Common Faults and Precautions in Pressure Gauge Calibration

Abstract: The calibration process of pressure gauges is susceptible to interference from a variety of factors. To ensure the accuracy and reliability of the calibration, it is essential to strengthen the control over the calibration process of pressure gauge measurements, establish management methods and procedures, and operate strictly in accordance with these protocols to ensure the smooth progress of the calibration work. This article discusses common faults and precautionary measures in the calibration of pressure gauges, with the aim of promoting the safe and efficient operation of pressure gauge calibration work.

Keywords: industry pressure gauge; measurement verification; common faults

Pressure gauges measure and indicate pressure above the atmospheric pressure, and they come in various types. Elastic element pressure gauges are widely used in agriculture, industry, and national defense. In safety production, pressure gauges play a crucial role. By measuring pressure values, potential safety hazards in production can be identified, allowing for intervention measures to mitigate risks and ensure production safety. Pressure gauge calibration is a critical aspect of ensuring safe production, as the calibration results directly impact safety indicators and outcomes. To ensure the accuracy and reliability of calibration results, it is important to analyze common faults in pressure gauge calibration and develop effective solutions. Through scientific fault analysis and management, the smooth progress of pressure gauge calibration work can be ensured, providing technical support for safe production.

1. Overview of Pressure Gauges and Calibration Process

1.1 Overview

Pressure gauges are mandatory measuring instruments subject to national verification. They have a wide range of applications and stable measuring performance, meeting the pressure measurement needs of various fields. National regulations mandate periodic calibration of pressure gauges to ensure they do not exhibit significant deviations during measurement work and can function correctly. Regular calibration allows users to detect problems in pressure gauges in a timely manner and carry out necessary repairs and maintenance, ensuring their optimal working condition and preventing subsequent measurement issues.

1.2 Calibration Process

The calibration of pressure gauges involves several steps. The first step is an appearance inspection. Calibration personnel must check whether the pressure gauge's appearance is intact, whether there are scratches or defects, and if the components are firmly assembled without looseness or falling off. The connections should also be checked for damage. If any issues are found, they must be addressed immediately to prevent faults during calibration. The second step is checking the pressure gauge readings. In a normal pressure state, the gauge needle should be at zero. Calibration personnel should start from zero, ensuring the gauge's internal chamber is connected to the atmosphere, and observe the readings. If discrepancies are found, adjustments should be made using a wrench or adjustment tool to align the needle with the zero mark. Pressure is then applied evenly to the first calibration point, and readings are taken after tapping the gauge housing. The process involves recording the values. The third step is vacuum state calibration, comparing the calibration gauge with a standard vacuum gauge in a vacuum environment, following procedural requirements, and recording the results to ensure compliance.

2. Common Faults and Solutions in Pressure Gauge Calibration

2.1 Inaccurate Pressure Readings

Pressure gauges often exhibit significant reading errors due to external factors, making them unsuitable for work requirements. For example, in high-temperature, high-humidity, or corrosive gas environments, the gauge readings may be inaccurate. This is due to environmental gas concentrations not meeting standards or unsuitable temperature and humidity levels, damaging key components like the internal mechanism and spring tube. Therefore, during calibration, attention should be paid to controlling the calibration environment, ensuring temperature, humidity, and gas concentration measurements meet requirements, and taking protective measures to ensure the accuracy of calibration results.

2.2 Needle Not at Zero

A pressure gauge's reading error beyond standard requirements affects calibration results. Long-term use and factors like wear and aging can cause the internal elastic components or spring tube to deform, leading to needle displacement. In such cases, calibration personnel can manually adjust the needle to zero or increase the spring torque. If these measures do not resolve the issue, they may consider detaching and repositioning the gears to enhance torque, ensuring the needle returns to the zero position.

2.3 Needle Movement Sensitivity Issues

When lightly tapping the gauge housing, significant needle movement indicates a common problem, often due to loose or damaged springs. Calibration personnel should inspect and clean the pressure gauge's internal components, removing obstructions and ensuring smooth movement. If internal damage persists, replacing the pressure gauge is recommended.

2.4 Needle Sticking or Jumping

During calibration, applying or releasing pressure may cause the needle to stick or jump, indicating internal wear, rust, aging, or obstructions. Inspecting and cleaning internal components, and using protective measures like buffer paper, can mitigate these issues and ensure stable needle movement.

2.5 Connection Thread Issues

Pressure gauge threads may be damaged or deformed during installation or transport, causing connection problems. Calibration personnel should use thread repair tools to restore damaged threads, ensuring proper installation and calibration.

2.6 Leakage Issues

First, check the tightness of the pressure gauge connection, using nuts for repair if necessary. Second, inspect internal seals for compatibility or damage, replacing or adding thicker seals as needed. Finally, ensure the internal and external threads match, using seal tape for reinforcement if required.

3. Precautions in Pressure Gauge Calibration

3.1 Pressure Resistance Testing

In calibration, pressure resistance tests evaluate the gauge's performance under maximum pressure. Accurate readings indicate stable measurement values. Calibration involves applying maximum pressure, tapping the gauge, and recording needle movement to ensure minimal error. After pressure application, the zero-point position is rechecked to confirm accuracy in a pressure-free state.

3.2 Allowable Error Calculation

During calibration, the allowable error for each pressure value must be calculated according to standards, ensuring values do not exceed the specified range. Discrepancies at maximum pressure should be evaluated carefully to determine if they impact gauge qualification.

3.3 Scientific Calibration Methods

Calibration personnel must continuously enhance their technical skills, adhering strictly to calibration standards and selecting appropriate methods. Tapping the gauge to check needle movement and adjusting values as needed ensures accurate readings. Using auxiliary tools can reduce observational errors, improving calibration accuracy.

3.4 Implementing Measures and Handling Errors

First, correct error values by ensuring pressure values remain within standard limits. Second, adjust unstable needle indications by repositioning or adjusting the needle mechanism. Third, reclassify unqualified gauges by lowering usage grades or adjusting accuracy levels. Lastly, ensure proper installation and tightening of calibration device screws.

4. Conclusion

Pressure gauge calibration is essential for safe production. Calibration personnel must follow standards strictly, scientifically analyze and address calibration issues, and implement effective measures to ensure accurate and reliable pressure measurements, reducing safety incidents in production.