Regarding the issue of modifying the negative pressure chamber in differential pressure transmitters
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The process flow of an orifice plate on-site has been changed; the orifice plate was removed and installed in reverse, and the pressure guide tube of the original differential pressure transmitter also needs to be modified to accommodate the negative pressure chamber. Is it possible to change the flow direction without removing the diaphragm box by simply adjusting the settings on the EJA transmitter? Specifically, could you please indicate which one can be used via the 475 menu?
Why remove the diaphragm box? Just reverse the pressure measurement tubes for positive and negative pressures, and that’s it.
Are the instrument and the orifice plate separate or integrated? If they are integrated, there’s no need to replace the tube either. It’s detachable; it can be removed from the transmitter end connector, and no welding is required.
If it is a three-valve assembly, it can be removed and rotated in the opposite direction； If it is a pressure guide tube connected to a waist flange, then it’s just a matter of changing the orientation of the gauge; no welding work is involved. The positive and negative pressure chambers of the transmitter cannot be replaced by oneself; they are already calibrated at the time of manufacture.
The last edit to this post was made by liangjian2 on 2018-1-19 at 16:58. The Brown protocol provides an option to directly change the direction of pressure measurement, while the HART protocol seems to lack such an option; however, it can be achieved by changing the range – for example, if it is set to 0-16 kPa, it can be tried setting it to 0~-16 kPa
Use 475 to change the upper and lower limits to -16-0 KPA
The Brown protocol can be modified using bt200, but not with Hart
If it is a table using the BRAIN protocol, you can modify the D45 value using the handheld controller. However, if it is a table using the HART protocol, it cannot be modified through the handheld controller. Here is the simplest method: there’s no need to remove the mounting brackets of the transmitter; instead, simply remove the vent and drain valves on the side opposite to where the three-valve assembly is installed, and use that side as the pressure sampling side. Then, install the vent and drain valves on the side where the three-valve assembly was originally located!