METHOD FOR SCREWING A BOLT SYSTEM

Description

[0001] The invention relates to a method for screwing a bolt system to a flange connection and to the use of a bolt clamping device for carrying out such a method.

[0002] Hydraulic pre-tensioning devices and their tightening methods are generally known from the prior art.

[0003] DE 10 2009 043 907 A1 describes a hydraulic threaded bolt clamping device for tightening and loosening highly stressed screws.

[0004] EP 2 942 156 A2 describes a clamping device for stretching a threaded bolt by pulling on its threaded end section.

[0005] All methods known from the state of the art have the disadvantage that reliable documentation of the screw connection cannot be guaranteed.

[0006] 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 is in particular verifiable or determinable and / or documentable.

[0007] The problem is solved according to the invention by the subject matter of the independent claims.

[0008] According to a first aspect, the invention proposes a method for bolting a bolt system to a flange connection, wherein the bolt system comprises at least one bolt, one nut and one abutment, wherein the flange connection comprises at least one first flange with at least one first flange recess and one second flange with at least one second flange recess, comprising the steps a) Determining the typical elongation behavior of the bolt system and the typical compression behavior of the bolt clamping device, b) Aligning the first flange recess with the second flange recess, c) Inserting a bolt system into the first and second flange recesses, d) Mounting a bolt clamping device on the bolts on the nut side of the flange connection, e) Applying a tensile force (Fb) to the bolt until a specific maximum force is reached, and determining, preferably continuously during the application of the tensile force (Fb), an elongation value that correlates with bolt elongation, bolt clamping device compression, and flange compression of the flange connection, f) Tightening the nut with a specific torque, g) Releasing the tensile force, preferably to a restoring force (Fbrück), h) Repeating steps e) to g) at least once, and 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 during pressurization and depressurization.

[0009] A bolt system for carrying out the aforementioned method comprises at least one bolt, an abutment, and a nut, wherein the bolt exhibits a bolt system-typical elongation behavior, which is determined using at least one identical bolt. The bolt system-typical elongation behavior of the identical bolt is preferably determined using a measuring system described below.

[0010] Preferably, the nut has an internal thread with a geometry that essentially corresponds to the geometry of the bolt, which is stretched or elongated by means of a specific maximum force, which can also be referred to as a specific preload force. Preferably, the bolt is elongated up to a yield strength. When the term "geometry" is used within the scope of the invention in relation to internal and / or external threads, it preferably refers to at least the thread pitch, the thread angle, and / or the thread diameter.

[0011] Preferably, the abutment has a screw head or a locknut. More preferably, the abutment is directly connected to the bolt material and is preferably designed as a locknut with a polygonal, preferably hexagonal, shape. Most preferably, the bolt has been stretched or elongated at least once to its yield strength.

[0012] According to a second aspect, the invention proposes the use of a bolt clamping device for carrying out a method designed according to the first aspect, wherein the bolt clamping device comprises a housing, a tensioning unit, an elongation value measuring device, a tensile force determination device and a calculation unit, wherein an elongation value can be measured by means of the elongation value measuring device, and wherein a flange compression can be calculated from the determined elongation value by means of the calculation unit.

[0013] A method for bolting a bolt system to a flange connection is proposed. The bolt system comprises at least one bolt, one nut, and a counter-bearing. In one embodiment, the counter-bearing has a bolt head that is directly connected to the bolt material. In another, particularly preferred embodiment, the counter-bearing has at least one locknut. 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 thread that corresponds to the external thread of a preloaded bolt. It is further preferred that the bearing surface of the nut is designed such that no washer is required. In particular, the nut has a flat bearing surface, which is further preferably perpendicular to a thread axis of the nut.If the abutment is designed as a locknut, the above statements regarding the nut also apply to the locknut 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 locknut, or whose external thread geometry, especially 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 locknut.

[0014] 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. In particular, the flange has a plurality of flange recesses into which a plurality of bolt systems can be inserted.

[0015] A measuring system is shown below for the bolt system-typical elongation behavior and the bolt clamping device-typical compression behavior to be determined in step a).

[0016] The preferably used measuring system, also according to the invention, at least for determining the elongation behavior typical of a bolt system, comprises a receiving device, a bolt clamping device, and a bolt elongation measuring device. The receiving device has a nut side, a support side opposite the nut side, and at least one flange recess. The bolt of the bolt system can be arranged in the flange recess. The bolt clamping device can be arranged on the nut side of the receiving device. A tensile force (Fb) can be applied to the bolt by means of the bolt clamping device, and a bolt elongation Δb can be measured with the bolt elongation measuring device. When the term "measuring system" is used within the scope of the invention, it preferably refers to a test rig, field test, and / or laboratory setup, etc.

[0017] Preferably, the bolt system comprises at least one bolt, one nut, and one abutment. Preferably, the nut of the bolt system is associated with the nut side of the receiving device, and the abutment of the bolt system is associated with the abutment side of the receiving device. In a preferred embodiment, the abutment comprises a further nut or locknut. In an alternative embodiment, the abutment is directly or integrally connected to the bolt material and preferably has a bolt head and, more preferably, a screw head. Preferably, the bolt has a longitudinal extension with a first end region and an opposing second end region. Preferably, the first end region is associated with the nut side of the receiving device, and the second end region with the abutment side of the receiving device.Preferably, the bolt has a first contact element, preferably centrally located, on a first end face associated with the first end region. More preferably, the bolt or the abutment has a second contact element, preferably centrally located, on a second end face associated with the second end region. Preferably, the first and / or the second contact element has a tip extending 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 recessed into the first and / or second end face and projects from the end face in a substantially dome-like manner.

