RU2193765C2 - Calibration procedure for force cells mounted on tension arrangements of reinforce cables in building structures - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: calibration procedure can be used for force cells testing tension of reinforced cable in protective envelopes of watermoderated water-cooled reactors. Procedure consists in simultaneous measurement of acting force by calibrated and model measurement aid and in comparison of their readings. Force cell continuously positioned under load of tensioned cable is unloaded with the use of jack by fixed value of force which is measured by means of more accurate sensors anchored on extendible plungers of jack and measured value is compared with force by which force measured by calibrated force cell is diminished. EFFECT: raised measurement accuracy. 1 cl, 1 dwg

Description

 The invention relates to the field of measurement technology and can be used to calibrate force sensors that control the tension of armored ropes of the protective shells of WWER reactors.

 A known method of calibrating force sensors, which consists in loading the calibrated sensor with a force, the value of which is set or measured more accurately than the sensor by a dynamometer and is compared with the readings of the calibrated sensor.

 This method is borrowed from state verification schemes of all force meters (both sensors and dynamometers) [1, 2].

This calibration method has the following disadvantages:
- the need in most cases to remove the sensor from the measurement object and test it either on an exemplary lever or direct loading dynamometer, or on a silo machine. In the latter case, the sensor is installed in series with a "DOCM" type dynamometer. These dynamometers have considerable height and very often the sensor together with the dynamometer form an unstable system;
- the inability in most cases to place a dynamometer of the type "DOCM" on the sensor without removing it from the object.

 However, in a number of cases, the sensor cannot be removed from the object due to its design features or a very short period of time available for this procedure. This also applies to force sensors for measuring the tension of armored ropes of the protective shells of WWER reactors of nuclear power plants.

 The strength of such shells during a reactor accident is guaranteed only with a certain amount of preliminary compression of the concrete from which the shell is made. The compressed state of the shell is carried out using reinforced ropes with tensioning devices. The force with which the armored ropes are stretched should be no less than the calculated value and controlled during the operation of the reactor. Therefore, the calibration of the force sensor, which controls the degree of tension of the armored ropes, is possible only during shutdown of the reactor to load it with nuclear fuel. This time is short.

 In the proposed technical solution, the calibration of the sensor mounted on the arm rope tensioner is carried out without removing the sensor from the arm rope tensioner using a hydraulic jack used to tension the rope and four force sensors, the accuracy of which is higher than the accuracy of the calibrated sensor.

 The essence of the proposed method is illustrated in the drawing.

 A calibrated sensor (1) is mounted on an arm-rope tensioner, consisting of a lining (7), a nut (5), a sleeve (6) with a thimble (9). The armored rope is passed inside the sleeve (6) and laid in the outer gutter of the thimble (9). The thimble (9) has a hole for the finger (8) of the jack (2).

The armored rope is tensioned with a jack (2) in the following sequence:
- using a finger (8), fix the jack (2) on the thimble (9);
- in the hydraulic system of the jack, the design pressure is created by the oil pump. This pressure provides the required output of the plungers (4) of the jack (2) and the corresponding tension of the armored rope;
- without relieving pressure in the hydraulic system of the jack (2), tighten the nut (5) of the tensioning device until the sensor (1) and the lining (7) are clamped to the base plate (10);
- relieve pressure in the hydraulic system of the jack (2), remove the finger (8) and remove the jack. The tension of the rope (P _n ) is controlled by the sensor (1).

Calibration of the sensor (1) is carried out in the following sequence:
- force sensors (3) are fixed on the plungers (4) of the jack (2);
- using a finger (8), fix the jack (2) on the thimble (9);
- in the hydraulic system of the jack the oil pump sets the pressure corresponding to the tensile force of the armored rope P _to . This pressure provides the corresponding output of the plungers (4) and the impact on the rope force P _to . The force P _to is fixed by the sum of the readings of the force sensors (3);
- the force P _{k is} compared with the value by which the reading of the force sensor (1) has decreased.

When calibrating the sensor in the proposed way, the magnitude of the force P _to which the sensor is calibrated (1) should always be less than the force P _n .

Sources of information
1. General purpose spring dynamometers. Methods and means of verification GOST 13782-68.

 2. Dynamometers exemplary figurative 3rd category. Methods and means of verification GOST 8.287-78.

Claims (2)

1. The method of calibration of the force sensors installed on the tension devices of the armored ropes of building structures, which consists in simultaneously measuring the acting force with calibrated and exemplary measuring instruments and comparing their readings, characterized in that the sensor, which is continuously under load P _{n of the} tensioned rope, is unloaded using a jack a fixed value of the force P _k , the value of which is measured using more accurate sensors mounted on the sliding rams of the jack, and compare it with the values th force, which decreases the force P _n measured by the calibrated sensor.  2. The method according to p. 1, characterized in that the magnitude of the unloading force of the calibrated sensor is set less than the magnitude of the force by which at the time of calibration the sensor of the tensioner of the armored rope is loaded.