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Experimental Determination of Minimum Transport Velocity for Sand in a Local Exhaust Ventilation (LEV) System Using Borescope Observation

Abstract No:

1713

Abstract Type:

Student Poster

Authors:

A Capestany Rivera¹, S Caporali Filho², E Perez Matias³

Institutions:

¹University of Puerto Rico, Toa Baja, PR, ²University of Puerto Rico, Fajardo, PR, ³University of Puerto Rico, Moca, PR

Presenter:

Amanda Capestany Rivera
University of Puerto Rico

Faculty Advisor(s):

Sergio Caporali Filho
University of Puerto Rico

Edgar Perez Matias
University of Puerto Rico

Description:

Minimum transport velocity is a critical parameter in the design of local exhaust ventilation (LEV) systems because it ensures that particulate contaminants remain suspended and are conveyed through ductwork without settling. Recommended transport velocities provided in Industrial Ventilation: A Manual of Recommended Practice for Design are commonly used in ventilation design; however, these values typically incorporate safety factors to account for complex operating conditions found in industrial systems.

Situation/Problem:

Designing an LEV system requires ensuring that airflow is sufficient to prevent particle accumulation in ducts. However, recommended transport velocities may be conservative due to safety factors, and the actual minimum velocity needed to convey specific particulate types, such as sand, under controlled conditions is not always experimentally verified. Understanding the true minimum transport velocity can improve system efficiency and evidence-based design.

Methods:

A laboratory-scale LEV duct system was used to experimentally determine the minimum transport velocity for sand particles. A controlled test rig equipped with a variable-speed fan and an adjustable-speed particle feeder simulated particulate transport. A borescope installed at a marked observation zone inside the duct allowed direct visualization and video recording of particle movement and accumulation. Static pressure (SP) and velocity pressure (VP) were measured using a manometer, and airflow velocity was calculated from VP measurements. Sand with a particle size of 35 mesh was used as a surrogate contaminant. Airflow conditions were gradually adjusted until the velocity was sufficient to remove settled particles from the observation zone.

Results / Conclusions:

Across multiple trials, particle removal consistently occurred within a velocity pressure range of approximately 0.11–0.13 in. w.g., corresponding to air velocities near 1380–1400 fpm. Variations in particle feed rate did not significantly affect the velocity required to clear the duct. These findings suggest that ACGIH-recommended transport velocities may include safety factors accounting for variables such as air density, eddy currents, and duct component aging. The experimental approach provides a practical method for determining minimum transport velocities and may support improved, evidence-based ventilation system design.

Core Competencies:

Engineering Controls and Ventilation

Secondary Core Competencies:

Exposure Assessment

Work Environments, Occupations, and Industrial Processes

Keywords

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Aerosol and airborne particulate monitoring

Labs – Health & Safety, Testing

Respiratory Protection

Ventilation

Targeted Audience (IH/OH Practice Level)

Based on the information that will be presented during your proposed session, please indicate the targeted audience practice level: (select one)

Practitioner: Practitioner is a job title given to persons in various occupational fields who are trained to assist professionals but are not themselves licensed or certified at a professional level by a certification body recognized by the National Accreditation Recognition (NAR) Committee of IOHA. The IH/OH practitioner performs tasks requiring significant knowledge and skill in the IH/OH field, such as conducting worker exposure monitoring and, in some cases, may even function independently of a professional IH/OH but may not be involved in the breadth of IH/OH practice nor have the level of responsibility of a professional IH/OH certified by examination. The IH/OH practitioner requires a certain level of education that can be obtained from an accredited university or equivalent. Additional training in specific skill sets that provide additional career paths to the IH/OH practitioner can also be obtained. IH/OH practitioners may also serve as team leaders or project managers.

Volunteer Groups

Was this session organized by an AIHA Technical Committee, Special Interest Group, Working Group, Advisory Group or other AIHA project Team?

Worker Exposure Data and/ or Results

Are worker exposure data and/or results of worker exposure data analysis presented?

Practical Application

How will this help advance the science of IH/OH?

This study advances the Industrial Hygiene field by providing experimentally determined minimum transport velocities for particulate control in LEV systems, offering a data-driven alternative to recommended values. By ensuring particles are effectively conveyed without settling, the findings support improved worker safety, reduce airborne exposure to hazardous dust, and optimize system efficiency by preventing over-engineering. Additionally, the borescope-based methodology offers a practical, reproducible approach for evaluating airflow requirements in diverse industrial settings, helping bridge the gap between theoretical design recommendations and real-world conditions.