[0018] 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 is approximately perpendicular to a height and 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 one above the other. Preferably, the two blocks arranged one above the other are a first flange and a second flange and form a flange connection.

[0019] When, within the scope of the present invention, including the measuring system according to the invention, the terms "approximately" or "essentially" are used in relation to values ​​or ranges of values, they shall be understood to mean what a person skilled in the art would consider customary in the given context. In particular, deviations of the specified values ​​of ±10%, preferably ±5%, and more preferably ±2% are included in the terms "approximately" and "essentially".

[0020] The longitudinal extent of the measuring system's receiving device is preferably in a ratio of approximately 2:1 to approximately 10:1 with its length to its height and / or depth. More preferably, the length of the longitudinal extent is in a ratio of approximately 4:1 to approximately 8:1 with its height and / or depth. Particularly preferably, the length of the longitudinal extent is in a ratio of approximately 6:1 with its height and / or depth.

[0021] Preferably, the bolt clamping device is arranged on the receiving device after the bolt of the bolt system has been positioned in the flange recess. More preferably, the bolt clamping device is integrated into the flange recess. Preferably, the bolt clamping device at least partially, and more preferably substantially completely, encloses the flange recess on the nut side.

[0022] Preferably, the bolt clamping device comprises a housing and a tensioning unit. The housing preferably encloses the tensioning unit. More preferably, the tensioning unit has an internal thread at a gripping area. Preferably, the bolt of the bolt system is not completely located within the flange recess. Preferably, the bolt protrudes partially from the flange recess on both the nut side and the abutment side of the receiving device. The internal thread of the tensioning unit is preferably designed to engage with an external thread of the bolt. Particularly preferably, the tensioning unit engages with the external thread of the bolt via its internal thread to lengthen the bolt in a single process step. In a subsequent process step, at least one nut is connected to the lengthened threaded bolt.Particularly preferably, the nut has an internal thread which, in its geometry, preferably almost or completely, corresponds to the elongated external thread of the bolt.

[0023] In a preferred embodiment of the measuring system, the bolt elongation measuring device comprises a stand and a frame, the stand having at least one bearing that supports the frame translationally on the frame. In one embodiment, the stand is formed as part of a wall. In an alternative embodiment, the stand is self-supporting and arranged on a base.

[0024] Preferably, the frame of the bolt elongation measuring device comprises a bolt elongation measuring rod and a bolt probe, wherein the bolt elongation measuring rod is associated with the nut side of the receiving device and the bolt probe is associated with 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, together with the bolt elongation measuring rod, makes contact with the first end region of the bolt. More preferably, the bolt elongation measuring rod makes contact with the first end face of the bolt. Particularly preferably, the bolt elongation measuring rod makes contact with the first contact element of the bolt. Preferably, the frame of the bolt elongation measuring device, together with the bolt probe, makes contact with the second end region of the bolt. More preferably, the bolt probe makes contact with the second end face of the bolt.Preferably, the bolt switch has a contact to the second contact element of the bolt.

[0025] 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. Preferably, the spring element is pre-tensioned to a certain extent by the support of the frame on this support. Preferably, the frame of the bolt elongation measuring device maintains continuous, bilateral contact with the bolt by means of the spring element. More preferably, at least the bolt probe maintains continuous contact with the bolt by means of the spring element.

[0026] In a particularly preferred embodiment, a tensile force (Fb) can be applied to the bolt by means of the bolt clamping device, and the bolt elongation (Δb) can be measured with the bolt elongation measuring device. Preferably, the bolt is elongated when the tensile force (Fb) is applied. More preferably, the bolt of the bolt system is arranged in the flange recess, and the abutment rests against the abutment side of the receiving device. Preferably, the bolt is elongated when the tensile force (Fb) is applied and held against the abutment side by means of the abutment. Preferably, the bolt is elongated substantially in the direction of its longitudinal extent. Preferably, the bolt is elongated substantially from the abutment to substantially the first end region. More preferably, the bolt is elongated substantially from the abutment to substantially the region where the bolt clamping device engages the bolt via the internal thread of the tensioning unit.Preferably, the bolt elongation measuring rod and the bolt probe each have contact with the bolt. Preferably, the bolt elongation measuring rod and the bolt probe maintain continuous contact with the bolt during elongation. Preferably, and due to factors such as the material and / or gaps of the receiving device, the receiving device lifts from the abutment side towards the nut side. More preferably, and also due to 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 each other. As the abutment side of the receiving device lifts, the bolt, and preferably the bolt system, is moved towards the bolt clamping device. Preferably, the frame of the bolt elongation measuring device rests on the spring element of the stand.The bolt probe, which preferably maintains continuous contact with the bolt, rises 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 raises the entire frame of the bolt elongation measuring device. The bolt elongation measuring rod, which preferably maintains continuous contact with the bolt during elongation, is preferably arranged at the first end region of the bolt, more preferably on the first end face of the bolt, and most preferably 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 compliance 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 a distance to which at least the receiving device yields upon application of the tensile force (Fb). The bolt elongation (Δb) or 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 resultant of the maximum movement of the bolt. Preferably, in the present invention, in all its embodiments, the term compression refers to the yielding of materials, such as those of the bolt clamping device, the receiving device, and, optionally, gaps, which close by a preferably increasing pressure.

