Test body and method, test stand and use of a test body for determining a mechanical load-bearing capacity of a sheathing system for buried steel pipes

Abstract

In order to achieve the object of allowing better determination of a mechanical load-bearing capacity of a sheathing system for buried steel pipes in a test method for testing the indentation resistance of sheathing systems for buried steel pipes by determining the residual layer thickness, a test body (10) is proposed, wherein the test body has substantially the shape of a truncated pyramid with a base surface and a top surface or substantially the shape of a truncated cone with a base surface and a top surface or substantially the shape of a hemispherical layer with a base surface and a top surface; the projection of the top surface onto the base surface lies within the base surface; and the top surface is substantially parallel to the base surface. Furthermore, a method for determining a mechanical load-bearing capacity of a sheathing system for buried steel pipes and a test stand (16) for determining a mechanical load-bearing capacity of a sheathing system for buried steel pipes are proposed.

Description

[0001] August 1, 2025

[0002] 752 PA 20012 WO

[0003] 1

[0004] 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

[0005] 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.

[0006] DENSO GmbH, based in Leverkusen, Germany, markets a cold-applied, two-band system under the name "DENSO-LEN®-AS40 Plus / -R20 HT" 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 constitutes a corrosion protection system for such pipes.It comprises a solvent-based primer – designated "DENSOLEN® HT Primer" – compliant with EN 12068 for corrosion protection with DENSOLEN® tapes, a co-extruded 3-layer plastic tape – designated "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 "DENSOLEN®-R20 HT" – made of stabilized polyethylene carrier film with 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 bonds completely with the outer layer of the DENSOLEN®-AS40 Plus 3-layer plastic tape.This two-band system exhibits fusion of the bands in the overlap area, forming a dense and durable tubular sheath for the pipe. 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, ​​GTE, and bitumen. August 2025.

[0007] 752 PA 20012 WO

[0008] 2

[0009] The two most important mechanical parameters in the installation of Meta II 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 is a long-term, continuous force. This can be simplified to the two stages of pipe laying as follows: The pipe, equipped with the 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.

[0010] 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, "General," discloses: "The test consists of verifying 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."

[0011] Annex G.2 "Testing apparatus" discloses: "a) A testing unit consisting of a vertically freely movable and low-friction guided cylindrical steel rod acting at a right angle to a specimen. The rod must have a platform at the top onto 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 Eq. I. August 2025"

[0012] 752 PA 20012 WO

[0013] 3

[0014] Table G.1: Stamp diameter and deformation pressure b) Dial gauge, readable to < 0.05 mm, to measure the vertical path 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."

[0015] Annex G.4 "Test Method" discloses: "The indentation die corresponding to the class is to be attached to the steel bar. The indentation die is to be placed on an uncovered area of ​​the steel plate or tube and the reading Ti is to be recorded. The indentation die 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 Eq.), 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 Ti and the final reading T2 is the residual coating thickness T3 (see Eq. Eq.): T3 = T2 - T! (Eq.)"

[0016] 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.

[0017] 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.

[0018] The object of the invention is to provide a testing method for indentation resistance. August 1, 2025

[0019] 752 PA 20012 WO

[0020] 4. The aim of the study was to enable a better determination of the mechanical load-bearing capacity of a covering system for buried steel pipes by determining the residual layer thickness.

[0021] Against this background, the invention proposes the subject matter of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0022] According to a first aspect of the invention, a test body is proposed, wherein

[0023] - 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;

[0024] - the projection of the top surface onto the base surface lies within the base surface; and

[0025] - the top surface is essentially parallel to the base surface.

[0026] 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.

[0027] 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

[0028] - 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;

[0029] - the pressing is carried out according to a predetermined path and / or according to a predetermined force curve;

[0030] - the penetration depth of the test specimen into the encapsulation system is recorded at a predetermined first time point; and

[0031] - the mechanical strength of the encapsulation system is determined depending on the measured penetration depth.

