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MF47-3.05 

 

Take care that nothing hits the elements when loading of unloading. 

3.5

 

Opening the Door 

Take great care when loading or unloading the furnace chamber. See section 3.3. Before you 
remove a hot object from the furnace make sure you have a safe place to put it down. 

Do not open the door at high temperatures. If possible, do not open it above 200°C. If it is 
necessary to load or unload work at elevated temperatures, keep the door open for as short a period 
as possible. The insulation cools quickly and may crack through thermal shock. 

The heating elements and the insulation are very susceptible to mechanical shock. At all times 
operate the door gently to avoid mechanical shock. 

Opening the door when the furnace is very hot can cause hot air to be sucked by the case cooling 
fans towards the thermal cutout and activate it (see section 3.13). Avoid excessive door opening 
and shut it as soon as possible. 

3.6

 

Insulation Cracking 

In these furnaces the insulation material is susceptible to surface cracking arising from high 
temperature cycling; this is a normal occurrence and such cracking is not detrimental to the 
performance of the furnace.  

3.7

 

Atmospheres & Corrosive Materials 

In oxidising atmospheres, metal oxides react with the silica layer on the surface of the elements 
and may lead to premature failure. Protect the elements from splashes of molten metal and dust 
when charging the furnace, and from fumes developed when melting, especially from fluxes. Also 
avoid compounds with a high alkali content. 

The furnace is designed for use up to its maximum temperature in oxidising atmospheres, but can 
also be operated successfully in neutral or carburising atmospheres. It may be used with nitrogen, 
argon or helium atmospheres to 1600°C. Reducing atmospheres are not recommended. Sulphur 
dioxide in normal concentrations is not harmful, but chlorine, and more so fluorine, strongly attack 
even oxidised elements and should be avoided. 

The furnace is not recommended for burning off carbonaceous materials. Other Carbolite furnaces 
are available for this application. 

When an optional gas inlet is fitted there is a label near the inlet saying "INERT GAS ONLY". In 
practice 

inert

 or 

oxidising

 gases may be used, but 

not combustible or toxic gases

. The furnaces are 

not gas tight, so it should be understood that gas usage may be high, and that the chamber is likely 
always to contain some air. Residual oxygen levels of at least 1% are to be expected. 

The hearth can be protected from abrasion, by the provision of a secondary plate. This consumable 
item can either be in light weight ceramic fibre or in dense, hard-wearing alumina refractory. 

3.8

 

Pesting 

The furnace is fitted with Molybdenum Disilicide elements and is therefore susceptible to pesting.  
Pesting can be seen as a yellowish crystal growth on the surface of the element.  It occurs when the 
element surface temperature is around 450°C and is caused by the air oxidising with the 
Molybdenum in the element compound.  Under normal operating conditions (above 800°C) 
pesting is not a problem and can often be seen occurring naturally on the element terminals. 

Running the furnace for prolonged periods at temperatures below 600°C will cause pesting to 
occur on the element surface and will eventually damage the elements.   

Heating on a slow ramp rate or dwelling at temperatures below 600°C for short periods will not 
cause a problem providing the furnace is run above 1400°C at regular intervals to recondition the 
element surfaces. 

Large amounts of pesting occurring on the element terminals must be removed in accordance with 
good health and safety practices. 

Содержание Carbolite HTF 17

Страница 1: ...is connected to the electricity supply Manuals for the furnace controller and overtemperature controller are supplied separately Please read the controller manuals before operating the furnace Contents Section Page 1 0 Introduction 2 2 0 Installation 3 3 0 Operation 5 4 0 Maintenance 8 5 0 Repairs Replacements Adjustments 10 6 0 Fault Analysis 15 7 0 Circuit Diagram 16 8 0 Fuses Power Control 18 9...

Страница 2: ...an or by someone with a thorough understanding of electrical components and safety Operating should be done by a person who has read this manual and is aware of and understands the safety issues in using high temperature electrically heated equipment Heat Light the adjacent light glows or flashes to indicate that power is being supplied to the elements DANGER of electrical shock read any warning p...

Страница 3: ...free space around the furnace and preferably 1 5m above Do not obstruct any of the vents in the case or leave objects of any kind on the top surface In particular the cooling fans in the case must not be obstructed If the furnace is to be used in a process which could liberate hazardous gases then it should be installed together with a suitable fume extraction system A direct connection to the fur...

Страница 4: ...nnecting device for the furnace The supply MUST incorporate an earth ground CONNECTION DETAILS supply type Supply Terminal label Cable colour Live Neutral Reversible or Live Live 1 phase L Brown to live to either power conductor N Blue to neutral to the other power conductor PE Green Yellow to earth ground to earth ground 2 phase L1 Black to phase 1 L2 Black to phase 2 N Light Blue to neutral PE G...

Страница 5: ...oling fans are still running if the furnace is above that temperature If the furnace is to be left off unattended and has cooled down isolate it from the electrical supply 3 2 Operator Safety Electrical The furnace incorporates a safety switch which interrupts the heating element circuit when the door is opened This prevents the user touching a live heating element but also prevents the furnace fr...

Страница 6: ...gen argon or helium atmospheres to 1600 C Reducing atmospheres are not recommended Sulphur dioxide in normal concentrations is not harmful but chlorine and more so fluorine strongly attack even oxidised elements and should be avoided The furnace is not recommended for burning off carbonaceous materials Other Carbolite furnaces are available for this application When an optional gas inlet is fitted...

