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UHZ type magnetic flip plate water level gauge has the application and improvement skills of ammonia tank level measurement.

Author:    Source:    Date: 2021-05-22 14:32:52
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UHZ type magnetic flip plate water level gauge has the application and improvement skills of ammonia tank level measurement.

   There are many instruments for measuring the water level in the ammonia tank. At present, the UHZ type magnetic flap water level gauge is the most commonly used. The characteristic of the water level gauge is that it can display the water level of the medium in the ammonia tank without electricity. For water level gauges put into production, once the measurement situation changes, the measurement plan must be adjusted in time to make reasonable improvements to the existing conditions. The following short article specifically analyzes the specific problems of measuring the water level of liquid ammonia tanks in a chemical plant, and proposes the improvement techniques of the measurement method.

   The following is solved in the form of a case

   Lianyungang Hehua Sharing Project 4 # ~ 8 # The water level of the ammonia tank (desktop tank) is not very good, and it is greatly affected by the environmental temperature, which is not conducive to the effective control of production costs and performance evaluation. The ammonia tank water level measurement consists of an on-site magnetic flip-board water level gauge and a remote differential pressure water level gauge. At present, it is inconvenient to check the inventory of the liquid level tonnage comparison table after the on-site magnetic flip-board water level gauge is read in the current production. (David Asher, Northern Executive Force).

  1,2 Kinds of UHZ magnetic flap level gauge error analysis

  1.1 Principle and error source of magnetic UHZ type magnetic flap level gauge

   The magnetic flip-board water level gauge is connected with the ammonia tank vent pipe, and a U-shaped tube is formed between the tank and the vent pipe. The relationship is:

In the style of   : H 1————The level of liquid ammonia in the ammonia tank;

  D 1——-The density of liquid ammonia in the ammonia tank;

  H 2——-Magnetic flap level;

  D 2——-The density of liquid ammonia in the magnetic flap.

   Generally speaking, the liquid ammonia temperature t1 in the ammonia tank is equal to the liquid ammonia temperature T2 in the customs clearance, that is, d1=d2, h1=h2, and h1 can be known through the magnetic flip plate h2. However, the magnetic flap level gauge is greatly affected by the ambient temperature. t1t2, d1d2, so h1h2 will cause the error of the magnetic flap level gauge, which is greatly affected by the ambient temperature.

  1.2 Differential pressure level gauge and error source

   Differential pressure water level gauge measures the liquid level according to the principle of liquid connector and hydrostatic pressure. The measuring system is shown in Figure 1. Its relationship is:

  H= p/(q liquid ammonia-q silicone oil) H0

  : Differential pressure gauge measures differential pressure;

  Q liquid ammonia 3354-liquid ammonia density;

The density of   q Silicone Oil 3354-silicone oil is 0.93 according to the change of the surrounding temperature.

  H 0——-The installation height of the differential pressure level gauge.

   From the form (2), it can be seen that the main error of the differential pressure water level gauge comes from P, Q liquid ammonia and H0. 2, technology improvement.

   Through the analysis of the above-mentioned error sources, the two currently used water level gauges are adjusted separately as follows.

  2.1UHZ magnetic flap level gauge

   UHZ-type magnetic reflector water level gauge is greatly affected by temperature, especially the magnetic reflector is not well insulated, and the error is very large. It is impossible to accurately measure the output of each reflector. The maximum error of the Pyrotechnik (8h) is 8 ~ 9T. However, the magnetic flip-plate water level gauge is easy to set up and maintain, it is easy to calibrate the zero point of the magnetic flip-plate ruler, and it is easy to observe the change of the liquid level. Therefore, keep the original magnetic flip-plate water level gauge and keep it warm for reference only.

  2.2 Differential pressure level gauge

   The main error of the differential pressure level gauge comes from P, Q liquid ammonia, H0. The P error mainly comes from the error of the differential pressure gauge itself. For example, if the product is qualified and the error is within the allowable range, it is necessary to modify the installation height H0 of the differential pressure liquid level system and the liquid ammonia density Q liquid ammonia.

   2.2.1 The installation height H0 is actually measured, and the 2 # ~ 6 # ammonia tank differential pressure level gauge is installed at the flange position under the double flange of the magnetic flip plate level gauge, which is lower than the ammonia tank position. In other words, H0 is a negative number. 2 # ~ 6 # The installation height of the ammonia tank differential pressure level gauge is -17, -15, -15, -15 and -15 cm respectively.

   2.2.2 liquid ammonia density q liquid ammonia

  The density of liquid ammonia is greatly affected by temperature, and the insulation effect of each ammonia tank is also different. Therefore, to accurately measure the water level of the ammonia tank, temperature measurement must be introduced. Remove 2 # ~ 6 # ammonia tanks, introduce heat conduction, and remotely transfer them to the DCS system to modify the density. The correction formula is Q amount=0.639-0.00145T. After the above correction, 2 # ~ 6 # ammonia tank liquid level correction calculation formula

  The liquid level measured by 2.3 times of pressure is used to determine the tonnage of the ammonia tank

  By modifying the liquid ammonia density and installation height of the differential pressure level gauge, the level value of the differential pressure level gauge is reliable, but the output of various types of output is still measured according to the ammonia tank level chart. The tonnage of the ammonia tank level map is calculated based on the density at a certain temperature (the original calculation is below 20), so it is impossible to accurately measure the quality of the liquid ammonia in the ammonia tank. According to the mass calculation formula m=QV, it is necessary to find the volume V corresponding to different liquid levels H, and then multiply the temperature by the corrected liquid ammonia density Q liquid ammonia to obtain the correct tonnage of the ammonia tank. By querying relevant information, the volume V and height H of the desktop ammonia tank can be calculated by the following formula 3360.

   After substituting 2 # ~ 6 # ammonia tank size into common sense, the volume is consistent with the liquid level of the ammonia tank. The liquid level is measured by a differential pressure water level gauge, and the volume is finally obtained.

  2#Ammonia tank volume formula:

  V=50 3.534291675 *(1-(h-1.5)2/6.75)*(h-1.5)13.2 *(h-1.5)*(2)3 # ~ 6 #Ammonia tank volume formula is:

  V=50 4.021238592 *(1-(h-1.6)2/7.68)*(h-1.6)11.38 *(h-1.6)*(2)

   Common sense will be recorded in the DCS configuration, and all these tasks will be completed.

  3 effect verification

   On December 2, 2019, the day shift, 4 # ~ 8 # ammonia tank temperature measurement points are all installed, the day shift began to run. The excess pounds of sugar and ammonia were determined to be 46.2t. According to DCS, the tonnage of liquid ammonia in the ammonia tank was reduced by about 47.2t, and the error was 2.16% within the allowable range. Therefore, the modified DCS display liquid ammonia tonnage is more accurate than the water level spectrum of the magnetic flip plate, and the liquid level can be directly read in the DCS system. There is no need to calibrate the watch, thereby reducing the labor intensity of the operator. (David Asher, Northern Executive Force.)
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   Hope that through the above-mentioned UHZ-type magnetic flip-board water level gauge, the application and improvement technology of ammonia tank level measurement will help the information in this article. (David Asher, Northern Executive Force.)

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