1 reply to this topic

[RobertJAnderson91]

Process info first:
Multiple reagents common to multiple production lines
Each tank has one centrifugal pump (canned magdrive)
Each tank has a pressure control automatic valve returning to the tank. Settings close to 100psig

Each line (7 of them) has specific metering requirements with auto control valves (electric w/ stepper motors) header pressure stays close to 100psig downstream pressure close to 50-60 bit varies over long periods due to changing process conditions. Their goal is precise metering close one for example is a SP of 1pph and we attempt control down to .01 alarm limits are around 2% change in flow.

One line after a valve change was bouncing on either side of alarm limits. Now this one specifally looks like some air trapped around a thermowell causing this trend to bounce a little higher.

When I trended all the lines together every line is cycling on the same period as the suppky tank pressure control. Any tips for trying to get better control? Is it better to have faster control for the pressure control at the tank to quiet all that down or are all 7 valves moving together causing the shift. In manual recirc the trends on all the lines quiets way down with only subtle cycling. I cant leave it in manual mode or the header pressure will increase beyond limits if I were to shut down a line unexpectedly and could possibly wreck the other lines in the process. They are all single direction to the production lines with no recirc. The fluid is like water in characteristics.

[PhilippM]

Do you have a common header for all 7 reagents (i.e. the reagents are mixed in the header which leads to the production lines)? I think a sketch or a PFD would be helpful to understand the process: "A picture is worth a thousand words"