screwing on the bolt tensioning device.

• Aufschrauben der Mutter auf dem Bolzen,
• Einführung des Bolzens in die Flanschausnehmung, im Wesentlichen bis zur Anlage der Mutter an den ersten Flansch,
• Aufschrauben des Widerlagers auf den Bolzen und
• Anziehen der Mutter auf dem Widerlager mit einem bestimmten Drehmoment.

In a further embodiment, it is provided that the introduction of the bolt system into the flange recess comprises the steps:

• Screwing the nut onto the bolt,
• Insertion of the bolt into the flange recess, essentially until the nut rests on the first flange,
• Screwing the abutment onto the bolt and
• Tightening the nut on the abutment with a specific torque.

In particular, this design provides that the abutment has a lock nut.

In step d), a bolt tensioning device is mounted on the bolt on a nut side of the flange connection. The bolt tensioning device is in particular screwed onto the bolt in such a way that at least an above-mentioned projection of the bolt over the nut is gripped by a tension unit of the bolt tensioning device, in particular a tension unit internal thread. The bolt tensioning device is further preferably supported by its housing on the flange.

During the following steps, as mentioned in step e), a tensile force is applied to the bolt and an elongation value is determined which correlates with a bolt elongation, a bolt clamping device compression and a flange compression of the flange connection. The applied tensile force is in particular the force that is applied to the bolt by means of the bolt clamping device. The bolt clamping device functions in particular hydraulically, with the pulling unit of the bolt clamping device being moved by means of hydraulic pressure. The tensile force is calculated based on the pressure applied to the pulling unit, in particular hydraulic pressure. The tensile force is further preferably characterized by the pressure applied to the pulling unit times the piston area. The bolt clamping device preferably measures the elongation value, with a distance traveled by the pulling unit relative to the housing being measured. The values of the elongation value and the tensile force are preferably related to one another so that they can be represented graphically, for example. The elongation value is in particular the sum of the bolt elongation, the bolt clamping device compression and the flange compression. Preferably, the bolt elongation, the bolt clamping device compression and the flange compression have a positive sign for the sum.

In step e), the tensile force is then applied to the bolt until a certain maximum force (Fmax) is reached. Preferably, the tensile force is increased continuously or step by step until the maximum force is reached. In a preferred embodiment, the maximum force corresponds to a (tensile) force that causes the bolt to elongate to a bolt system-typical Yield limit (RE), also called yield point. The maximum force (Fmax) can also be lower or higher than the tensile force required to reach the yield point (RE). In a further embodiment, the maximum force is a force that causes the bolt to be elongated by about 80% to about 120% of the typical bolt yield point, preferably about 90% to about 120%, more preferably about 95% to about 120% of the typical bolt yield point. The bolt is preferably stretched or elongated at least once, whether in the first step e) or in the at least one repetition after step h), up to its yield point or yield point. The maximum force can also be above the yield point. Applying a certain maximum force up to or slightly above the yield point causes plastic deformations in the material of the bolt. These can no longer be detected after two to four repetitions of the stretching or elongation of the bolt. Preferably, when the elongation is repeated at least once, a maximum force is applied that corresponds to that of the first elongation and is preferably close to or slightly above the yield point, preferably in a range of about 95% to about 110%.

In step f), the nut is retightened with a specific torque. In one embodiment, the nut is retightened by hand. Preferably, the nut is screwed in the direction of the first flange or the flange connection and tightened with a specific torque. Preferably, the specific torque is about 10 Nm to about 100 Nm, preferably about 25 Nm to about 60 Nm, more preferably about 50 Nm.

In step g), the tensile force is set to a restoring force of approximately 0 N. In particular, the flange connection below the nut experiences a flange compression force, which presses the two flanges together.

In step h), steps e) to g) are repeated at least once and the tensile force is repeatedly applied to the bolt.

