SU1320701A1 - Method of bursting tests of pipes - Google Patents

Abstract

The invention relates to a testing technique and can be used to test pipes for fracture resistance. The purpose of the invention is to increase confidence by approximating the test conditions to real ones. On the test pipe 1, a crack initiating incision 2 is applied and a collar consisting of two semi-branches 3 and 4 interconnected by a hinge 5 is installed. When pressure P inside the pipe 1 is equal to the test, by means of the lever 8, remotely act on it the locking device 7 is opened. After removing the circumferential compressive stresses created by the clamp, the wall. pipe 1 under notch 2 is destroyed. At fracture, the nature of the fracture, the deformation-velocity characteristics of the pipe materials, and the extent of crack propagation are evaluated. The thickness of the cf-wall of the pipe 1 under the notch 2 is chosen from the condition f 0.7PD / 26, where D is the diameter of the pipe 1; 6 - yield strength of the material of the pipe 1. 1. f-ly, 2 ill. From 9 ate 00 to

Description

one

The invention relates to an analytical technique and can be used to determine the resistance of pipes to failure, in which the nature of the fracture, the deformation-velocity characteristics of the pipe materials, the extent of crack propagation under given test conditions are assessed.

The purpose of the invention is to increase the reliability of tests by accurately setting the fracture pressure.

Figure 1 shows a pipe with a clamp, a cross-section; in figure 2 13

the same, the clamp in the open position.

The method of testing pipes for fracture resistance is carried out as follows.

On the outer surface of the pipe 1, a longitudinal incision 2 is made initiating a crack. To prevent destruction before reaching the specified test pressure, pipe 1 in notch zones 2 is compressed by circumferential stresses. To create circumferential stresses, a detachable clamp of two half-rings 3 and 4 on hinge 5 with clamping bolts 6 and locking device 7 is used. The wall thickness of pipe 1 under the notch 2 initiating the crack is determined by the formula

. 0.7 e;

where f is the wall thickness under notch 2;

P - test pressure; D is the external diameter of the pipe 1; d - yield strength of the material

pipes 1.

The coefficient O, 7 takes into account the error in determining the wall thickness of pipe 1 under notch 2, which is + 10%, as well as the deepening of notch 2 by 10%, which ensures guaranteed destruction of pipe 1 at test pressure.

The collar is installed in the center of the length of the initiating notch 2. The ends of the half-rings 3 and 4 are inserted into the grooves of the locking device 7 at a fixed position of the lever 8, after which they are tightened by bolting 6 two parts of the half-ring 4.

When the pressure inside the pipe 1, corresponding to the value of the test set, is reached, by means of the lever 8, the force acting on it

fO

207012

P remotely open the locking device 7.

After removing the compressive circumferential stresses created by the clamp, the remaining wall of the pipe 1 under the notch almost instantly collapses under the effect of the internal pressure in the test pipe 1, which at the time of the removal of the circumferential stresses exceeds the specified test depth for the initiating notch 2.

The collar providing compressive circumferential stresses is positioned in the center of the notch length 2. Moreover, it is not necessary to completely cover the entire notch 2 with the collar, but it is sufficient that the length of the initiating notch 2 on either side of the collar does not exceed the critical crack length for these test conditions and properties of metal pipe 1.

15

20

The method allows to simulate the conditions of the crack that are closest to real, since the structure of the pipe material and the geometry of the cylindrical shell around the initiating notch are not disturbed. In addition, safety conditions are improved.

The test results allow one to assess the consequences of failure in the event of a pipeline accident and thereby recommend the use of pipes under various environmental conditions.

Claims (2)

1. The method of testing pipes for fracture resistance, consisting in that a longitudinal initiating notch is applied to the outer surface of the test pipe, the wall thickness under the notch is chosen proportional to the test pressure, and the pressure inside the pipe is raised to the test pressure, that, in order to increase reliability, before the pressure builds up in the pipe in the notch zone, they create compressive circumferential stresses exceeding the stresses from test-. pressure, and after the pressure is increased, the notch zone is freed from circumferential compressive stresses. 313207014 2. The method according to Claim 1, where I is the thickness of the wall under the notch; u and with the fact that the walls of P - test pressure; under the incision is chosen from the ratio D is the external diameter of the pipe; d is the yield strength of the pipe material.  0.7 | 5, wall thickness under, notched test pressure; external diameter of the pipe; yield strength of the pipe material. Fia. 2 Editor N.Slobod nickname Compiled by B.Grabov Tehred A. Kravchuk Proofreader d.Obruchar Order 2652/46 Circulation 776 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4