Страница 7: ...uples low temperatures The thermocouples fitted to these models give very low outputs below about 600 C and do not give accurate readings at low temperatures They may show a negative temperature when the furnace is started from cold The furnaces are designed for operation over 800 C they may be run below this temperature but accurate temperature measurement and stability is not assured 3 13 Therma...

Страница 8: ...cked from time to time If the glaze has gone it may be restored by heating the furnace up to 1500 C without load for 2 hours or so 4 2 Calibration After prolonged use the controller and or thermocouple could require recalibration see the warning about 1700 1800 C thermocouples in section 3 11 This would be important for processes which require accurate temperature readings or which use the furnace...

Страница 9: ...s case the power limit is accessible to the operator and may be reset to its standard value of 100 4 6 Power Adjustment Thyristor The current limiting thyristor stacks which control power to the elements are fitted with an adjustable resistor which is factory set to limit the maximum current supplied In the event of a change of supply voltage or the fitting of a new thyristor re adjustment is requ...

Страница 10: ...ion Wool industry www ecfia eu We can provide further information on request Alternatively our service division can quote for any repairs to be carried out at your premises or ours 5 3 Side Panel Removal Except where explicitly stated always disconnect the electrical supply before removing the side panel Remove the panel by slackening the four fixing screws behind plastic caps at the left hand end...

Страница 11: ...back panel 1700 models or top cover 1800 models Make a note of the thermocouple connections The negative leg of the thermocouple is marked blue The compensating cable for 1700 1800 C thermocouples is plain copper Disconnect the thermocouple from its terminal block Undo the screw to release the thermocouple sheath withdraw the sheath and shake out any fragments of thermocouple Re assemble with a ne...

Страница 12: ...n above on initial installation Remove the aluminium braids and clips using the clip tool provided with the furnace Lift out the old elements and the insulation blocks handle the insulation pieces with care as they are fragile Carefully loosed and remove the clamps Prepare and install the new elements as explained above Heat up the furnace to a moderate temperature and ensure that the furnace is c...

Страница 13: ...MF47 3 05 13 Element Connections 4 Elements Element Connections 5 Elements Terminal Block Element Braid Terminal Block Element Braid ...

Страница 14: ...lternatively be L1 and L2 for a live to live supply The L side should be connected to the correct tapping to match the supply voltage The link wire should be in position as shown unless the supply voltage is always low in which case there is the option of moving one end to the 2 terminal Important Changing the transformer primary tapping including the 2 requires adjustment of the thyristor current...

Страница 15: ...as activated There are no lights glowing on the controller Check the supply fuses and any fuses in the furnace control compartment The controller may be faulty or not receiving a supply due to a faulty switch or a wiring fault B Furnace Overheats 1 The HEAT light goes OFF with the instrument switch The controller shows a very high temperature The controller is faulty The controller shows a low tem...

Страница 16: ...pply fuses present if supply cable fitted F2 Auxiliary circuit fuses 2A F4 Thyristor protection fuse Ferraz Protistor BU Blue R Red P Pink G Grey GR Y Green Yellow Coil N Elements Contactor BU R Thyr istor BU R OTC P G TC Control thermocouple O temp thermocouple Door Switch Element Transformer Heat Light Case Cooling Fans F2 F1 GR Y PE L EMC Filter F4 Thermal Cutouts Fault Light Instrument Switch ...

Страница 17: ...f supply cable fitted F2 Auxiliary circuit fuses 2A F4 Thyristor protection fuse Ferraz Protistor BL Black BU Blue P Pink G Grey GR Y Green Yellow Coil L2 Elements Contactor BU BL Thyr istor BL BU OTC P G TC Control thermocouple O temp thermocouple Door Switch Element Transformer Case Cooling Fans F2 F1 GR Y PE L1 EMC Filters F4 Thermal Cutouts N F1 Fault Light BL 94KΩ Heat Light Instrument Switch...

Страница 18: ...ld be 100 for all models The current limiting thyristor stacks are set to the maximum element currents given in the table TABLE OF FUSE AND CURRENT LIMIT VALUES Model Phases volts supply fuse rating thyristor fuse rating current limit element circuit HTF 17 5 1 phase 208 20A 30A 150A HTF 17 5 1 phase 220 240 20A 30A 150A HTF 17 10 1 phase 208 30A or 32A 50A 150A HTF 17 10 1 phase 220 240 30A or 32...

Страница 19: ... 5 106 HTF 18 4 1800 C 4 6 141 140 205 4 2 92 HTF 18 8 1800 C 6 2 210 190 205 8 2 4 113 Maximum power as measured included ancillary components and transformer losses 9 2 Environment The furnaces contain electrical parts and should be stored and used in indoor conditions as follows temperature 5 C 40 C relative humidity maximum 80 up to 31 C decreasing linearly to 50 at 40 C altitude not exceeding...

Страница 20: ...es manufactured by Carbolite for laboratory and industrial use For further details of our standard or custom built products please contact us at the address below or ask your nearest stockist Copyright 2014 Carbolite Limited For preventive maintenance repair and calibration of all Furnace and Oven products please contact Carbolite Engineering Services Telephone 44 0 1433 624242 Fax 44 0 1433 62424...

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