In step i), the values for tensile force and elongation value are evaluated and the flange compression and from this the flange compression force are determined. The flange compression force corresponds to the tensile force applied to the bolt to tighten the nut to loosen or lift off the flange, or the force at which the nut rests on the flange without force being introduced into the flange. In particular, the flange compression force can be determined by determining the slope of the measured Hooke's line of the elongation value or the bolt elongation. The slope of the ratio of force to bolt elongation is steeper up to the point at which the nut lifts off the flange.

The evaluation can preferably be carried out while the method is being carried out, so that the flange compression force and the flange compression are known after the screwing method according to the invention has been completed. In particular, it is provided that the flange compression (Δf) is determined from the elongation value (Δl) as follows: Δf = Δl - Δb - Δs, where (Δb) is the bolt elongation and (Δs) is the bolt clamping device compression. Since the bolt elongation (Δb) is known as is typical for bolt systems and the bolt clamping device compression is known for all tensile forces as is typical for bolt clamping devices and the elongation value corresponds to the measured value, the flange compression can be calculated as described above.

The proposed method can advantageously be used to securely press the exposed flanges, particularly if they have tolerances that can lead to gaps between the flanges. In the wind turbine sector in particular, very large flange connections are used which, unlike in normal mechanical engineering, cannot be manufactured and/or calculated precisely. This means that when the bolt is tightened, gaps between the flanges are closed first and only then can a force build up to compress the flanges on top of each other. It is known from the prior art to tighten the bolts with a certain force, for example around 70% to around 80% of the yield strength, and to assume that the force used to tighten the bolt corresponds approximately to the flange compression force.

With the proposed system, it is now possible to determine and document both the flange compression and the deformation of the flange under the nut of the bolt system as well as the flange compression force, i.e. the force with which the bolt system presses the two flanges together. Determining the expansion behavior typical of the bolt system and the compression behavior typical of the bolt device, in particular with the measuring system according to the invention described above and the measuring method described therein, has the advantage that at least the bolts and bolt clamping devices of one batch, more preferably of one product series, more preferably of one product series, can be used to carry out the method. Since the behavior of the bolts or the bolt system and the bolt clamping device for the respective tensile force is known, especially when the bolt is repeatedly tightened and released, clear conclusions can be drawn about the behavior of the flanges.

In one embodiment, steps e) to g) are repeated at least once. In particular, steps e) to g) are repeated with a maximum force that guides the bolt to its yield point typical of the bolt system. This has the advantage that settling phenomena occur within the structure of the bolt, which prevent aging or creep due to aging and are consequently anticipated in the flange connection. As a result, the bolt remains in the flange connection with essentially the same tension even after a considerable period of time, so that costly retightening of at least one nut of the bolt system can be omitted.

In a further embodiment, it is provided that before step h) a tensile force is applied to the bolt, in particular until the maximum force is reached, the nut is loosened, the tensile force is set to zero and then the tensile force is set to a target force (F _target ), which is preferably smaller than the maximum force. This procedure is particularly advantageous if the maximum force corresponds to the force at which the yield point of the bolt is reached in order to clamp the bolt system to the flange connection with a lower clamping force. This has the advantage that with large changing loads the bolt is not loaded beyond its yield point. In particular, it is provided that an elongation value for determining the flange compression is determined at a tensile force that corresponds to a calibration force. Preferably, the calibration force is about 1% to about 5%, more preferably about 1% to about 3%, more preferably about 2% to about 3% of the maximum force. In one embodiment, the calibration force is approximately 10 kN to approximately 100 kN, more preferably approximately 20 kN to approximately 50 kN, more preferably approximately 40 kN. This has the advantage that the bolt clamping device is securely clamped and, more preferably, the gaps and openings typical of bolt clamping devices are avoided. closed in order to produce an accurate measurement. It is further preferred that values are used for measurements which are measured during pressure build-up and preferably not during pressure reduction.

