Objective Practice Test Refractory Technology - Set 13 - ObjectiveBooks

Objective Practice Test Refractory Technology - Set 13

Practice Test: Question Set - 13

1. Refractory bricks with lower permeability is produced by using
    (A) Higher firing temperature
    (B) Higher moulding pressure
    (C) Finer grog size
    (D) All (a), (b) and (c)

2. Quartz is
    (A) Stable form of silica upto 870°C
    (B) Converted to Tridymite on firing between 870 to 1470°C
    (C) Transformed to Cristobalite on heating above 1470°C
    (D) All (a), (b) and (c)

3. Pure oxide refractories are generally monocrystalline in nature and are self bonded _________ bricks are generally used as moderator in nuclear reactors.
    (A) Beryllia
    (B) Carborundum
    (C) Corundum
    (D) Thoria

4. Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except
    (A) Cost
    (B) Electrical conductivity
    (C) Thermal conductivity
    (D) Fusion point

5. Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of
    (A) Fireclay
    (B) Silicon carbide
    (C) Corundum
    (D) Siliceous fireclay

6. Water content in ground refractory material to be shaped into bricks by hand moulding is about _________ percent.
    (A) 5
    (B) 20
    (C) 40
    (D) 55

7. Refractory bricks having lower porosity have
    (A) High insulating properties
    (B) Low heat capacity
    (C) Low thermal conductivity
    (D) Greater strength

8. Maximum alumina content in high alumina refractory can be as high as ________ percent.
    (A) 30
    (B) 50
    (C) 70
    (D) 90

9. Silica bricks are never used for lining the
    (A) Beehive coke ovens
    (B) By-product coke ovens
    (C) Dome of blast furnace stoves
    (D) Roof of open hearth furnace

10. Panel test determines the _________ of refractories.
    (A) Fusion point
    (B) Spalling resistance
    (C) Slag penetration resistance
    (D) Refractoriness under load (RUL)

11. Fireclay refractories
    (A) Are not resistant to the action of basic slags
    (B) Combine with salts (e.g. chlorides sulphates etc.) & bases (e.g. lime, magnesia etc.) forming fusible aluminates silicates etc
    (C) Shrink during firing
    (D) All (a), (b) and (c)

12. Chemically, mullite refractories is
    (A) 3Al2O3.2SiO2
    (B) Al2O3
    (C) ZrSO4
    (D) ThO2

13. Fireclay bricks is not used for lining the
    (A) Cupola
    (B) Gas producer
    (C) Bottom of hot metal mixer
    (D) Roof of open hearth furnace

14. Presence of MgO in alumino-silicate refractories _________ its refractoriness.
    (A) Increases
    (B) Lowers
    (C) Does not affect
    (D) Either (a) or (b); depends on its quantity

15. In panel test for spalling resistance, the average face temperature of panel assembly is maintained at _________ °C for 24 hours.
    (A) 700
    (B) 1000
    (C) 1600
    (D) 2000

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