Portables for flow meter calibration in industrial hygiene

Portables for flow meter calibration in industrial hygiene

Industrial hygiene is the science of protecting and enhancing the health and safety of people at work and in their communities. Federal organizations including OSHA and the NIOSH strictly enforce industrial hygiene regulations to ensure workers are safe from hazardous substances within the air they breathe. Industries required to practice industrial hygiene include construction, agriculture, oil & gas, mining, maritime, and metalworking.

Here we discuss the use of flow meters in industrial hygiene applications, as they are important for measuring particulate levels and ensuring measurement equipment is properly calibrated.

What is industrial hygiene?

Industrial hygiene involves sampling the air to check for particulates and gas contaminants in dusts, fumes, mists, and aerosols. Most often, personal sampling pumps are used to draw air at a known flow rate through a collection medium. While many types of pumps are suitable for industrial hygiene applications, the best choice will be based on desired features beyond basic airflow.

A wide operating range and the ability to maintain a constant flow rate are two common pump features. For applications that require sampling across a wide range of flow rates, from a few milliliters to several liters per minute, a pump with a large operating range can be very useful. This feature ensures that a single pump can be used for the entire span of flow rates required by the application. These pumps are generally more expensive, but have lower lifetime costs of ownership due to the broad use cases and minimal need for other equipment.

For applications with less variation in flow rates, finding a pump with the firmest set point and a constant flow rate may be a priority. Because the sampled air may contain high levels of particulates, pumps for industrial hygiene are particularly prone to clogged filters and a subsequently decreased flow rate. However, pump systems that are able to detect changes in pressure drop can then compensate to maintain the desired flow rate.

What role do flow meters play?

The levels of particulates in the air sample are used to evaluate a worker’s exposure to hazardous materials. It is therefore critical to ensure that the pump sustains a set air flow and provides highly accurate measurements.

Flow meters ensure pump accuracy in a couple ways. The pumps themselves contain flow meters that measure air flow through the collection medium. Higher-accuracy flow meters are then used to calibrate these pumps and ensure they are operating within their specifications. To ensure accurate measurements, industrial hygiene pumps should be calibrated both before and after the sampling period.

Rotameters within pumps

Variable area flow meters, or rotameters, are commonly used to measure air flow through the pumps. These meters are low cost and simple to calibrate, operate, and read. They are less accurate than other flow meters, but sufficient for confident calculations of workplace safety.

Flow meter calibration

To ensure the pumps are reading accurately, higher accuracy flow meters can be used for calibration. Portable, battery-powered flow meters are extremely convenient for this type of servicing, as they can be brought to point-of-use and used for calibration without requiring time spent wiring, powering, or waiting for a device to warm up.

MWB portable flow meter

MWB low pressure drop mass flow meter

Advantages of Alicat portables for calibration

Alicat flow meters are multivariate. As the ambient temperature and pressure in the workplace influence the particulate levels in the air, the ability of the flow meter to simultaneously measure temperature, pressure, mass flow, and volumetric flow simplifies overall testing operations. It provides the maximum amount of information about the environment from a single instrument and ensures the air is safe for workers to breathe. Further, to minimize the pressure drop when calibrating a rotameter and ensure the best possible calibration, an Alicat MWB-Series portable flow meter can be used to maintain a pressure drop as low as 0.07 PSID at full scale.

Given that flow meter calibration is a key component of industrial hygiene, using the appropriate calibration tools is critical to human health and safety.