Airborne pumps are used in all cases where it is not a complete source of shelter hazards. Airborne pumps are especially effective in tanks, vats, vacuum devices, and so forth, loading and unloading are carried out periodically by means of lifting mechanisms. At round machines onboard pumps arranged a ring section with suction pipes underneath. The amount of air removed by suction board, depends on the toxicity hazard and intensity of its allocation.
With a diameter of a circular vehicle within 500-700 mm can recommend the following rules specific volume of air exhausted by 1 m2 of surface of the mirror separation hazards.
For hazards with the allowable concentrations to 1 mg / m 3 amount of exhaust air is:
during hot during 9000 m] hr-m2, with a cold during the 6000 - 7000 m3/ch-m2. For hazards with the allowable concentration of 10 mg / m 3 amount of exhaust air is:
during hot during 7000 m-/ch-m1; a cold during 4000-5000 m3/ch-m2. For hazards with the allowable concentration of 100 mg / m 3 amount of air exhausted by any process m3/ch-m2 2500.
When you select a particular hazardous substances listed rates should be increased, and assign specific volume of air exhausted within 10 000-14 000 m3/ch-m2.
In laboratory buildings all work related to the release of harmful substances are produced in a fume hood. Laboratory fume hoods - the most common equipment research n industrial laboratories. Unfortunately, in most cases, fume hoods are made handicraft, very often on outdated and inappropriate patterns. Unsuccessful design cabinet burrow nullifies even well done ventilation.
Laboratory cabinets must be performed with metal, steel or aluminum, as well as plastics, but not wooden. Wood - a material capable of swelling and dry when the humidity. Made of wood cabinets are almost always a gap and is characterized by tightly closed doors. Closet doors are raised and lowered with difficulty that impairs their operation by some makes the impossible! lock the doors.
Laboratory cabinets must have an adjustable hood from the top and bottom of its zones. Cabinets with only the top PLI only the lower hood for laboratory work are not recommended. Inside the cabinet should be smooth with no protruding parts, air ducts inside the cabinet will not be tolerated. The most rational design of a cabinet with dual rear wall, forming a flat exhaust duct communicating with the working cavity of the cabinet openings, fitted with regulators engines. The holes should be placed evenly along the length of the cabinet. Scheme of a laboratory cabinet with double rear wall is shown in Fig. 53.
Laboratory cabinets come with a lockable door, two and three. Four-door cabinets are not commonly found and replaced with two-door. Two-door cabinets, as a rule, should have a lock, allowing the simultaneous opening of all doors but one, perhaps opening doors on both the PA for a fraction of their height, such as two doors in half. In the three-door cabinets usually two doors are locked, and the third is free. In such cabinets can be fully opened two doors simultaneously. There are, of course, there are other options, such as full disclosure of all doors in the two-door and three-door cabinets.
Common sizes of laboratory cabinets doors - 500 mm X X700. In some cases enlarged openings
length of 800 mm and a height of 600 mm. Openings are still large - already an exception.
When calculating the amount of air removed from the laboratory cabinet considered the terms of allocation of hazards and their composition, as well as the required disclosure doors. For metal lab cabinets into account the looseness factor can be taken from 1 to 1.1.
design speed for the cabinets, which are produced analytical work should be in the range 0,7 - 0,8 m / sec, while working with mercury - 1-1,2 m / sec, when heated - up to 1,3 m / sec.
The amount of air removed from the usual two-door cabinet with locking doors in the production of analytical work (aperture size 700 X 500 mm),
For the three-door cabinet air volume 2200 m3 / h. In most laboratory and industrial premises - except for local suction, provides general exchange stretching from the upper zone (with few exceptions). The volume of air is determined by the multiplicity adopted by no less than one. In most areas one-time sharing is not enough. In areas of small volume, in which there is a selection of vapors, gases and aerosols, the multiplicity of the general exchange extraction should take between 2 to 5.
In areas with some heat, moisture or body fluids or with local suction air is determined by calculation. Only in those areas where the allocation of pollutant indefinitely and can not be taken into account, possibly to determine the air exchange of practical information - on the multiplicity of exchange.