TEST STAND AS WELL AS METHOD, TEST STAND AND USE OF A TEST STAND FOR DETERMINING THE MECHANICAL STRENGTH OF A WRAP SYSTEM FOR UNDERGROUND STEEL PIPES

Abstract

A test specimen (10), in particular for pressing into an object (12) to be tested, which is, for example, a covering system for buried steel pipes (14), has the shape of a truncated pyramid, truncated cone or a hemispherical layer with a base area (10g) and a top surface (10d), wherein - the projection of the top surface onto the base surface lies within the base surface; - the top surface is parallel to the base surface. A method for determining the mechanical strength of a casing system for buried steel pipes includes the following: - the test specimen is pressed from the outside against the encapsulation system with the top surface facing forward, according to a predetermined path and / or force profile; - the penetration depth of the test specimen into the encapsulation system is recorded; - the load-bearing capacity is determined depending on the measured penetration depth. A test rig (16) for determining the mechanical strength of a casing system for buried steel pipes comprises - a holding system (18); - a material testing machine (20) that can press the test specimen with the top surface forward against the encapsulation system; - a measuring device (22) that can detect the penetration depth of the test specimen into the encapsulation system; - a control device (24) which, according to the procedure, can control the material testing machine and the measuring device and determine the load-bearing capacity. The test specimen is used to determine the mechanical load-bearing capacity according to the procedure.

Description

[0001] The invention relates to a test specimen, and in particular a test specimen for pressing into an object to be tested, which is, for example, a casing system for buried steel pipes. The invention further relates to a method and a test rig for determining the mechanical load-bearing capacity of a casing system for buried steel pipes, as well as the use of a test specimen for determining the mechanical load-bearing capacity of a casing system for buried steel pipes.

[0002] DENSO GmbH from Leverkusen, Germany sells under the name "DENSO-LEN" ®-AS40 Plus / -R20 HT" is a cold-applied, two-band system for the corrosion protection coating of metal pipes and pipelines under extreme corrosion conditions and mechanical stresses. This two-band system complies with the standard EN 12068 "Cathodic corrosion protection - Organic coatings for the corrosion protection of steel pipelines laid in soil and water in conjunction with cathodic corrosion protection - Tapes and shrinkable materials" and represents a corrosion protection system for such pipes. It includes a solvent-based primer - designated "DENSOLEN". ® HT Primer" - according to EN 12068 for corrosion protection with DENSOLEN ® Tapes, a co-extruded 3-layer plastic tape - designated with "DENSOLEN" ® -AS40 Plus" - made of stabilized polyethylene carrier material with butyl rubber adhesive on both sides and a co-extruded 2-layer plastic tape - designated with "DENSOLEN" ®-R20 HT" - made of stabilized polyethylene carrier film with a butyl rubber adhesive on one side. The excellent bond between the adhesive and the carrier film is ensured by the co-extruded intermediate layer. The adhesive layer fuses completely with the outer layer of the DENSOLEN 3-layer plastic tape. ® -AS40 Plus. This two-band system exhibits interlocking of the bands in the overlap area, forming a dense and durable tubular sheath for the pipe, and it is virtually impermeable to water vapor and oxygen, resistant to soil bacteria and electrolytes, and compatible with factory coatings made of PE, PP, FBE, PU, ​​CTE, and bitumen.

[0003] The two most important mechanical parameters in the installation of metal pipes and pipelines – collectively referred to here as pipe laying – are impact resistance and indentation resistance. While impact resistance is a measure of short-term, but sometimes high-force, stress, indentation resistance refers to long-term, continuous stress. This can be simplified to the two stages of pipe laying as follows: The pipe, equipped with a corrosion protection system, is subjected to a short, intense impact load during its placement in the trench and its subsequent bedding. This can be described by its impact resistance.The subsequent backfilling of the trench and the pipe's resting on the trench bottom result in continuous stress on the corrosion protection system applied to the pipe from various types of loads. These loads result from the grain shape and size of the backfill material and the material at the trench bottom and can be described by the indentation resistance. The backfilling itself can also involve impact loading if larger particles fall or are thrown onto the corrosion protection system.

[0004] The European standard EN 12068 defines requirements for the testing of such corrosion protection systems. Impact resistance is tested according to Annex H, and indentation resistance according to Annex G. Annex G.1 “General” discloses: “The test consists of demonstrating the functionality of a coating using a high-voltage device and / or by determining the residual layer thickness after the coating, applied to a flat plate or tube, has been subjected to compression deformation by an indenter with a specified pressure.”

