Refractory Technology

111. Porosity is induced in insulating refractories by adding

1. Powdered naphthalene
2. Ammonium chloride/sulphate
3. Calcium phosphate
4. All (A), (B) and (C)

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112. Porosity of fireclay refractories is _________ percent.

1. 44109
2. 45931
3. 25-35
4. 35-50

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113. Porosity of silica bricks varies from _________ percent.

1. 5 to 10
2. 20 to 30
3. 45 to 60
4. 60 to 75

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114. Presence of MgO in alumino-silicate refractories _________ its refractoriness.

1. Increases
2. Lowers
3. Does not affect
4. Either (A) or (B); depends on its quantity

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115. Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as _________ percent.

1. 55
2. 70
3. 80
4. 90

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116. Pure oxide refractories are generally monocrystalline in nature and are self bonded _________ bricks are generally used as moderator in nuclear reactors.

1. Beryllia
2. Carborundum
3. Corundum
4. Thoria

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117. Pyrometric cone equivalent (PCE) of a refractory is the measure of its

1. Spalling resistance
2. Fusion point
3. Resistance to slag penetration
4. Resistance to carbon monoxide attack

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118. Pyrometric cone equivalent (PCE) value (Segar cone) of 'Superduty refractories' is more than 33 which corresponds to a temperature of _________ °C.

1. 1520
2. 1630
3. 1670
4. 1730

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119. Quartz is

1. Stable form of silica upto 870°C
2. Converted to Tridymite on firing between 870 to 1470°C
3. Transformed to Cristobalite on heating above 1470°C
4. All (A), (B) and (C)

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120. Ramming masses are used for

1. Obtaining monolithic working faces
2. Repairing construction of various furnace parts
3. Both (A) & (B)
4. Neither (A) nor (B)

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