US 7,116,428 B2Granted

Method and device for measuring wall thickness of a pipe in a pipe-rolling mill

AssigneeSMS Meer GmbH

InventorsMartin Sauerland, Gerd-Joachim Deppe

Life of this patent

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Abstract

A method and device for measuring the wall thickness of a pipe in a pipe-rolling mill wherein a Fabry-Pérot interfero-meter has its mirror spacing set by providing an input to a linear activity for one of the mirrors from a controller receiving an input from a photodiode at the output side of the interferometer. A second control circuit regulates the amplification of that photodiode with at least one parameter derived from the rolling system, for example, the input optical signal to the interferometer or a disturbance value representing for example the temperature of the rolled product and obtained through an optical pyrometer. The incoming optical signal may be tapped to another photodiode also with a variable amplification amplifier and both amplifiers may be controlled by a second controller.

Claims24

Dependent claims

A method of measuring a wall thickness of a pipe in a pipe rolling line, comprising the steps of:

(a) launching an ultrasonic pulse into a wall of a pipe whereby an ultrasonic wave is transmitted across a thickness of said wall and an ultrasonic echo is returned to a surface of the pipe;
(b) training a laser beam from an illuminating laser onto said surface whereby a laser-light reflection from said surface is modulated by said echo;
(c) collecting laser light reflected from said surface and modulated by said echo as an input optical signal and feeding said input optical signal to a Fabry-Pérot interferometer having two mirrors spaced apart by a predeterminable distance (a), said Fabry-Pérot interferometer having an output optical signal;
(d) passing said output optical signal to a first photodiode and converting said output optical signal into an electrical signal and evaluating said electrical signal to determine transit time for echoes spanning the thickness of said pipe and, from said transit time and a speed of sound in material of the pipe, said wall thickness;
(e) at least one of the steps of:
(e1) deriving a photodiode-measurement control signal from said electrical signal,
(e2) deriving a input-measurement control signal from said input optical signal, and
(e3) deriving a rolling-line control signal representing a fabrication process variable;
(f) controlling a linear actuator determining a position of at least one of said mirrors directly or indirectly through a controller for said linear actuator with at least one of said control signals;
(g) regulating said photodiode with the output from a variable amplification amplifier;
and
(h) during steps (e), (f), and (g)
(h1) varying a signal measured by said first photodiode as a function of the input optical signal as measured by a second photodiode and feeding the varied signal to said controller, each of said first and second photodiodes having respective amplifiers for amplifying the signals measured thereby, and
(h2) controlling the amplifiers in a respective control circuit based upon at least one predeterminable command variable.

11 more elements

A device for measuring a wall thickness of a pipe in a pipe rolling line, the device comprising:

a laser ultrasonic measuring unit having an excitation laser trained on a surface of a pipe for launching an ultrasonic pulse into a wall of the pipe whereby an ultrasonic wave is transmitted across a thickness of said wall and an ultrasonic echo is returned to the surface of the pipe, an illuminating laser directing a laser beam onto said surface whereby a laser-light reflection from said surface is modulated by said echo, and an interferometer receiving laser light reflected from said surface and modulated by said echo as an input optical signal and having two mirrors spaced apart by a predeterminable distance (a), said interferometer having an output optical signal evaluatable to determine transit time for echoes spanning the thickness of said pipe and, from said transit time and a speed of sound in material of the pipe, said wall thickness, said interferometer having a linear actuator for relatively displacing said mirrors to adjust said distance;
and
a control system acting upon said linear actuator and including:
a first photodiode receiving said output optical signal,
a controller responsive to a signal obtained from said first photodiode and controlling said linear actuator, and
a second photodiode receiving said input optical signal,
respective amplifiers connected to said photodiodes for amplifying respective signals measured thereby, and
a control circuit including a further controller for regulating amplifications of said amplifiers to predetermined values.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/764,144Filed 23 Jan 2004
Published: US 2005/0162662 A128 Jul 2005
Granted: 3 Oct 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01B 17/02
Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations: for measuring thickness
G01B 9/02023
Characterised by the beam path configuration: indirect probing of object, e.g. via influence on cavity or fibre
G01B 9/02052
Characterised by particular mechanical design details: protecting, e.g. shock absorbing, arrangements
G01B 9/02067
Active error reduction, i.e. varying with time: by electronic control systems, i.e. using feedback acting on optics or light