[0005] Annex G.2 “Testing apparatus” discloses: “a) Testing unit consisting of a vertically freely movable and low-friction guided cylindrical steel rod which acts at a right angle on a specimen. The rod must have a platform at the top on which weights can be placed and be equipped at the lower end with indentation dies having a flat end face of 11.3 mm, 5.65 mm or 1.8 mm in diameter (see Table G.1).” Table G.1: Stamp diameter and deformation pressure Klasse Pressure (± 5%) N / mm 2 Eindruckstempeldurchmesser mm A 0,1 11,30 ± 0,10 B 1,0 5,65 ± 0,05 C 10,0 1,80 ± 0,05 b) Dial gauge, readable to ≤ 0.05 mm, for measuring the vertical displacement of the steel rod. c) Steel plate, 8 mm thick x 75 mm x 75 mm, for strips or internally supported pipe sections DN 100, 100 mm long, minimum wall thickness 3 mm, for shrinkable materials. d) High-voltage device with a test probe, adjustable to a test voltage up to (15 ± 0.5) kV.

[0006] Annex G.4 “Test Method” discloses: “The indenter corresponding to the class is to be attached to the steel bar. The indenter is to be placed on an uncovered area of ​​the steel plate or tube and the reading T1 is to be recorded. The indenter is then to be placed centrally on the specimen, the appropriate weight is to be placed on the bar platform to apply the deformation pressure corresponding to the class (see Table G.1), and the time is to be recorded. After (72 ± 1) h of testing time at test temperature, a measurement is to be taken and the final reading T2 is to be recorded. The difference between the initial reading T1 and the final reading T2 is the residual coating thickness T3 (see Equation (G.1)):” T3=T2−T1

[0007] Then the weight and indentation stamp must be removed and within 3 minutes the dented area must be tested with the high-voltage device at a test voltage of 5 kV / mm of the original thickness of the coating, but at most at 15 kV.

[0008] In this known test method, the prescribed indentation die has a diameter of 11.30 ± 0.10 mm or 5.65 ± 0.05 mm or 1.80 ± 0.05 mm, and the prescribed test time of (72 ± 1) h is very long.

[0009] The object of the invention is to enable a better determination of the mechanical load-bearing capacity of a coating system for buried steel pipes by determining the residual layer thickness in a test method for the indentation resistance of coating systems for buried steel pipes.

[0010] Against this background, the invention proposes the subject matter of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0011] According to a first aspect of the invention, a test body is proposed, wherein - the test specimen essentially has the shape of a truncated pyramid with a base and a top surface, or essentially the shape of a truncated cone with a base and a top surface, or essentially the shape of a hemispherical layer with a base and a top surface; - the projection of the top surface onto the base surface lies within the base surface; and - the top surface is essentially parallel to the base surface.

[0012] The proposed test specimen is specifically designed and / or intended and / or suitable for pressing into an object to be tested, which is, for example, a covering system for buried steel pipes.

[0013] According to a second aspect of the invention, a method for determining the mechanical load-bearing capacity of a sheathing system for buried steel pipes is proposed, wherein - a test specimen designed according to the first aspect, is pressed from the outside against the encapsulation system at a test point with the cover surface leading; - the pressing is carried out according to a predetermined path and / or according to a predetermined force curve; - the penetration depth of the test specimen into the encapsulation system is recorded at a predetermined first time point; and - the mechanical strength of the encapsulation system is determined depending on the measured penetration depth.

[0014] According to a third aspect of the invention, a test rig for determining the mechanical load-bearing capacity of a sheathing system for buried steel pipes is proposed, comprising - a holding system for the encasing system; - a material testing machine comprising a test specimen designed according to the first aspect and designed in such a way that it can press the test specimen with the cover surface forward against the encapsulation system at a test point; - a measuring device designed to detect the penetration depth of the test specimen into the encapsulation system at a predetermined time; and - a control device designed in such a way that it can control the material testing machine and the measuring device and determine the mechanical load-bearing capacity according to a procedure designed according to the second aspect.

[0015] The proposed test rig is specifically designed and / or intended and / or suitable for use in a procedure that is configured according to the second aspect, or for carrying out such a procedure.

[0016] According to a fourth aspect of the invention, it is proposed to use a test specimen designed according to the first aspect to determine the mechanical load-bearing capacity of a sheathing system for buried steel pipes.

[0017] In the proposed use, the determination is carried out in particular according to a procedure that is designed according to the second aspect.

