Implementation of on-line verification of pressure gauges
2.1 The configuration of standard equipment and supporting equipment for verification.
According to the requirements of the verification regulations, a suitable standard pressure gauge or a 0.05-level digital pressure gauge is selected as the standard device. The pressure generator in the supporting equipment is selected as a portable pressure calibrator, which is used as the online pressure source for verification. Other supporting equipment is configured as required.
2.2 Verification of appearance and zero error of seismic pressure gauge.
Before the verification, confirm that the on-site environment and the meter being inspected meet the verification requirements, close the D gate valve, slowly open the B gate valve and the C gate valve, and verify the appearance and zero error after standing for 2 hours.
2.3 Verification of indication error and return error.
After the appearance and zero error verification is completed, install the standard device at the B end, and connect the pressure generator to the C end, and perform the verification of the indication error and the return error according to the verification regulations. The schematic diagram of the verification installation is shown in Figure 4.
2.4 Verification of other verification items.
If necessary, other verification items can be completed at the same time as the indication error verification. Otherwise, the verification should be performed after the standard device and the pressure generator are removed from the seismic pressure gauge.
2.5 Processing after the end of the verification.
After the verification is completed, release the pressure, remove the standard device, and disconnect the C-side pressure source. If the meter to be inspected is not qualified, you can replace the qualified pressure gauge before connecting the pipeline pressure after the verification is completed. If the verification is qualified, no disassembly and assembly actions are required for the meter to be inspected.
2.6 Recovery of the pressure gauge in daily use.
After the calibration is completed, the standard device and other supporting equipment are removed, the B gate valve and C gate valve are closed, and the A gate valve is slowly opened to prevent the pressure gauge from damaging the pressure gauge or other safety accidents caused by the pressure of the pipeline.
3 Comparison of online verification and traditional verification results.
For the same pressure gauge with a measuring range of (0～1.6) MPa and an accuracy grade of 1.6, after online verification, it will be disassembled and sent to the laboratory for offline verification using traditional verification methods. Verification and offline verification strictly follow the current verification regulations. [1, 2] In order to facilitate verification of verification results, the standard pressure gauge selected for online verification is (0～1.6) MPa, and the standard pressure gauge with accuracy level of 0.25, offline verification The standard instrument selected at the time is (0～1.6) MPa, and the accuracy grade is a digital pressure gauge of grade 0.05.
According to the verification method of the verification results, the difference between the two verification data of the same verification point of the stainless steel pressure gauge does not exceed the uncertainty of the measured value of the offline verification (a higher level of measurement standard). The online verification result is verified, which proves the online verification method. reliable.
4 Precautions for online verification.
(1) The on-site use of pressure gauges is under complicated environmental conditions. In online verification, attention should be paid to check whether the on-site environmental conditions meet the requirements of the verification regulations.
(2) When the daily use medium of the tested meter is inconsistent with the medium used during verification, the daily use medium should be used after the standard device and the pressure generator are removed and before the D gate valve is connected (that is, the original pipeline is connected) Clean the four-way pipe to prevent pipeline contamination, and pay attention to isolation during online inspection of the oil-free gauge
