Application of 1151 double flange differential pressure transmitter
Our plant caustic soda evaporation process uses a three-effect downstream evaporation process. Reliable measurement and accurate indication of the evaporator level is critical during the production process. The detection of the liquid level of the three evaporators of our factory originally used the electrode type liquid level converter. Only the high and low level of the liquid level is reported, and the intermediate relay is also required to be converted. The liquid level of the dry evaporator sometimes fluctuates greatly, and the lye is boiling, which often causes the stainless steel electrodes to swing side to side, collide with each other or come into contact with the container wall, thereby causing frequent false alarms. Process operators report that the high and low limits of this level are extremely unreliable. In addition, the sight glass on the evaporator often appears to be blocked by salt crystals during use, which makes it impossible to observe the liquid level. In addition, the glass mirror is susceptible to corrosion in high temperature alkaline liquids. Short life and unsafe. In response to these situations, according to the existing liquid level indications and alarms proposed by the craftsman, and the reliability is high, we re-select the design and rectification. The on-site measuring instruments adopt the 1151DP double-flange remote transmission differential pressure transmission. (1151 and 3051 are the same) The control room meter adopts the alarm indicator with indication, and the alarm output connector of the alarm indicator is led to the flash alarm, which is a good solution to the previous measurement of the inverter. The problem of existence, from the time of commissioning in 2009 to the present has been normal.
At the time of transmitter selection, attention should also be paid to the inner wall of the evaporator. In particular, some dead angles are prone to salt crystals. Therefore, a flange measuring device with flushing water L is required. Because caustic soda is highly corrosive at high temperature and high concentration, it is necessary to use SUS316 alloy, Hastelloy C alloy and better Monel alloy which are better in alkali corrosion resistance. In order to increase the sensitivity of the transmitter, the capillary should be as short as possible according to the field installation. The body of the transmitter must be installed away from the evaporator to avoid high temperatures. Due to the different concentrations, pressures and temperatures of the measured medium (alkali) in the three evaporators, the measured ranges of the three transmitters are also different. The following uses the 1-effect liquid level transmitter as an example to illustrate the calculation of the range and the selection of the scheme.
Instrument use name: 1 effect level measurement transmitter
Measured medium: 16% NaOH electrolyte
Density of measured medium: ρ1=1.239×1000kg/m3
Capillary filling fluid (silicone oil) Density: ρo=0.95×1000kg/m3
Flange spacing: h = 1.4m
The liquid level range: h=1.4m, where Ho=0, the liquid level range is equal to the center distance of the two source ports.
According to the above calculation results, refer to the l-code 1 series transmitter selection manual, and decide to use the transmitter and secondary instrument of the following specifications:
[1) Double flange remote differential pressure transmitter: 115lDP4E22S2M1B3D [Select the Rosemount selection sample provided by the company]
Flange remote transmission device: 1199RFW21AllA71
Capillary: 1199CAP13A10All (L side)
1199CAP13A05A11 (H side)
Remote transmission filling liquid: silicone oil, C10485-0007
(2) The secondary indicating instrument adopts the alarm given device: XM6 digital display. The selection scheme is shown in Figure 1.
Installation of 1151 double flange differential pressure transmitter in caustic soda evaporation unit
From the use situation, as long as the selection and calculation are correct, the 1151 double flange differential pressure transmitter is used for the caustic evaporation process. The liquid level measurement of the evaporator is highly reliable and accurate compared with other methods, ensuring the safety of production. In progress, the situation that affected the production due to false liquid level alarm and mirror rupture was eliminated, which was recognized by the process operators.