[0018] The invention enables the reliable determination of the mechanical load-bearing capacity of a coating system for buried steel pipes, thereby providing a more practical representation of the coating system's performance compared to the method known from EN 12068. This more practical representation allows for a more reliable assessment of the coating system's suitability. This advantageous effect is attributed to the special shape of the test specimen, whose cross-sectional area, measured at the level of the initial contact point of the test specimen with the object under test, increases with increasing penetration depth.In contrast, the indentation stamp known from EN 12068 has a predetermined diameter, which means it has the shape of a circular cylinder whose cross-sectional area, measured at the level of the initial contact point of the indentation stamp on the sample, remains constant with increasing penetration depth. The applicant has determined that the current difficulty lies in the consistently cylindrical shape of the indentation stamp. This shape does not reflect the actual contact points or the geometry of the soil constituents. Real grains are shaped differently and, in particular, have differently pointed protrusions and elevations. This is taken into account with the proposed test specimen. The test duration can be similar to that of the method known from EN 12068, but can also be shorter if necessary. Creep processes of the coating system will also continue to be considered.After the testing period, a final stage of penetration may be reached, or this can be inferred from calculations if necessary. This becomes particularly relevant when the bedding and / or backfilling of the trench is no longer carried out with sand with a very fine grain size, but with a bulk material with a coarser grain size. This has the economic advantage that excavated material, processed excavated material, or backfill material coarser than sand can be used. However, in this case, confirmation of the corrosion protection material's load-bearing capacity under the bedding and backfill material used must be provided.

[0019] Mechanical resilience can be classified, for example, by indentation resistance, remaining layer thickness, and impact resistance.

[0020] The specific geometric shape of the test specimen allows for the representation of different soil classes with their varying maximum grain sizes and their frequency distribution within that soil class. Furthermore, a strictest soil class, which represents the greatest stress on the encapsulation system and imposes the most stringent requirements, and the corresponding test specimen can be defined, so that meeting the load-bearing capacity of this strictest soil class also covers all less stringent soil classes.

[0021] In one exemplary embodiment, it is determined that the truncated pyramid or the truncated cone is straight or oblique.

[0022] Preferably, the base of the truncated cone is an ellipse or a circle.

[0023] In an exemplary embodiment, it is specified that the base and / or the top surface is convex and / or that the base of the truncated pyramid and / or the top surface of the truncated pyramid is equilateral, equiangular, or regular.

[0024] In one exemplary embodiment, it is specified that the base surface and / or the top surface is essentially flat.

[0025] In one exemplary embodiment, it is determined that - the base is an equilateral polygon or equilateral triangle with a first edge length k1; - the top surface is an equilateral polygon or equilateral triangle with a second side length k2; and - the second edge length k2 is smaller than the first edge length k1.

[0026] The polygon of the base has the same number of vertices as that of the top surface.

[0027] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first edge length k1 and larger than the second edge length k2.

[0028] In one exemplary embodiment, it is determined that - the base is a circle with a first diameter d1; - the top surface is a circle with a second diameter d2; and - the second diameter d2 is smaller than the first diameter d1.

[0029] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first diameter d1 and larger than the second diameter d2.

[0030] In one exemplary embodiment, it is determined that - the base is an ellipse with a first principal axis a1; - the top surface is a circle with a second principal axis a2; and - the second principal axis a2 is smaller than the first principal axis a1.

[0031] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first principal axis a1 and larger than the second principal axis a2.

[0032] In an exemplary embodiment of the proposed method, it is specified that the determination of the mechanical load-bearing capacity is carried out depending on a predetermined reference value.

[0033] In an exemplary embodiment of the proposed method, it is determined that the mechanical load-bearing capacity B is achieved by: B=T:V or B=V−T is calculated, where T is the measured penetration depth and V is the comparison value.

[0034] In an exemplary embodiment of the proposed method, it is specified that - it is checked whether B≥N applies, where N is a standard requirement value; - a result signal with the value "Mechanical strength test passed" is generated if the result of this test is positive, and otherwise a result signal with the value "Mechanical strength test failed" is generated.

[0035] In an exemplary embodiment of the proposed method, it is determined that - the coating system has a starting layer thickness before pressing at the test point; and - the initial layer thickness is the reference value V.

[0036] In an exemplary embodiment of the proposed method, it is determined that a residual layer thickness R of the coating system after pressing at the test point is determined by the following: R=V−T is calculated.

[0037] The penetration depth can be measured in any way required, for example continuously over a predetermined period of time and / or discontinuously at predetermined discrete times.

