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IN-SITU ARC-SAW CUTTING OF HEAT EXCHANGER TUBES AND OF PIPES FROM THE INSIDE.

Objective

THE PRINCIPLE OF UNDERWATER METAL CUTTING BY ELECTRIC ARC-SAW PRESENTS SOME SIMILARITIES WITH THE ARC GOUGING PROCESS AND ELECTRODE ARC CUTTING. BESIDES ITS NUMEROUS OTHER ADVANTAGES AS HIGH PRECISION WORK AND SMALL PRODUCTION OF CUTTING WASTE, THIS METHOD IS ESPECIALLY APPROPRIATE FOR TELEMANIPULATION BY ROBOTS; PARTICULARLY BECAUSE OF SMALL INDUCED VIBRATIONS AND CUTTING FORCES INVOLVED IN THIS PROCESS, AND BY THE POSSIBILITY TO USE SMALL DIMENSION CUTTING DISCS ALLOWING FOR HIGH ACCESSIBILITY TO COMPLEX AREAS.
THE PRESENT WORK IS MAINLY AIMED AT AN ADAPTATION OF THIS PROCEDURE TO IN-SITU CUTTING BY ROBOTS, ESPECIALLY INSIDE OF TUBES AND PIPES, WITH A SPECIAL OBJECTIVE TO DISMANTLING STEAM GENERATORS AND OTHER HEAT EXCHANGERS IN NUCLEAR INSTALLATIONS.
THIS DEVELOPMENT COMPRISES DESIGN STUDIES FOR APPARATUS TO BE ADAPTED ON SPECIAL CRAWLER OR ROBOT ARMS, LABORATORY STUDIES OF THE CUTTING PARAMETERS, MINIATURISATION OF CUTTING HEADS FOR THEIR INTRODUCTION INTO SMALL DIAMETER DUCTS.
THROUGH A SUPPLEMENTARY AGREEMENT CONCLUDED IN 1987, THE WORK PROGRAMME HAS BEEN EXTENDED TO THE DEVELOPMENT AND TESTING OF AN INTERNAL CUTTING TOOL BY AXIAL ACTION.
An arc saw cutting process has been studied for application on 3 different types of cutting tools.
Parameters for transversal cutting for steam generator (SG) tubes are: 60 amps, an orbital rotation of 1000 rpm and a cutting time of 90 s. The wearing of the electrode allows only 2 successive cuts. A flexible tool and a representative bench for SG conditions have been realised.
For longitudinal cutting for SG tubes the electrode is mechanically driven. The cutting speed is 12mm/s, the intensity is 50 amps and the electrode rotation is 1750 rpm. The wearing of the electrode is negligible.
For internal cutting of thick walled pipes an experimental correlation has been elaborated which relates the cutting speed to the maximum intensity available and to the geometrical parameters. According to this formula, it is necessary to go up to 1500 amp for cutting a 0.89 x 6 mm thick pipe with a speed of 0.84 mm/s (cutting time about 5 minutes).
B.1. DEVELOPMENT OF METHODS AND TOOLS FOR INTERNAL ARC-SAW CUTTING OF STEAM-GENERATOR TUBES (INTERNAL DIAMETER OF ABOUT 19 MM) TO PRODUCE CIRCUMFERENTIAL CUTS.

B.1.1. DESIGN, CONSTRUCTION AND TESTING OF A MINIATURISED CUTTING TOOL FOR PWR STEAM GENERATOR CHANNEL HEAD.
B.1.2. DEVELOPMENT AND CONSTRUCTION OF A LABORATORY TESTING BENCH TO CHECK PROCESS CHARACTERISTICS BY EXTERNAL AND INTERNAL CUTTING.
B.1.3.DESIGN AND FABRICATION OF A COMPLETE DEVICE FOR INTERNAL CUTTING, BASED ON TEST RESULTS OBTAINED UNDER B.1.1 AND COMPLYING WITH IN-SITU WORKING LIMITATIONS.
B.1.4. PERFORMANCE TESTS ON REPRESENTATIVE INCONEL TUBES (UNDER WATER).
B.1.5 FINAL ASSESSMENT ON REALISTIC FULL-SCALE SAMPLES SUPPLIED BY EDF.

B.2. DEVELOPMENT OF METHODS AND TOOLS FOR INTERNAL ARC-SAW CUTTING OF PIPES (INTERNAL DIAMETER ABOUT 200 MM) TO PRODUCE CIRCUMFERENTIAL CUTS.
B.2.1 DESIGN OF A SUITABLE CRAWLER FOR HOISTING THE CUTTING TOOL.
B.2.2. FABRICATION OF AN APPROPRIATE CUTTING TOOL AND LABORATORY TESTS TO DETERMINE THE CUTTING PARAMETERS IN ACCORDANCE WITH THE PIPE DIAMETER AND THICKNESS AND WITH THE TOOL WORKING LIMITATIONS.
B.2.3. TESTING OF THE CUTTING TOOL.

B.3. DEVELOPMENT OF METHODS AND TOOLS FOR INTERNAL ARC-SAW CUTTING OF STEAM GENERATOR TUBES TO CUT ALONG A GENERATING LINE.
B.3.1. DESIGN AND CONSTRUCTION OF A MINIATURISED TOOL FOR INTERNAL AXIAL CUTTING.
B.3.2. PERFORMANCE TESTS ON ICONEL AND STAINLESS STEEL TUBES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Field Automation SARL
Address
46 Rue Sainte-anne
75002 Paris
France