KARBIDY, professional harm

From Big Medical Encyclopedia

CARBIDES, professional harm — carbon compounds with metals and nek-ry nonmetals which can have adverse effect on a human body. Natural To. are found as a part of deep breeds of crust, sometimes in meteorites. Receive To. hl. obr. heating of powders of metals and carbon (coal, soot) in the environment of inert or reducing gas. To. are applied in the nuclear equipment, astronautics, electronics, in the equipment of high temperatures, mechanical engineering, metallurgy, and also for receiving acetylene (see. Acetylene ) and cyanamide (see. Defoliants ).

On the nature of interaction with water K. subdivide on decomposed and not decomposed. To decomposed by water carry To. alkali and alkaline earth metals (calcium, strontium, barium), and also magnesium, beryllium, aluminum, lanthanides and actinoids. To not decomposed by water carry covalent To. boron and silicon, and also To. IV—VIII d-transition metals of groups of a periodic system of D. I. Mendeleyev.

In production To. release of dust of initial components, a ready-made product and gases (carbon monoxide) is possible. Intensive heat release takes place.

At use To., decomposed by water, methane and acetylene are emitted. If the technical product contained impurity of phosphorus, arsenic, sulfur, then receipt in air of very toxic gases is possible (arsine, phosphine, etc.).

Dust decomposed by water K. (especially CaC 2 ) causes irritation of a mucous membrane of respiratory tracts, in particular nasal cavities, and also mucous membranes of an eye. Additional toxic action is caused by inhalation of acetylene. At hit on skin, especially wet, dust K. causes irritation, ulcerations and inflammatory reaction. During the receiving and use To. calcium provide actions for the prevention of receipt in air of dust, acetylene and other gases. Protection of skin and mucous membranes during the work with decomposed by water K is necessary.

In production of products from To. use technology of powder or plasma metallurgy. Processing of products from To. carry out abrasive, ultrasonic or electrospark in the ways. During the crushing To., weighing of components of furnace charge, pro-sowing, loading and unloading, packaging, processing the aerosol of disintegration is formed. At service of arc furnaces the low frequency noise is registered (see. Noise ). During the casting melted To. release of vapors of hydrocarbons and carbon monoxide is possible.

To., the malotoksichna which are not decomposed by water, practically. Effect of dust K. on a respiratory organs of experimental animals it is shown in the form of the unsharp fibrous reactions which were more expressed at administration of dust of boron carbide. In pulmonary fabric the diffusion thickening of interalveolar partitions, especially around the centers of dust accumulations is noted. The peribronchial sclerosis develops in late terms and pneumosclerosis (see).

At dry sanding and grinding of products with use of artificial abrasives a peculiar high-quality pnevmokoniotichesky process — a pneumoconiosis of shlifovalshchik can develop (see. Pneumoconiosis ).

During the work with To. holding preventive actions is necessary. In the USSR maximum allowable concentrations of aerosols of a number of carbides for air of a working zone are established: SiC — 5,0 mg/m 3 , WC — 6,0 mg/m 3 , ZrC — 6,0 mg/m 3 , B 4 With — 6 mg/m 3 . Sealing of the equipment and vehicles, local aspiration during the performance of the operations which are followed by a pylevydeleniye is required (grind, having sunk, transportation, an overload of powder materials, etc.). For pressing of products from To. it is necessary to apply automatic and semi-automatic the press, equipped with local aspiration.

It is the most reasonable to use for agglomeration of products from To. the furnaces equipped with mechanical charging apparatuses and the automatic control of a temperature schedule, use of defensors (heat insulation, screens, veils) from infrared radiation. At periodic medical examinations it is recommended to carry out a X-ray analysis of lungs, a research of function of external respiration.

Bibliography Brakhnova I. T. Toxicity of powders of metals and their connections, Kiev, 1971, bibliogr.; Harmful substances in the industry, under the editorship of N. V. Lazarev and E. N. Levina, t. 1 — 2, L., 1976; Occupational diseases, under the editorship of A. A. Letavet, M., 1973; Samsonov G. V. and Kosolapova T. Ya. High-temperature carbides, Kiev, 1975.

N. Yu. Tarasenko.