CALIBRATE IN GAS DETECTION: The 7 * KEY * facts about the sense (and nonsense) of calibration [Gas meter]
In the following section you will read useful facts about the calibration, adjustment and maintenance of your personal protection equipment (PPE) regarding gas detection.
Gas detection and calibrations
- Is an ISO 17025 possible in gas detection?
- Does it make sense to achieve an ISO 17025 for gas detection?
- Which standards are available?
- What is wise when calibrating a gas detector?
- Is the programming in the device leading for recalibration, the sticker or the certificate?
- Where can I best calibrate my device and what is recommended?
- What is the most important thing with gas detection?
Gas detection and calibrations
After lots of Google-work, we soon concluded that finding a company with an ISO 17025 for calibrating, maintaining and repairing a gas detector is not easy. An ISO 17025 certificate is a kind of ISO 9000 where additional competence requirements are required from the people who perform the actual gas detection calibration. Issues such as Uncertainty Calculation, Test Uncertainty Ratio (TUR) do business. In Australia we have found a company that has a certificate according to ISO 17025. We ourselves have just chosen ISO 9000. We thought: "What would be the sense and nonsense of certification of the calibration laboratories according to this standard?" We thought of the 7 things that are important in gas detection when calibrating a gas meter. We explain it briefly, through the bend.
Is an ISO 17025 possible in gas detection?
The simple answer is: yes. You come up with a specification that you want to meet, such as 30%, you make an uncertainty calculation for your calibration device, you participate in ring comparisons and ensure that you have everything set up in accordance with ISO 9000. You can have this all certified by a Notified Body and ready. You have an ISO 17025 certificate, then briefly through the bend
Does it make sense to achieve an ISO 17025 for gas detection?
There is a large cost item if you want to maintain such a system. The certification costs, the audits, the training of staff, a designated Quality Manager, the design and an expert belong to some of the requirements. The question will be answered if an analysis is made of the number of calibrations that are then awarded the ISO 17025 designation and that one can estimate that. In short, how large the market is. Given that the number will be very small, calibration prices can quickly rise high, making the market smaller again and so on. If a calibration costs € 600, many will opt for the alternative. A gas detector usually costs € 600 and many customers will compare the maintained costs with the purchase. There are also no manufacturers that supply a gas meter from the factory with an ISO 17025 certificate. So, buying a new device every time to manage the problem of maintenance costs is not possible. In addition, the manufacturer's advice must be considered during the recalibration period. Given that a gas detector is rather a beeper, a canary, intended to go off when there is a gas hazard, the requirements for the equipment will be different from that of regular measuring instruments where accuracy, uncertainty, calibration, linearity repeat accuracy and inter alia hysteresis are important elements. The requirement for gas detection will rather lie with testing whether the device works before using it. This is because there is a lot involved with liability and human lives. A gas detector is therefore used to warn someone about gas danger. A gas detector manufacturer therefore rarely specifies a recalibration period as advice and not an accuracy statement. It must therefore be up to the company itself which specs they want the device to comply with and the associated calibration device.
What standards are available?
In the gas analysis world we can perhaps get some ideas. There are primary standards, secondary standards (derived from the primary) and batch produced calibration gases. The Primary standards are created and ordered from an organization designated for this. In every country there is an institution that deals with this. In the USA is the NIST (National Institute for Standards and Technology). In the Netherlands that was the Dutch Meetist Institute (NMI) now the VSL. These organizations make it possible to purchase calibration gases of the highest standard, they weigh the gases with incredible high accuracy, with a balance. The Kilo is part of the SI system so you can do a lot with it. The Temperature, pressure etc everything must be guaranteed. Such a bottle can cost many € 1000 and euros. A secondary standard is much cheaper and can be purchased at many companies such as AirLiquide, Praxair and Air Products. The bottles can be purchased certified to ISO 17025 or with an "ordinary" certificate. A batch of produced gas bottles is often derived from this, a master cylinder is often made with the correct specifications and hundreds of small bottles are filled through a distributor. A gas detection manufacturer usually writes these last bottles before performing a so-called Bump Test. This is a test to make sure that the device has worked before it has been used. There is still no question of a calibration. Only a check on functioning. This is also the most important and supports the underlying idea of a gas detector. It must work when it's dangerous.
What is the best thing to do when calibrating a gas detector?
