Abstract: Disclosed is an apparatus for observing the interior of a hot furnace. The apparatus is equipped with a camera arranged in a case whose inner surface is cooled by means of cooling water and into whose inner space cooling air is blown, the apparatus comprising: a quartz-glass plate, a heat-ray-reflecting-glass plate, a heat-ray-absorbing-glass plate, and a heat-ray-transmitting mirror arranged in order of decreasing distance to the camera in an optical path through which a ray of light entering at the front surface of the case is led to the camera; and an illuminating lamp which is provided on the front surface of the case and whose luminance can be remote-controlled. With this construction, the temperature in the camera case can be kept at 50.degree. C. or less, and damage to the camera due to the radiation heat entering through the glass window can be avoided. With this apparatus, the interior of a hot furnace can be observed over a temperature range of room temperature to 1200.degree. C.

Abstract: The present invention was developed to solve the problems inherent in conventional dry type and wet type gunning methods. The main point of the present invention is a novel method for gunning a refractory composition for obtaining a lining body having high density and high strength by premixing a refractory composition with water amounting to 1/5-3/4 of the total amount of water for the lining, and subsequently adding and mixing the rest of the water at the inside of the gunning nozzle of the dry gunning equipment while gunning.

Abstract: Unshaped refractories are disclosed which have incorporated therein granules comprising fine powder refractory and carbonaceous material. The fine powder refractory may be the refractories of magnesia clinker, dolomite, magnesia-dolomite, high alumina, recovered materials of such refractories recovered after use, and mixtures of two or more thereof. The carbonaceous material may be any one of: thermosetting resin, a thermoplastic resin to which has been added pitch and hardening agent, other resins, or mixtures of two or more thereof.

Abstract: A gunning refractory of the mean particle diameter in the range 1-10 mm, characterized in that a molten liquid of pitch having softening point higher than 100.degree. C. is mixed with refractory inorganic fine particles where the proportion to the total weight is in the range 5-85% by weight, and thereafter the mixture is hardened.