I have a question for the seniors here? ? Differential pressure boundary detection

Lower range limit: 740*9.8*1.5 – 963*9.8*1.5; Upper range limit: 1000*9.8*1.5 – 963*9.8*1.5

Stop doing those silly calculations; the numbers you get are extremely inaccurate – they might be as bad as shit... Why? Brother is too lazy to speak. Bro, tell me how to calibrate it – that’s right. At full oil level, the corresponding pressure difference is the lower limit of the interface. At full water level, the corresponding pressure difference is the upper limit at the interface. Additionally, the capillary tube with double flanges is an instrument with rather poor accuracy; to calibrate it, it’s necessary to use water and oil multiple times, and then take the median values of those results to use as the lower and upper limits of the interface.

It is difficult to determine the upper and lower limits of the level with a liquid level gauge like this, due to the non-uniformity of the medium and large variations in density. Additionally, with capillary liquid level gauges that use silicone oil, the liquid level is greatly affected by temperature, as the silicone oil itself changes in volume with temperature, which in turn leads to changes in pressure

Excerpts from the “SH3005-1999 Standards for the Design of Automation Instruments in Petrochemical Industries” regarding the selection and design specifications for level and interface measurement instruments: Level and interface measurement typically involves the use of instruments such as glass plate level gauges, magnetic float level gauges, differential pressure transmitters, float-type level gauges, ball float level gauges, and ultrasonic level gauges. Selection and design specifications for differential pressure level gauges: The selection of differential pressure level gauges shall comply with the following rules: 1. For level (interface) measurement, differential pressure transmitters are preferred; 2. For corrosive liquids, viscous liquids, molten liquids, or liquids that tend to precipitate, differential pressure transmitters can also be used when measures such as filling with an isolation fluid, blowing air, or flushing are employed; 3. For corrosive media, viscous liquids, liquids that easily vaporize, or liquids containing suspended solids, single-flange level transmitters are preferable; 4. For liquids that tend to crystallize, highly viscous liquids, gelling liquids, or liquids that precipitate, insert-type flange differential pressure transmitters are suitable; 5. When there is a large amount of condensate or sediment in the liquid being measured, double-flange remote differential pressure transmitters are recommended; 6. When using differential pressure instruments to measure the level of water in boiler drums, a two-chamber balanced container should be utilized; 7. Differential pressure transmitters used for level measurement should be equipped with a drift compensation mechanism, and the positive and negative drift amounts should be determined when selecting the instrument’s range; 8. For media whose density changes significantly under normal operating conditions, differential pressure transmitters are not suitable.

This post was last edited by ZhiGE on 2018-12-7 at 12:26. 1. It is theoretically possible to determine the level using differential pressure, provided that the liquid level remains above the upper flange opening and that the densities of both fluids remain constant. The pressure difference within the measurement range is 10.878~14.7 kPa, and this value is independent of the density of silicone oil. The level percentage is calculated as (%)=(X-10.878)/(14.7-10.878), where X represents the actual measured differential pressure. The disadvantage is that the differential pressure range is small and the measurement accuracy is not high ； The quench tower used in ethylene plants works well (with a height of 2.5 meters); 2. For media such as gasoline and water, which are relatively clean, with a range of 1.5 meters, it is recommended to use a float to determine the level – it is necessary that the densities of the two media remain constant, otherwise the measurement accuracy will be affected ； 3. If the medium is dirty and the float is prone to clogging, radio frequency admittance is recommended.