[0027] Preferably, the bolt clamping device of the measuring system includes an elongation measuring device with which an elongation value (ΔI) can be measured. Preferably, the bolt clamping device measures a correlated elongation value (ΔI), whereby the distance traveled by the pulling unit when the tensile force (Fb) is applied can be measured. The elongation value (ΔI) is, in particular, the sum of the bolt elongation (Δb) and any compressions in the measuring system. Preferably, the elongation value (ΔI) is the sum of the bolt elongation (Δb), a bolt clamping device compression (Δs), and a flange compression (Δf).

[0028] Preferably, the bolt clamping device compression (Δs) is the compression of the bolt clamping device that occurs when at least the bolt clamping device elongates the bolt of the bolt system with the tensile force (Fb). Preferably, when the tensile force (Fb) is applied, the bolt clamping device is pressed towards the receiving device on its nut side, while the drawbar elongates the bolt in the opposite direction.

[0029] 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, the abutment side, and at least one second flange recess, wherein the first contact side and the second contact side are associated with each other, and wherein the first flange recess and the second flange recess are associated with each other. Preferably, the bolt of the bolt system can be arranged in the first and the second flange recess.

[0030] It is possible 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 irregularities and therefore a gap at least in the area of ​​the first and second contact sides. Even under these conditions, an accurate determination of the flange compression force is possible with the method according to the invention and the bolt clamping 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 apart from the second contact side. Preferably, the spacer element replicates the irregularities of the receiving device.

[0031] Preferably, at least one flange compression tester is arranged in and / or on the receiving device, comprising a flange compression test rod. The flange compression test rod is at least partially arranged in a flange compression test recess of the receiving device. Preferably, the flange compression test recess extends completely through the receiving device from the abutment side to the nut side. Preferably, the flange compression (Δf) can be measured with the flange compression test rod. In one embodiment, the flange compression test recess on the nut side of the receiving device borders an area in which the bolt clamping device is arranged on the nut side. Preferably, the bolt clamping device, more preferably with its housing, rests on the flange compression recess on the nut side. More preferably, the bolt clamping device covers the flange compression recess on the nut side.The flange compression test rod, which extends through the flange compression recess, preferably makes contact with the bolt clamping device. Preferably, the receiving device exhibits flange compression as soon as the bolt clamping device applies the tensile force (Fb). Preferably, the flange compression test rod is arranged next to the arrangement in the flange compression recess on the abutment side of the receiving device. The flange compression test rod measures the flange compression (Δf). Preferably, the flange compression test rod measures the flange compression (Δf) on the abutment side by measuring the length of the flange compression test rod that extends from the flange compression recess when the tensile force (Fb) is applied.

[0032] In a preferred embodiment, a first and a second flange compression tester are provided. Preferably, the first and the second flange compression tester are arranged in and / or on the receiving device and comprise a first and a second flange compression tester. Preferably, the first flange compression tester comprises the first flange compression tester and the second flange compression tester comprises the second flange compression tester. Preferably, a first flange compression (Δf1) can be measured with the first flange compression tester. More preferably, a second flange compression (Δf2) can be measured with the second flange compression tester. Preferably, the first flange compression tester is arranged at least partially in a first flange compression test recess of the receiving device.Preferably, the second flange compression test rod is arranged at least partially in a second flange compression test recess of the receiving device. Particularly preferably, the first flange compression recess is the one that adjoins the bolt clamping device on the nut side and, more preferably, the housing. Preferably, the first flange compression test rod, which extends through the first flange compression recess, makes contact with the bolt clamping device. Preferably, the first flange compression test rod measures a flange compression (Δf1) under the bolt clamping device.

[0033] In an embodiment where the bolt system has a nut on the nut side, the second flange compression recess is preferably arranged directly or indirectly below the nut. Preferably, the second flange compression recess is the one adjacent to the nut of the bolt system on the nut side. Preferably, the second flange compression probe, which extends through the second flange compression recess, has direct or indirect contact with the nut of the bolt system. Preferably, the second flange compression probe measures a flange compression (Δf2) below the nut of the bolt system.

[0034] Preferably, the measuring system can measure and / or determine any measured variables such as at least the elongation value (ΔI), bolt elongation (Δb), flange compression (Δf), and bolt clamping device compression (Δs). Particularly preferably, the measuring system can measure the measured variables such as the elongation value (ΔI), bolt elongation (Δb), and flange compression (Δf), and determine the bolt clamping device compression (Δs). In particular, the measuring system is designed so that the bolt clamping device compression (Δs) can be determined as follows: Δs = ΔI - Δb - Δf. Preferably, the bolt clamping device's typical compression behavior can be derived from the documentation of the bolt clamping device compression (Δs) in relation to the increasing tensile force (Fb).

[0035] A preferred measuring method, at least for determining a bolt system-typical elongation behavior of a bolt system, with a measuring system as described above, wherein the bolt system comprises at least one bolt, one nut and one abutment, comprises the steps a) Inserting the bolt system into at least one flange recess of the receiving device, b) Applying an increasing tensile force (Fb) to the bolt using a bolt clamping device, c) Measuring a bolt elongation (Δb), preferably continuously during the application of a tensile force, and d) relating the tensile force (Fb) to the bolt elongation (Δb) and determining a bolt system-typical elongation behavior.

[0036] The bolt clamping device, preferably arranged on a nut side of the receiving device, engages an external thread of the bolt via an internal thread of a tensioning unit. The increasing tensile force (Fb) preferably does not exert a sudden force on the bolt. Preferably, the bolt is subjected to a steadily increasing tensile force (Fb) and elongated.