[0038] In an exemplary embodiment of the proposed method, it is determined that a rate of change or slope of the time-penetration depth curve is calculated from at least two of the penetration depth measurements acquired at different times. This is preferably done at a predetermined time interval at the end of a predetermined acquisition period. If the value of the rate of change or slope exceeds a predetermined threshold, the acquisition can be continued for a predetermined time interval; otherwise, the acquisition is terminated.

[0039] In an exemplary embodiment of the proposed method, it is determined that - the penetration depth of the test specimen into the encapsulation system is recorded at at least one predetermined second time point; and - the mechanical resilience of the encapsulation system is determined as a function of the penetration depths recorded at the first time point and at least one second time point.

[0040] In an exemplary embodiment of the proposed method, it is determined that - an extrapolation depth is extrapolated from the recorded penetration depths to a predetermined target time; and - the determination of the mechanical load-bearing capacity is carried out as a function of the extrapolation depth.

[0041] In an exemplary embodiment of the proposed test rig, it is determined that - the material testing machine is designed in such a way that it can exert a constant force on the test specimen in order to perform the pressing.

[0042] In an exemplary embodiment of the proposed test rig, it is determined that - the top surface faces downwards and the base surface faces upwards; and - the material testing machine includes a weight that rests on the base, is supported on the base, or engages the base.

[0043] In an exemplary embodiment of the proposed test rig, it is determined that - the control unit is designed in such a way that it can store and evaluate measurement data acquired by the measuring device in accordance with the procedure for determining the mechanical load-bearing capacity.

[0044] The explanations relating to one aspect of the invention, in particular to individual features of that aspect, apply analogously to the other aspects of the invention.

[0045] When the terms "approximately" or "about" or "essentially" are used in this disclosure in connection with values ​​or ranges of values, or with properties or geometries, they are to be understood as a tolerance range that a person skilled in the art considers customary in this field. In particular, when using the terms "approximately" or "about" in connection with values ​​or ranges of values, a tolerance range is ±20%, preferably ±10%, and more preferably ±5%. Lower limits of value ranges may thus be undershot by 5% to 20%. Upper limits of value ranges may thus be exceeded by 5% to 20%. Where different value ranges, for example, preferred and more preferred value ranges, are specified in the present invention, the lower limits and the upper limits of the different value ranges can be combined with one another.

[0046] In the following, embodiments of the invention are explained in more detail by way of example with reference to the accompanying drawings. The individual features resulting therefrom are not limited to the individual embodiments, but can be combined with individual features described above and / or with individual features of other embodiments. The details in the drawings are to be interpreted as illustrative only, not as limiting. The reference numerals contained in the claims are not intended to limit the scope of protection of the invention in any way, but merely refer to the embodiments shown in the drawings.

[0047] The drawings show in Fig. 1 a top view of a first embodiment of a test body for pressing into an object to be tested; Fig. 2. The side view from the front. Fig. 1; Fig. 3 a top view of a second embodiment of the test specimen; Fig. 4. The side view from the front. Fig. 3; Fig. 5 a top view of a third embodiment of the test specimen; Fig. 6. The side view from the front. Fig. 5; Fig. 7 a top view of a fourth embodiment of the test specimen; Fig. 8 the side view from the front Fig. 7; Fig. 9 a top view of a fifth embodiment of the test specimen; Fig. 10 the side view from the front to Fig. 9; Fig. 11 a top view of a sixth embodiment of the test specimen; Fig. 12 the side view from the front to Fig. 11; Fig. 13 a top view of a seventh embodiment of the test specimen; Fig. 14 the side view from the front to Fig. 13; Fig. 15 a top view of an eighth embodiment of the test specimen; Fig. 16 the side view from the front to Fig. 15; Fig. 17 a side view of a preferred embodiment of a test rig for determining the mechanical load-bearing capacity of a casing system for buried steel pipes; Fig. 18 A first embodiment of a method for determining the mechanical load-bearing capacity of a casing system for buried steel pipes, wherein the method uses the test rig from the Fig. 17 is executed; and Fig. 19 a second embodiment of the method.

[0048] In Fig. 1 and Fig. Figure 2 is a first embodiment of a test body 10 according to the invention, shown schematically, which is designed, intended and suitable for pressing into an object 12 to be tested, which is for example a covering system 12 for buried steel pipes 14.

