Full-range standardised calibration procedures for pressure gauges and practices for accurate measurement — Systematic testing specifications based on the AILEIKE ALKT803 hydraulic calibration bench a

Full-range standardised calibration procedures for pressure gauges and practices for accurate measurement — Systematic testing specifications based on the AILEIKE ALKT803 hydraulic calibration bench and the ALKC400T precision digital pressure gauge

Pressure gauges are core metrological monitoring devices in industrial pressurised systems; their measurement accuracy and stability determine the quality of production processes and the operation of equipment, necessitating regular standardised calibration and testing. In this instance, the Y-100BF pressure gauge was selected for calibration, and an ALKT803 hydraulic calibration bench and an ALKC400T precision digital pressure gauge were used to carry out full-range measurement operations. The entire calibration process was carried out in a standard, interference-free environment at (20±2) °C and a relative humidity of ≤85% RH. Through standard operating procedures—including proper filling and venting, secure wiring, and stepwise pressure ramping—combined with the metrological practice of tapping the dial to read the value, the pressure gauge’s indication error was precisely measured at multiple points. This comprehensively verified the instrument’s operational performance, ensuring that metrological data is compliant and accurate, and meeting the requirements of industrial production.

I. Pressure Gauge Calibration Tools

The entire verification process must be carried out in strict accordance with current metrological technical specifications. The main references include:JJG52-2013 ‘General Pressure Gauges, Pressure-Vacuum Gauges and Vacuum Gauges with Elastic Elements’, which applies to the initial verification, subsequent verification and in-service inspection of general pressure gauges, pressure-vacuum gauges and vacuum gauges with elastic elements, and covers on-site indicating pressure measuring instruments commonly used in industry.

II. Detailed Explanation of the Operational Process

(1) Preliminary Preparations

1. Environmental Requirements

The temperature must be maintained at (20±2) °C, with relative humidity ≤85% RH and no condensation. Ensure that the site is free from vibration, dust and corrosive gases.

2. Filling, Pressurising and Connecting the Hydraulic Test Bench to Tools

• Prepare the pressure-transmitting medium (purified water or calibration oil).

• First, unscrew the pressure relief valve on the ALKT803 hydraulic calibration bench and fill the reservoir with the medium, ensuring it is at least two-thirds full. Once filling is complete, reattach and tighten the pressure relief valve.

• Next, purge any excess air from the hydraulic bench. First, unscrew the plugs from the three outlet ports, open the pressure-regulating valve, relief valve and overpressure shut-off valve, and turn the fine-adjustment valve anti-clockwise until it can be adjusted no further; then close the relief valve. Next, apply pressure using the lever to force the fluid through to the three outlet ports; once the excess air has been purged, securely connect the standard gauge ALKC400T and the pressure gauge under test (Y-100BF) to the ALKT803 outlet ports.

(2) Pressure Gauge Calibration Procedure

1. Pressure build-up procedure

• Apply pressure using the ALKT803 lever, stopping at approximately 5–10 MPa. Then, use the fine-adjustment valve to increase the pressure clockwise to the test point of 10 MPa. Once the pressure has stabilised and the standard reading no longer fluctuates, note the pressure reading on the pressure gauge under test. Next, gently tap the side of the pressure gauge’s casing with your finger (under no circumstances should the glass be tapped or struck forcefully), observe the position of the pointer, and record the reading once it has stabilised after the tap. Use the reading after tapping as the actual calibration reading for that pressure point, and calculate the error.

• Use the fine-adjustment valve to increase the pressure clockwise to 20 MPa. Once the pressure has stabilised, tap the pressure gauge under test and record the reading.

• Before adjusting to the next test point, first close the pressure-stabilising valve and the overpressure shut-off valve. Use the fine-adjustment valve to increase the pressure clockwise to 30 MPa, 40 MPa, 50 MPa and 60 MPa. Check the pressure gauge reading, tap the pressure gauge under test lightly, and record the reading once it has stabilised after the tap.

2. Pressure reduction process

• Use the fine-adjustment valve directly to reduce the pressure anticlockwise to 50 MPa, 40 MPa, 30 MPa, 20 MPa and 10 MPa. Observe the pressure readings on the pressure gauge, tap the pressure gauge under test lightly, and record the reading once it has stabilised after the tap.

3. Depressurisation procedure

Open the relief valve, the pressure-stabilising valve and the overpressure shut-off valve in sequence to reduce the pressure to 0. The test is now complete.

III. Precautions

Proper Use

• During calibration, ensure that the permissible error of the standard gauge is less than that of the gauge under test, to ensure that the calibration results are accurate and reliable, and comply with metrological standards.

• The pressure-transmitting medium must be clean and free of impurities to prevent blockages in the pipework and damage to the hydraulic test bench and pressure gauge.

• Operations must follow standard procedures; when pressurising or depressurising the ALKT803 hydraulic calibration bench, do so slowly to avoid pressure surges.

• Pressurise to the calibration point and record the reading once the value on the standard gauge has stabilised; for the pressure gauge under test, once the pressure has stabilised, tap the case lightly and take the reading immediately after tapping to ensure accuracy.

• Upon completion of the test, first slowly depressurise to zero and ensure there is no residual pressure before removing the instrument under test.

Maintenance and Calibration Intervals

• The ALKC400T precision digital pressure gauge should undergo periodic metrological verification (recommended once a year) to ensure measurement accuracy meets standards.

• When the pressure gauge is not in use, the power supply should be switched off; if not used for an extended period, it should be recharged once every three months.

• If the hydraulic test bench is to be stored for an extended period, it must be depressurised beforehand; empty the fluid from the reservoir and cover it with a cloth cover to prevent dust from entering the instrument.

IV. Conclusion

This pressure gauge calibration involved systematic testing across the full measurement range. Through gradient pressure ramp-up and ramp-down tests, the indication deviation, linear accuracy and operational stability of the instruments under various operating conditions were comprehensively verified. The work was carried out using AILEIKE hydraulic calibration equipment and high-precision standard instruments, strictly adhering to standardised metrological procedures to effectively minimise various measurement errors and ensure the authenticity and accuracy of the test data. Systematic calibration enables a precise assessment of a pressure gauge’s metrological performance and suitability for specific operating conditions. Conducting such testing on a regular basis helps to stabilise the instrument’s measurement accuracy, providing reliable data support for industrial process control and pressure-bearing equipment, thereby effectively ensuring the compliant, stable and efficient operation of industrial production systems.