Overcomes arc blow
Magnetic effects on the welding process
The Diverse Zeromag ZM100 is a demagnetising system for steel tubes and plates. It is used to reduce the magnetic field levels in welding joint preparations to levels which are low enough to enable welding to proceed. Zeromag is used to eliminate arc blow which can occur when the parts to be welded are magnetic - this shows up as high magnetic field levels in the joint preparation. The following table lists the most common effects of magnetism on welding processes. The table shows how welding arcs can be expected to behave in increasing magnetic field levels.
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When even weak magnetic fields are present in the parent material, the effect of the reduction in face area serves to concentrate the magnetic flux. Consequently, the value in the joint preparation can easily be several hundred gauss and fields over 1000 gauss are not unusual.
Zeromag is designed to provide reduce magnetic field levels to below 10 gauss even with residual field levels of over 1000 gauss.
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| Max. magnetic field cancelling capability |
±2000 gauss in most pipeline steels. The exact performance is dependent upon the material, geometry and remanence of the specific magnetic arrangement |
| Maximum diameter pipe size |
4 metres. |
| System includes: |
Zeromag100 power supply, demagnetising cable, built in magnetic field meter and magnetic field probe |
| Demagnetising magnetic field strength |
+/- 100A times the number of turns around workpiece |
| Time to reduce field to minimum |
Typically 5 seconds |
| Manual mode |
Level of magnetism in the joint manually adjusted |
| Pre-preparation temperature |
100C - above this thermal blanket is required |
| Automatic mode |
Automatically sorts out the direction of the magnetising field. Continuously reduces it to <10gauss |
| Subsea |
Zeromag can be used topside or subsea - but must be protected for hydrobaric operations. |
| Options |
Demagnetising cable extension to double the demagnetising magnetic field strength |
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Probe cable extension for large work pieces |
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Gas cooled probe (compressor not supplied) available to enable the magnetic field to be continually monitored and removed close to the point of welding, even with preheat. Cooling gas directed away from the weld - and has no effect on weld process. |
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