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Maintain And Determine Calibration Frequency Of Equipment

The quality of the products manufactured by any enterprise can directly be associated with the accuracy of the instruments producing them. If the instruments are not calibrated properly, or if they are damaged and need repair work, they will surely affect the end products.

Iso calibration lists out the general requirements for the competence of testing and calibration laboratories. All the labs must adhere to service specifications developed by the international organization for standardization.

It is important to remember that instruments and equipment will not always stay calibrated. At some point, the level of calibration will go down and it will affect the final measurements and quality of the products. You must keep the instruments and equipment in excellent condition at all times. Make sure that you conduct preventive maintenance and repair, and recalibrate the instruments regularly. So how do you know when it is time to recalibrate your equipment?

A lot of different variables determine how frequently your instruments should be calibrated or re-calibrated. Let us look at some of them:

Manufacturers’ recommendations:
Every manufacturer mentions the ideal time frame of when you should recalibrate an instrument. Follow these instructions and specifications to the letter and you will face minimum maintenance issues. It is extremely important to remember that critical measurements may call for greater frequency.

Annually or biannually:
Some instruments need to be re-calibrated once or twice every year. It depends on how often the critical measurements are taken. Additionally, the amount of damage sustained by the instruments during use also plays a role.

After a damaging incident:
If any instrument was damaged in an accident, if it was dropped hard or if it sustained any kind of injury, you must calibrate it immediately. Events where the instruments sustain damage usually experience a sharp impact that directly affects their readings. Check if the calibration was altered and carry out the necessary calibration procedures.

As demanded by projects:
When you carry out certain assignments, you have to use certified and calibrated test equipment, irrespective of how big or small the project is. When assignments call for such calibration based on project requirements, you must follow it.

Before or after a major project:
Some major projects require extremely accurate measurements. This means that the instruments must be calibrated before the project starts. However, it doesn’t end there. You must calibrate all the instruments that were used after the project comes to an end. Post-project calibration will show you if the testing that you conducted is indeed reliable or not, if the correct and consistent measurements were observed throughout the project.

Semiannually, quarterly or monthly:
Some instruments, based on their use and functions, need to be calibrated frequently. If you deal with critical measurements quite frequently, it would be ideal that you conduct frequent and consistent calibration check-ups, like every month or every three to six months.

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A Diy Guide To Calibrating A Torque Wrench

A torque wrench is a tool that can measure the tension and twist of nuts and bolts to ensure that they are tight enough without over-tightening them. This instrument looks like a long-armed wrench which bends when you apply the turning force to the handle.


Its handle contains an internal mechanical indicator which is connected to a calibrated scale. You must stop twisting the bolt as soon as the indicator determines that you have reached the desired torque. Just like any other measuring instrument, precise calibration of a torque wrench is important to provide accurate results.

Calibrating a Torque Wrench Yourself

It’s important to calibrate the torque wrench properly to ensure that the fastener has the exact tension it needs to function safely. You can use the calibration services of accredited laboratories to calibrate your torque wrench, but you must also know how to do it yourself.

The following 7 steps will help you with a diy calibration of a torque wrench:

Step 1 Measure the length from the square drive to the point of the torque wrench where your hand rests while using the tool.

Step 2 Secure the wrench by placing the square drive in the vise. Do not lock any other part of the wrench in the vise.

Step 3 Align the torque wrench to the value of the settings you got in step one (the distance from the square drive to your hand) and multiply it by 20 pounds.

Step 4 Tie the 20-pound weight with a thin rope to the wrench from the position your hand rests.

Step 5 It is important that you keep the wrench in a horizontal position during this step. If you hear a click from the wrench, lift the weight and move it towards the head of the wrench until the clicking stops. If you don’t hear a click, then move the weight farther from the head of the wrench and try again. Make a definitive mark after two or three stops in the same location of the wrench.