[0037] To measure the bolt elongation (Δb), as described in step c), the measuring system preferably includes a bolt elongation measuring device. Preferably, the bolt elongation measuring device comprises a bolt elongation measuring rod and a bolt probe, each contacting the bolt at one end. The bolt elongation (Δb) describes the difference in length between an elongated bolt and an unelongated bolt. Preferably, the bolt elongation (Δb) is measured continuously during the increase of the tensile force (Fb).

[0038] To determine the typical elongation behavior of the bolt system 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 represented in a stress-strain diagram. Preferably, the values ​​relating to each other have a slope that particularly preferably corresponds to Hooke's law. In order to determine a maximum force (Fmax) and thus a preferred yield strength (RE), the region and, more preferably, the point at which the slope no longer follows or corresponds to Hooke's law is important. Particularly preferably, measurements are taken using a 0.2% yield strength (Rp0.2) to determine the yield strength (RE) and the maximum force (Fmax). Preferably, the 0.2% yield strength represents the stress at which a permanent elongation of 0.2% is achieved.

[0039] In an exemplary embodiment, in which the bolt system includes 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.

[0040] Furthermore, the measurement procedure preferably includes the following steps e) Tightening the nut of the bolt system with a specific torque and f) releasing the tensile force (Fb).

[0041] A residual force (Fbrück) is established in the bolt system. Preferably, the nut is tightened onto the bolt of the bolt system. Preferably, the bolt has been elongated before the nut is tightened, 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 thread that essentially corresponds to the external thread of the elongated bolt. The nut is preferably tightened with a torque in the range of approximately 20 Nm to approximately 100 Nm, more preferably with a torque in the range of approximately 30 Nm to approximately 70 Nm, and most preferably with a torque of approximately 50 Nm.

[0042] The restoring force (Fbrück) is lower than the tensile force (Fb). It describes the force that remains in the bolted connection of the bolt system to a flange connection after elongation or stretching of the bolt when no tensile force (Fb) acts on the bolted connection.

[0043] 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. Most preferably, steps b) to f) are repeated five times. However, more frequent repetitions are also possible.

[0044] In an embodiment with an M48 HV nut and a flange thickness of 200 mm, for example, the flange compression force (Ff) under the nut after a single execution (without repetition) of steps b) to f) is approximately 48% of the previously applied maximum force (Fmax) of 1326 kN. Furthermore, after six executions (five repetitions) of steps b) to f), the flange compression force (Ff) under the nut is approximately 55% of the previously applied maximum force (Fmax) of 1326 kN.

[0045] In another embodiment with an HV bolt and a TTG nut, for example, the flange compression force (Ff) under the nut after a single execution (without repetition) of steps b) to f) is approximately 79% of the previously applied maximum force (Fmax) of 1326 kN. Furthermore, after six executions (five repetitions) of steps b) to f), the flange compression force (Ff) under the nut is approximately 88% of the previously applied maximum force (Fmax) of 1326 kN.

[0046] Preferably, the bolt clamping device of the measuring system comprises an elongation 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 clamping device compression (Δs). Preferably, the elongation value (ΔI) is the sum of the bolt elongation (Δb), the bolt clamping device compression (Δs), and the flange compression (Δf).

[0047] Preferably, the measuring system comprises at least one flange compression tester. Preferably, the flange compression (Δf) is measured using the flange compression tester.

[0048] Preferably, the flange compression tester comprises a flange compression test rod. The flange compression test rod is at least partially arranged in a flange compression test recess of the receiving device and is in contact with the bolt clamping device and / or the nut. Preferably, a compression force can be determined at least via the flange compression (Δf).

[0049] Preferably, the measuring system comprises at least one first flange compression gauge and one second flange compression gauge. Preferably, the first flange compression gauge measures a first flange compression (Δf1) of the receiving device under the bolt clamping device, and the second flange compression gauge measures a second flange compression (Δf2) of the receiving device under the nut of the bolt system. Preferably, at least one compression force under the bolt clamping device (Fs) can be determined from the first flange compression (Δf1). More preferably, at least one compression force under the nut (Fm) can be determined from the second flange compression (Δf2).

[0050] Preferably, the bolt clamping device compression (Δs) of a bolt clamping 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 clamping device can be derived from the documentation of the bolt clamping device compression (Δs) in relation to the increasing tensile force (Fb).

[0051] The inventive method for screwing together a bolt system comprises, as mentioned at the outset, the following steps: a) Determining the typical elongation behavior of the bolt system and the typical compression behavior of the bolt clamping device, b) Aligning the first flange recess with the second flange recess, c) Inserting the bolt system into the first flange recess and the second d) flange recess, e) Mounting a bolt clamping device on the bolt on one nut side of the flange connection, f) Applying a tensile force to the bolt until a specific maximum force is reached, and determining an elongation value that correlates with bolt elongation, bolt clamping device compression, and flange compression of the flange connection, g) Tightening the nut with a specific torque, h) Releasing the tensile force (Fb), i) Repeating steps e) to g) at least once, and

[0052] Evaluating the determined values ​​for tensile force and elongation, determining the flange compression and from this determining the flange compression force, in particular during the execution of the method, preferably for each point in time of pressurization and depressurization.

