3.3　Equipments

3.3.1　Newly-built ferroalloy plant shall select reasonable capacity and type of electric arc furnace（EAF）according to product and scale.The capacity of SAF should be over 25000kV·A.Short fume hood is adopted for the furnace requiring tapping hole operation，and closed type furnace should be adopted for other types of product.The capacity of refining furnace should be over 3500kV·A.

3.3.2　Type selection of main equipment of SAF workshop shall include furnace capacity and type，power supply mode of transformer，electrode system，electrical control mode，hydraulic system，cooling water system，raw material and proportioning and loading equipment，furnace top charging equipment，tapping equipment and casting equipment，etc.

3.3.3　Type selection of main equipment of refining furnace workshop shall include furnace transformer，furnace equipment，material feeding equipment，hot charging equipment，shaking ladle，tapping equipment and casting equipment，etc.

3.3.4　The clearance height of closed furnace roof shall not be smaller than 1.10 times of its electrode diameter.

3.3.5　The fume hood height and furnace door opening size of semi-closed EAF shall be in accordance with the following requirements:

1　It shall be capable of storing instantaneous peak fume flow.

2　It shall be capable of pulling out electrode in case of electrode breakage.

3　It shall meet requirements of charging stoking machine operation.

3.3.6　The EAF busbar shall be in accordance with the following requirements:

1　Section size and current carrying capacity of busbar shall be selected according to current density，and it shall be capable of short time overload.The current density of busbar should be controlled at 3A/mm2-4A/mm2.

2　It shall feature perfect ground insulation performance.

3　It shall have good mechanical strength.

4　The busbar hanger and wall tube shall be made of magnetic isolating material and shall be insulated.

5　Busbar resistance and itself inductive reactance shall be reduced，and the 3-phase impedance unbalance shall be lower than 5%.

3.3.7　The busbar at low voltage side of SAF shall adopt water cooled copper tube and water cooled cable in terms of its structure type.

3.3.8　The intensity of pressure between electrode and copper contact shoes shall be controlled at 0.09MPa-0.12MPa.

3.3.9　Copper contact shoes of large EAF shall be forged，and material with copper content over 99.5%shall be used，and its thickness shall not be smaller than 70mm.

3.3.10　The contact element and slipping unit of fin-type holder shall be interchangeable.

3.3.11　The inner surface of copper contact shoes shall be machined in group，and good contact surface with electrode shall be guaranteed.

3.3.12　The electrode regulating speed of SAF shall be controlled at 0.50m/min，and 0.40mm/min-1.50m/min for refining furnace.

3.3.13　The top and bottom clamping brakes of electrode shall be interlocked.

3.3.14　Slipping length of electrode shall be capable of free adjustment within 0-100mm.

3.3.15　The lifting position detection device of electrode shall be composed of electrode position indicator and secondary display instrument.

3.3.16　The water cooled framework and water cooled cover plate of EAF fume hood and roof shall be subject to hydrostatic test and water passing test after completion of manufacturing.The test pressure shall be 0.6MPa，with duration of 30min without leaking，and each water passage shall be smooth.

3.3.17　The water cooled cover plate close to water cooled framework of roof and fume hood and around electrode shall be made of anti-magnetic stainless steel material.Coated or precast fire resistance concrete material shall be applied under water cooled cover plate for heat insulation，and its thickness shall not be smaller than 50mm.

3.3.18　Perfect sealing shall be formed between fume hood，roof and holder and tube.

3.3.19　Connection between conducting copper tube and copper contact shoes shall adopt pressed fitting structure with taper socket，and the wall thickness of copper tube shall not be smaller than 10mm.

3.3.20　Conducting tube should be made up of two sections，with one section connected with water cooled cable and the other section connected with copper contact shoes.Welding shall be adopted between two sections，and the gap at connection shall be welded with 307 silver-copper welding rod for joint filling.

3.3.21　The hydraulic system shall be in accordance with the following requirements:

1　Hydraulic power unit，accumulator and hydraulic pipeline shall be equipped with pressure valve and shut-off valve，and emergency opening/closing device shall be equipped between accumulator and oil pipeline.

2　While installing high pressure hose，it shall meet max.stroke requirement of electrode，and torsion is not allowed.

3　The vent valve shall be installed at highest point of pipeline system.

4　The painting of hydraulic system shall be in accordance with relevant stipulations specified in current national standard GB 7231 Basic identification color，identification symbol and safety marking of industrial pipeline.

5　The installation of hydraulic system shall be in accordance with relevant stipulations specified in current industrial standard YBJ 207 Code for construction and acceptance of metallurgical mechanical equipment installation-hydraulic，pneumatic and lubrication system.

6　The media of hydraulic system should adopt water-glycol.

7　The hydraulic system of EAF shall be subject to pressure test after installation is completed，and the test pressure shall be 120% of working pressure，with duration of 15min-20min without leaking.

3.3.22　The elements of pressure ring holder shall not use flammable media.

3.3.23　In case of power failure，the accumulator shall be capable of hoisting electrode to a certain height.