Critical Facts About Pressure Gauge Calibration You Need to Know

August 21, 2024
5 Hal Penting Tentang Kalibrasi Pressure Gauge - Bawalaksana ID

Regular calibration of pressure gauges is critical to ensuring accurate measurements and maintaining quality and safety in industrial manufacturing processes.

While calibration is sometimes seen as an unnecessary operational cost, it is actually crucial to ensuring reliable measurement and preventing costly issues in the future.

Did you know?

Even modern, robust pressure gauges experience wear and a gradual loss of accuracy over time.

When pressure gauges aren’t correctly calibrated, several serious risks can arise, including:

  • Inaccurate readings can compromise safety in the production process.
  • Increased equipment wear leads to higher maintenance costs.
  • Poor process quality, resulting in inconsistent, non-compliant final products.
  • Material waste if entire production batches need to be discarded.

To avoid these risks, regular pressure gauge calibration is essential.

Key Points Discussed

In this article, the Bawalaksana team will explore critical aspects of pressure gauge calibration, covering:

  • The definition of calibration
  • Understanding accuracy in pressure gauges
  • Accuracy vs. uncertainty
  • Accuracy vs. tolerance
  • When to calibrate pressure gauges
  • Tools used for pressure gauge calibration
The risk of not calibrating pressure gauges - Bawalaksana CO

What is Calibration?

According to Wikipedia, calibration is the process of comparing the measurement values from an instrument under test to a reference standard with known accuracy.

So, what does calibration really mean?

Well, when we calibrate a pressure gauge, we’re basically making sure it’s on the same page as a recognized accuracy standard.

During the calibration process, both the pressure gauge being tested and the reference gauge (calibration standard) are subjected to the same pressure within a controlled system.

This setup allows for a direct comparison of the readings from both devices. Any discrepancies between the two readings are recorded in a calibration report.

These recorded differences are then used to adjust the pressure gauge, ensuring its readings are accurate and compliant with international standards.

It’s essential to note that any discrepancies are expressed as a percentage (%) of the full-scale measurement range.

Read Also: 4 Key Reasons to Calibrate Pressure Gauges
Pengukur tekanan yang akurat untuk integritas produk dan kepuasan pelanggan - Bawalaksana ID
Precise pressure gauges are essential for ensuring product integrity and enhancing customer satisfaction.

What is Accuracy in Pressure Gauges?

According to SJ-Gauge, accuracy is a combination of “precision” and “repeatability,” indicating how close the measured pressure value (the reading displayed on the gauge) is to the actual pressure value.

It means that the reading on the gauge may sometimes match the actual pressure exactly.

The closer the gauge’s reading is to the actual pressure, the more precise the indicator.

Regarding repeatability, if the gauge consistently provides the same reading when measuring the same fluid multiple times, it demonstrates good accuracy.

What are the accuracy standards for pressure gauges?

Under European standards (EN837-1), pressure gauge accuracy is classified as a percentage of the full-scale range, with classes like Class 0.6, Class 1.0, and Class 1.6, among others.

How do you determine the accuracy class of a pressure gauge?

You can identify a pressure gauge’s accuracy class by checking the markings on the gauge dial (the pressure indicator window).

The accuracy class is typically labeled on the dial with terms like “Acc,” “Class,” “Cl,” or “Kl” (e.g., Cl 1.0 means 1% of the full-scale range).

Dial Design Example for Pressure Gauge - Bawalaksana ID
Pressure gauge dial design example with Accuracy Class “Cl. 1.6” on the lower right.

How to Interpret Accuracy Class in Measurement Results?

Accuracy class defines how precise a pressure gauge is. It’s important to note that every pressure gauge will have some level of deviation, whether it reads slightly higher or lower than the actual pressure.

The lower the accuracy class, the smaller the deviation (or error). This means that the pressure gauge is more accurate.

A higher accuracy class reflects greater pressure precision and ensures consistent accuracy across repeated measurements.