[0053] In step a), the 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 the elongation of the bolt as a function of the tensile force applied to it is preferably determined, for example with the measuring system and measuring method described above according to the invention. Preferably, when determining the elongation behavior typical of the bolt system, the bolt is stretched and then relaxed once or several times, in particular twice, more preferably three times, more preferably four times, more preferably five times or more frequently, with an increasing force up to a maximum force. In one embodiment, the maximum force corresponds to a force that stretches the bolt to its yield strength.Preferably, the bolt is repeatedly stretched to its yield strength, 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, and more preferably a similarly manufactured bolt, particularly with the same dimensions, thread, thread pitch, alloy, and length, behaves identically to the tested bolt. Therefore, a bolt with the same dimensions and essentially the same alloy as the tested bolt exhibits the typical elongation behavior of the tested bolt system.

[0054] Furthermore, a compression behavior typical of a bolt clamping device is determined, for example, using the measuring system and measuring method described above according to the invention, wherein a bolt clamping device is tested or used that is essentially identical to the bolt clamping device employed. In this process, a bolt is clamped using the bolt clamping device, and the compression behavior is determined. Preferably, the compression behavior typical of the bolt clamping device is determined simultaneously with the elongation behavior typical of the bolt system by inserting a bolt system into a receiving device and / or a flange connection and clamping it with the bolt clamping device up to the maximum force, in particular up to the force that brings the bolt to its yield strength.As explained above regarding 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, a structurally identical bolt exhibiting the typical elongation behavior of the bolt system and a bolt clamping device exhibiting the typical compression behavior of the bolt clamping device can be used for the proposed method.

[0055] 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.

[0056] In step c), the bolt system is inserted into the first flange recess and the second flange recess, which are preferably aligned with each other. In an embodiment where the abutment has a bolt head that is integrally bonded to the bolt, the bolt is guided into the flange recess essentially until the abutment abuts the second flange. Consequently, 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 to a specific torque. Particular care must be taken to ensure that the nut is screwed onto the bolt in such a way that the bolt projection between the nut-side end of the bolt and the nut is of a minimum length necessary for screwing on the bolt clamping device.

[0057] In a further embodiment, the insertion of the bolt system into the flange recess comprises the following steps: Screw the nut onto the bolt, insert the bolt into the flange recess, essentially until the nut rests against the first flange, screw the abutment onto the bolt and tighten the nut on the abutment with a specified torque.

[0058] In particular, this design provides for the abutment to have a locknut.

[0059] In step d), a bolt clamping device is mounted on the bolt on the nut side of the flange connection. The bolt clamping device is screwed onto the bolt in such a way that at least one of the aforementioned bolt projections beyond the nut is engaged by a tensioning element of the bolt clamping device, in particular an internal thread of the tensioning element. The bolt clamping device preferably rests on the flange with its housing.

[0060] During the following steps, as described in step e), a tensile force is applied to the bolt, and an elongation value is determined that correlates with bolt elongation, bolt clamping device compression, and flange compression of the flange connection. The applied tensile force is, in particular, the force exerted on the bolt by means of the bolt clamping device. The bolt clamping device operates, in particular, hydraulically, with the tensioning 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 tensioning unit, especially hydraulic pressure. More preferably, the tensile force is characterized by the pressure applied to the tensioning unit multiplied by the piston area. Preferably, the bolt clamping device measures the elongation value by measuring the distance traveled by the tensioning unit relative to the housing.Preferably, the values ​​of the elongation value and the tensile force are related to each other 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, for the purpose of calculating the sum, the bolt elongation, the bolt clamping device compression, and the flange compression have a positive sign.

[0061] In step e), a tensile force is applied to the bolt until a specific maximum force (Fmax) is reached. Preferably, the tensile force is increased continuously or incrementally until the maximum force is reached. In a preferred embodiment, the maximum force corresponds to a (tensile) force that causes the bolt to elongate up to a yield strength (RE) typical for the bolt system. However, the maximum force (Fmax) can also be lower or higher than the tensile force required to reach the yield strength (RE). In a further embodiment, the maximum force is a force that causes the bolt to elongate by approximately 80% to approximately 120% of the bolt's typical yield strength, preferably by approximately 90% to approximately 120%, and more preferably by approximately 95% to approximately 120% of the bolt's typical yield strength.Preferably, the bolt is 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 strength. The maximum force can also be higher than the yield strength. Applying a specific maximum force up to or slightly above the yield strength causes plastic deformation in the bolt material. This deformation is no longer detectable after two to four repetitions of the stretching or elongation of the bolt. Preferably, in at least one repetition of the elongation, a maximum force is applied that corresponds to that of the first elongation and is preferably close to or slightly above the yield strength, preferably in a range of about 95% to about 110%.

[0062] In step f), the nut is tightened to a specific torque. In one embodiment, the nut is tightened by hand. Preferably, the nut is screwed in towards the first flange or the flange connection and tightened to a specific torque. Preferably, the specified torque is approximately 10 Nm to approximately 100 Nm, more preferably approximately 25 Nm to approximately 60 Nm, and more preferably approximately 50 Nm.

[0063] In step g), the tensile force is reduced 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.

[0064] In step h), steps e) to g) are repeated at least once, and the tensile force is repeatedly applied to the bolt.

[0065] In step i), the values ​​for tensile force and elongation are evaluated, and the flange compression and, consequently, the flange compression force are determined. The flange compression force corresponds to the tensile force applied to the bolt to loosen or lift the nut from the flange, or the force at which the nut rests on the flange without any force being applied to it. Specifically, the flange compression force can be determined by calculating the slope of the measured Hookean trajectory of the elongation value or the bolt elongation. The slope of the ratio of force to bolt elongation is steeper up to the point where the nut lifts off the flange.