In a further embodiment, it is provided that the flange compression is determined from the elongation value as follows: flange compression = elongation value - bolt elongation - bolt clamping device compression, wherein the bolt elongation is known from the bolt system-typical elongation behavior for each tensile force and the bolt clamping device compression is known from the bolt clamping device-typical compression behavior for each tensile force.

In a further embodiment, the application of tensile force to the bolt is interrupted if the elongation value indicates that the bolt system is behaving in a way that is not typical for a bolt system, in particular that the bolt system is stretching unusually. If the yield point of the guided bolt is determined to be at a force that does not correspond to the yield point force that is typical for the bolt system, this indicates that the bolt is faulty or incorrect. In order to avoid damage to the flange connection, the surrounding equipment or the bolt tensioning device and in particular to avoid injuries to people in the vicinity of the bolt tensioning device, in one embodiment, when a yield point of the bolt system that is not typical for a bolt system is detected, the pressure is released in a controlled manner and an error message is issued so that the bolt can be replaced.

An exemplary embodiment of the method for screwing a bolt system provides that, prior to screwing, at least one test bolt is tested for a bolt system-typical expansion behavior, preferably determined using the above-described measuring system according to the invention and the measuring method described therein. Furthermore, a bolt clamping device-typical compression behavior of the bolt clamping device is determined, preferably determined using the above-described measuring system according to the invention and the measuring method described therein. This can be done using the bolt clamping device itself or using a product of the same construction. The flanges are then aligned with one another so that the bolt systems can be inserted into the flange recesses. For this purpose, in one embodiment provided that the bolts are already placed on the first flange in such a way that they do not protrude downwards from the flange. In particular in the case of a wind turbine device, the bolt and the first flange can be placed on the second flange at the same time using a crane. The flange recesses of the first and second flanges are aligned with one another, and then the bolt systems are inserted into the first flange recess and the second flange recess. The bolt tensioning device is mounted on the nut side of the flange connection, that is the side of the flange connection on which the nut of the bolt system is arranged. In particular, the bolt tensioning device is screwed onto the bolt. A tensile force is then applied to the bolt, which is preferably increased to a maximum force, which preferably leads to elongation typical of the bolt system up to the yield point of the bolt. The nut is then tightened with a certain torque so that it is tightened with preferably 50 Nm. The tensile force is brought to the restoring force of approximately 0 N so that the nut of the bolt system and the flange connection are loaded with the maximum force that can be applied with the bolt system. The tensile force is then applied to the bolt again and this is preferably increased to the maximum force. The nut is then loosened and the force is set back to the restoring force. A tensile force is again applied to the bolt so that it is stretched to a required target force, which is preferably between 70% and 100% of the maximum force. The nut is then tightened again with a certain torque of preferably 50 Nm and the tensile force is reset to the restoring force. During the entire process, the tensile force on the bolt and an elongation value, which is the sum of the bolt elongation, the bolt clamping device compression and the flange compression, are determined. The values determined with a calibration force of preferably around 40 kN are saved and documented. Furthermore, the tensile force when the nut is loosened from the flange connection is documented and saved as the flange compression force. All other values recorded during the process are also saved as documentation, particularly graphically.

FIG. 1A

eine erste Ausführungsform eines Bolzensystems und eine Flanschverbindung in einer seitlichen Schnittansicht;

FIG. 2B

eine zweite Ausführungsform eines Bolzensystems und eine Flanschverbindung in einer seitlichen Schnittansicht;

FIG. 3C

eine dritte Ausführungsform eines Bolzensystems und eine Flanschverbindung in einer seitlichen Schnittansicht;

FIG. 4

eine vierte Ausführungsform eines Bolzensystems ohne Mutter, eine Flanschverbindung und eine Bolzenspannvorrichtung;

FIG. 5

eine Mehrzahl von Dehnverhalten eines Messverfahrens mit einem Messsystem;

