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This article was originally published on October 11, 2021, and updated on January 29, 2025.
Did you know that your pressure gauge will lose accuracy over time? No gauge can stay completely accurate forever. That's why it is important to regularly check the instrument's accuracy to ensure it continues to provide correct readings for your application.
If you don’t check, inaccurate pressure readings can cause your equipment to malfunction and break down or, even worse, result in injury to workers. All of these scenarios can impact system efficiencies and lead to downtime for your business.
Ashcroft has been a leading manufacturer of pressure gauges since 1952, so the question relating to calibration frequency is one we encounter a lot. While there are no universally defined requirements for calibration, I can provide insights that can help you determine what may be the most appropriate times to check your pressure gauge accuracy.
Why calibration matters
Consider how periodic replacement or routine maintenance is required for everyday items such as a driver's license, smoke alarm batteries, furnace filters and car oil changes, for example. These items are regularly checked, updated or replaced to ensure equipment and personal safety. Ignoring any of these items can lead to significant issues.
This principle also applies to pressure measurement instruments. Maintaining accurate, reliable, and repeatable pressure readings is important in virtually all operations. Calibration is the process of adjusting an instrument to ensure it is providing the specified accuracy limits for an application to ensure optimal system performance and efficiency.
The period between an instrument's most recent confirmed calibration and its upcoming scheduled evaluation is referred to as the calibration interval.
What the calibration process involves
The calibration process requires the instrument to be removed from the application for validation. This can occur onsite or the instrument can be sent to an external service provider.
In either case, the downtime of the operation can last between several days or weeks, depending on the extent of the service required. For this reason, it is advisable to maintain an inventory of identical models and implement a rotation schedule as needed.
Replacement units should also adhere to the same calibration interval, ensuring they are not solely reserved for emergency use, like the spare tire in your vehicle.
Who establishes calibration intervals for pressure gauges?
Generally speaking, the American Society of Mechanical Engineers (ASME) sets the standards for pressure gauge design and construction. However, no organization sets calibration intervals for these instruments. That means you cannot rely on external parties to decide when to reassess your instruments.
This responsibility falls on you, the end-user. You are the most knowledgeable about the application and the conditions under which the instrument operates so you must determine the appropriate interval frequency.
For general industrial installations without any process events, Good Manufacturing Practice (GMP) recommends scheduling calibration checks every 12 months. However, if process conditions become more unstable or vary significantly, you should consider shortening this interval, as each instrument may have a distinct correlation with its calibration interval.
Determining Pressure Gauge Calibration Intervals
When setting the calibration interval for your instrument, your goal is to be sure it will consistently deliver accurate, reliable and repeatable pressure readings throughout the scheduled period.
Since accuracy can decline over time, it's important to:
- Actively manage when your instrument calibration schedule. Establishing a schedule may take time, but it's preferable to verify gauge accuracy sooner rather than extending intervals to save time or money.
- Recalibrate immediately if the gauge pointer is not at zero or outside the zero box to minimize process disruption. Instruments exposed to harsh conditions will need more frequent calibration because demanding environments can cause them to quickly degrade. For instance, high vibration, pulsation, or rapid cycling can cause mechanical wear and negatively affect accuracy, repeatability, and reliability. Read Six Reasons Pressure Gauges Fail Instrument Audits to learn more.
- Mark recently calibrated units with a serial number and calibration date. This will make it easy to track and identify trends that might indicate future issues.
Recommended Calibration Intervals
Typically, the suggested time to check instrument calibration is once every 12 months. But, as mentioned before, this timing should be reduced by the end-user depending on both application and process parameters.
In certain situations, recalibrating your instrument may not be feasible. For instance, some gauges are designed with a non-removable front ring, making recalibration impossible. Additionally, low-cost gauges are generally not intended for recalibration, as the expense of recalibrating them may exceed the cost of purchasing a new gauge. Therefore, it is important to evaluate the cost-effectiveness for your business—consider whether it is more economical to recalibrate or to simply buy a new product.
Finally, your quality assurance department can assist in establishing calibration intervals for your products based on your company’s internal checks and balances. It is our collective responsibility to ensure that instruments are accurately calibrated and safe for use, benefiting ourselves, our customers, and our distributors.
Ready to learn more?
Now that you understand it is your responsibility to properly oversee the calibration of your instruments by establishing a schedule to support their maintenance. If you want more information about pressure gauges and calibration, watch this webinar from our resource center.
You can also check out some of our other blog posts about pressure gauges:
- How To Identify Your Pressure Gauge and Get the Proper Replacement
- Three Components of Pressure Instrument Calibration
- 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. In the meantime, check out our guide to learn how to avoid pressure equipment failure. 