Validating, verifying, and calibrating flows
Validation, verification, and calibration all share the common goal of ensuring a process is working as intended. Here, we discuss these three interrelated but distinct processes and detail how to go about validating, verifying, or calibrating your system.
At a basic level, the three terms may be defined as follows:
- Validation ensures a system satisfies its stated functional intent
- Verification ensures a process or equipment operates according to its stated operating specifications
- Calibration ensures the measurement accuracy of an instrument meets a known standard
Validation: Is it producing the right results?
During validation, the user checks to ensure the outputs of a process conform with some expected standard. This standard is typically enforced by an external organization, however it may also be required to meet internal standards. A common example is found in power plants and refineries, where users must validate that stack gas outputs comply with EPA requirements.
Verification: Is it working correctly?
The goal of verification is to make sure a piece of equipment or sub-process is working according to the manufacturer’s technical design specifications. Verification may be performed as a part of routine maintenance, or to ensure that newly purchased instruments work properly prior to installation. This oftentimes involves temporarily inserting a flow meter into a process and measuring parameters such as flow rate or pressure.
Performing validation and verification
While validation and verification have distinct goals, the procedure is the same for both: Read a value and check to see if it falls within a specified range. Portable mass flow meters are particularly well-suited for quick and easy validation and verification.
- These battery powered devices last up to 18 hours, ensuring that multiple processes/instruments can be quickly checked.
- Multivariate measurement allows for validation or verification of process pressure, mass flow rate, or volumetric flow rate – all with one device.
- Low pressure drop configurations are available for processes with low system pressures and/or to minimize system impact.
In cases where the flow range of a single device isn’t quite enough, a portable calibration unit can be used. These units contain three high-accuracy battery-powered mass flow meters. They are specifically designed for easy, rapid verification of multiple process parts operating across a wide range of flow rates.
Calibration: Is it still accurate?
Calibration is a two-step process, where the user first uses a calibration standard to read a flow value and then adjusts the device under test to match the reading on the standard.
There are two types of standards:
- A primary standard is a universal measurement reference standard, such as those from the National Institute of Standards and Technology (NIST).
- A transfer standard is an instrument which has been directly calibrated using a primary standard.
Primary standards tend to be very expensive, so transfer standards are oftentimes used instead. For flow and pressure calibrations, Alicat’s high accuracy mass flow meters and pressure transducers can be used as transfer calibration standards.
When determining which instrument(s) to use for calibration, it is important to consider both accuracy requirements and operating range.
- A single mass flow meter can be used to calibrate devices. These instruments measure with NIST-traceable accuracy to ±0.5% of reading or ±0.1% of full scale and have a flow measurement range of 0.01% to 100% of full scale (10,000:1).
- Higher accuracy calibrations may require an additional device, with a setup consisting of either two high-accuracy mass flow meters or one high-accuracy meter and one high-accuracy controller.
- Wider operating range calibrations may require a portable calibration unit, with a 100,000:1 operating range.
- Alicat also offers an FP-25 complete calibrator kit specifically designed for air quality monitoring applications.
Our applications engineers are always available to discuss your application and determine which solution is best for your process validation, verification, or calibration needs.