FIG. 6

ein bolzensystemtypisches Dehnverhalten eines HV Bolzens und einer HV Mutter;

FIG. 7

ein bolzensystemtypisches Dehnverhalten eines Stud-Bolzens und zwei TTG Muttern;

FIG. 8

eine Ausführungsform eines Bolzens und ein Widerlager eines Bolzensystems;

FIG. 9

eine Ausführungsform eines Messsystems in einer Vorderansicht;

FIG. 10

das Messsystem aus FIG. 7 in einer Seitenansicht;

FIG. 11

eine Bolzenspannvorrichtung und eine Aufnahmevorrichtung in einer Seitenansicht; und

FIG. 12

ein Bolzensystem, die Bolzenspannvorrichtung und die Aufnahmevorrichtung aus FIG. 9 in einer seitlichen Schnittansicht.

Further advantageous embodiments can be seen from the following drawings. Identical parts or parts with the same function can have the same reference numerals. They show:

FIG. 1A

a first embodiment of a bolt system and a flange connection in a side sectional view;

FIG. 2B

a second embodiment of a bolt system and a flange connection in a side sectional view;

FIG. 3C

a third embodiment of a bolt system and a flange connection in a side sectional view;

FIG. 4

a fourth embodiment of a bolt system without nut, a flange connection and a bolt tensioning device;

FIG. 5

a plurality of strain behaviors of a measuring method with a measuring system;

FIG. 6

a bolt system-typical expansion behavior of a HV bolt and a HV nut;

FIG. 7

a bolt system-typical expansion behavior of a stud bolt and two TTG nuts;

FIG. 8

an embodiment of a bolt and an abutment of a bolt system;

FIG. 9

an embodiment of a measuring system in a front view;

FIG. 10

the measuring system FIG. 7 in a side view;

FIG. 11

a bolt clamping device and a receiving device in a side view; and

FIG. 12

a bolt system, the bolt tensioning device and the receiving device made of FIG. 9 in a lateral sectional view.

FIG. 1A shows a first embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 has a bolt 20, a nut 12 and an abutment 32. The bolt 20 is designed as a HV bolt. Furthermore, the nut 12 is designed as a HV nut and the abutment 32 has a screw head that is directly connected to the bolt material. A washer (not specified in more detail) is arranged under the abutment 32. The flange connection 81 has a first flange 82 with a first flange recess 84 and a flange surface 86 and a second flange 92 with a second flange recess 94. The bolt 20 of the bolt system 10 is inserted into the first flange recess 84 and the second flange recess 94.

FIG. 1B shows a second embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 has a bolt 20, a nut 12 and an abutment 32. The bolt 20 is designed as an HV bolt. Furthermore, the nut 12 is designed as a TTG nut and the abutment 32 has a screw head that is directly connected to the bolt material. A washer (not designated in more detail) is arranged under the abutment 32. The TTG nut 12 has an internal nut thread that corresponds to an external thread of an elongated bolt 20. The flange connection 81 has a first flange 82 with a first flange recess 84 and a flange surface 86 and a second flange 92 with a second flange recess 94. The bolt 20 of the bolt system 10 is inserted into the first flange recess 84 and the second flange recess 94.

FIG. 1C shows a third embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 has a bolt 20, a nut 12 and an abutment 32. The bolt 20 is designed as a stud bolt which has an external thread on two end regions of the bolt 20. Furthermore, the nut 12 is designed as a TTG nut and the abutment 32 is also designed as a TTG nut. The flange connection 81 has a first flange 82 with a first flange recess 84 and a flange surface 86 and a second flange 92 with a second flange recess 94. The bolt 20 of the bolt system 10 is inserted into the first flange recess 84 and the second flange recess 94.