[0066] The evaluation can preferably be carried out during the execution of the method, so that the flange compression force and the flange compression are known after completion of the bolting method according to the invention. 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, as is typical for bolt systems, the bolt elongation (Δb) is known and, as is typical for bolt clamping devices, the bolt clamping device compression is known for all tensile forces, and the elongation value corresponds to the measured value, the flange compression can be calculated as described above.

[0067] The proposed method advantageously allows for the reliable crimping of exposed flanges, particularly when these flanges exhibit tolerances that can lead to gaps. Especially in wind turbines, very large flange connections are used which, unlike in conventional mechanical engineering, cannot be manufactured and / or calculated with absolute precision. This results in a situation where, when the bolt is tightened, gaps between the flanges are closed first, and only then can a force be generated to compress the flanges against each other. Prior art dictates tightening the bolts with a specific force, for example, approximately 70% to 80% of the yield strength, and assuming that the force used to tighten the bolt corresponds approximately to the flange compression force.

[0068] 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 typical elongation behavior of the bolt system and the typical compression behavior of the bolt device, particularly with the measuring system and method described above according to the invention, has the advantage that at least the bolts and bolt clamping devices of each batch, more preferably of a product series, can be used for carrying out the method. Since the behavior of the bolts or bolt clamping devices is not directly related to the bolt system, the system can be used to determine the specific elongation behavior of the bolt system and the compression behavior of the bolt device.Since the bolt system and the bolt tensioning device are known for the respective tensile force, especially when the bolt is repeatedly tensioned and relaxed, clear conclusions can be drawn about the behavior of the flanges.

[0069] In one embodiment, steps e) to g) are repeated at least once. Specifically, steps e) to g) are repeated with a maximum force that guides the bolt to its typical yield strength for the bolt system. This has the advantage of inducing settling phenomena within the bolt's microstructure, which prevent aging or creep and are therefore 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, thus eliminating the need for costly retightening of at least one nut in the bolt system.

[0070] 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 (Ftarget), which is preferably smaller than the maximum force. This procedure is particularly advantageous when the maximum force corresponds to the force at which the yield strength 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, under large alternating loads, the bolt is not subjected to stresses exceeding its yield strength. In particular, it is provided that an elongation value is determined to ascertain the flange compression at a tensile force corresponding to a calibration force.Preferably, the calibration force is approximately 1% to approximately 5%, more preferably approximately 1% to approximately 3%, and more preferably approximately 2% to approximately 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, and more preferably approximately 40 kN. This has the advantage that the bolt clamping device is securely clamped and, more preferably, that any gaps and openings typical of bolt clamping devices due to their design are closed, thus enabling accurate measurement. It is further preferred that the measurements used are those taken during pressure build-up and preferably not during pressure release.

[0071] 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.

[0072] In a further embodiment, the application of tensile force to the bolt is interrupted if the elongation value indicates a non-typical bolt system behavior, particularly unusual elongation behavior. If a yield strength of the guided bolt is detected at a force that does not correspond to the typical yield strength for the bolt system, this indicates a defective or incorrect bolt. To prevent damage to the flange connection, surrounding equipment, or the bolt tensioning device, and especially to prevent injuries to people in the vicinity of the bolt tensioning device, one embodiment, upon detection of a non-typical yield strength of the bolt system, releases the pressure in a controlled manner and issues an error message, allowing the bolt to be replaced.

[0073] An exemplary embodiment of the method for bolting a bolt system provides that, prior to bolting, the bolt system-typical elongation behavior is determined on at least one test bolt, preferably using the measuring system and method described above according to the invention. Furthermore, the bolt clamping device's compression behavior, also preferably determined using the measuring system and method described above according to the invention, is determined. This can be done either using the bolt clamping device itself or using a structurally identical product. Subsequently, the flanges are aligned relative to each other so that the bolt systems can be inserted into the flange recesses.In one embodiment, the bolts are pre-mounted on the first flange in such a way that they do not protrude downwards from the flange. Particularly in a wind turbine assembly, this allows the bolt and the first flange to be simultaneously lifted onto the second flange using a crane. The flange recesses of the first and second flanges are aligned, and then the bolt systems are inserted into the first and second flange recesses. The bolt tensioning device is mounted on the nut side of the flange connection, i.e., the side of the flange connection where the nut of the bolt system is located. Specifically, the bolt tensioning device is screwed onto the bolt. A tensile force is then applied to the bolt, preferably increased to a maximum force that ideally results in the bolt system's characteristic elongation up to the bolt's yield strength.The nut is then tightened to a specific torque, preferably 50 Nm. The tensile force is reduced to the restoring force of approximately 0 N, so that the nut of the bolt system and the flange connection are subjected to the maximum force that the bolt system can withstand. The tensile force is then reapplied to the bolt and preferably increased to the maximum force. The nut is then loosened and the force reduced to the restoring force. A tensile force is again applied to the bolt, stretching it to a required target force, preferably between 70% and 100% of the maximum force. The nut is then tightened again to a specific torque, preferably 50 Nm, and the tensile force is reduced to the restoring force.Throughout 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, obtained with a calibration force of preferably approximately 40 kN, are recorded and documented. Furthermore, the tensile force upon loosening the nut from the flange connection is recorded and documented as the flange compression force. All other values ​​recorded during the process are also documented, particularly graphically.