Step 6 Measure the distance from the square drive to the location of the rope after step five. Multiply the finding distance by 20 pounds.

Step 7 Use the formula ta = ts x (d1/d2) to calculate the applied torque with your findings, where

Ta – applied torque
Ts – torque setting
D1 – distance measured in step 1
D2 – distance measured in step 5

Factors Affecting Calibration

No matter how well you have calibrated your torque wrench, it will lose its accuracy over a period of time. This means that you must constantly calibrate to ensure that it stays accurate and provides you with the perfect results. You must understand the factors that will affect calibration and learn how to make a calibration last longer.

One of the main factors that affect calibration is the average temperature at which the wrench is used. This will determine how accurately the tool is calibrated. Regardless of whether you work with the tool in warm or cold conditions, you must set the measurements of the tool to a comfortable setting, preferably in the climate in which the instrument will be used. This helps in reducing the chances of errors in and provides accurate results.

Make sure that the mathematics is applied correctly to determine the set measurements at which the tool will be used. If any factor is incorrect, you will observe an offset in the calibration, which in turn will cause major errors in results. Ensure that you measure the distance between the square drive and the hand position, at both the times absolutely accurately to make sure that there are no discrepancies in the equation.

When you learn to calibrate the torque wrenches and understand the various factors affecting them, you will be able to correct the performance of the wrench every single time and attain reliable results, thus assuring high quality of the products.

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When Must You Calibrate Your Test Equipment

Calibration of an instrument involves comparing the measurements of two instruments, one which has a known magnitude (also known as the standard) against the instrument whose unit measure is under the test. The calibration standard must be more accurate than the instrument under test.

Calibration establishes a relation between a) the quantity values with measurement uncertainties provided by the measurement standards, and b) corresponding indications with associated measurement uncertainties of the calibrated instrument or secondary standard. You can use this information to establish a relation for obtaining a measurement result from an indication.

Importance of Regular Calibration

Regular calibration of instruments is necessary as the accuracy of their measurements start to drop over time. You have to make sure the instruments don’t get ‘out of calibration’. You will observe that the accuracy of major components of instruments like voltage references, current shunts and input dividers will start to shift over time. However, this shift is minor and wouldn’t affect the measurements if you maintain a good calibration schedule as it will find and correct the shift.

Calibration of instruments must be done at accredited laboratories. There are a number of risks of not calibrating, some of which include —

  • Compliance and safety issues
  • Wastage of resources and raw materials
  • Low quality of the final products
  • Increased downtimes
  • Litigation issues

How Often Should You Calibrate

You are aware that you must calibrate the instruments regularly, but how often do you have to calibrate them? You don’t have a ‘one-size-fits-all’ kind of an answer to this. Every instrument has different calibration frequency requirement. Let us see how you can approach this aspect and how you can send in the instruments for calibration services.

  • Follow the calibration interval recommended by the manufacturer

Every manufacturer recommends when you must calibrate their tools. Keep up with their recommended frequency, but also remember that critical measurements may require different intervals.

  • Before you start a major critical measuring project

If you have to carry out highly accurate measurements for a project, decide which instruments you will be using for the testing. Once you have the list of instruments, send them out for calibration and do not use them until the test. Keeping them on a ‘lock down’ till the testing begins will ensure that you get absolutely accurate results.

  • After a major critical measuring project ends

It is important to calibrate instruments before a major critical measuring project; however, it is equally important to send the same instruments for calibration after the project is finished. Once the calibration is done post project, you can confirm the accuracy of your testing results for that project.

  • After an unforeseen accident

If your instruments took a hit, like a sharp physical impact or if something knocked out the internal overload, you must send them out for calibration. At the same time, you must have the safety integrity checked as well.

  • As per project requirements

Every project and measurement job has a different calibration requirement. Some may require certified and calibrated test equipment regardless of the project size, and some may not require stringent calibration standards. These requirements may not be explicitly stated, which is why you must review the specs before the test.