For example, consider a pressure gauge with a 0–100 Psi measurement range.

If it has an accuracy class of 1.6, the allowable margin of error would be ±1.6% of the full-scale range.

You can calculate the tolerance for measurement errors using the following formula:

Gauge Range x Accuracy Class = Tolerance

100 Psi x 1.6% = 1.6 Psi

This means the acceptable error tolerance for this pressure gauge would be ±1.6 Psi.

Using this principle, a reading of 50 Psi would have a tolerance range from 48.4 Psi (lower limit) to 51.6 Psi (upper limit).

Read Also: Pressure Gauge Anatomy: Accuracy, Components, Materials & Design

Accuracy vs. Uncertainty

Uncertainty in calibration represents the potential variation between the measured and actual values. It is the opposite of accuracy and can arise from environmental factors, reference equipment, or even the operator conducting the measurement.

In everyday language, uncertainty is often conveyed with phrases like “approximately” or “give or take.” For instance, you might say, “The pressure in the pipe is 150 BAR, give or take 1 BAR, with a 95% confidence level.”

So, what’s the difference between accuracy and uncertainty in pressure gauge calibration?

  • Accuracy is a qualitative term that describes how close a measurement is to the actual value. It’s about the degree of agreement between the measured result and the exact value of the pressure.
  • Uncertainty is a quantitative measure that expresses the level of doubt about the measurement result. It reflects the range within which the actual value is likely to lie.

In pressure gauge calibration, uncertainty typically follows a normal distribution and can be calculated to determine how far the measurement is from the actual value. This is done using statistical methods or by comparing it with other laboratories for conformity testing.

In essence, no measurement is entirely exact; it represents a range of values around the actual quantity. The smaller the uncertainty, the higher the accuracy of the measurement.

To assess uncertainty, tools such as the TUR (Test Uncertainty Ratio) or TAR (Test Accuracy Ratio) calculators can be used. These methods help quantify uncertainty and ensure accurate results.

Calibration Reference Standards for Pressure Gauges

When calibrating a pressure gauge, operators must refer to international standards to ensure that the readings reflect accurate, globally recognized values.

For pressure gauges, particularly those utilizing a Bourdon tube, two primary international standards can serve as references:

  1. European Standard: EN 837-1
  2. American Standard: ASME B40.100

This article will focus on the EN 837-1 standard established by the European Committee, which is not only widely acknowledged but also sets the benchmark for Bourdon tube pressure gauges globally.

Additionally, we will highlight the calibration standards for pressure gauges used in Indonesia, which are set by the National Standardization Agency (BSN).

Diagram Bourdon tube pada perangkat pressure gauge - Bawalaksana ID
Diagram of the Bourdon tube used in a pressure gauge.

Referring to the European Standard Code

During calibration, operators can consult the table below to ensure a precise calibration process:

Accuracy classPermissible error margin
0.1 0,1%
0.250,25%
0.60,6%
1.0 ​​1,0%
1.61,6%
2.5 2,5%

Using this table, operators can identify the permissible margin of error based on the pressure gauge’s accuracy class.

As a best practice, when verifying the calibration of a pressure gauge, it is recommended to use a standard value four times the specified range, often referred to as the 4:1 ratio.

For example, a gauge with a range of 0–100 Psi and an accuracy class of 1.6 (with a tolerance of ±1.6 Psi) should be verified against a pressure standard capable of measuring ±0.4 Psi or less.

This method is endorsed by the American Society of Mechanical Engineers (ASME) and helps ensure that the pressure gauge’s calibration results are accurate and precise.

Test Pressure Gauge
Test Pressure Gauge to compare, test, and calibrate process instruments, ensuring accuracy and reliability.

Calibration Classification According to BSN

According to R. Rudi Anggoro Samodro, a researcher at the National Standardization Agency (BSN), the calibration of pressure gauges can be classified into three categories:

  1. Calibration of pressure gauges to Test Pressure Gauges and similar instruments.
  2. Calibration of test pressure gauges (and similar instruments) to Dead Weight Testers (DWT).
  3. Calibration of DWT to DWT.