[0049] In this embodiment, the test specimen 10 has the shape of a truncated cone with a base area 10g and a top surface 10d. The truncated cone is, for example, an oblique truncated circular cone whose base 10g is a circle, so that its top surface 10d is also a circle. The base 10g has a first diameter d1, and the top surface 10d has a second diameter d2, which is smaller than the first diameter d1. The center of the top surface 10d is offset from the center of the base 10g, but only to the extent that the projection of the top surface 10d onto the base 10g lies within the base 10g. The top surface 10d and the base 10g are parallel to each other and planar. The test specimen 10 has a height h that is smaller than the first diameter d1 and larger than the second diameter d2. The height h essentially corresponds to the distance between the top surface 10d and the base surface 10g.

[0050] In Fig. 3 and Fig. Figure 4 schematically depicts a second embodiment of the test specimen 10. This embodiment is similar to the first embodiment, so the differences will be explained in more detail below.

[0051] In this embodiment, the truncated cone is, for example, a right truncated circular cone, such that the center of the top surface 10d is not offset from the center of the base surface 10g, but lies above it.

[0052] In Fig. 5 and Fig. Figure 6 schematically depicts a third embodiment of the test specimen 10. This embodiment is similar to the first embodiment, so the differences will be explained in more detail below.

[0053] In this embodiment, the truncated cone is, for example, an oblique truncated ellipse cone whose base 10g is an ellipse, so that its top surface 10d is also an ellipse. The base 10g has a first principal axis a1, and the top surface 10d has a second principal axis a2, which is smaller than the first principal axis a1. The test specimen 10 has a height h, which is smaller than the first principal axis a1 and larger than the second principal axis a2.

[0054] In Fig. 7 and Fig. Figure 8 schematically depicts a fourth embodiment of the test specimen 10. This embodiment is similar to the third embodiment, so the differences will be explained in more detail below.

[0055] In this embodiment, the truncated cone is, for example, a right truncated ellipse cone, such that the center of the top surface 10d is not offset from the center of the base surface 10g, but lies above it.

[0056] In Fig. 9 and Fig. Figure 10 is a schematic representation of a fifth embodiment of the test specimen 10. This embodiment is similar to the first embodiment, so the differences will be explained in more detail below.

[0057] In this embodiment, the test specimen 10 has the shape of a truncated pyramid with a base area 10g and a top surface 10d. The truncated pyramid is, for example, an oblique square truncated pyramid whose base area 10g is a square, so that its top surface 10d is also a square. The base area 10g has a first edge length k1, and the top surface 10d has a second edge length k2, which is shorter than the first edge length k1. The test specimen 10 has a height h, which is shorter than the first edge length k1 and longer than the second edge length k2.

[0058] In Fig. 11 and Fig. Figure 12 schematically depicts a sixth embodiment of the test specimen 10. This embodiment is similar to embodiment 5n, so the differences will be explained in more detail below.

[0059] In this embodiment, the truncated pyramid is, for example, a straight square truncated pyramid, such that the center of the top surface 10d is not offset from the center of the base surface 10g, but lies above it.

[0060] In Fig. 13 and Fig. Figure 14 schematically depicts a seventh embodiment of the test specimen 10. This embodiment is similar to the sixth embodiment, so the differences will be explained in more detail below.

[0061] In this embodiment, the test specimen 10 has the shape of a right triangular truncated pyramid with a base area 10g and a top surface 10d. The base area 10g is an equilateral triangle, so its top surface 10d is also an equilateral triangle. The base area 10g has a first edge length k1, and the top surface 10d has a second edge length k2, which is shorter than the first edge length k1. The test specimen 10 has a height h, which is shorter than the first edge length k1 and longer than the second edge length k2. Fig. 15 and Fig. Figure 16 schematically depicts an eighth embodiment of the test specimen 10. This embodiment is similar to the second embodiment, so the differences will be explained in more detail below.

[0062] In this embodiment, the test specimen 10 has the shape of a hemispherical layer with a base area 10g and a top surface 10d, such that the base area 10g and the top surface 10d are circles. The base area 10g has a first diameter d1, and the top surface 10d has a second diameter d2, which is smaller than the first diameter d1. The test specimen 10 has a height h, which is smaller than the first diameter d1 and larger than the second diameter d2.

