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Did you know that your pressure gauge can lose accuracy over time? No gauge can stay completely accurate forever. You need to regularly check the gauge’s accuracy to ensure it continues to provide correct readings for your application.
If you don’t, inaccurate pressure readings can cause your equipment to malfunction and break down or, even worse, result in injury to workers, all of which can mean downtime for your business.
So, how often should you check the accuracy of your pressure gauge?
This is a question we receive often at Ashcroft, as there is no official defined accuracy interval for the entire industry. In this article, I will explain our accuracy interval for pressure gauges here at Ashcroft.
Why Does Calibration Matter?
Think about the everyday items that require periodic renewal or replacement: a driver’s license, smoke alarm batteries, furnace filter, etc. Each is maintained for safety and ignoring any of them can cause problems.
Now, let’s apply that same thought to measurement instruments. Pressure readings are important to almost all operations, so accurate, reliable and repeatable devices must be maintained to ensure their maximum performance and efficiency.
The calibration interval is the period between the instrument’s last verified calibration and its next scheduled checkup. Keep in mind that units are often removed from the process and either validated onsite or forwarded to an outside party for servicing.
This will mean you’ll have to contend with downtime – but for how long? This can take several days to weeks depending upon the scope of service, so it may be wise to inventory identical models and rotate as necessary.
Remember, replacement units will also need to follow the same calibration check interval and should not only be used in times of trouble like a spare tire on your car.
Generally, organizations such as the National Institute of Standards and Technology (NIST) or ASME do not establish calibration intervals, and you can’t depend on an outside party to determine when you should reevaluate your instruments.
This places the ultimate responsibility on the end-user, as they are the most familiar with the application and the conditions the instrument will need to operate. As such, the user will need to determine the duration of the interval.
However, Good Manufacturing Practice (GMP) for calibration checks would be to schedule one every 12 months if it is a general industrial installation without any process events.
You will need to consider reducing this interval as process conditions become more unstable or fluctuate by degrees, so each instrument may have a distinct correlation with the calibration interval.
Determining Pressure Gauge Calibration Intervals
When determining your instrument’s calibration interval, be sure that the instrument provides accurate, reliable and stable pressure readings over the scheduled period.
The instrument’s accuracy may degrade over time, so you will need to proactively manage when it must be checked. This takes time to establish, but it is better to check gauge accuracy early rather than extending any interval to save time and/or cost.
Schedule recalibration immediately if the gauge pointer is off zero or out of the zero box. This will reduce the impact on your process.
Units applied to extreme elements will require more frequent (shorter) calibration intervals because harsher environments can quickly degrade instruments.
Process conditions with excessive vibration, pulsation, and/or high cycle rates can result in mechanical wear and have an adverse effect on accuracy, repeatability and reliability. Refer to Lou Altieri’s blog, “Why Did My Pressure Equipment Fail?” to learn more.
Units recently calibrated should be clearly identified with a serial number and the date it was calibrated. This allows for easy tracking and identifying process trends that can provide an alert to future process issues.
Recommended Calibration Intervals
Typically, the suggested time to check instrument calibration once every 12 months, or annually. But, as mentioned before, this timing should be decreased by the end-user depending on both application and process parameters.
In some instances, it may not even be possible to recalibrate your instrument. For example, some gauges have a non-removable front ring making recalibration impossible. Low-cost gauges are typically not meant to be recalibrated, as they would cost more to be calibrated than simply buying a new gauge.
So, be sure to look at cost-effectiveness for your business – is it worth it to calibrate or should you simply buy a new product?
Also, your quality assurance department should help you develop calibration intervals for your products based on your company’s own checks and balances.
We have a responsibility to ourselves, customers and distributors to ensure instruments are properly calibrated and safe.
We don’t like to pressure you, but we have more information.
In summary, your main goal should be to properly oversee instruments by establishing a schedule to support their maintenance. Get to know the application and be aware of process elements that could lead to bigger concerns.
If you want to learn more about pressure gauges and calibration, watch this webinar from our resource center.
You can also check out some of our other blog posts about gauges:
- How To Identify Your Pressure Gauge and Get the Proper Replacement
- How Do I Select the Right Pressure Gauge Range?
- How Much Do Mechanical Pressure Gauges Cost?
Feel free to contact us today to talk to one of our industry experts and get all your pressure gauge questions answered.