Common Troubleshooting Methods for Pressure Gauge Measurement Verification Process
As a kind of pressure measuring instrument with the elastic element as the sensitive element, pressure gauge has been widely used in the industrial field since its research and development and application, relying on the technical advantages of high accuracy, convenient detection, and simple operation. Since the pressure gauge is mainly used for the detection of important links in the industrial field, once the problem of inaccurate measurement verification of the pressure gauge occurs, it will inevitably have a greater impact on the stability and safety of products in the industrial field. With the further application and promotion of pressure gauges, the accuracy of pressure gauge measurement verification has received widespread attention. How to perform correct measurement verification and calibration of pressure gauges is a very prominent problem in the development of pressure gauges.
- Selection and use of pressure gauges
The pressure gauge uses elastic elements as sensing elements for sensing. It can measure and indicate instruments that are higher than the ambient pressure so that the measurement personnel can understand the pressure value of the measuring instrument through the display of the pressure change. According to the use classification of pressure gauges, pressure gauges can be divided into ordinary pressure gauges, ammonia pressure gauges, oxygen pressure gauges, shockproof pressure gauges, electrical contact pressure gauges, digital compact pressure gauges, and double-needle pressure gauges. In the application, the selection of the pressure gauge type needs to be performed according to the requirements of the measuring instrument. In general, the maximum range of the pressure gauge is 1.5-3.0 times the maximum working pressure of the container. However, in order to ensure the accuracy and safety of pressure gauge pressure detection, the multiple needs to be controlled at about 2 times during actual measurement, and the diameter of the pressure gauge Cannot exceed the range of 100 mm.
2. The Installation Settings of the Pressure Gauge
When installing the pressure gauge, a comprehensive analysis of the installation environment is required to properly install the pressure gauge according to the actual installation environment to ensure that the pressure gauge is in a stable and safe environment. Operate according to the installation specifications of the pressure gauge. Pay attention to the following aspects during installation:
2.1 The Pressure Gauge Needs to be Installed in an easily Observable Position
When selecting the installation position of the pressure gauge, it is necessary to choose an easy-to-observe position for installation, so that the pressure gauge can perform comprehensive observation and dirt treatment. In order to improve the accuracy of the pressure gauge, the pressure gauge needs to be installed in a place where it is not exposed to direct sunlight and high temperatures, to avoid the radiant heat, freezing, and vibration of the pressure gauge due to external factors.
2.2 The Pressure Gauge Body Needs to be in the Vertical Direction
When installing the pressure gauge body, the pressure gauge body needs to be controlled in a vertical direction so that the staff can read the displayed value of the pressure gauge. If the pressure gauge needs to be installed in a higher position, it can be adjusted vertically by tilting forward, but the tilt angle cannot exceed 30 degrees.
2.3 Install a Buffer Tube in front of the Pressure Gauge
After the installation of the pressure gauge is complete, a buffer tube needs to be installed in front of the pressure gauge to prevent the pressure gauge from being affected by external gases. The buffer tube, as a safeguard for the pressure gauge, can alleviate the gas in the spring tube, and the buffer tube has a certain condensate collection function, which can prevent the pressure gauge from having too much gas.
2.4 Install Three-way Plug or Valve
In the bending part of the pressure gauge buffer tube, a three-way plug or valve needs to be installed at an appropriate intermediate position, so that the three-way plug or valve can ensure the safety of the pressure gauge.
3. Operation Steps for Measurement and Verification of Pressure Gauges
Before the pressure gauge is installed, it needs to be inspected by the relevant national measurement unit, and the relevant inspection qualification certificate will be presented after the inspection is qualified. To ensure the qualification and accuracy of the pressure gauge, it can be determined according to the frequency of use. Generally, a measurement verification of the pressure gauge is performed within 6 months, and the verification operation steps need to comply with the following operations:
3.1 Carry out Measurement Verification Operations in Accordance with Specifications
The verification personnel can carry out the development of pressure gauge measurement and verification through the regulations of the elastic element general pressure gauge, pressure vacuum gauge and vacuum gauge JJG52-2013. According to the range of the pressure gauge to be tested, the verification staff needs to select the corresponding calibration instrument for the range, and at the same time, according to the specified inspection operation, the validity period of the label of the standard gauge is checked, so that the inspection of the pressure gauge meets the verification requirements.
3.2 Calibration Equipment Installation According to Pressure Gauge Type
For pressure gauge measurement and testing, the standard gauge and the pressure gauge to be tested need to be installed on the calibration instrument. If the pressure gauge to be tested is an oxygen-free oil pressure gauge, the pressure gauge to be tested must be installed on the oil-proof joint that is connected to the oil-water separator, and the verifier is adjusted after the installation operation so that various parts Can be in a good state of verification.
3.3 Observe the Temperature and Humidity in the Test Room
To ensure the accuracy of the pressure gauge measurement verification, it is necessary to perform the measurement of the room temperature and humidity measurement before the pressure gauge measurement verification to check whether the room temperature and humidity meet the specified operating limits.