[0063] In Fig. Figure 17 schematically shows a preferred embodiment of a test rig 16 according to the invention for determining the mechanical load-bearing capacity of a covering system 12 for buried steel pipes 14, wherein the covering system 12 is, by way of example, a two-band system of the type “DENSOLEN”. ®-AS40 Plus / -R20 HT" and the mechanical load-bearing capacity is exemplified by an indentation resistance or a residual layer thickness. The test rig 16 comprises a holding system 18 for the coating system 12, a material testing machine 20, a measuring device 22, and a control unit 24, which is designed to control the material testing machine 20 and the measuring device 22 according to a predetermined procedure and to determine the mechanical load-bearing capacity. The holding system 18 includes, for example, a substantially V-shaped holding channel into which the coating system 12 to be tested, together with the steel tube 14, can be inserted. Alternatively, instead of the steel tube 14 provided with the coating system 12, a flat plate (not shown) onto which the coating system 12 has been applied can also be used in the test rig 16 for the determination.In this case, the holding system 18 includes, for example, a horizontal holding plate (not shown) instead of the V-shaped holding channel, onto which the enclosure system 12 to be tested, including the plate, can be placed.

[0064] The material testing machine 20 comprises a test specimen 10, designed according to the second embodiment, a weight 26, a crossbeam 28, a guide system 30 for the crossbeam 28, and a locking device 32 for the guide system 30. The guide system 30 comprises two vertical guide rails on which the crossbeam 28 is mounted so as to be vertically movable, allowing the vertical distance between the crossbeam 28 and the holding system 18, or the covering system 12 including the steel tube 14 inserted in its holder groove, to be changed. The locking device 32 can selectively lock and release the crossbeam 28 relative to the guide rails. The test specimen 10 is detachably attached to the underside of the crossbeam 28 with its base area 10g, so that the top surface 10d points downwards and thus towards the holding system 18 or towards the covering system 12 including the steel tube 14 inserted in its holder groove.The weight 26 rests on the top of the crossbeam 28 and thus acts on the base 10g. Consequently, the material testing machine 20 is designed such that it can press the test specimen 10, with its top surface 10d facing forward, against the enclosure system 12 at a desired test point and thereby exert a constant force on the test specimen 10. This constant force is the weight force, which is essentially generated by the masses of the test specimen 10, the weight 26, and the crossbeam 28.

[0065] The measuring device 22 detects the, in particular vertical, position of the crossbeam 28 and thus of the test specimen 10 attached to it relative to the holding system 18 or to its holder groove and thus to the covering system 12 including the steel tube 14 inserted in the holder groove, and it is designed in such a way that it can detect the penetration depth of the test specimen 10 into the covering system 12 at a predetermined time.

[0066] The control unit 24 is coupled to the material testing machine 20 and in particular to its locking device 32 as well as to the measuring device 22, so that it can actuate and in particular lock and release the locking device 32 and can read, store and evaluate the measurement data recorded by the measuring device 22.

[0067] In Fig. Figure 18 schematically illustrates a first embodiment of a method according to the invention for determining the mechanical load-bearing capacity of a covering system 12 for buried steel pipes 14, which can be exemplified using the test rig 16 from the Fig. 17 and in particular its control device 24 can be executed.

[0068] In step S1, the test bench 16 is made of Fig. 17 provided, and the control unit 24 controls the guide system 30 to move the crossbeam 28 into an upper position, which represents an assembly position and in Fig. Figure 17 shows the following steps. The test specimen 10, with its base area of ​​10g, is then detachably attached to the underside of the crossbeam 28, and the weight 26 is placed on the top of the crossbeam 28. Furthermore, a coating system 12 to be tested, together with the steel tube 14 it encases, is placed horizontally in the retaining groove of the holding system 18 and aligned relative to the test specimen 10 such that a predetermined test point on the surface of the coating system 12 is located vertically below the top surface 10d. At this point, the coating system 12 has an initial layer thickness at the test point, which serves as a reference value V and is, for example, 3.0 mm.

[0069] In step S2, which follows step S1, the control unit 24 controls the guide system 30 to move the crossbeam 28 into a starting position in which the cover surface 10d rests on the test point without pressure. The control unit 24 also actuates the locking device 32, thus fixing the crossbeam 28 relative to the guide rails. The starting position is detected by the measuring device 22 and stored as a zero depth T0 = 0 mm.

[0070] In step S3, which follows step S2, the control unit 24 releases the locking device 32 and simultaneously activates the measuring device 22 to start a time measurement. By releasing the locking device 32, the cover surface 10d is pressed against the enclosure system 12 at the test point by the masses of the test specimen 10, the weight 26, and the crossbeam 28 with a predetermined constant force. The enclosure system 12 yields at this point, allowing the test specimen 10 to penetrate the material of the enclosure system 12 and the crossbeam 28 to move downwards relative to the guide rails.

