SU1767373A1 - Threaded joint assembly quality control method - Google Patents

Abstract

Summary of the Invention: when controlling the quality of the assembly, one of the elements of the threaded pair is fixed, and a torque is applied to the other and the angle of rotation p is measured. On mating surfaces, the contact pressure is determined from the amplitude or velocity of ultrasonic vibrations with a given discreteness. The build quality is determined by the rate of change of sign and the magnitude of the derivative d of pressure from the allowable values. 2 Il. and the deviation of the value of the contact

Description

The invention relates to a measuring and control technique, in particular, to methods for controlling the quality of assembly of threaded joints, and can be widely used in industry for assembling threaded joints of petroleum equipment, in mechanical engineering.

There is also known a method of controlling the tightening torque of threaded joints, which includes tightening the joint from the initial state to the required and subsequent measurement of power parameters, the tightening is performed in several steps, the power parameters after each tightening step are determined by the maximum angular acceleration of the wrench 1 .

There is also a way to control the tightening torque of a threaded joint, which consists in initially tightening the nut to zero position by a predetermined force and further tightening it with simultaneous measurement of torque and angle of rotation. Zero Angle Position

the nut is determined by the ratio of the product of the total moment applied by the increment of the angle to the moment increment, and the final angle of rotation, by which the tightening force is judged, is determined by the difference of the required and zero angles of rotation of the nut 2.

The main disadvantage of the listed technical solutions is their low reliability due to the measurement of indirect parameters (μc, pb) of the build quality.

As a prototype, a method is implemented that is implemented in a device for tightening a threaded joint. The method is determined using MKp graphical dependencies. ffy), the value of the derivative of t-, multiplies it by the wave f

the angle of rotation p, which, in accordance with the experimentally established stiffness of the threaded joint, corresponds to the desired axial force in (L

WITH

xi o vi

with

Vj

WITH

tzhki. The resulting product corresponds to the torque value at which the joint assembly must be terminated to achieve the desired axial pulling force 3.

The main disadvantage of the prototype method is the low reliability of the quality control of the assembly assembly, since torque and angle of rotation are indirect parameters and do not provide complete information about the quality of the threaded connection. In addition, to implement this technical solution, it is necessary to have a fairly representative sample of experimental and calculated material, in which the influence of external factors must be taken into account (ambient temperature, quality of machined screwed threads, type of lubricant, etc.).

The aim of the invention is to increase the reliability of the control. In this case, the quality of screwing is controlled during the assembly process and the end of the assembly process is determined.

The goal is achieved by the following differences in the method of controlling the assembly of threaded connections: as a parameter that determines the quality of the assembly, select the contact pressure P on the mating surfaces, which is determined by the amplitude or velocity of ultrasonic vibrations with discreteness and compare its with acceptable values (maximum and minimum) contact pressures. Single

temporarily with the same discreteness

l are the magnitude and sign of the derivative j-, and o

about p

the quality of the assembly is judged by the deviation of the contact pressure from the allowable values and by the rate of change of the sign and

the value of the derivative -.

Oy

A positive effect is achieved by increasing the reliability of the control, which ensures an increase in the service life of the threaded joint.

Figure 1 shows the scheme of implementation of the method; Fig. 2 shows the dependence of the measured parameter on the number of revolutions.

In implementing this goal, two well-known positions were taken into account.

Monotonically increasing dependence of the amplitude of ultrasonic oscillations on the magnitude of the contact pressure (in our case, the number of revolutions of one part relative to another). (Khimchenko N.V. and Bobrov V.A. Non-destructive testing in chemical and petroleum engineering. M .:

Mechanical Engineering, 1978). With an increase in the contact area of the interfaced surfaces, an increasing amount of ultrasonic energy passes through the interface zone and, consequently, the amount of energy reflected from the interface boundary decreases (see also ed. St. 905778).

The presence of theoretically calculated for each type of compounds (e.g., by the formulas Lme) the dependences of the magnitude of the contact pressure occurring in the mating surfaces on the number of revolutions. These dependencies are subsequently recorded in the microprocessor memory.

The proposed method for controlling the quality of the assembly of threaded connections is implemented as follows.

The element 1 of the threaded pair (see FIG. 1) is fixed and mounted on it in the area of the threaded portion of the piezotransducer 2. The second element 3 of the threaded pair is engaged with the first. After that, a second piezo transducer 2 and a rotational speed sensor 4 are installed in the interface zone. A torque is applied to the element 3 and the counting of the speed r is started. In the process of screwing, one of the piezotransducers 2 emit, and the second receive ultrasonic vibrations that pass through the interface, and determine the current value of the contact pressure PI on the mating surfaces. With discreteness Ap, the contact pressure limits Pimin and Pimax (see Fig. 2) are calculated for a given speed and are compared with current PI values.

Simultaneously with the same discreteness, youj p

calculate the derivative — the dependences of the contact pressure on the number of revolutions and determine its sign.

Screwing process is normal

if Pimin Pi Pimax, a 0.

If, at several (at least three) measurements, the current values of Pi are beyond the allowable Pimin and Pimax, the assembly is stopped, and the compounds are rejected, since the geometrical parameters of the thread have unacceptable deviations.

The build is complete if at several

А Р (not less than three) measurements podra d 5- -0,

and the contact pressure value Pi Pimin.

The proposed method was tested when assembling a set (24 pcs.) Of drill pipes according to GOST 631-75 with a diameter of 140 mm with locks according to GOST 5286-75. The discreteness of the reference was taken equal to D 10 °. Contact pressure limits were calculated using the formulas

P Nmln E p Nmax E

Kmln (Q, + Cb) GtaX (Ca + Ch) where P is the contact pressure arising in the joint, MPa;

Ca, Cf are the coefficients taking into account the properties of the mating materials: Ca 3.96; Sat 2.59;

Nmin, Nmax - minimum and maximum values of tension, mm: Nmin 0.3 mm; Nmax 0.54 mm;

Е - modulus of elasticity of the material: Е 2 105 MPa;

d is the diameter of the conjugation.

As a result, two threaded connections were rejected: the first at the beginning of the assembly, the second after seven turns. As a follow-up check showed, in the first case the lock thread did not comply with GOST 5286-75, and in the second case thread contamination took place. If traditional assembly methods were used, the thread would be torn off in both joints and both threaded pairs would fall into irreparable defects. The application of the proposed method made it possible to preserve and use 3 threaded parts out of four: two pipes and one lock.

Claims (1)

Claims The method of controlling the quality of the assembly of threaded joints is that one of the elements of the threaded pair is fixed, the torque is communicated to the other, the angle of rotation is measured (p relative to the fixed element, a parameter characterizing the quality of the assembly, and its derivative is determined angle of rotation, characterized in that, in order to increase the reliability of the control, as a parameter characterizing the quality of the assembly, choose the contact pressure P on the mating surfaces of the threaded connection, oroe is determined by the amplitude or velocity of ultrasonic oscillations with a given discreteness Dy, the magnitude of the contact pressure is compared with the permissible maximum and minimum values, the magnitude and dP derivative sign -t- and build quality determined by the rate of change of the sign and the magnitude of the derivative and the deviation of the contact pressure from the allowable values. 1 / f / v / 74-4yЈ P / rvx O f-- li FIG. 2