Recovery processing of Fuji FKA Transmitter in -a work field
Time2023-05-17 13:46 linkS：
The recovery processing of Fuji FKA Absolute pressure transmitter in-a working field.
The following is based on the failure of the FKA absolute pressure transmitter in actual work, combined with the basic theory, analyze the cause of the faulty and the solution.
In 2014, our factory dismantled the original decompression tower and replaced the new tower due to expansion. After replacement, according to the design requirements, the tower top pressure measuring instrument uses an FKA absolute pressure transmitter with a design range of 0-100kPa. This measurement value reacts in the tower's real vacuum.
According to the process production requirements, when the vacuum is displayed or close to 100%, its production efficiency is very good. After installing the transmitter, the single school, and the joint school, it was found that the value of the transmitter was transmitted to the upper machine and the readings of the vacuum pressure gauge on the upper machine were very different.
Here are how I solve this problem：
The pressure defined in the project refers to the force of uniform and vertical effects in the unit area. There are three ways to represent pressure, namely: absolute pressure, table pressure, negative pressure or vacuum. The relationship between them is shown in Figure 1.
Absolute pressure is the actual pressure that objects bear, and its zero point is absolute vacuum.
Table pressure refers to the difference between absolute pressure and atmospheric pressure when it is higher than atmospheric pressure.
The difference between the vacuum (negative pressure) is the absolute stress when the atmospheric pressure is lower than the atmospheric pressure.
According to the international unit system, the unit of pressure is Pascalka, referred to as PA (PA). It indicates that the pressure formed by 1N vertical and uniformity in the 1m2 area, that is, 1Pa = 1N/m2
1. The absolute pressure is the real pressure of the medium (liquid or gas) in the container. The absolute pressure of the container intermediary can be higher than the external pressure of the outside world or the atmospheric pressure lower than the outside world. When we measure the pressure with a pressure gauge, the pressure value measured by the atmospheric pressure in the atmosphere in the atmosphere is 1st than that of an absolute pressure.
We call the pressure measured by instrument as the surface pressure. When the pressure forms we see on the dial are the surface pressure value. The absolute pressure of the medium is equal to the pressure value of the surface pressure. P absolute= p gauge pressure+atmospheric pressure.
When the medium is absolutely more than or equal to atmospheric pressure, the surface pressure is positive or zero. When the medium is absolutely less than the atmospheric pressure, the surface pressure measured by the instrument is negative. At this time, the surface pressure is called negative pressure or vacuum.
The ratio of negative pressure (vacuum) value to atmospheric pressure in engineering is commonly used in engineering to indicate the negative pressure state of the medium, which is called real vacuum.
The instrument that measures the absolute pressure is called a stressometer. For ordinary industrial pressure gauges, the pressure value is measured, that is, the differential pressure value of absolute pressure and atmospheric pressure. When the absolute pressure is greater than the atmospheric pressure value, the surface voltage value is positive, called positive surface pressure; the surface pressure measured when the absolute pressure is less than the atmospheric pressure value is negative, called the negative surface pressure, that is, the real vacuum.
2.The zero point of the absolute pressure is absolutely zero, that is, the influence of the local atmospheric pressure is eliminated. Under normal pressure, the gauge shows the local atmospheric pressure value, that is, about 100kPa. In the vacuum state, the number of views is increased. Decrease, to positive value (as shown in Figure 2, the real pressure gauge measurement tower real vacuum)
The local atmospheric pressure of the table pressure table is zero point. If the vacuum is measured, the instrument represents the negative number (as our common vacuum table), as the vacuum increases, the table shows Differential pressure transmitter measuring the tower's vacuum).
In general, in order to measure the true vacuum, we use a stress. Use the vacuum value expressed by the absolute pressure, and the vacuum value represented by the meter pressure is negative. In practical applications, if the value of the pressure movement is given, use the meter pressure switch to directly replace it with the same negative number. If the surface pressure movement is pressed at the standard atmosphere, the conversion is called the surface pressure value of the local atmospheric pressure. If the surface pressure given is -67, the local atmospheric pressure is 101kPa, the action value should be -67.67kPa
Problem solve：
Understanding the similarities and differences between the FKC differential pressure transmitter and the absolute pressure gauge transmitter, we began to check the cause of the fault at the scene. First check the installation and wiring of instruments, and conclude that it fully meets the design requirements and construction standards. Then check the internal parameter settings of the transmitter. According to the setting options in the instrument instructions, check it one by one. It is found that the setting of the meter range is -100-0kPa, and the range range in the design drawing is 0-100kPa.
This is where the problem lies. The construction unit mistakenly regards the absolute pressure transmitter as a normal pressure transmitter to set the range range that causes the display of the upper machine to display the actual situation.
Find the problem of the problem. The range of the absolute pressure transmitter at the scene is set to 0-100kPa, and the range of the instrument in the control system is set to -100-0kPa. 0 take absolute value
Why set this way? Looking at Figure 4, assuming that our current pressure is at a position of 25%of the range, the current value is 8mA, the absolute pressure transmitter at the scene is displayed as 25kPa, the instrument in the control system is converted to -75kPa. The instrument is displayed in the upper machine display. It is 75%, which is set according to process production requirements. 100%is displayed when the vacuum is completely drawn to meet the production needs.
It can be seen through fault analysis. When setting the internal parameters of the transmitter, the type of the transmitter should be carefully distinguished by the operation.
