Precautions for on-site use of pressure calibrator
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ARIPY
Time : 2020-03-02 18:37 Pageviews : 30
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Environmental conditions and verification of pressure instrument work site
The environmental conditions of the pressure instrument work site are completely different from those of the verification laboratory. Some of the on-site working conditions are harsh, and the verification laboratory cannot meet the needs of the actual working conditions of the site; the laboratory verification must use the instrument to be inspected. Remove it from the equipment used, and reinstall it back to the equipment after verification.
This operation is not only intensive, but also cumbersome and complicated, which greatly reduces work efficiency.
Therefore, it is very necessary to calibrate pressure gauges on site. Today, we have compiled the on-site inspection of pressure gauges for everyone.
The development of pressure calibrators
Due to the urgent need for on-site calibration of pressure instruments due to scientific research and production practices, it has driven the development of on-site calibration instruments by domestic and foreign instrument manufacturers.
In 1994, the British Transmation company introduced the compact and lightweight 1292 portable automatic pressure calibrator.
It realizes automatic calibration from automatic generation of standard pressure to automatic recording of verification results, and is particularly suitable for on-site rapid calibration of pressure instruments used in industrial production.
In 2008, Ai Rui Puyuan Instrument (Beijing) Co., Ltd. successfully developed the PY801 series of intelligent digital pressure calibrators.
This kind of pressure calibrator can measure pressure in the range of (-0.1～250)MPa, and its test error is 0.02%FS.
Using the pressure field calibrator to calibrate the pressure gauges, pressure sensors and pressure measurement control system at the production and work sites can represent the real operating conditions of the production and work sites, reducing and avoiding errors caused by different environments and working conditions , Improve the test accuracy, ensure the quality of the produced products, and improve the work efficiency.
Features of pressure calibrator
The pressure calibrator is a special pressure calibrator for calibrating various pressure transmitters, pressure sensors, pressure switches, differential pressure transmitters, and digital pressure gauges.
The pressure calibrator is a portable instrument for both AC and DC. It can measure the current while measuring the pressure, and it is displayed on the LCD at the same time, and it is equipped with a DC24V output; it is divided into two types: modular and integrated. The front panel of the tester is equipped with a hand pump or a built-in electric pump.
At present, the integrated pressure calibrator represents the future direction of the product due to its portability and other characteristics.
Precautions for on-site use of pressure calibrator
In the process of on-site use, you need to pay attention to the following points:
Matters needing attention
During the test, the pressure gauge under test should be completely disconnected from the equipment pipeline, and the dirt in the pressure chamber should be removed, and then connected to the standard device.
When measuring low-pressure gas source pressure equipment of -0.1 to 1.6 MPa, the built-in pressure module and pressure generating equipment of a general pressure calibrator are fully capable of testing. When measuring 1.6 to 10 MPa gas source pressure equipment, the general The pressure calibrator needs to use an external pressure module with a portable hand pump for testing.
What needs attention is the cleaning of the pressure gauge under test.
After the pressure meter is disassembled on site, if it is not cleaned or cleaned, it is connected to the pressure calibrator for calibration. The dirt will follow the pressure fluctuations and enter the measuring system of the pressure calibrator, contaminating the pressure sensor and pressure generation. Mechanism, block or block the internal pressure pipeline, wear or scratch the sealing member, affect the measurement accuracy of the pressure calibrator or make it unable to work normally, or even directly damage it.
In the case of inconvenient cleaning on site, it is recommended to use a filter between the device under test and the pressure calibrator.
Matters needing attention two
When detecting a pressure transmitter or sensor with a pressure measurement system composed of an intelligent digital display instrument in the field, the display value can be corrected and linearly adjusted through the corresponding calibration software on the computer or display panel.
However, in practical measurement tasks, sometimes we encounter some unknown reasons that cause the system pressure display value to deviate greatly or display abnormally, and it cannot be adjusted to the normal value through software.
There are two steps to deal with such problems:
(1) Turn off the power supply of the pressure measurement system, separate the terminal of the pressure transmitter or sensor from the system, and use a pressure calibrator to separately provide power to the transmitter or sensor and measure its output signal to determine whether it is working normally;
(2) According to the difference of the signal received by the digital display meter, input the corresponding signal to the digital display meter on the circuit where the transmitter or sensor is disconnected.
It should be noted that when the digital display meter itself outputs DC24V, the received signal is a current signal and the wiring method is two-wire system, you must not directly use the signal source to input the current signal.
Connect the resistance box and the ammeter to the circuit in series, adjust the resistance value, the ammeter will display the standard current value of the input digital display meter, calculate the corresponding standard pressure value, and compare it with the digital display meter.
If the difference is too large and does not meet the technical requirements for use, adjustments should be made.
After the transmitter or the sensor and the digital display meter are adjusted, they should be connected together, and the overall inspection should be performed once, and the adjustment should be made appropriately.
Matters needing attention three
During the calibration, you should also pay attention to whether the pressure equipment is an oil-prohibited equipment. The pressure calibrator, its external modules, and hand pumps need to be oil-prohibited, and an oil-water separator can also be connected to ensure the safety of the equipment.
If it is unavoidable to perform measurement in flammable and explosive places, it is necessary to select the corresponding pressure calibrator, isolation barrier and safety barrier according to the explosion-proof mark, terminal explosion-proof parameters and other explosion-proof requirements, and carry out the pressure verification of the safety instrument.
The pressure calibrator is often used in the field operation process. If you do not pay attention to the above three points in the application process, it will affect the use of the pressure calibrator, and errors and failures will occur, which will affect the measurement.
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