[0032] 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, in order to- August 1, 2025 752 PA 20012 WO

[0033] comprising 5

[0034] - a holding system for the encasing system;

[0035] - 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;

[0036] - a measuring device designed to detect the penetration depth of the test specimen into the encapsulation system at a predetermined time; and

[0037] - 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.

[0038] 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.

[0039] 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.

[0040] In the proposed use, the determination is carried out in particular according to a procedure that is designed according to the second aspect.

[0041] 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 that 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 specimen, remains constant with increasing penetration depth. The applicant has determined that the Schwie- I. August 2025.

[0042] 752 PA 20012 WO

[0043] 6. The current design of the indentation stamp is cylindrical. This shape does not reflect the actual contact points or the geometry of the soil constituents. Real grains have different shapes and, in particular, vary in the degree of pointed projections 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 should also continue to be considered. After the test duration, a final stage of penetration may have been reached, or this can be deduced by calculation 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 load-bearing capacity of the corrosion protection material due to the bedding and backfill material used must be provided.

[0044] Mechanical resilience can be classified, for example, by indentation resistance, remaining layer thickness, and impact resistance.

[0045] 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.

[0046] In one exemplary embodiment, it is determined that the truncated pyramid or the truncated cone is straight or oblique.

[0047] Preferably, the base of the truncated cone is an ellipse or a circle.

[0048] In one exemplary embodiment, it is specified that the base and / or the top surface is convex and / or that the base and / or the top surface of the truncated pyramid is equilateral, equiangular, or regular. August 1, 2025 752 PA 20012 WO

[0049] 7

[0050] In one exemplary embodiment, it is specified that the base surface and / or the top surface is essentially flat.

[0051] In one exemplary embodiment, it is determined that

[0052] - the base is an equilateral polygon or equilateral triangle with a first edge length kl;

[0053] - the top surface is an equilateral polygon or equilateral triangle with a second side length k2; and

[0054] - the second edge length k2 is smaller than the first edge length kl.

[0055] The polygon of the base has the same number of vertices as that of the top surface.

[0056] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first edge length kl and larger than the second edge length k2.

[0057] In one exemplary embodiment, it is determined that

[0058] - the base is a circle with a first diameter dl;

[0059] - the top surface is a circle with a second diameter d2; and

[0060] - the second diameter d2 is smaller than the first diameter dl.

[0061] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first diameter dl and larger than the second diameter d2.

[0062] In one exemplary embodiment, it is determined that

[0063] - the base is an ellipse with a first principal axis al;

[0064] - the top surface is a circle with a second principal axis a2; and

[0065] - the second principal axis a2 is smaller than the first principal axis al.

[0066] In an exemplary embodiment, it is determined that the test specimen has a height h that is smaller than the first principal axis al and larger than the second principal axis a2.

[0067] 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.

[0068] In an exemplary embodiment of the proposed method, it is specified that August 1, 2025

[0069] 752 PA 20012 WO

[0070] 8. The determination of the mechanical load-bearing capacity B is carried out by the fact that

[0071] B = T : V or

[0072] B = V - T is calculated, where T is the measured penetration depth and V is the comparison value.

[0073] In an exemplary embodiment of the proposed method, it is determined that

[0074] - it is checked whether

[0075] B > N holds, where N is a standard requirement value;

[0076] - 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.

[0077] In an exemplary embodiment of the proposed method, it is determined that

[0078] - the coating system has a starting layer thickness before pressing at the test point; and

[0079] - the initial layer thickness is the reference value V.

[0080] 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:

[0081] R = V - T is calculated.

[0082] 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.

[0083] 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 recorded at different times. This is preferably done within a predetermined time interval at the end of a predetermined recording section. If the value of the rate of change or slope exceeds a predetermined value, the method is then evaluated. (August 1, 2025)

[0084] 752 PA 20012 WO

[0085] If the threshold of 9 votes is exceeded, data collection can continue for a predetermined period of time; otherwise, data collection will be terminated.

[0086] In an exemplary embodiment of the proposed method, it is determined that

[0087] - the penetration depth of the test specimen into the encapsulation system is recorded at at least one predetermined second time point; and

[0088] - 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.