[0074] Further advantageous embodiments are shown in the following drawings. Identical parts or parts with the same function may 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. 2 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 a nut, a flange connection, and a bolt clamping device; FIG. 5 A plurality of strain behaviors of a measuring method with a measuring system; FIG. 6 A bolt system-typical strain behavior of an HV bolt and an HV nut; FIG. 7 A bolt system-typical strain 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 made of 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 clamping device and the receiving device made of FIG. 9 in a side sectional view.

[0075] FIG. 1A Figure 1 shows a first embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 comprises a bolt 20, a nut 12, and an abutment 32. The bolt 20 is designed as a high-strength bolt. The nut 12 is also designed as a high-strength nut, and the abutment 32 has a bolt head that is directly connected to the bolt material. A washer (not specified) is arranged below the abutment 32. The flange connection 81 comprises 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.

[0076] FIG. 1B Figure 1 shows a second embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 comprises a bolt 20, a nut 12, and an abutment 32. The bolt 20 is designed as a high-strength bolt. 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 specified) is arranged below the abutment 32. The TTG nut 12 has an internal thread that corresponds to an external thread of an elongated bolt 20. The flange connection 81 comprises 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.

[0077] FIG. 1C Figure 1 shows a third embodiment of a bolt system 10 and a flange connection 81 in a side sectional view. The bolt system 10 comprises a bolt 20, a nut 12, and abutment 32. The bolt 20 is designed as a stud bolt with an external thread at two end regions. Furthermore, the nut 12 and the abutment 32 are both designed as TTG nuts. The flange connection 81 comprises 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.

[0078] FIG. 2 Figure 1 shows a fourth embodiment of a bolt system 10, but without a nut 12, a flange connection 81, and a bolt clamping 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. The bolt clamping device 200 is arranged on a flange surface 86 of a nut side 83 of the first flange 82, with a bearing surface 204 on the first flange 82. The bolt clamping device 200 comprises a housing 202 and a tensioning unit 210. The housing 202 encloses the tensioning unit 210 on substantially three sides. The housing 202 has an open side facing the first flange 82, through which the tensioning unit 210 engages the bolt 20 of the bolt system 10.

[0079] FIG. 3 shows a plurality of strain behaviors of a measurement method with a measuring system 100. In FIG. 3 A diagram is illustrated showing the tensile force Fb on the bolt on the ordinate (y-axis) and elongations and compressions, all with a positive sign, on the abscissa (x-axis). For the measurement procedure, the measuring system 100 comprises an M48 stud bolt 20 and two M48 TTG nuts 12 and 32. The stud bolt 20 is a bolt with threads at two ends into which the TTG nuts 12 and 32 can engage. To perform the measurement procedure, the tensile force Fb is continuously increased until it reaches a maximum force Fmax of approximately 1326 kN. The following are illustrated: compression behavior of the flange compression 54, bolt-typical elongation behavior 50, bolt clamping device-typical compression behavior 52, and measured elongation behavior 56. 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 elongation behavior 50, a bolt elongation Δb is considered in relation to the tensile force Fb. Furthermore, for the bolt clamping device-typical compression behavior 52, a bolt clamping device compression Δs is considered in relation to the tensile force Fb, and for the measured elongation behavior 56, an elongation value Δl is considered in relation to the tensile force Fb.

[0080] Once 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 FIG. 4 und 5 ).

[0081] FIG. 4 shows a bolt system-typical elongation behavior of an M48 HV bolt and an M48 HV nut. FIG. 4 Figure 1 shows a diagram where the ordinate (y-axis) represents the tensile force Fb on the bolt and the abscissa (x-axis) represents the bolt elongation Δb. In a first step, a tensile force Fb is applied to the bolt 20 until a maximum force Fmax of approximately 1326 kN is reached. The tensile force Fb is continuously increased until the maximum force Fmax is reached. The maximum force Fmax corresponds to the force required to elongate the bolt 20 up to a yield strength RE typical for this bolt system. In a second step, the nut 12 is tightened to a specific torque of approximately 50 Nm. The nut 12 is screwed in towards the flange connection 81 and tightened to the specified torque. In a third step, the tensile force Fb is set to a calibration force Fk. Preferably, the calibration force Fk is in the range of approximately 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 to be determined), 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 applied to the bolt 20 to lift the nut 12 off the flange 82, or to the force at which the nut 12 rests on the flange 82 without any force being applied to it. In particular, the flange compression force Δf can be determined by calculating the slope of the Hookean 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.

[0082] FIG. 5 This shows the typical elongation behavior of an M48 stud bolt and two M48 TTG nuts in a bolt system. FIG. 5 A diagram is illustrated that shows the tensile force Fb on the bolt on the ordinate (y-axis) and the bolt elongation Δb on the abscissa (x-axis). The principle or procedure of the method does not differ from that of the FIG. 4 In particular, the diagram illustrates FIG. 5 , that after tightening the TTG nut 12 on the bolt 20 with a specific torque and removing the tensile force Fb, the bolt elongation Δb does not decrease as significantly as in FIG. 4 clarifies.

[0083] FIG. 6 Figure 1 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 by way of 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 centrally located on the first end face 23. Furthermore, the abutment 32 has a second contact element 31 on the second end face 33. The first and second contact elements 21, 31 are recessed into the first and second end faces of the bolt 20 and the abutment 32 and project from the end faces 23, 33 in a substantially dome-like shape. 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 extending from the first end face 23, which is formed on the bolt 20 in the direction of the abutment 32. The length 24 is illustrated. FIG. 6 a bolt elongation Δb, which is the difference in length of an elongated bolt ( FIG. 6 not to be removed) describes an unlengthened bolt 20.