  • Monthly, quarterly, or semiannually

If you use certain equipment for critical measurements often, it would be ideal to have a shorter time span between calibrations. Depending on their usage, you have to calibrate equipment on a monthly, quarterly or semiannually basis.

  • Annually and biannually

If you carry out a mix of critical and non-critical measurements, annual calibration would be a good option to choose. Biannual calibration is ideal if you carry out critical measurements and do not expose your meter to an event, as calibration at lengthy frequencies can be cost-effective.

Don’t consider calibration as an action that merely fine-tunes your test instruments. Calibration ensures that you can use equipment safely and reliably. You will always get precise results when you use calibrated test equipment. You can thus consider calibration as a form of quality assurance.

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The Calibrate Temperature Sensors In The Process Industry

Numerous processes have certain temperature requirements. It is critical that this temperature is achieved and maintained throughout the process. Thus, temperature sensors must be located in the processes and instrumentation.

Usually, they are embedded on valves, turbines, motors, bearings, etc. They can be a part of smart devices like flow meters, level transmitters and pressure transmitters. They can also be stand-alone devices such as thermometers, temperature indicators, recorders and controllers.

Importance of calibrating temperature devices within a facility

When you calibrate temperature devices, it ensures that the devices measure accurate temperatures at all times. This helps in making sure that the quality control of the entire process and the end product is maintained throughout. When the temperature is accurate, you can be sure that the process runs at the right temperature, ingredients are included in their correct dosages and that the end product adheres to the specifications.

In industries such as pharmaceutical, food and beverages, and nuclear sites, the importance of having the right temperature is highly crucial. You must have a dedicated calibration team or personnel who can implement robust calibration practices, and who can identify and handle process issues within the plant. Quality systems such as iso recommend periodic calibration of all temperature sensors within the facility.

Types of temperature calibrators

There are numerous ways in which you can calibrate temperature devices, however, the four primary calibration methods include:

Intrinsic standards or fixed-point cells
Intrinsic standards offer the most accurate form of temperature calibrators, such as melting point of metals such as zinc, aluminum, or indium, and the triple point of water. These methods are intrinsic and occur naturally. However, they are expensive standards and are mostly limited to calibration labs or in plants with a department specializing in high-end metrology. Additionally, multiple standards are required to cover the entire range of typical temperature calibrations.

Liquid bath calibrators
These calibrators incorporate a liquid (oil in most cases), a stirring mechanism and a heating/cooling element. Liquid baths usually have uniform specifications throughout, due to the constant stirring and the liquid being circulated through the bath. Moreover, they are ideal for calibrating odd-shaped or extremely small sensors due to the uniformity of the liquid. A few negatives of liquid bath calibrators are that they cannot be transported to different locations with ease and are stationary, they are difficult to maintain, they get quite messy, and they take longer to reach the desired temperature. The oil/liquid in the bath must be drained and refilled periodically. It is critical to dispose of the liquid carefully.

Dry-block calibrators
These calibrators consist of a heating ‘block’, an internal sensor, and control mechanism to reach and maintain the desired temperature range. They do incorporate a heating/cooling element, however, no liquids are used in the process. They are portable due to their structure and are less messy. One of their biggest advantages is that they reach the desired temperature much faster as compared to traditional baths but are less accurate and less stable than them. Technological developments are improving the performance of dry-blocks in terms of accuracy and stability.

Electronic calibrators
Electronic calibrators have the ability to simulate the sensors under test (sut) and provide readout results on the sensor’s performance. The one drawback of electronic calibrators is that the integrity of the sensor is not tested since there is no temperature source to subject the sensor to. On a positive note, they cost a lot less than traditional liquid baths or dry-block calibrators, and are quite portable.

All temperature sensors must be calibrated periodically to ensure that the processes run smoothly, product specifications are met and that measurements are always accurate. This ensures that the quality of end product always stays high.

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