[0089] In an exemplary embodiment of the proposed method, it is determined that

[0090] - an extrapolation depth is extrapolated from the recorded penetration depths to a predetermined target time; and

[0091] - the determination of the mechanical load-bearing capacity is carried out as a function of the extrapolation depth.

[0092] In an exemplary embodiment of the proposed test rig, it is determined that

[0093] - 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.

[0094] In an exemplary embodiment of the proposed test rig, it is determined that

[0095] - the top surface faces downwards and the base surface faces upwards; and

[0096] - the material testing machine includes a weight that rests on the base, is supported on the base, or engages the base.

[0097] In an exemplary embodiment of the proposed test rig, it is determined that

[0098] - 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.

[0099] 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.

[0100] In the context of this disclosure, the term “approximately” or “about” or “essentially” is used in connection with values ​​or ranges of values, or with proprietary information. August 1, 2025 752 PA 20012 WO

[0101] When the terms "approximately" or "about" are used in connection with values ​​or ranges of values, they refer to a tolerance range that is considered customary by those skilled in the art in this field. In particular, when using the terms "about" or "approximately" in connection with values ​​or ranges of values, a tolerance range is ±20%, preferably ±10%, and more preferably ±5%. Lower limits of ranges of values ​​may thus be undercut by 5% to 20%. Upper limits of ranges of values ​​may thus be exceeded by 5% to 20%. Where different ranges of values, for example, preferred and more preferred ranges of values, are specified in the present invention, the lower limits and the upper limits of the different ranges of values ​​can be combined with one another.

[0102] 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.

[0103] The drawings show in

[0104] Fig. 1 shows a top view of a first embodiment of a test body for pressing into an object to be tested;

[0105] Fig. 2 shows the side view from the front compared to Fig. 1;

[0106] Fig. 3 shows a top view of a second embodiment of the test specimen;

[0107] Fig. 4 shows the side view from the front compared to Fig. 3;

[0108] Fig. 5 shows a top view of a third embodiment of the test specimen;

[0109] Fig. 6 shows the side view from the front compared to Fig. 5;

[0110] Fig. 7 shows a top view of a fourth embodiment of the test specimen;

[0111] Fig. 8 shows the side view from the front compared to Fig. 7;

[0112] Fig. 9 shows a top view of a fifth embodiment of the test specimen;

[0113] Fig. 10 shows the side view from the front compared to Fig. 9;

[0114] Fig. 11 shows a top view of a sixth embodiment of the test specimen;

[0115] Fig. 12 the side view from the front to Fig. 11; August 1, 2025 752 PA 20012 WO

[0116] 11

[0117] Fig. 13 shows a top view of a seventh embodiment of the test specimen;

[0118] Fig. 14 shows the side view from the front compared to Fig. 13;

[0119] Fig. 15 shows a top view of an eighth embodiment of the test specimen;

[0120] Fig. 16 shows the side view from the front compared to Fig. 15;

[0121] Fig. 17 shows 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;

[0122] Fig. 18 shows a first embodiment of a method for determining the mechanical load-bearing capacity of a casing system for buried steel pipes, wherein the method is carried out using the test rig from Fig. 17; and Fig. 19 shows a second embodiment of the method.

[0123] In Fig. 1 and Fig. 2, a first embodiment of a test body 10 according to the invention is schematically shown, 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.

[0124] In this embodiment, the test specimen 10 has the shape of a truncated cone with a base area 10g and a top surface lOd. The truncated cone is, for example, an oblique truncated circular cone whose base 10g is a circle, so that its top surface lOd is also a circle. The base 10g has a first diameter dl, and the top surface lOd has a second diameter d2, which is smaller than the first diameter dl. The center of the top surface lOd is offset from the center of the base 10g, but only to the extent that the projection of the top surface lOd onto the base 10g lies within the base 10g. The top surface lOd 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 dl and larger than the second diameter d2. The height h essentially corresponds to the distance between the top surface lOd and the base 10g.

[0125] Figures 3 and 4 schematically depict 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.

[0126] In this embodiment, the truncated cone is, for example, a right truncated circular cone, August 1, 2025 752 PA 20012 WO

[0127] 12 so that the center of the top surface lOd is not offset from the center of the base surface 10g, but lies above it.