FIG. 2 shows a fourth embodiment of a bolt system 10, but without nut 12, a flange connection 81 and a bolt tensioning device 200. The bolt 20 of the bolt system 10 is inserted into a first and a second flange recess 84, 94 of the flange connection 81. On a flange surface 86 of a nut side 83 of the first flange 82, the bolt tensioning device 200 is arranged with a support surface 204 on the first flange 82. The bolt tensioning device 200 comprises a housing 202 and a Tension unit 210. The housing 202 encloses the tension unit 210 on essentially three sides. The housing 202 has an open side in the direction of the first flange 82, via which the tension unit 210 grips the bolt 20 of the bolt system 10.

FIG. 3 shows a plurality of strain behavior of a measuring method with a measuring system 100. In FIG. 3 a diagram is illustrated which shows a tensile force on the bolt Fb on the ordinate (y-axis) and elongations and compressions on the abscissa (x-axis), all with a positive sign. For the measuring method, the measuring system 100 comprises an M48 stud bolt 20 and two M48 TTG nuts 12, 32. The stud bolt 20 is a bolt which has a thread on two end areas into which the TTG nuts 12, 32 can grip. To carry out the measuring method, the tensile force Fb is constantly increased until it has a maximum force Fmax of approximately 1326 kN. A compression behavior of the flange compression 54, a bolt-typical expansion behavior 50, a bolt clamping device-typical compression behavior 52 and a measured elongation behavior 56 are shown. For the compression behavior of the flange compression 54, a flange compression Δf is seen in relation to the tensile force Fb. Furthermore, for the bolt-typical expansion behavior 50, a bolt elongation Δb is seen in relation to the tensile force Fb. Furthermore, for the bolt clamping device-typical compression behavior 52, a bolt clamping device compression Δs is seen in relation to the tensile force Fb and for the measured elongation behavior 56, an elongation value Δl is seen in relation to the tensile force Fb.

As soon as the maximum force Fmax of approximately 1326 kN is reached, one of the TTG nuts 12 is tightened onto the bolt 20 with a torque of approximately 50 Nm. The tensile force is then reduced to a calibration force Fk of approximately 40 kN (see FIGS. 4 and 5 ).

FIG. 4 shows a bolt system-typical expansion behavior of an M48 HV bolt and an M48 HV nut. FIG. 4 shows a diagram that shows a tensile force on the bolt Fb on the ordinate (y-axis) and the bolt elongation Δb on the abscissa (x-axis). In a first step, a tensile force Fb is applied to the bolt 20 until a maximum force Fmax of about 1326 kN is reached. The tensile force Fb is increased steadily until the maximum force Fmax is reached. The maximum force Fmax corresponds to a force that is necessary to elongate the bolt 20 up to a yield strength RE typical of the bolt system. In a second step the nut 12 is tightened with a specific torque of about 50 Nm. The nut 12 is screwed in the direction of the flange connection 81 and tightened with the specific torque. In a third step, the tensile force Fb is set to a calibration force Fk. Preferably, the calibration force Fk is in a range of about 40 kN for this M48 bolt system. In particular, the flange connection 81 below the nut 12 experiences a flange compression force Δf ( FIG. 4 not visible), which presses the two flanges 82, 92 together. In a fourth step, the tensile force Fb is repeatedly applied to the bolt 20 until it exceeds at least a flange compression force Δf. The flange compression force Δf corresponds in particular to the tensile force Fb that is applied to the bolt 20 in order to lift the nut 12 off the flange 82 or the force at which the nut 12 rests on the flange 82 without force being introduced into the flange 82. In particular, the flange compression force Δf can be determined by determining the slope of the Hooke's line of the bolt elongation Δb. The slope of the ratio of force Fb to bolt elongation Δb is steeper up to the point where the nut 12 lifts off the flange 82.

