Portable devices for calibrating flow meters in industrial hygiene.
Industrial hygiene is the science of protecting and improving the health and safety of people at work. The Working Environment Agency (https://www.av.se/inomhusmiljo/) applies strict rules to ensure that workers are not exposed to dangerous substances in the air they breathe. Some of the industries covered by industrial hygiene are process industry, construction, agriculture, oil and gas, mining, shipping and engineering.
Here we discuss the use of flowmeters in industrial hygiene applications as they are important for measuring particle levels and ensuring that measuring equipment is properly calibrated.
What is industrial hygiene?
Industrial hygiene involves sampling the air to measure particle content and gaseous contaminants such as dust, vapors, and aerosols. Most commonly, personal sampling pumps are used to flow air at a known flow rate through a collection filter. Although several types of pumps can be used for industrial hygiene applications, it is the different functions of different models that determine which one is best suited for the specific application.
A wide flow range and the ability to maintain a constant flow rate are two common pump features. For applications that require sampling over a large flow range, from a few milliliters to several liters per minute, a pump with a large flow range may be suitable. This feature ensures that a single pump can be used for all flow ranges required by the application. These pumps are generally more expensive but have a lower total cost due to minimized need for other equipment such as several different pumps to cover different flow ranges.
For applications with less flow variation, finding a pump with more fixed flows and a constant flow rate may be a priority. As the tested air can contain high levels of particulates, industrial hygiene pumps are particularly vulnerable to clogged filters resulting in reduced flow rates. However, pump systems that can detect changes in pressure drop can then compensate to maintain the desired flow rate.
What role do flow meters play?
The levels of particles in the air samples are used to evaluate a worker's exposure to hazardous air. It is therefore important to ensure that the pump maintains a set airflow to achieve very accurate measurements.
Flow meters ensure pump accuracy in several ways. The pumps themselves contain flow meters that measure the air flow through the collection filter. Higher accuracy flow meters are then used to calibrate these pumps and ensure they stay within their specifications. To ensure accurate measurements, industrial hygiene pumps should be calibrated both before and after the sampling period.
Rotameters in pumps
Flowmeters with variable flow range or rotameters are often used to measure air flow through the pumps. These meters are inexpensive and easy to calibrate, use and read. They are less accurate than other flowmeters, but sufficient for workplace safety calculations.
Flowmeter calibration
To ensure that the pumps read accurate flow, higher accuracy flow meters can be used for calibration. Portable, battery-powered flowmeters are extremely convenient for this type of service, as they can be commissioned and used for calibration without having to install data and power lines or wait for a flowmeter to warm up to its specified accuracy.
Advantages of Alicat portable for calibration - model MWB portable flowmeter with extremely low pressure drop
Since the ambient temperature and pressure in the workplace affect the particle levels in the air, the flow meter's ability to simultaneously measure temperature, pressure, mass flow and volume flow simplifies the overall test operations. It provides maximum information about the environment from a single instrument and ensures that the air is safe for workers to breathe. 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 5 mbarD (0.07 PSID) at full scale.
Given that flowmeter calibration is an important part of industrial hygiene, it is important to use appropriate calibration tools for human health and safety. Alicat air and gas flowmeters are multivariable and provide extreme flexibility with their unique ability to change gases or gas mixtures in the field while presenting multiple variables from the measurement (Mass Flow, Volume Flow, Pressure, Temperature) at the same time.
– Alicat Portable Whisper with low pressure drop
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Posted by Jonas Lindgren at Kompauto Nordic AB and Kompauto Norway AS. jonas.lindgren@kompauto.com, Mob.+46 70 684 00 01
