How to control the electric valve with the SIS emergency stop button
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The device should be integrated into the SIS system upon request; however, the existing DCS system uses electric control valves. The problem is that the emergency stop button in the SIS system relies on a 24V relay to shut off the valves and pumps in an emergency situation. Since electric valves are being used as these shut-off valves, it is not possible to control their operation using a relay. Solenoid valves can be used, but they do not provide feedback regarding their position, so it is not possible to determine whether the valve is open or closed. Without a gas supply, pneumatic valves cannot be used either. Could some expert please help? How can I make the relay turn off the electric valve when the emergency stop button is pressed? What is the wiring scheme? I am extremely grateful. The electric valve has a backup power supply. This is the interlock logic diagram
According to the standards, the actuator for a SIS must be a pneumatic valve; electric valves are not allowed. Once the safety authorities discover this, it constitutes a serious hazard, and they can issue an order to suspend operations.
The design institute said there is no mandatory requirement regarding the type of valve to be used
Refer to clause 7.1.2 of standard GB/T50770-2013
The standards do indeed specify that electric control valves should not be used in the safety instrument systems of the petrochemical industry
It’s not suitable; it can only be used barely. There is no sense of coercion.
It needs to be replaced with an electro-hydraulic actuator to operate in the power-off mode. The electric valve remains in its position when power is lost.
Putting aside the requirements of the specifications for now, my approach is as follows: 1. It would be best if the electric valve had a position control mode; the wiring should be adjusted to enable position control, so that when the relay loses power, the valve closes completely； 2. If there is no positional control, then implement a selection control in the SIS. The circuit electric valve can be adjusted under normal conditions. When the interlock signal is received, it switches to the emergency circuit, sending a command to close the electric valve, and this signal has the highest priority. Another point is that after the valve interlock shuts down, and once the process is confirmed, the electric valve needs to be manually reset before it can be used again
If it is said that it is not suitable for certain reasons, then why choose an electric valve?
It’s impossible to shut off the valves in case of a power outage; everything else can be resolved.
Electric valves cannot achieve fail-safe operation