FIG. 5 shows a bolt system-typical expansion behavior of an M48 stud bolt and two M48 TTG nuts. In FIG. 5 A diagram is shown which shows a tensile force on the bolt Fb on the ordinate (y-axis) and the bolt elongation Δb on the abscissa (x-axis). The principle or the procedure of the method does not differ from that of the FIG. 4 In particular, the diagram from FIG. 5 that after tightening the TTG nut 12 on the bolt 20 with a certain torque and removing the tensile force Fb, the bolt elongation Δb does not decrease as significantly as in FIG. 4 clarified.

FIG. 6 shows an embodiment of a bolt 20 and an abutment 32 of a bolt system 10. The abutment 32 has a screw head and is directly connected to the bolt 20. The bolt 20 is designed as an HV bolt, for example. The bolt 20 has a first end face 23 and the abutment 32 has a second end face 33. The bolt 20 has a first contact element 21 in the middle of the first end face 23. The abutment 32 also has a second contact element 31 on the second end face 33. The first and second contact elements 21, 31 are embedded in the first and second end faces of the bolt 20 and the abutment 32 and protrude essentially in a dome shape from the end faces 23, 33. The bolt 20 and the abutment 32 have a length 24, which is the length of the bolt 20 and the abutment 32 in the direction of a longitudinal extension of the bolt 20. Furthermore, the bolt 20 has an external thread 26 starting from the first end face 23, which is formed on the bolt 20 in the direction of the abutment 32. In addition to the length 24, FIG. 6 a bolt elongation Δb, which is the difference in length of an elongated bolt ( FIG. 6 not to be taken) to an un-lengthened bolt 20.

FIG. 7 shows an embodiment of a measuring system 100 in a front view. The measuring system 100 comprises a receiving device 80, a bolt tensioning device 200 and a bolt elongation measuring device 102. The bolt elongation measuring device is used to measure a bolt elongation Δb. The receiving device 80 has a first flange 82 and a second flange 92 and forms a flange connection 81. The receiving device 80 or the flange connection 81 has the first flange 82 and the second flange 92, the first flange 82 having a nut side 83 with a flange surface 86 and a first contact side 85 and the second flange 92 having a second contact side 95 and an abutment side 93. The first contact side 85 and the second contact side 95 are assigned to one another. Furthermore, the bolt tensioning device 200 is arranged on a flange surface 86 of the nut side 83 of the receiving device 80 or the flange connection 81. The receiving device 80 is connected to two spacing elements 140 on the underside or abutment side. The second flange 92 rests with the abutment side 93 on the spacing elements 140 at two end regions of a longitudinal extension of the receiving device 80.

The bolt elongation measuring device 102 comprises a tripod 104 and a frame 110, wherein the tripod 104 has at least one bearing 105 (see FIG. 8 ) which supports the frame 110 in a translational manner. The tripod 104 is arranged as a supporting element on a base. A first and a second flange compression measuring device 120, 130 are arranged at least on the abutment side 93. A first flange compression Δf1 is measured with the first flange compression measuring device 120 and a second flange compression Δf2 is measured with the second flange compression measuring device 130.

FIG. 8 the measuring system shows 100 FIG. 7 in a side view. The measuring system 100 comprises the receiving device 80, the bolt clamping device 200 and the bolt elongation measuring device 102. The receiving device 80 has the first flange 82 and the second flange 92 and forms the flange connection 81. The first flange 82 has the nut side 83 with a flange surface 86 and the first contact side 85 and the second flange 92 has the second contact side 95 and the abutment side 93. Furthermore, FIG. 8 that the second flange 92 rests on at least one of the two spacing elements 140. The bolt elongation measuring device 102 comprises the tripod 104 and the frame 110, wherein the tripod 104 has two bearings 105 (see FIG. 8 ) which support the frame 110 in a translational manner. The frame 110 of the bolt elongation measuring device 102 rests on the stand 104 via a spring element 108. The spring element 108 is pre-tensioned to a certain extent by the support of the frame 110. The frame 110 of the bolt elongation measuring device 102 has a bolt elongation measuring rod 112 and a bolt probe 117 ( FIG. 8 not to be removed). The bolt elongation measuring rod 112 is assigned to the nut side 83 of the receiving device 80 and the bolt sensor 117 to the abutment side 93 of the receiving device 80. The bolt tensioning device 200 of the measuring system 100 has an elongation value measuring device 230 with which an elongation value Δl is measured. The bolt tensioning device 200 measures a correlating elongation value Δl, whereby a distance travelled by a pulling unit 210 (see FIG. 10 ) is measured by applying a tensile force Fb. Furthermore, the bolt tensioning device 200 has a tensile force determination 272 and a computing unit 270. The computing unit can not only be integrated into the device, but can also be spatially separated from it in the form of a workstation computer or similar.

