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Correct selection pressure gauge
| Correct selection pressure gauge |
| ¡¾Update Time¡¿2015-08-13 16:13:52 ¡¾Hits¡¿3705 |
The correct selection of pressure gauges including instrument to determine the type, scale, scope, accuracy and sensitivity, shape size and whether or not to long-distance transmission, and other functions, such as indicating, record, control, alarm and other.
The main basis for the selection of pressure gauges:
1 process requirements for measurement, including measuring range and accuracy. In the case of static test (or slow change), the maximum value of the measured pressure is 2/3 of the full scale value of the pressure gauge, and the maximum value of the measured pressure is 1/2.
The accuracy level of the pressure measuring instrument is 0.05, 0.1, 0.25, 0.4, 1, 1.5 and 6 grade 2.5 grades. The accuracy requirement and the most economical choice of the production process should be selected. The maximum allowable error of the meter is the product of the range of the pressure gauge and the percentage of accuracy. If the error exceeds the accuracy of the process, it is necessary to replace the pressure gauge with high accuracy.
2 the nature of the measured medium, such as the state (gas, liquid), temperature, viscosity, corrosion, the degree of pollution, flammable and explosive, etc.. Such as oxygen table, acetylene table, with the "no oil" signs, dedicated to the special medium of corrosion resistance, high temperature pressure gauge, pressure gauge, etc..
3 environmental conditions, such as environmental temperature, corrosion, vibration, humidity, etc.. Such as the vibration pressure gauge used for vibration environment.
4 suitable for staff observation. According to the location of the instrument and the selection of lighting conditions ranging from meter diameter.
Two, pressure gauge calibration and calibration
Before use, the instrument must be calibrated and calibrated. Long - term use of the instrument should be regularly checked, the cycle should be considered the use of frequent degrees and focus. When the instrument with a long distance transmission system and the two meter, should be together with the two instrument calibration, calibration.
Three, the correct installation of pressure gauge
Pressure detection, in fact, the need for a measurement system to achieve. To achieve accurate measurement, in addition to the correct selection and calibration of the instrument, but also must pay attention to the correct installation of the whole system. If just vibration proof pressure gauge itself is accurate, its indicating value cannot represent the actual data of the measured medium, because the error of the measurement system is not equal to the gauge error.
The correct installation of the system includes the opening position of the pressure port, the reasonable laying of the connecting pipe, and the correct position of the instrument installation.
1 Location Selection (1) of the pressure mouth to avoid in the pipe bending, bifurcation and flow of the formation of the vortex flow area. (2) when the pipe is a prominent object (such as temperature measurement element), the pressure should be taken in front of it. (3) when the valve is necessary to take the pressure near the pressure, if the pressure in the front, the valve should not be less than 2 times the diameter of the pipe diameter; if the pressure in the next, then the valve should not be less than 3 times the diameter of the pipe. (4) for a broad container, the pressure inlet should be in a stable and non - current flow of the fluid. In a word, the position in the process flow is determined to ensure that the process parameters are selected.
2 the laying of the connecting pipe
The horizontal section of the connecting pipe shall have a certain degree of inclination, in favor of the exclusion of condensate or gas.
When the medium is a gas, the catheter should be inclined to the direction of the pressure drop. When the medium is liquid, the catheter should be inclined to the direction of the pressure measuring instrument. In addition, such as pipe is at the next corner, depending on the circumstances of the catheter in the medium and at the lowest point placement condensed liquid device for excretion or exhaust device placed at the highest point, to ensure that in quite a long period of time not because of the catheter in the accumulation of condensate liquid or gas and affect the measurement accuracy. Condensate liquid or gas to be regularly discharged.
Four, the use of pressure measuring instruments
(1) the instrument should be vertical to the horizontal plane. (2) instrument measuring point and instrument installation are in the same horizontal position, no considering additional height error correction; (3) instrument installation and measuring points should be short, lest indicate delay; (4) to ensure the sealing, no leakage phenomenon occurs, especially flammable and explosive gas medium and toxic and harmful medium.
The instrument should be used in the following circumstances, but should be added to the device, but should not produce additional errors, otherwise it should be considered amendments.
(1) in order to ensure that the stainless steel pressure gauge is not affected by the erosion of the measured medium and the effect of the viscosity, the isolation device should be installed;
(2) in order to ensure that the instrument is not subject to the rapid change of the measured medium or the effect of the pulsation pressure, the installation of a buffer. Especially in the steep, pressure increasing and pressure drop, the most easy to damage gauge even spring tube burst apart and leakage phenomenon;
(3) in order to ensure that the instrument is not subject to vibration, the pressure gauge shall be equipped with a shock absorber and a fixing device;
(4) in order to ensure that the instrument is not affected by the high temperature of the measured medium, a pipe bending device which is filled with liquid should be added;
(5) special instrument, which is forbidden to use it, and it is forbidden to measure it in the absence of special and reliable apparatus;
(6) the pressure measuring instrument for the new purchase must be measured before installation, in order to prevent the damage of the pressure, damage or other factors in the transportation of the pressure gauge.
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