IEC 60519-8 pdf – Safety in installations for electroheating and electromagnetic processing – Part 8: Particular requirements for electroslag remelting furnaces

IEC 60519-8 pdf – Safety in installations for electroheating and electromagnetic processing – Part 8: Particular requirements for electroslag remelting furnaces
lf the power circuit is multiple-earthed，care shall be taken with the current which flows
between the earthing points and through components of the furnace.
2) The circuit of any melting station which is not working shall be isolated from the supply but
not from earth.
8Protection against hazards from electric or magnetic fieldsThis clause of Part 1 is applicable.
9 Protection against hazards from radiation
This clause of Part 1 is applicable.
10 Protection against hazards from thermal influencesThis clause of Part 1 is applicable,except as follows.
10.1General
Additions:
10.1.101 Perforation of the crucible and base plate can cause a fire or an explosion due tothe cooling-water flow into liquid metal and slag. The following special measures for designand operationof equipment shall be taken to ensurethe protection of personnel andequipment.
a) Sufficient water-cooling to the crucible and base plate shall be ensured in the hot state.For further details, see 10.5.
b) The size of electrode(s)relative to the crucible shall be carefullydesigned andmanufacturedin such a way that they remain at a reasonable distance between the
crucible and the electrode(s) to avoid the occurrence of arcing. The position of electrode(s)
relative to the crucible shall be monitored during melting and aligned.
c) The mechanical properties of graphite electrode(s) and consumable electrode(s) shall be
ensured to avoid cracking and a part of electrode dropping into the crucible that can cause
arcing during the operation. The electrode(s) with horizontalcracks in the surface orinside is (areyunacceptable.
d) The strength of the welded zone between the consumable electrode and the electrode
stub in the operation condition shall be sufficient to avoid it breaking away.
e) The voltage and current in the secondary circuit shall be carefully set and controlled to the
limited values in the starting phase，especially in the case of cold starting with solidconductive slag， in order to avoid the electrode arcing or short circuit occurring with thebase plate that can cause perforation of the base plate.
10.1.102Slag materials shall be sufficiently dried before use in order to decrease themoisture so that molten slag cannot be ejected from the crucible during the melting of the slag.
10.1.103 The relative positions between the mould and the base plate shall be fixed and thegap between them shall be so narrow that the molten slag cannot leak out.
10.1.104 Water accumulationin the area around the melting station shall be avoided.Measures shall be taken to remove any water from this area in the event of leakage.
10.3 Hazards caused by working conditionsAdditions:
10.3.101 The control station and the melting power supply shall be completely protectedagainst the liquid metal and slag being ejected from the melting area.
10.3.102The electrical,mechanical and hydraulicequipment as well as the flexibleconnections of cooling circuits shall be protected against heat radiated directly from the slagand electrodes and convected hot gases. They shall also be protected against heating inexcess of admissible limits due to electric and electromagnetic phenomena(resistive orinductive).
So as not to impair safety, all metal parts which are subjected to high-intensity magnetic fields
and are in contact with oil， shall be made of non-magnetic material and installed in such away as to avoid formation of closed loops.
10.3.103 Access to the supporting structure above and under the melting area shall beforbidden whenever the furnace is energized. Operators who have to service the workingfurnace (for example, temperature measurement, changing electrodes) and be near live or hot
parts shall wear protective clothing: gloves,footwear，visors (goggles), non-metallic safetyhelmets, etc.
10.3.104 The slag melting furnace and ingot moulds shall be covered by a collecting systemto extract fumes from the working area.
10.5Cooling
Additions:
10.5.101Special precautions shall be taken to ensure continuance of the cooling of the ingotmould and the ingot base in the event of power failure.
10.5.102 The followingindications and measurements shall be provided for importantcooling circuits, for example, moulds, base plates, electrode clamps:
– monitoring of the cooling water flow;
measurement of the cooling water outlet temperature. Optimally，measurement of thecooling water inlet temperature shall be applied.The inlet temperature of the cooling water
shall not be less than the dew point of the environment temperature to avoid moisturecondensation on the surface of water-cooled components.