FIG. 9 shows a bolt clamping device 200 and a receiving device 80 in a side view. Furthermore, FIG. 9 a part of a bolt elongation measuring device 102 is illustrated, which reproduces a bolt elongation Δb and documents it if necessary. The receiving device 80 has the first flange 82 and the second flange 92 and forms the flange connection 81. The first flange 82 has the nut side 83 with a flange surface 86 and the first contact side 85 and the second flange 92 has the second contact side 95 and the abutment side 93. The second flange 92 rests with the abutment side on two spacer elements 140.

At least on the abutment side 93, a first and a second flange compression measuring device 120, 130 are arranged, with the first flange compression measuring device 120 a first flange compression Δf1 and a second flange compression Δf2 is measured with the second flange compression measuring device 130.

FIG. 10 shows a bolt system 10, a bolt clamping device 200 and a receiving device 80 in a side sectional view. The side sectional view is a section AA from FIG. 9 . The receiving device 80 has the first flange 82 and the second flange 92 and forms the flange connection 81. The first flange 82 has the nut side 83 with a flange surface 86 and the first contact side 85 and the second flange 92 has the second contact side 95 and the abutment side 93. The first flange 82 has a first flange recess 84 and the second flange 92 has a second flange recess 94. A bolt 20 of the bolt system 10 is inserted into the first flange recess 84 and the second flange recess 94.

The bolt tensioning device 200 comprises a housing 202, a tension unit 210 and the elongation measuring device 230 (see FIG. 8 ). The traction unit 210 has a traction unit internal thread 216 on a gripping area 218.

Furthermore, the bolt system 10 has the bolt 20, a nut 12 and an abutment 32. The abutment 32 has a screw head and is directly connected to the bolt 20. The bolt 20 has an external thread 26 and the nut 12 has an internal nut thread 16. The internal nut thread 16 has a geometry that essentially corresponds to a geometry of the external thread 26 of the bolt, which is stretched or elongated by means of a tensile force Fb. Furthermore, the internal tensile unit thread 216 engages in the external thread 26 of the bolt 20.

Furthermore, a first flange compression measuring device 120 and a second flange compression measuring device 130 are arranged on the abutment side 85 of the second flange. The first flange compression measuring device is used to measure a first flange compression Δf1 of the receiving device 80 under the bolt tensioning device 200 or under the housing 202 of the bolt tensioning device 200. The second flange compression measuring device is used to measure a second flange compression Δf2 of the receiving device 80 under the nut 12 of the bolt system 10.

At least over the first flange compression Δf1 a compression force is under the bolt tensioning device Fs must be determined. Furthermore, a compression force under the nut Fm must be determined at least over the second flange compression Δf2.

A first flange compression recess 98 and a second flange compression recess 99 run through the receiving device 80. The first and second flange compression recesses 98, 99 penetrate the receiving device 80 completely, starting from the abutment side 85 to the nut side 95. The first flange compression measuring device 120 comprises a first flange compression measuring rod 122, which reaches through the first flange compression recess 98 and has a contact with the bolt tensioning device 200. The second flange compression measuring device 130 comprises a second flange compression measuring rod 132, which reaches through the second flange compression recess 99 and indirectly, due to a washer, has a contact with the nut.

