By the term “tool” we mean any physical item that can be used to achieve a goal, especially if the item is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose.
There are a variety of tools used in industry, worksites or even in the army and aviation industry. Production and quality control are highly dependant on the correct performance of the tools we are using. But how can we be sure that all these tools are functioning properly? The reply is a single word: calibration! The only way to ensure that our tools are inside their correct specifications is to regularly calibrate them and monitor their performance.
The next question that arises is “which tools need calibration”? Of cours, simple mechanical tools such as hammers and mechanical screwdrivers don’t, as they don’t rely on any measurements. Depending on the process, we can see below some examples of equipment that is considered to be a tool and needs to be calibrated.
When a high pressure gas station is manufactured, most of the connections of pipes and critical equipment (valves, gas meters, etc.) are flanged. For the flange connections various nuts and bolts are used, which must be tightened by using torque wrenches. The torque that must be applied to each nut is specified by the manufacturer. If the torque is less than the nominal value, leakages or even disconnections may occur. If it is of a higher value, injuries or even damage to the critical equipment are possible to happen. The only way to be sure that the proper torque is applied is to have the torque wrench being used calibrated.
The pipes used for the high pressure gas station are manufactured according to international specifications. These pipes are also coated and painted according to these specifications. In order to test the coating and the painting, coating thickness testers and holiday detectors are used. A coating thickness tester measures the thickness of the painting while a holiday detector generates a high voltage and by this way detects any film discontinuities. Both of these measurements are very important in order to avoid corrosion of the pipes. Thus, both coating thickness testers and holiday detectors are deemed as tools that need to be properly calibrated.
In a worksite, many tools are used for construction. Some of them are laser distance meters, level meters and measuring tapes. All of them are considered to be critical equipment that needs calibration.
In the aluminium industry, aluminium must be heated up to a certain temperature in order to melt and produce aluminium profiles. This is performed in high temperature ovens which are programmed at a temperature setting and have an indicator that shows the oven’s temperature. But how can we be sure that the oven’s reading is correctly indicating the temperature inside the oven? We need to periodically calibrate the oven as a system with its indicator.
Another example of tools that need calibration is Electrical Testers. These testers are used for measuring voltage, current, continuity, etc. Since they are used mainly for safety applications, it is very important that they measure correctly. Earth ground and Insulating testers belong also to the category of tools used for safety measurements. All kinds of testers need calibration.
So, depending on the application, there are many tools that need to be calibrated.
Some of them are listed below:
- Torque Wrenches
- Torque screwdrivers
- Laser distance meters
- Coating thickness testers
- Holiday detectors
- Level meters
- Tapes and steel rulers
- Electrical Testers
- PAT Testers
- Cable Testers
- Insulation Testers
- Socket Testers
- Gas detectors
- Hardness Testers
- Vernier Callipers
- Feeler gages
- Electrofusion welding machines
These are just some examples of tools that need to be calibrated. Many more tools, depending on their application and the importance of their usage, need to be regularly checked.
Of course, a simple tool calibration every now and then, is not enough. The industry or the organization must have a well established quality system in order to control and document all the tools. Such a quality system must contain at least the following in order to be complete:
A master list of all the tools that need calibration.
This list must include all the tools that must be calibrated. For each tool, the number, the manufacturer, the serial number, the location, the calibration date, the calibration interval, the next calibration date and any other relevant information must be mentioned. This list allows for the maintenance responsible personnel to manage the tools and their calibration.
The calibration procedure for each type of tool
In some cases, in industry for example, many tools are calibrated internally by transfer standards. These standards are sent for calibration in external laboratories. Transfer standards can be reference thermometers for ovens calibration, gauge blocks for dimensional calibrations such as callipers, rulers and tapes, etc. The internal calibration procedures must be documented and validated within the quality system.
Either internal or external, calibration records for each tool must be kept. By having this historical data, the user can export useful information which can help him define the recalibration interval.
Procedure for the usage, handling and storage of the tools
Every tool must be used and handled as specified by the manufacturer. Also it must be stored in certain environmental conditions. It is very important to have procedures that describe all the above and also to train the personnel for the correct usage, handling and storage, because this will definitely increase the lifetime of the tools.
Determine the identification of the tools
There must be a procedure defining how the tools are identified according their calibration requirements. For tools that do not need calibration at all, a sticker “No Calibration Required” can be placed on them. Other stickers can be “Calibrate before Use”, “Not Calibrated” or “Do not Use”. The tools that are properly calibrated and functioning correctly can be distinguished by their “Calibration Label”.
All the aforementioned can help us in the control of the tools. We can be sure by this way, that we will not forget to calibrate them, and that the tools we are using are within specifications. By studying the calibration reports of each tool over time, we can understand its performance and decide whether to increase or reduce its calibration interval.
Even the best of the tools can go off-specification over time; this is why regular calibration is required. Calibration is of course time consuming and has a financial cost. But imagine having to recall a whole batch of vehicles in the automotive industry, or suffering an airplane crash because of a non-properly calibrated tool!
Written by Sofia