[0071] In step S4, which follows step S3, the measuring device 22 records the penetration depth T of the test specimen 10 into the encapsulation system 12 at a predetermined first time point, which is determined by time measurement, and stores this as a first penetration depth T1, which is, for example, 1.2 mm. The first time point is, for example, 10 h.

[0072] In step S5, which follows step S4, the control unit 24 determines a mechanical load-bearing capacity B of the enclosing system 12 as a function of the penetration depth T, by B=V−T1=3.0mm−1.2mm=1.8mm The calculation involves T1 being the measured initial penetration depth and V being the reference value. Thus, the mechanical load-bearing capacity is determined as a function of a predetermined reference value.

[0073] In step S6, which follows step S5, the control unit 24 checks whether B≥N The following applies, where N is a standard requirement value specified for the respective enclosure system 12 to be tested and is, for example, 1.7 mm. The control unit 24 generates a result signal with the value "Mechanical strength test passed" if the result of this test is positive, and otherwise a result signal with the value "Mechanical strength test failed". In the present example, the result signal has the first value.

[0074] In Fig. Figure 19 schematically illustrates a second embodiment of the method. This embodiment is similar to the first embodiment, so the differences will be explained in more detail below.

[0075] In this embodiment, the time measurement continues without interruption.

[0076] In step S7, which lies between steps S4 and S5, the measuring device 22 records the penetration depth T of the test specimen 10 into the coating system 12 at a predetermined second time point, which is determined by time measurement, and stores this as a second penetration depth T2, which is, for example, 1.4 mm. The second time point is, for example, 20 h.

[0077] In this embodiment, in step S5, the control unit 24 determines the mechanical load-bearing capacity B as a function of the first and second penetration depths T1 and T2 by extrapolating an extrapolation depth TE to a predetermined target time, for example 72 h, from the zero depth T0 and the detected penetration depths T1 and T2. The extrapolation can be performed in any desired manner, for example according to Richardson extrapolation. In the present case, the points (0 h; 0 mm), (10 h; 1.2 mm), and (20 h; 1.4 mm) are used as reference points from which, for example, the desired point (72 h; 1.5 mm) is extrapolated, resulting in an extrapolation depth TE of 1.5 mm. Then, B=V−TE=3.0mm−1.5mm=1.5mm The calculation is performed. Thus, the determination of the mechanical load-bearing capacity is carried out as a function of the extrapolation depth.

[0078] In this embodiment, the standard requirement value N is reduced in step S6, for example to 1.55 mm. In the present example, the result signal has the second value, since the test result B≥N is negative. REFERENCE MARK LIST 10 test specimens 10d / 10g Coverage area / Base area of ​​10 12. Item to be inspected, packaging system 14 steel pipes 16 Test bench 18 holding system for 12 20 material testing machines 22 Measuring device 24 Control unit 26 weights 28 crossbeams 30 Management system 32 locking devices a1 / a2 first / second principal axis of 10g / 10d B mechanical load capacity of 12 d1 / d2 first / second diameter of 10g / 10d h height of 10 k1 / k2 first / second edge length of 10g / 10d N standard requirement value for B R residual layer thickness of 12 T Penetration depth of 10 in 12 V comparison value, initial layer thickness of 12 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Standard EN 12068

[0004] Annex G. Annex G.1 “General

[0004]