The bolt 20 has a first end face 23 (see FIG. 6 ) has a first contact element 21. Furthermore, the abutment 32 has a second end face 33 (see FIG. 6 ) has a second contact element 31. The bolt elongation measuring device 102 from FIGS. 7 and 8 have a bolt elongation measuring rod 112 and a bolt probe 117 (see schematic FIG. 8 ) has a contact with the first and second contact elements 21, 31 of the bolt 20. The bolt elongation measuring rod 112 has a contact with the first contact element 21.

The embodiments shown in the figures are not to be interpreted as limiting.

Claims (8)

1. Method for screwing a bolt system (10) to a flange connection (81), wherein the bolt system (10) comprises at least one bolt (20), a nut (12) and an abutment (32), wherein the flange connection (81) comprises at least one first flange (82) with at least one first flange recess (84) and a second flange (92) with at least one second flange recess (94), comprising the steps of

   a) Determining a bolt system-typical elongation behaviour (50) and determination of a bolt tensioning device-typical compression behaviour (52),

   b) Aligning the first flange recess (84) with the second flange recess (94),

   c) Inserting the bolt system (10) into the first flange recess (84) and the second flange recess (94),

   d) Mounting a bolt tensioning device (200) on the bolt (20) on one nut side (83) of the flange connection,

   e) Applying a tensile force (Fb) to the bolt (20) until a certain maximum force (Fmax) is reached, and determining an elongation value (Δl) (56) which correlates with a bolt elongation (Δb) (50), a bolt tensioning device compression (Δs) and a flange compression (Δf) (54) of the flange connection (81),

   f) Retightening the nut (12) with a specific torque,

   g) Releasing the tensile force (Fb),

   h) Repeating steps e) to g.) at least once, and

   i) Evaluating the values determined for tensile force (Fb) and elongation value (Δl), determining the flange compression (Δf) and use this to determine the flange compression force (Ff).
2. Method according to claim 1, characterised in that the determined maximum force (Fmax) corresponds to a tensile force (Fb) at which a elongation strength (RE) typical of a bolt system is reached.
3. Method according to one or more of the preceding claims, characterised in that steps e) to g) are repeated at least once.
4. Method according to one or more of the preceding claims, characterised in that before step h)

   - a tensile force is applied to the bolt,

   - the nut (12) is loosened,

   - the tensile force is set to zero and

   - the tensile force is set to a target force (Fsoll)
5. Method according to one or more of the preceding claims, characterised in that

   - the flange compression (Δf) is averaged from the elongation value (Δl) as follows: Flange compression (Δf) = elongation value (Δl) - bolt elongation (Δb) - bolt tensioning device compression (Δs)

   - the bolt elongation (Δb) is known from the bolt system-typical elongation behaviour (50) for each tensile force (Fb) and the bolt tensioning device compression (Δs) is known from the bolt tensioning device-typical compression behaviour (52) for each tensile force (Fb).
6. Method according to one or more of the preceding claims, characterised in that the flange compression force (Ff) is determined at which the nut (12) disengages from a flange surface (86) of the nut side (83) of the flange connection (81).
7. Method according to one or more of the preceding claims, characterised in that the application of tensile force (Fb) to the bolt (20) is interrupted if the elongation value (Δl) is used to determine a behaviour of the bolt system (10) that is not typical of the bolt system, or if the flange connection is not closed by the tensile force Fb.
8. Use of a bolt tensioning device (200) for carrying out a method according to one or more of claims 1 to 7 wherein

   - the bolt tensioning device (200) comprises a casing (202), a tension unit (210), an elongation value measuring device (230), a tension force determination device (272) and a calculation unit (270),

   - an elongation value (Δl) can be measured using the elongation value measuring device (230),

   - a flange compression (Δf) can be calculated from the determined elongation value (Δl) by means of the calculation unit (270).

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