What equipment is required to calibrate marine pressure gauges on board ships?

Marine pressure gauges are essential for ensuring the safe navigation of vessels and the stable operation of their equipment; the accuracy of their readings affects the reliability of pressure monitoring, and therefore calibration, verification, testing and measurement must be carried out rigorously. For this verification, the AILEIKE101SE handheld air pump was used as the pressure source, paired with the ALKC400HA1 precision digital pressure gauge as the reference instrument. In a controlled environment meeting specifications for temperature, humidity, and free from vibration and corrosion, step-by-step measurements were carried out across the full range at multiple points by increasing and decreasing the pressure. Following stabilisation of the pressure, the standard procedure of gently tapping the case to take a reading was performed. By strictly adhering to operational procedures throughout the process, the error in the indicated value can be precisely verified, ensuring that the verification results are accurate and reliable.

I. Tools for Calibrating Marine Pressure Gauges on Vessels

The entire verification process must be carried out in strict accordance with current metrological technical specifications. The main references include: JB/T 5527-2005 ‘Marine Pressure Gauges’, which covers mechanical pointer-type measuring instruments using a Bourdon tube as the measuring element, suitable for use on ships and offshore equipment.

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. The site must be free from vibration, dust and corrosive gases.

2. Connecting the equipment

• Connect the standard gauge ALKC400HA1 to the output port of the AILEIKE101SE handheld air pump.

• Connect the marine pressure gauge on the vessel under test to the output port of the AILEIKE101SE handheld air pump.

(2) Calibration Procedure for Marine Pressure Gauges

1. Pressurisation Process

• First, pressurise the gauge by manually operating the AILEIKE 101SE pressure-application lever, stopping when the pressure reaches approximately the calibration point to be tested, then use the fine-tuning mechanism to adjust the pressure to 4 bar. Once the pressure has stabilised and the standard reading no longer fluctuates, check the pressure reading on the pressure gauge under test. Next, gently tap the side of the marine pressure gauge’s casing with your finger (tapping the glass or striking it forcefully is strictly prohibited), observe the position of the pointer, and record the reading once it has stabilised after the tap. Use this post-tap reading as the actual calibration reading for that pressure point, and calculate the error.

• Continue to apply pressure by hand using the pressure-application lever, increasing the pressure to approximately the calibration point to be verified, then use the fine-adjustment knob to set the pressure to 8 bar at the calibration point. Once the pressure has stabilised, tap the marine pressure gauge under test and record the reading.

• Repeat the same procedure, increasing the pressure to 12 bar and 16 bar at the calibration point. Once the pressure has stabilised, tap the marine pressure gauge under test and record the readings.

2. Depressurisation procedure

• First, slowly open the relief valve and reduce the pressure until it reaches the test point, then stop. Close the relief valve and use the fine-adjustment valve to set the pressure to 12 bar at the test point. Once the pressure has stabilised, tap the marine pressure gauge under test and record the reading.

• Repeat the same procedure to adjust the pressure to the test points of 8 bar and 4 bar. Check the pressure reading on the marine pressure gauge under test, tap the gauge, and record the reading once it has stabilised.

3. Depressurisation procedure

Open the relief valve to gradually release the pressure within the pipework. Once the pressure has been reduced to 0, the test is complete.

III. Points to Note

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.

• Operations should follow standard procedures; when using the AILEIKE 101SE hand-operated air pump to increase or decrease pressure, do so gradually to avoid pressure surges.

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

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

Maintenance and Calibration Intervals

• The ALKC400HA1 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, switch off the power supply; if not used for an extended period, cover it with a cloth cover to prevent dust from entering the instrument.

• The handheld air pump should be depressurised before storage if not used for an extended period, and covered with a cloth cover to prevent dust from entering the instrument.

IV. Conclusion

The calibration, inspection and measurement of these marine pressure gauges have been completed in accordance with standard specifications. Through full-range testing involving both pressure increase and reduction, strict adherence to the standard procedure of tapping the casing to take readings and control of environmental conditions, and the systematic calculation of the indicated value errors of the instruments under test, we have ensured that the testing process was compliant and rigorous, and that the measurement data is accurate. The precise calibration of marine pressure gauges is a vital foundation for the reliable operation of a vessel’s pressure systems; it enables the timely identification of potential instrument inaccuracies and ensures accurate and effective monitoring of operating conditions. Adhering to regular calibration and standardised maintenance, whilst routinely carrying out inspections and measurements, provides assurance for the long-term, stable operation of marine equipment.