(37c) The Design and Operation of Multi-Point Dust Collection Systems

Authors: 
Fan, Y., The Dow Chemical Company
Jacob, K., The Dow Chemical Company
Koch, J. F., The Dow Chemical Company
It is very common in particulate-producing plants to have a vacuum dust collection system to collect fugitive dust from all manner of unit operations such as container filling, container dumping, size reduction, transfer points, etc. The design methods have been well established in the Industrial Ventilation manual published by the American Conference of Governmental Industrial Hygienists [1]. Nevertheless, in practice these systems are not always properly designed or maintained, thereby not providing the dust collection and subsequent worker protection for which they are intended. Following the guidance of the ACGIH manual, we will first outline the philosophy and methodologies to design a multi-point vacuum pick up system. At first glance, this would appear to be an easy task, however when one considers the multiple requirements (saltation velocity, minimum velocity to meet NFPA guidelines, required volumetric flow rate of air for dust collection at each pickup point, etc.), the problem is considerably more difficult. In practice, many systems will either not operate as expected or performance will degrade over time. We will highlight some of the pitfalls in the design and operation of these systems, such as intermittent operation of branches of a system, unintended extension of the system by adding longer lengths of flexible tubing, etc. This highlights the need for the design engineer and the system operator to work together to conceptualize and design a system which provides the level of dust collection needed and can be easily maintained for the life of the process plant.

[1]

Industrial Ventilation: A Manual of Recommended Practice, 29th Ed, American Conference of Governmental Industrial Hygienists (ACGIH), 2016.