Determination of volumes of air, remove local suction
Until relatively recently, in determining the amount removed by aspiration of air existed only departmental standards. The main drawback of all standards was recommended ones low volumes of air to be removed by aspiration.
In recent years, rates for foundries MIOTa, Giprotisa, Mekhanobr and Leningrad Promstroyproject for crushing and transport equipment concentrators, and finally came out instructions on designing sanitation facilities of the main shops and offices of the refractory plants - SN 155-61. Latest most valuable as to the completeness of the exposition, and because of what is a publication of the official. Some guidelines for determining the volume of suction aspiration in foundries are in CH 111-60. According to other industries such instructions are available in other similar publications.
of nationwide standards for determining the volume of air removed by aspiration, not yet available. Thus, full of clarity and consistency in determining the volume of suction aspiration has not yet established.
Very significantly, nor in some rules there is no indication of change in the volume of exhausted air depends on the properties of dust, such as its toxicity. This is very annoying gap. Impersonal approach to determining the amount of suction air in the aspiration can not be regarded as correct.
Any local suction will never give one hundred percent recovery hazards, some of them always erupts in the room - indifferent gas is a hazard or dust. Only in exceptional cases, such as trapping of radioactive substances, it is possible to completely remove harmful local suction.
Dusty rooms with aspiration, independent (not touching the secondary dust) on the "breakthrough" of dust in the room, ie, from the perfection of the local shelter or local exhaust. To the concentration of dust in the room did not exceed permissible to dust and toxic silikoznyh need a sharp decrease in "breakthrough" in the room compared to the dust neutral.
Regulated or determined by calculation volumes of air removed from aspiriruemyh shelters, we should recognize acceptable only for neutral dust, the allowable concentration of which ranges from 6 to 10 mg/m3. With regard to dust containing more than 10% free Si02, asbestos dust and toxic dusts, to determine the volume of air exhausted from aspiriruemyh shelters, we recommend the following values of multiplying factor p.:
for the dust to the permissible concentration:
3-5 mg / m *......... 1,2
1-2 mg / me ......... 1,3
for toxic dusts allowable concentration: up to 0.3 mg / me. 1.4 below 0.3 mg/m3 .. 1,5-1,6
If the amount of air removed from the aspiriruemogo shelter at neutral dust designate La, then silikoznoy, asbestos and toxic dust required volume of L is expressed as:
La = [iLa [m * / h]. (50)
Enter into the calculation of the coefficient is proposed in all cases, dust control, except for the aspiration of elevators. In the latter case, the coefficient of P1 can be taken to be 1.