[0084] FIG. 7 Figure 1 shows an embodiment of a measuring system 100 in a front view. The measuring system 100 comprises a receiving device 80, a bolt clamping device 200, and a bolt elongation measuring device 102. The bolt elongation measuring device measures 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, wherein the first flange 82 has a nut side 83 with a flange surface 86 and a first contact side 85, and the second flange 92 has a second contact side 95 and a buttress side 93. The first contact side 85 and the second contact side 95 are aligned with each other. Furthermore, the bolt clamping 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 on its underside, or abutment side, to two spacer elements 140. The second flange 92 rests on the spacer elements 140 at two end regions of a longitudinal extension of the receiving device 80 with its abutment side 93.

[0085] The bolt elongation measuring device 102 comprises a stand 104 and a frame 110, wherein the stand 104 has at least one bearing 105 (see FIG. 8 ) which supports the frame 110 translationally. The tripod 104 is arranged as a load-bearing element on a substrate. At least on the abutment side 93, a first and a second flange compression gauge 120, 130 are arranged. A first flange compression Δf1 is measured with the first flange compression gauge 120 and a second flange compression Δf2 is measured with the second flange compression gauge 130.

[0086] FIG. 8 The measuring system displays 100. FIG. 7 in a side view. The measuring system 100 comprises the holding device 80, the bolt clamping device 200, and the bolt elongation measuring device 102. The holding 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 It can be seen that the second flange 92 rests on at least one of the two spacer elements 140. The bolt elongation measuring device 102 comprises the stand 104 and the frame 110, the stand 104 having two bearings 105 (see FIG. 8 ) which translationally supports the frame 110. The frame 110 of the bolt elongation measuring device 102 rests on the stand 104 via a spring element 108. Due to the support of the frame 110, the spring element 108 is pre-tensioned to a certain extent. 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 probe 117 to the abutment side 93 of the receiving device 80. The bolt clamping device 200 of the measuring system 100 has an elongation value measuring device 230 with which an elongation value Δl is measured. The bolt clamping device 200 measures a correlating elongation value Δl, whereby a distance traveled by a pulling unit 210 (see FIG. 10 ) is measured by applying a tensile force Fb. Furthermore, the bolt clamping device 200 has a tensile force determination unit 272 and a computing unit 270. The computing unit can not only be integrated into the device, but also be spatially separated from it in the form of a workstation computer or similar.

[0087] FIG. 9 Figure 200 shows a bolt clamping device 200 and a receiving device 80 in a side view. Furthermore, Figure 200 shows a bolt clamping device 200 and a receiving device 80. FIG. 9 Figure 1 illustrates a part of a bolt elongation measuring device 102, which displays a bolt elongation Δb and, if necessary, documents it. 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 abutment side of the second flange 92 rests on two spacer elements 140.

[0088] At least on the abutment side 93, a first and a second flange compression gauge 120, 130 are arranged, wherein a first flange compression Δf1 is measured with the first flange compression gauge 120 and a second flange compression Δf2 is measured with the second flange compression gauge 130.

[0089] FIG. 10 Figure 1 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 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.

[0090] The bolt clamping device 200 has a housing 202, a pulling unit 210 and the elongation value measuring device 230 (see FIG. 8 ). The pulling unit 210 has an internal thread 216 at a gripping area 218.

[0091] Furthermore, the bolt system 10 comprises the bolt 20, a nut 12, and 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 thread 16. The internal thread 16 has a geometry that essentially corresponds to the geometry of the external thread 26 of the bolt, which is stretched or elongated by a tensile force Fb. Furthermore, the internal thread 216 of the tensioning unit engages in the external thread 26 of the bolt 20.

[0092] Furthermore, a first flange compression gauge 120 and a second flange compression gauge 130 are arranged on the abutment side 85 of the second flange. The first flange compression gauge measures a first flange compression Δf1 of the receiving device 80 under the bolt clamping device 200 or under the housing 202 of the bolt clamping device 200. The second flange compression gauge measures a second flange compression Δf2 of the receiving device 80 under the nut 12 of the bolt system 10.

[0093] A compression force Fs under the bolt clamping device must be determined at least via the first flange compression Δf1. Furthermore, a compression force Fm under the nut must be determined at least via the second flange compression Δf2.

[0094] The receiving device 80 has a first flange compression recess 98 and a second flange compression recess 99. The first and second flange compression recesses 98, 99 extend completely through the receiving device 80 from the abutment side 85 to the nut side 95. The first flange compression gauge 120 comprises a first flange compression probe 122, which extends through the first flange compression recess 98 and makes contact with the bolt clamping device 200. The second flange compression gauge 130 comprises a second flange compression probe 132, which extends through the second flange compression recess 99 and indirectly makes contact with the nut via a washer.

[0095] The bolt 20 has a centrally located first end face 23 (see FIG. 6 ) a first contact element 21. Furthermore, the abutment 32 has a second end face 33 (see FIG. 6 ) a second contact element 31. The bolt elongation measuring device 102 from FIG. 7 und 8 indicate via a bolt elongation measuring rod 112 and a bolt probe 117 (see schematic) FIG. 8 ) makes contact with the first and second contact elements 21, 31 of the bolt 20. The bolt elongation measuring rod 112 makes contact with the first contact element 21.

[0096] The embodiments shown in the figures are not to be interpreted as restrictive.

Claims

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: - 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).