Can a pneumatic control valve be used as an emergency shut-off valve?
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Can pneumatic control valves be used as emergency shut-off valves? According to SH/T 3005-2016, Standards for the Selection and Design of Automation Instruments in Petrochemical Industries, 10.1.1.4 states that, unless there are special requirements specified in the process, the allowable leakage level for control valves should be at level IV as defined by GB/T4213 or ANSI/FCI 70-2 standards； When the process requires a tight shut-off (TSO) function from the control valve or involves emergency shut-off interlocks, the allowable leakage class for such valves should be Grade V or higher as specified in the GB/T4213 or ANSI/FCI 70-2 standards. This specification states that control valves can have requirements for tight shutoff and can be part of emergency shutdown interlocks. However, it’s not entirely clear whether such a control valve can function as an emergency shutdown valve itself, or whether it is not an emergency shutdown valve at all but merely serves to assist the emergency shutdown valve
This issue should be addressed by distinguishing between valve functions. It is usually not replaceable; and if it were possible, it would need to have the relevant functions. Emergency shut-off valves require a shutdown speed, whereas control valves do not have such a requirement. For reference.
I’ve encountered many cases where users employ this approach: a two-position three-way solenoid valve is installed in the air supply line of the pilot-operated control valve; when the solenoid valve loses power, the air supply is cut off and the control valve closes.
The second floor is the correct approach; that’s how it should be done. If you look at the national standards for the design of safety instrument systems, SIL1-rated systems allow for this approach, enabling both regulation and shutdown.
Sure, but the emergency shut-off valve has requirements regarding speed, and these cannot be met solely with a positioner; usually, an electromagnetic valve needs to be added.
That’s how things work in our factory: we install a solenoid valve to allow rapid exhaust during fast shutdown
Sure, as long as the speed of operation is sufficient, solenoid valves, pneumatic control valves, speed boosters, and similar components can be used
I’m not sure if there are any regulations in this regard, but the systems that our company needs to shut off urgently are those with dual valves: a control valve is used to regulate the flow rate, and an additional shut-off valve is placed in front of it. Moreover, by installing a shut-off valve on the main pipeline, the bypass can also be cut off.
The text is intended to specify the leakage level requirements for control valves. If participating in a chain, the leakage level should be increased. Any valve serves as a shut-off point, but ball valves have higher reliability than direct-acting valves. If the control valve is involved in interlocking, it is possible to: 1. DCS interlocking can be achieved through positioners or solenoid valves. 2. SIL 1 interlock, control valve + solenoid valve – this is generally sufficient to meet the requirements. 3. For SIL 2 interlocks, two isolation points are required. If a control valve is already available, adding an electromagnetic valve to that valve along with another isolation point, usually in the form of a ball valve, generally meets the requirements. If this cannot be done, perform a stroke test on the ball valve and the actuator.
The leakage level of control valves is the minimum of the pressure difference and 0.35 MPa; the airtightness test for shut-off valves is different, right?
Some control valves can be used as emergency shut-off valves