3.4 Check whether the Pressure Gauge Meets the Operating Requirements
During the measurement verification of the pressure gauge, the appearance and internal parts of the pressure gauge should be tested to see if they meet the operational requirements of the measurement verification, and after the test is completed, the corresponding test results should be recorded.
3.5 Properly Carry out Verification of the Displayed Value of the Pressure Gauge
For the measurement verification of the displayed value of the pressure gauge, it is necessary to carry out the verification of the pressure increase and decrease in accordance with the digitally marked graduation line, and the stable and slow operating requirements must be followed during the verification so that the standard gauge should point to the corresponding position. , Can carry out the accurate recording of recorded values.
3.6 Use Standard Methods for Measurement Verification
The indication value of the pressure gauge shall be verified by one-fifth of the division value. During the verification process, the standard gauge shall be verified by means of line readings, and the verified meter shall be verified by means of estimated readings. For errors generated during the verification process, the errors need to be performed in accordance with the specifications, and relevant records should be made after the error verification operation.
4. Solutions for Pressure Gauge Measurement and Verification Failure
4.1 The Pointer cannot Turn when the Pressure Rises
The pointer of the pressure gauge cannot turn, mainly because the cock of the pressure gauge is not open, or the pointer is blocked due to the plug of the pressure gauge and the pressure gauge being blocked. For the measurement verification failure of the pressure-raising pointer, it is necessary to repeat the installation of the pointer at the position of the first measurement verification to correlate the measurement verification value of the pressure gauge.
4.2 Jitter Occurs when the Pressure Gauge Pointer Works
After the hairspring of the pressure gauge is damaged, the pointer will continue to shake during the measurement verification of the pressure gauge, and the bending of the central axis of the pressure gauge will also cause the corresponding shake. After the pointer of the pressure gauge shakes, the pressure gauge needs to be inspected. The damaged part needs to be resolved in time to avoid the situation of the pressure gauge re-shaking.
4.3 The Pressure Gauge Pointer cannot Return to Zero when there is no Pressure
The pressure gauge finds that the pointer is not at the zero position or cannot be returned after tapping, the verification work will be affected, and the error of the indication of each pressure value will exceed the allowable error, which will cause the pressure gauge verification to fail. The main reason is that after the elastic element is used for a period of time, the elastic deformation of the spring tube of the pressure gauge causes the initial displacement of the spring tube to change, that is, after a long period of elastic deformation, it makes it inert and cannot automatically rebound. It may be that the hands are bent or deformed or the pressure gauge movement is damaged. The way to eliminate this fault is usually to fix the needle and increase the balance spring torque. The fixed needle is to open the pressure gauge case when it is not pressurized and return the pointer to the zero position, so that the initial position of the pressure gauge pointer is restored to Zero points, realize zero adjustments. If there is still a fault, the strength of the balance spring torque should be increased. The sun gear is separated from the fan gear, and the reverse rotation of the center gear increases the reverse torque of the balance spring so that the internal balance spring can be more compactly linked. value.
4.4 Inaccurate Display of Pressure Gauge
After abrasion occurs at the wheel shaft of the pressure gauge gear, the pressure gauge is extremely susceptible to incorrect display of the response due to improper gear operation. It is also easy to cause corresponding disturbances and blockages due to improper operation when the metering check of the spring and the cock of the pressure gauge is performed incorrectly. This kind of failure needs to repair or replace the worn parts and clear the blockage now. After ensuring that there is no failure in each part of the pressure gauge, the failure of the pressure gauge to display the value is not accurate enough.
4.5 The Pressure Gauge Pointer Taps out of Tolerance
Larger tapping displacement of the pressure gauge pointer is more common in the test, that is, during the pressure increase or decompression process, the pointer appears a few graduations after a certain pressure value is tapped on the case. The main reason for the abnormal displacement of the pressure gauge pointer is that the balance spring is loose or damaged, or the counter-torque of the sun gear has lost control. The pressure gauge can be installed on the calibration platform to increase the pressure to the maximum pressure value, and the valve is slowly opened. After observing the pressure is stabilized, the valve can be opened to the maximum and the pressure of the pressure gauge pipeline can be used to clean up the dirt blockage of the pipeline. If it is not because the pressure gauge pipe is blocked due to uncontrolled pressure and the pointer sways, it may also be due to internal component damage or insufficient control of the gear torque, which does not rise and fall smoothly with the pressure, resulting in unqualified pressure gauge verification. If the pressure gauge is installed on a pressure vessel with relatively high pressure, it is not recommended to continue to use it for maintenance, but to replace it with a new gauge and install it.
Pressure gauge measurement and verification work are very important. Common faults in the verification process are analyzed and solutions are proposed. Carry out the measurement verification in strict accordance with the pressure gauge verification procedures, correctly understand and carefully implement the details that are easily overlooked in the verification steps, and avoid data deviations in the verification results due to poor handling of the details, resulting in inaccurate pressure gauge values. Bring major hidden dangers to production and construction.