Claims

[1] Test body (10), in particular for pressing into an object (12) to be tested, which is for example a sheathing system (12) for buried steel pipes (14), wherein - the test specimen (10) has essentially the shape of a truncated pyramid with a base (10g) and a top surface (10d) or essentially the shape of a truncated cone with a base (10g) and a top surface (10d) or essentially the shape of a hemispherical layer with a base (10g) and a top surface (10d); - the projection of the top surface (10d) onto the base surface (10g) lies within the base surface (10g); and - the top surface (10d) is essentially parallel to the base surface (10g). [2] Test specimen (10) according to claim 1, wherein - whether the truncated pyramid or cone is straight or oblique. [3] Test specimen (10) according to one or more of the preceding claims, wherein - the base (10g) and / or the top surface (10d) is convex or equilateral or equiangular or regular. [4] Test specimen (10) according to one or more of the preceding claims, wherein - the top surface (10d) is essentially flat. [5] Test specimen (10) according to one or more of claims 1 to 4, wherein - the base (10g) is an equilateral polygon or triangle with a first edge length k1; - the top surface (10d) is an equilateral polygon or triangle with a second side length k2; and - the second edge length k2 is smaller than the first edge length k1. [6] Test specimen (10) according to claim 5, wherein - the test specimen (10) has a height h that is smaller than the first edge length k1 and larger than the second edge length k2. [7] Test specimen (10) according to one or more of claims 1 to 4, wherein - the base area (10g) is a circle with a first diameter d1; - the top surface (10d) is a circle with a second diameter d2; and - the second diameter d2 is smaller than the first diameter d1. [8] Test specimen (10) according to claim 7, wherein - the test specimen (10) has a height h that is smaller than the first diameter d1 and larger than the second diameter d2. [9] Test specimen (10) according to one or more of claims 1 to 4, wherein - the base area (10g) is an ellipse with a first principal axis a1; - the top surface (10d) is a circle with a second principal axis a2; and - the second principal axis a2 is smaller than the first principal axis a1. [10] Test specimen (10) according to claim 9, wherein - the test specimen (10) has a height h that is smaller than the first principal axis a1 and larger than the second principal axis a2. [11] Method for determining the mechanical load-bearing capacity of a covering system (12) for buried steel pipes (14), wherein - a test body (10) designed according to one or more of claims 1 to 10, is pressed from the outside against the covering system (12) at a test point with the cover surface (10d) leading; - the pressing is carried out according to a predetermined path and / or according to a predetermined force curve; - the penetration depth of the test specimen (10) into the encapsulation system (12) is recorded at a predetermined first time point; and - the mechanical strength of the encapsulation system (12) is determined as a function of the detected penetration depth. [12] Method according to claim 11, wherein - the determination of the mechanical load-bearing capacity is carried out depending on a predetermined reference value. [13] Method according to claim 12, wherein - the determination of the mechanical load-bearing capacity B is carried out by the fact that B=T:V or B=V−T is calculated, where T is the measured penetration depth and V is the comparison value. [14] Method according to claim 13, wherein - it is checked whether B≥N applies, where N is a standard requirement value; - a result signal with the value "Mechanical strength test passed" is generated if the result of this test is positive, and otherwise a result signal with the value "Mechanical strength test failed" is generated. [15] Method according to one or more of claims 12 to 14, wherein - the coating system (12) has an initial layer thickness before pressing at the test site; and - the initial layer thickness is the reference value V. [16] Method according to claim 15, wherein - a residual layer thickness R of the coating system (12) after pressing at the test point is determined by the fact that R=V−T is calculated. [17] Method according to one or more of claims 11 to 16, wherein - the penetration depth of the test specimen (10) into the encapsulation system (12) is recorded at at least one predetermined second time point; and - the mechanical strength of the encapsulation system (12) is determined as a function of the penetration depths recorded at the first time point and at least one second time point. [18] Method according to claim 17, wherein - an extrapolation depth is extrapolated from the recorded penetration depths to a predetermined target time; and - the determination of the mechanical load-bearing capacity is carried out as a function of the extrapolation depth. [19] Test rig (16) for determining the mechanical load-bearing capacity of a casing system (12) for buried steel pipes (14), comprising - a holding system (18) for the enclosing system (12); - a material testing machine (20) comprising a test specimen (10) designed according to one or more of claims 1 to 10 and designed in such a way that it can press the test specimen (10) with the cover surface (10d) forward at a test point against the encapsulation system (12); - a measuring device (22) designed to detect the penetration depth of the test specimen (10) into the encapsulation system (12) at a predetermined time; and - a control device (24) configured such that it can control the material testing machine (20) and the measuring device (22) and determine the mechanical load-bearing capacity according to a method configured according to one or more of claims 11 to 18. [20] Test stand (16) according to claim 19, wherein - the material testing machine (20) is designed in such a way that it can exert a constant force on the test specimen (10) in order to perform the pressing. [21] Test stand (16) according to claim 20, wherein - the top surface (10d) faces downwards and the base surface (10g) faces upwards; and - the material testing machine (20) comprises a weight (26) that rests on the base (10g) or is supported on the base (10g) or engages the base (10g). [22] Test stand (16) according to one or more of claims 19 to 21, wherein - the control device (24) is designed in such a way that it can store and evaluate measurement data acquired by the measuring device in accordance with the procedure for determining the mechanical load-bearing capacity. [23] Use of a test specimen (10) designed according to one or more of claims 1 to 10 for determining the mechanical strength of a covering system (12) for buried steel pipes (14), wherein the determination is carried out in particular according to a method designed according to one or more of claims 11 to 18.

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