Rudi elaborated that the calibration methods for pressure gauges to test gauges and for test gauges to DWT include the following:

  • DKD-R 6-1 (2014): The uncertainty of the standard must be one-third or less (≤1/3) of the expected uncertainty.
  • EURAMET cg-17 v.4 (2019): The uncertainty of the standard should be two times or more (≥2) of the expected uncertainty.
  • BS-EN 837-1 (1998): The accuracy of the standard must be at least four times better than that of the instrument being calibrated (this standard is specifically intended for manufacturers of pressure gauges).
Read Also: 9 Types of Industrial Pressure Gauges and Specifications
Pemeriksaan dan pencatatan terhadap tekanan dalam proses industri minyak dan gas
Monitoring and documentation of pressure in oil and gas industrial processes.

When Should Pressure Gauge Calibration Be Performed?

There are several compelling reasons to calibrate a pressure gauge regularly, whether due to usage, the passage of time, or changes in environmental conditions.

As a complex mechanical device, pressure gauges are susceptible to various external factors.

This vulnerability is heightened in unstable environments characterized by vibrations, pressure spikes, high temperatures, or mechanical shocks.

These conditions can adversely affect the mechanical components within the gauge casing, compromising the accuracy of pressure measurements.

Additionally, calibration becomes even more essential when measuring aggressive or corrosive fluids or those prone to crystallization and clogging the Bourdon tube.

The primary purpose of calibration is to verify the accuracy of the pressure measurement device and, if necessary, to restore its precision to optimal levels.

Here are some recommended scenarios or intervals for performing calibration on pressure gauges:

Before Installation

Calibration of pressure measurement devices is essential before installation to ensure they deliver accurate measurement values tailored to industrial applications.

Pre-installation calibration is critical for:

  • New Instruments: Ensuring they meet accuracy standards from the outset.
  • Repaired or Modified Instruments: Confirm that any repairs or modifications have not compromised their accuracy.
  • Spare Instruments: Validating instruments stored for extended periods before being used.
  • Improperly Stored Instruments: Addressing any potential issues with instruments stored in environments prone to vibrations or extreme temperatures.

Calibration Frequency

Calibration should be performed at specified intervals (e.g., annually, every 6 months, or quarterly).

In most industrial sectors, calibrating instruments at least once a year or during annual ISO audits is standard practice.

However, more frequent calibration is crucial for instruments used in highly regulated industries such as pharmaceuticals, biotechnology, healthcare, food and beverage, and petrochemicals.

For these sectors, calibration every 6 months or even quarterly is advisable.

Implementing a more frequent calibration schedule enhances quality control and helps prevent costly mistakes, such as discarding entire production batches or facing substantial fines due to inaccurate pressure measurements.

After Potentially Damaging Incidents

You should not wait for the scheduled calibration if your pressure measurement device has encountered a potentially damaging incident, such as:

  • Significant pressure spikes
  • Severe vibrations or shocks
  • Unstable or unusual vibrations
  • Extreme changes in environmental conditions
  • Blockages in the connector (socket) of the pressure gauge

Severe pressure spikes or extraordinary vibrations can damage the gauge casing’s internal components, such as hinges or gears. In some cases, extreme pressure spikes can cause the Bourdon tube to rupture or lead to the pointer (needle) on the dial gauge breaking or detaching.

To safeguard the accuracy and reliability of your pressure gauge, it is crucial to perform calibration immediately following any of these incidents. This ensures that you can verify the precision of the device’s measurements and maintain optimal performance.

Jenis-Jenis Pressure Gauge untuk Industri dan Spesifikasinya - Bawalaksana ID
Process Pressure Gauge with bayonet bezel for industrial pressure measurement – Manufactured by Instruments To Industry (ITI).

Before Critical Measurements

Calibration should be conducted whenever necessary, especially before performing critical measurements, in industries where high accuracy and stringent regulations are paramount.

