New Mersonilan control valve added to Deltav AO card
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An additional control valve of type SVII AP (Mason Lan) has been added; the project documentation states that it is equipped with HART protocol support. 1. I selected the HART AO channel type in the IO list. 2. After configuring it, I found that the circuit was not functional; moreover, the red triangle light at the bottom of the field AO card was flashing, as well as the light corresponding to that channel. (The wires are all connected and have been checked to be correct.) 3. Changed the AO type in the IO list (AO output was selected, without HART protocol). 4. Everything returned to normal during configuration, and current output was also available. 5. Then it was found that the control valve on site was not moving. 6. Checking the input side of the safety barrier showed a 4–20mA current variation (the valve was controlled manually by the DCS), with a voltage of 14V. The safety barrier output means there is no current or voltage. 7. The safety barrier was replaced (P+F’s KFD2-SCD-Ex1); the same thing happened here (it was swapped with the safety barrier that was already in use). 8. A signal source was used to apply an active current signal at the input terminal of the safety barrier, thereby causing the control valve to move. 9. The AO channel was also replaced, and the same situation occurred there as well. Under the group. . . I asked Emerson’s engineers as well, and they said they had never encountered it.
If it’s changed to a non-HERT model, problems still occur; external factors need to be taken into account. Verify that the wiring of the valve actuator is correct On the DCS side, the output detection can be disabled; a 4-20MA output is used. If there are no issues, then it’s an external problem
There is a problem with the AO output; check the configuration. Although current is present at the AO output, the voltage is incorrect.
I copied the configuration from another module. This morning, I applied an active signal at the front end of the safety barrier, and everything worked fine. Even when I bypassed the safety barrier and sent the signal directly to the field locator via the AO channel to control the valve, I observed severe fluctuations in the current level (my DCS sent a signal of 4 mA, but the measured value fluctuated rapidly between 4 mA and 10 mA)
This post was last edited by sdlyml on 2020-8-3 at 14:34. Have you checked the wiring between the Emerson card and the CD isolator? Are the positive and negative terminals connected correctly? It is suspected that the positive and negative connections of this circuit are reversed
It’s possible that the selection of whether the signal is active or passive during configuration was incorrect; if that doesn’t work, try adding an AO function block and installing it – sometimes the modules can also malfunction.