A gas detector can sometimes fail with its bump test. It is then important to adjust the device, because the failure of a bump test involves two things, or the device does not work, or the device is too inaccurate. As a manufacturer rarely issues specifications, the latter will entail a bit of ambiguity. Most manufacturers say little about it and leave it to the imagination of the user. That is also the reason why most manufacturers market a docking station where the device is placed for bump testing. If the gas detector then fails the bump test, these machines will automatically adjust ("calibrate" in English). But where exactly that limit lies is not easy to find and there are no standards or requirements for that either. There are also docking stations that automatically produce a calibration certificate, whether on paper. The difference between a docking station and the other can be that the value as found is not registered, only adjustment and the read-out (calibration) after adjustment. So, you cannot find back how much power the device has lost over time (span drift). For that reason, it is good to agree on what you want on a certificate. Usually there are 2 certificates. As found, and as issued. Keep in mind that calibration is always a snapshot. Results from the past therefore offer no guarantee for the future, certainly if you take the circumstances into account when using it.
What is leading for recalibration? The programming in the device, the sticker of the certificate?
Here we follow the ISO 17025 standard where all scholars agree which requirements must be met. The certificate must meet around 11 points, including applicant, publisher, date, TUR, specifications of the device, measurement results but especially the Identification of the device and an explanation of the uncertainty with associated data. It is for that reason that often the standard 3X must be better than the specification of the device, otherwise you will not reach the 95% uncertainty limit that is common. Once the calibration is complete, the certificate is created. The certificate may not say anything about the recalibration period and is leading. The calibration advice is always communicated separately to the applicant. In the gas detection world that is not done, the recalibration recommended is simply put on the certificate (as a result of which the certificate strictly no longer meets the ISO17025 requirements!). The calibration sticker is affixed to the device. There are no requirements because the sticker only serves as a convenience for the user, so that he does not always have to consult the certificate. However, we do recommend that the applicant always keep a copy of the certificate with him in the case of the device. Some gas detector manufacturers offer the option to program the calibration date and the calibration date into the device. So that you can immediately see what the current status is at start-up. There are even manufacturers that store the entire certificate history in the device! This programming can take place in several ways; Automatic, with a tool (whether only owned by the manufacturer) or manually. Keep in mind that the ISO 17025 still finds the ISO 9000 a programming guiding principle. In short, the date of the certificate can be different from what was programmed by the manufacturer and therefore does not imply anything. Often this is applied by a manufacturer as market protection so that the applicant must always go to the manufacturer for calibration. So, make sure you choose a manufacturer that leaves you free in your choice where you want the device to be calibrated, otherwise you might be surprised.
Where can I best calibrate my device and what is recommended?
Make sure you have calibration, maintenance and testing done at a reputable company. A company that employs trained people, with knowledge. Preferable a company specialized in gas detection, there are quite a few different gases that can be measured. The application is also important during a calibration and in this way good advice can be obtained about the use, recalibration periods and further maintenance. If the company has ISO 9000, it is a good idea because the work procedures are established and there is continuity, experience and consistency. An ISO 17025 gas detection company will be difficult to find and very expensive. It also surpasses the purpose for which the average gas detector is intended.
What is the most important thing with gas detection?
Make sure you follow the manufacturer's guidelines, test the device with gas and, above all, make sure that everything remains well documented (with or without your trading partner) and make clear agreements on this. Many companies have databases that comply with the Privacy Act in which the calibration data is stored. Purchase a gas detector where you can prove that it was used and above all make sure that your knowledge about gas detection is at a high level, but also that of your users.
It is technically not convenient to ask for an ISO 17025 calibration certificate. It is almost impossible to find such a company. A gas detector is an indicative and non-selective measuring instrument, so that it more clearly demonstrates the presence of something and not the quantity. Therefore, according to ISO 9000, if you want to work like this, it is not recommended to calibrate at that level. The certificate is leading when there is doubt about the calibration, based on each standard. The re-calibration dates are taken from "case law" rather than from the calibration regime. Testing the device is central, certainly in critical processes. A gas detector is sometimes called an analyser, in order to earn this designation, manufacturers must become clearer with specifications. Analyzer manufacturers go further. There will be more fusion between gas detector and analysers, but we are not there yet. Therefore, make sure that your people work safely and that you can prove that you have done everything, at least in line with the market.