Daily Question - 2020.11.04 - Installation height of double-flange level gauge
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Due to limited skills, I’m posting some simple questions here; updates may stop, and if any expert is available, they could pick up where I left off. Daily Question - 2020.11.04 - Installation height of double-flange level gauges. When installing and adjusting double-flange level gauges, it is necessary to take into account the density of the silicone oil in the capillary tube in order to account for any migration that may occur. Question: After changing the installation height of the gauge for a double-flange transmitter, is it necessary to re-migrate it? Answer: It is not necessary, because regardless of how the height of the header changes, the height difference between the high-pressure side and the low-pressure side capillaries remains unchanged. In other words, the differential pressure resulting from the weight of the silicone oil on the high-pressure and low-pressure sides stays constant.
Since the double-flange level transmitter transmits pressure through capillaries, there is silicone oil inside the capillaries on the negative pressure side. When the liquid level is at zero, the pressure on the negative pressure side is greater than that on the positive pressure side; therefore, negative migration is required
Theoretically, the migration force is due to the gravity of the silicone oil resulting from the height difference between the two flanges; no migration should occur. However, in practical applications, various factors such as the installation location and variations in the forces acting on the flanges can cause some deviation, so it is best to perform migration again.
Theoretically, the migration force is due to the gravity of the silicone oil resulting from the height difference between the two flanges; no migration should occur. However, in practical applications, various factors such as the installation location and variations in the forces acting on the flanges can cause some deviation, so it is best to perform migration again.
The specific gravity of the silicone oil in the capillaries on the positive and negative sides of a double-flange transmitter is the same; therefore, no recalibration is required when the installation height of the transmitter’s gauge head is changed.
The calibration range of the instrument is independent of the installation height h of the level gauge; therefore, changing the installation location after the instrument has been calibrated does not affect its output
Theoretically, the migration force is due to the gravity of the silicone oil resulting from the height difference between the two flanges; no migration should occur. However, in practical applications, various factors such as the installation location and variations in the forces acting on the flanges can cause some deviation, so it is best to perform migration again.
After installation, a negative migration must always be performed for double-flange level gauges; the amount of migration is equal to -(distance between the two flanges × gravitational acceleration × density of silicone oil). This amount of migration is independent of the installation position of the gauge. For more details, refer to question 2-137 on page 39 of the Field Instruments section in the \"Instrumentation Technician Question Bank\" (2nd edition).
Migration is necessary, as double flanges are used to create a pressure difference for measurement
Since the double-flange level transmitter transmits pressure through capillaries, there is silicone oil inside the capillaries on the negative pressure side. When the liquid level is at zero, the pressure on the negative pressure side is greater than that on the positive pressure side; therefore, negative migration is required