[0128] Figures 5 and 6 schematically depict 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.

[0129] 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 lOd is also an ellipse. The base 10g has a first principal axis al, and the top surface lOd has a second principal axis a2, which is smaller than the first principal axis al. The test specimen 10 has a height h, which is smaller than the first principal axis al and larger than the second principal axis a2.

[0130] Figures 7 and 8 schematically depict 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.

[0131] In this embodiment, the truncated cone is, for example, a right truncated ellipse cone, such that the center of the top surface lOd is not offset from the center of the base surface 10g, but lies above it.

[0132] Figures 9 and 10 schematically depict 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.

[0133] In this embodiment, the test specimen 10 has the shape of a truncated pyramid with a base area 10g and a top surface lOd. The truncated pyramid is, for example, an oblique square truncated pyramid whose base area 10g is a square, so that its top surface lOd is also a square. The base area 10g has a first edge length kl, and the top surface lOd has a second edge length k2, which is shorter than the first edge length kl. The test specimen 10 has a height h, which is shorter than the first edge length kl and longer than the second edge length k2.

[0134] Figures 11 and 12 schematically depict a sixth embodiment of the test specimen 10. This embodiment is similar to embodiment 5n, so that in the following, prior to August 1, 2025, 752 PA 20012 WO

[0135] 13

[0136] All the differences will be explained in more detail.

[0137] In this embodiment, the truncated pyramid is, for example, a straight square truncated pyramid, such that the center of the top surface lOd is not offset from the center of the base surface 10g, but lies above it.

[0138] Figures 13 and 14 schematically depict 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.

[0139] 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 lOd. The base area 10g is an equilateral triangle, so its top surface lOd is also an equilateral triangle. The base area 10g has a first edge length kl, and the top surface lOd has a second edge length k2, which is shorter than the first edge length kl. The test specimen 10 has a height h, which is shorter than the first edge length kl and longer than the second edge length k2.

[0140] Figures 15 and 16 schematically depict 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.

[0141] In this embodiment, the test specimen 10 has the shape of a hemispherical layer with a base area 10g and a top surface lOd, such that the base area 10g and the top surface lOd are circles. The base area 10g has a first diameter dl, and the top surface lOd has a second diameter d2, which is smaller than the first diameter dl. The test specimen 10 has a height h, which is smaller than the first diameter dl and larger than the second diameter d2.

[0142] Figure 17 schematically illustrates a preferred embodiment of a test rig 16 according to the invention for determining the mechanical strength of a sheathing system 12 for buried steel pipes 14, wherein the sheathing system 12 is, by way of example, a two-band system of the type "DENSOLEN®-AS40 Plus / -R20 HT" and the mechanical strength is, by way of example, an indentation resistance or a residual layer thickness. The test rig 16 comprises a holding system 18 for the sheathing system 12, a material testing machine 20, a measuring device 22 and a control device 24, which is designed such that it is in accordance with August 1, 2025.

[0143] 752 PA 20012 WO

[0144] The material testing machine 20 and the measuring device 22 can be controlled according to a predetermined procedure and the mechanical load-bearing capacity can be determined. The holding system 18 includes, for example, a substantially V-shaped holding trough into which the encapsulation system 12 to be tested, together with the steel tube 14, can be inserted. Alternatively, instead of the steel tube 14 with the encapsulation system 12, a flat plate (not shown) can be used in the test rig 16, onto which the encapsulation system 12 has been applied. In this case, the holding system 18 includes, for example, a horizontal holding plate (not shown) instead of the V-shaped holding trough, onto which the encapsulation system 12 to be tested, together with the plate, can be placed.

[0145] 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 lOd 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 10g leading, 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.

[0146] 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.

[0147] 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.

[0148] Fig. 18 schematically shows 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 carried out by way of example using the test rig 16 from -FIG, 1 and in particular its control device 24.