Critical measurements are vital in pharmaceuticals, biotechnology, healthcare, and food and beverage sectors.

These industries carry significant risks, and measurement inaccuracies can endanger many lives. Consequently, substantial fines may be imposed for measurement errors in these sectors.

However, other industries are also responsible for calibration before critical measurements.

In fact, calibration is essential for any critical processes related to safety and infrastructure investments.

Additionally, even if a measurement is not deemed critical, calibration should still be performed if the measurement values appear questionable.

This practice ensures that instruments operate within acceptable limits and that the safety of the industrial environment is consistently upheld.

During Planned Maintenance

One of the optimal times for calibration is during preventive maintenance.

During this phase, instruments in storage can be activated to replace used devices that require calibration.

Therefore, companies must maintain an adequate supply of spare pressure gauges. This ensures a smooth and efficient replacement of old units with new or backup units during preventive maintenance.

Please remember that spare pressure gauges must also be calibrated on-site before they are scheduled for installation.

Simultaneously, the removed pressure gauges should be sent to a calibration laboratory for testing, allowing them to be kept as backups for future use in the next cycle.

It is important to note that pressure gauges that remain unused for extended periods do not retain their calibration indefinitely; their accuracy may deteriorate over time, even if previously calibrated.

This decline in accuracy can be attributed to factors such as mechanical wear or temperature fluctuations.

Thus, establishing a regular calibration cycle is a vital routine that minimizes the risk of inaccurate pressure readings. This practice also enhances the quality of measurements, monitoring, and oversight of processes within your organization.

Read Also: Benefits of Pressure Gauge Calibration: Enhancing Safety in Industry and Sustainability
Alat kalibrasi pressure gauge (Dead Weight Tester) - Pressure Calibration Tools - Bawalaksana ID
Pressure Gauge Calibration Equipment – Manufactured by Instruments To Industry (ITI).

Calibration Tools for Pressure Gauges

Understanding the importance of calibration and knowing when to perform it is crucial for maintaining the accuracy of your instruments. One essential tool used for this purpose is the Dead Weight Tester (DWT).

What is a Dead Weight Tester?

A Dead Weight Tester is a precise calibration device that applies a known weight to generate pressure measurements in units such as BAR, Pa, or Psi. By applying this pressure load, you can accurately compare the values displayed by the tested pressure gauge.

Why Choose Dead Weight Testers?

DWTs are considered high-precision primary standards (comparison standards) that provide reliable testing, adjustment, and calibration of pressure gauges. As calibrated by the manufacturer, these devices can achieve an impressive accuracy of better than 0.02%.

Due to their compact design, Dead Weight Testers are an excellent choice for calibration laboratories and service providers specializing in pressure gauge calibration.

They are precious for companies regularly calibrating their instrumentation to ensure optimal performance.

With a straightforward calibration process and consistent results, your organization can regularly verify the accuracy of your pressure measurement instruments.

Innovative Calibration Solutions

PT. Bawalaksana Central Industrial is the official distributor for Instruments To Industry (ITI), a renowned manufacturer based in England that specializes in pressure gauges and Dead Weight Testers.

ITI has also introduced the Pressure Comparator, an innovative and practical calibration tool. This device offers functionality similar to Dead Weight Testers but with a more compact and lightweight design. It can be easily mounted on a workbench or utilized flexibly in various locations.

We can supply various pressure measuring instruments and high-accuracy calibration devices directly from ITI.

For comprehensive information about ITI products and datasheets, don’t hesitate to get in touch with us or consult our Sales Engineer team at Bawalaksana Central Industrial.

Click the consultation button below for the best information and offers tailored to your needs.


Romanta Pinrih Linuwih - Managing Director at PT. Bawalaksana Central Industrial - Square

Romanta Pinrih Linuwih

Pneumatic Automation Systems Expert

This article was written in collaboration with Romanta Pinrih Linuwih, an expert in Pneumatic Automation System, to ensure accuracy and high quality.

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