Interlock for high level control valve of hydrogenation hot fractionator – Emergency
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The high-temperature liquid level is below 55; interlock activation occurs, the control valve closes, and adjusting the control valve has no effect. How can this be brought back to normal?
After the cut-off valve is interlocked, the control valve does not respond; by resetting the cut-off valve, the control valve can be operated again.
How can it be reset? The computer used for interlock control doesn’t have this type of high-temperature interlock function, nor does it have a level interlock for the liquid being poured in as raw material; yet such functions exist in the actual system. By manually adjusting the control valves, one can set a certain opening degree, but in automatic mode the control valves are still at 0. Is that the same in automatic mode as well?
The original poster is a bit confused. When the control valve is set to 0, it has no effect; aren’t the control valve and the regulating control valve two different things? Do you want to restore that to normal?
Once the liquid level is normal, the interlock can be reset. Remember to set the DCS output to 0 during reset
If there is no cut-off valve, the control valve can be changed on-site to local manual control. If there is a shut-off valve, the interlock must be set to the bypass position before operation can proceed after it has been reset.
The low-low interlock for the high temperature and high liquid level triggers the closure of the quick shut-off valve; at the same time, the control valve is forced to switch from automatic mode to manual mode, with its output set to 0. The quick shut-off valve can be reopened only when the liquid level returns to the normal control range, after which the control valve is used to regulate the liquid level
For interlock reset, go to the instrumentation team; ask the management for a penalty – how should one read the liquid level?
Does preventing high pressure from penetrating into low pressure involve the shutdown of the interlock valve, preventing the control valve from performing its regulating function?； After the interlock level returns to normal, press the reset button on the SIS screen or disable the level interlock for reset (however, when disabling the interlock, set the control valve to 0) ；
If there is no cut-off valve, the control valve can be changed on-site to local manual control. If there is a shut-off valve, the interlock must be set to the bypass position before operation can proceed after it has been reset.
1. If the high-temperature fractionation level remains very low, the bypass is activated via interlock; once reset, the control valve can then be operated； II. The high-temperature level has moved away from the very low position; after it is reset, the control valve can then be operated. The involvement of control valves in interlock control involves adding solenoid valves to their air supply lines; when an interlock is triggered, the solenoid valves lose power, the air supply is cut off, and the control valve closes – no matter what signal is sent from the control system, the valve will not move. If the above two conventional methods cannot be used, contact the technician to go to the site and manually supply power to the solenoid valve, thereby allowing the control valve to be adjusted for a short period of time.