IEC 60519-8-2005 pdf – Safety in electroheat installations – Part 8: Particular requirements for electroslag remelting furnaces

IEC 60519-8-2005 pdf – Safety in electroheat installations – Part 8: Particular requirements for electroslag remelting furnaces.
1 Scope and object This part of IEC 60519 applies to electroheat installations for remelting and, in some cases, for refining processes of metals through direct resistance heating of a conductive slag. The particular requirements for the safety of persons in or around an electroslag remelting furnace are the object of this standard. The general requirements are included in IEC 60519-1. Test methods for electroslag remelting furnaces are specified in IEC 60779. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050-841, International Electrotechnical Vocabulary – Part 841: Industrial electroheat IEC 60519-1:2003, Safety in electroheat installations – Part 1: General requirements IEC 60779:2005, Industrial electroheat equipment – Test methods for electroslag remelting furnaces 3 Terms and definitions For the purposes of this standard, the terms and definitions given in IEC 60050-841, IEC 60519-1 and IEC 60779, as well as the following apply. 3.1 multi-station configuration electroslag remelting furnace configuration having more than one melt station 4 Classification of electroheat equipment according to voltage bands Clause 4 of IEC 60519-1 is applicable except as follows.
5 Classification of electroheat equipment according to frequency bands Clause 5 of IEC 60519-1 is applicable. 6 General requirements The requirements of Clause 6 of IEC 60519-1 and Annex A of this standard apply, except as follows. 6.1.2 Addition: The slag melting furnace and ingot moulds shall be covered by a collecting system to extract fumes from the working area. 6.2 Addition: 6.2.13 The following requirements shall be met to ensure adequate safety in operation. 1) The supply system shall be designed to withstand sudden current fluctuations occurring at the start of the melting process with dry slag. 2) The circuit-breaker shall be designed for frequent operation. 6.2.14 The following requirements apply to the power circuit. 1) This circuit shall include an earthing connection preferably at the base plate, which supports the ingot. If the installation enables several melting stations to be supplied from the same power supply, each station shall be provided with an earth connection. For the particular case of a single-head multi-station co-axial electroslag remelting furnace, it is preferable to ground the power circuit at the power supply instead of at the base. In no case shall the operating personnel be exposed to harmful voltages. If 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.
6.6.9 The cooling system shall be designed to meet the following requirements. 1) The supply of cooling water shall be adequate to prevent undue heating of the cooled walls. 2) Cast and/or welded ingot moulds shall be free from porosities, cracks, etc., which could have a detrimental effect on watertightness and heat transfer. 3) The use of seals likely to come into contact with molten materials shall be prohibited. 7 Isolation and switching The requirements of Clause 7 of IEC 60519-1 apply, except as follows. Addition: 7.3 High-voltage circuit-breaker closing conditions 1) The isolator shall be in the closed position. 2) The setting of the secondary voltage shall be checked. 3) Correct furnace operating conditions shall be established. NOTE It is desirable that provision be made for an illuminated or other signal indicating that the start-up conditions are satisfied and that the circuit-breaker can be closed. 7.4 Switching-on in power circuit The following conditions shall be satisfied for the power circuit before switching on. a) The melting station change-over switches shall be in the closed position. The station in operation shall be indicated on the control board. b) The electrode and the ingot mould shall be aligned in the melting position. c) The base plate shall be in the operating position. d) Removable contact-making devices shall be in the closed position; in particular, electrode clamps or contact shoes, either closed or at least with minimum pressure if a hydraulic or pneumatic system is used, or locked if the system is mechanically operated. The same requirement shall be met by the clamping of the ingot base plate. e) The connections of the cooling circuit, if provided, shall be in working order (flow, pressure and temperature).