1.0 Calibration Gas and its uses
What is calibration gas?
Calibration gases, also known as span gases, are very accurate gas mixtures that are used as referencing tools and a comparative standard in the calibration of instruments such as gas analyzers and gas detectors. By exposing the gas detector to a verified concentration of test gas, this will assess the accuracy of the sensor to react accurately to that gas. Given their use, calibration gases must be as close to the exact concentration as possible, and therefore must be traceable to international standards.
Importance of Calibration
The annual calibrations of Gas detectors are essential to ensure that the detectors are performing up to manufacturer’s standards. Gas detectors often operate in harsh environments: e.g., High/Low humidity and temperatures, exposed to harmful chemicals and solvents, gas exposure and general sensor aging. This can result in a sensor drift, where the detector may read 45%LEL when the true level is 50%LEL.
Calibrating the Gas detector means exposing it to a known concentration of calibration gas for a specific amount of time. This reading will become the gas detector’s reference point for further readings. This process will be repeated by a predetermined calibration interval to ensure accurate readings and it’s also a good method to determine the condition of the sensor (If its due for replacement, slow response time etc.) so preventive actions can be taken to ensure the detector is performing up to standard.
The difference between bump testing and calibration is that bump test is a very brief exposure to gases to verify the functionality of the gas detector: e.g., sensor response time, alarm response time. This test verifies that the sensors of the gas detector will respond, and alarm will go off as expected. It’s important to know that bump testing is not to check the accuracy of the gas detector. It’s a test to check the functionality of the alarm of the gas detector.
2.0 Importance of the accuracy of calibration gas
As the calibration gas used for calibration of the gas detectors will directly affect the accuracy of it, it is vital that the calibration gas used is as close to the actual value indicated as possible. Impurities in the calibration gas significantly affects the sensitivity and accuracy of the gas detector.
Quality of Calibration Gas
The international gas standards establish an accurate reference point for the verification and the quality and purity of the gases produced. When substandard gases are used in calibrations, the gas detector will not measure gas concentration accurately and timely. For example, if the measurement accuracy of the gas detector is rated at 2%, the calibration gas with an accuracy of 5% or more does not help the gas detector to perform at 2% accuracy. It is crucial to use the calibration with rated accuracy equal to or better than the accuracy of the gas detector.
Calibration gases should be gravimetrically manufactured and traceable to the National Institute for Standards and Technology (NIST). The traceability and certification are the verification of accuracy by the standard authority.
It is also important to inspect the expiry dates of the calibration gases before use. The specification of the calibration gas is well maintained before the expiration date and the shelf life varies among the different manufacturers. The duration of shelf live is a good indication of the calibration gas quality because less impurities can prolong the quality deterioration rate. It is important to ensure the calibration gas has very minimal impurities and meets all the international standards stipulated by the National Institute for Standards and Technology (NIST) because impurities can damage the sensor modules in the gas detectors.
3.0 Calibration Gas Used by Riken Keiki Malaysia
Riken Keiki Malaysia (RKM) provide gas detector calibration service regularly. We only use calibration gases that are certified by National Institute for Standards and Technology (NIST).
Our calibration gases are produced in facilities that are ISO 9001 and ISO 17025 certified. The calibration gases are manufactured, mixed, analyzed and tested by specific and documented methods that are nationally or internationally recognized.
Our calibration gas comes with a NIST traceable certificates for each gas cylinder produced. Once the gas mixture has been blended, a certified gas mixture will require laboratory certifications of all its component’s concentration. The laboratory must address the customer’s traceability by conducting a comparison against an appropriate reference standard. Certificates of Analysis of our calibration gases are traceable to NIST.
ISO 9001 and ISO 17025 Accreditation
Our calibration gas mixtures are being produced and calibrated within the scope of an ISO17034 or ISO17025 accredited organization. Accreditation is a proof of the manufacturer’s technical capabilities in measuring and stating traceability in SI units as well as being thoroughly assessed by the relevant national testing authorities. ISO17025 Accreditation additionally proves that the laboratory where our gases are being produced has an acceptable quality management system in place and has the ability and competence to provide the required testing and calibration results. ISO9001 Accreditation is defined as the international standard for a quality management system (QMS). By having this accreditation, our calibration gases demonstrates that they are consistently meeting the standards of our customer’s and their regulatory requirements.
Aside from the accuracy of calibration gases, the cylinder is also a very important factor. Reactive gases such as Chlorine, Hydrogen Chloride, and Silane, might react with the metal of the cylinder. Our reactive gases are always stored in Seamless Aluminum Alloy Cylinders to ensure that the toxic gases do not react with the metals of the cylinder and compromise the concentration of the gases that are contained within the cylinder.
Our calibration gas cylinders are ISO 11118 and DOT 39 certified where each cylinder will be pressure tested and are compliant with the standards for international transportations.
Figure 1.0: Certificate of Product testing for our Calibration Gas Cylinders
Figure 2.0: Riken Keiki Malaysia Calibration Gases
Riken Keiki Gas Specification
Our calibration gases are verified with accuracy of ±2.0%. The certificate issued are NIST traceable and are following ISO 9001 and ISO 17025 standards. Each cylinder will have its unique cylinder number and certificate. Below are examples of the certificates that comes with our calibration gases.
Figure 3.1, 3.2: Examples of Certificates of Analysis of our Calibration Gases
Written By: Brian Chai Weng Jie
Background of the Writer: Brian Chai is a Service and Application Engineer from Riken Keiki Malaysia with years of experienced in gas detector calibration, general maintenance, and services. He graduated from Monash University with a degree in Mechanical Engineering (Hons). He has been conducting services in semiconductor wafer manufacturing facilities, solar cell fabrication and assembly lines, food processing plants and Petrochemical refineries.
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