Lessing ring is formed by the addition of a partition across the centre of a raschig ring, which results in an area increase of about ______________ percent?

Related Mcqs:

1. Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as ______________ percent?

   A. 10
   B. 15
   C. 20
   D. 30

2. Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of ______________ percent respectively?

   A. 80 and 20
   B. 20 and 80
   C. 50 and 50
   D. 60 and 40

3. 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

4. Porosity of silica bricks varies from ______________ percent?

   A. 5 to 10
   B. 20 to 30
   C. 45 to 60
   D. 60 to 75

5. The maximum linear expansion of silica bricks during firing is about ______________ percent?

   A. 0.5
   B. 1
   C. 2
   D. 3.5

6. Grog addition in fireclay during brick manufacture is done to_________________?

   A. Reduce its shrinkage on heating
   B. Impart greater spalling resistance
   C. Enhance the strength of fired refractories
   D. All A., B. and C.

7. 10 to 30% magnesite is added to Chromite to produce chrome-magnesite refractories. Magnesite addition is mainly done to improve the _____________ of Chromite?

   A. Spalling resistance
   B. Refractoriness
   C. Crushing strength
   D. Resistance to slag

8. Addition of grog in fireclay brick during its manufacture is advantageous, because it results in_____________________?

   A. Less shrinkage in heating, decreased apparent porosity & increased specific gravity
   B. High strength & thermal spalling resistance
   C. Less addition of water to get a workable plasticity & lesser time required for drying the raw
   refractories and hence increased rate of production
   D. All A., B. and C.

9. Addition of zircon to silica refractory brick improves its_____________________?

   A. Crushing strength
   B. Resistance to slag attack
   C. Both A. and B.
   D. Neither A. nor B.

10. Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, because of its_______________?

    A. Non-wetting characteristic
    B. High thermal conductivity
    C. High crushing strength
    D. None of these