[0149] In step S1, the test stand 16 from FIG. 1 is set up, 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 is shown in FIG. 17. Then, the test specimen 10 with its base area 10g is detachably attached to the underside of the crossbeam 28, and the weight 26 is placed on the top of the crossbeam 28. In addition, 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 lOd. 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.

[0150] 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 lOd 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.

[0151] 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 timing measurement. August 1, 2025 752 PA 20012 WO 16

[0152] By releasing the locking device 32, the cover surface lOd 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, so that the test specimen 10 penetrates the material of the enclosure system 12 and the crossbeam 28 moves downwards relative to the guide rails.

[0153] 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 TI, which is, for example, 1.2 mm. The first time point is, for example, 10 h.

[0154] 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

[0155] B = V - TI = 3.0 mm - 1.2 mm = 1.8 mm is calculated, where TI is the measured initial penetration depth and V is the reference value. Thus, the mechanical load-bearing capacity is determined based on a predetermined reference value.

[0156] In step S6, which follows step S5, the control unit 24 checks whether

[0157] B > N 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.

[0158] 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.

[0159] In this embodiment, the time measurement continues without interruption. August 1, 2025 752 PA 20012 WO

[0160] 17

[0161] 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.

[0162] 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 TI and T2 by extrapolating an extrapolation depth TE to a predetermined target time, for example 72 h, from the zero depth TO and the detected penetration depths TI 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,

[0163] B = V - TE = 3.0 mm - 1.5 mm = 1.5 mm is calculated. Thus, the mechanical load-bearing capacity is determined as a function of the extrapolation depth.

[0164] 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

[0165] B > N is negative.

[0166] REFERENCE MARK LIST

[0167] 10 test specimens

[0168] 10d / 10g Coverage area / Base area of ​​10

[0169] 12. Item to be inspected, packaging system

[0170] 14 steel pipes

[0171] 16 Test bench

[0172] 18 Holding system for 12 I. August 2025

[0173] 752 PA 20012 WO

[0174] 18

[0175] 20 material testing machines

[0176] 22 Measuring device

[0177] 24 Control unit

[0178] 26 weights

[0179] 28 crossbeams

[0180] 30 Management system

[0181] 32 locking devices al / a2 first / second principal axis of 10g / 10d

[0182] B mechanical load capacity of 12 dl / d² first / second diameter of 10 g / 10 d h height of 10 kl / k² first / second edge length of 10 g / 10 d

[0183] N standard requirement value for B

[0184] R residual layer thickness of 12

[0185] T Penetration depth of 10 in 12

[0186] V comparison value, initial layer thickness of 12

Claims

August 1, 2025 752 PA 20012 WO 1 REQUIREMENTS 1. Test specimen (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 area (10g) and a top surface (lOd) or essentially the shape of a truncated cone with a base area (10g) and a top surface (lOd) or essentially the shape of a hemispherical layer with a base area (10g) and a top surface (lOd); - the projection of the top surface (lOd) onto the base surface (10g) lies within the base surface (10g); and - the top surface (lOd) 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 (lOd) 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 (lOd) 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 kl; - the top surface (lOd) 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 kl.

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 kl and August 1, 2025 752 PA 20012 WO 2 greater 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 dl; - the top surface (lOd) is a circle with a second diameter d2; and - the second diameter d2 is smaller than the first diameter dl.

8. Test specimen (10) according to claim 7, wherein - the test specimen (10) has a height h that is smaller than the first diameter dl 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 al; - the top surface (lOd) is a circle with a second principal axis a2; and - the second principal axis a2 is smaller than the first principal axis al.

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 al 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 (lOd) facing forward; - 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 - determining the mechanical load-bearing capacity depending on a pre-existing condition August 1, 2025 752 PA 20012 WO 3 votes were cast for comparison.

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 holds, 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 enclosing system (12) depending on the values ​​recorded at the first time point and at least one second time point August 1, 2025 752 PA 20012 WO 4 Penetration depths are determined.

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 (lOd) forward at a test point against the covering 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 (lOd) 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 rig (16) according to one or more of claims 19 to 2120, wherein August 1, 2025 752 PA 20012 WO 5 - 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 load-bearing capacity 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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