Questions about the solenoid valve when the regulating valve is shut off with interlock

Generally speaking, the interlocking valve should be required to move fast enough. The solenoid valve should be added behind the positioner. If it is added in front, it will first come through the positioner and then exhaust the solenoid valve. The exhaust speed is not fast enough. If DCS control is used directly without adding a solenoid valve, the small amount of air output from the positioner cannot meet the time requirement of this interlock.

When setting the start interlock in DCS, a fully open or fully closed signal is given to the regulating valve, which cannot guarantee quick shutoff.

If you don’t know something, you should humbly ask the design institute for advice. The design institute’s answer proves your knowledge.* manner. This kind of behavior is common among newcomers. When they come up, they first treat similar things with a censorship mentality. This is on the diagram, and some is on the device. After I came here, I didn’t ask for advice from an open-minded standpoint based on principles. * , but start to find faults before you understand it, and you must standardize it,,,,,,. Learn with humility * , communication and communication should also adopt this attitude. Settings like this are general, mainly for speed considerations, otherwise they are in the scope of adjustment. Well-intentioned suggestions for reference.

Chain and DCS are two systems and should be set up separately.

　　The regulating valve has interlocking shutdown, which must be achieved by adding a solenoid valve between the regulating valve and the positioner. The reasons are: Sometimes the positioner moves relatively slowly (the output power of the positioner is usually a fixed value, while the diaphragm heads of the regulating valves vary in size) and cannot meet the "fast" requirement. ； The positioner input-valve position relationship is often not very accurate, and when the difference is not very large, it may not necessarily affect the system operation without being noticed (in actual maintenance, it is often found that the positioner needs to be adjusted during shutdown and maintenance, which can prove this), so it is not necessarily reliable to realize the control valve shut-off through the control signal of the positioner ； The reliability of the safety interlock requires that the interlock action signal and the fault signal be consistent (the form of the interlock action signal is consistent with the signal line breakage), and the positioner's closing signal is 4mA or 20mA, which cannot meet this requirement. 　　The above analysis is not necessarily comprehensive, but it should be done as required for the chain system.: There is a power outage in the control room or the signal line from the control room to the regulating valve fails (such as: The regulating valve can ensure shut-off when the bridge is broken), and it must also have universal guiding significance (form a specification). "The regulating valve has interlocking shut-off, and a solenoid valve must be added between the regulating valve and the positioner to achieve it." This has become a principle that must be followed. .

Solenoid valve is a requirement in SIS

Adding a solenoid valve is the best choice and can withstand inspection. Since it is an interlock, it is an emergency trigger. For small valves, the action time of the interlock and the signal given to the positioner to fully open or fully close are almost the same. The big valve has a time lag. If designing from the beginning, please add a solenoid valve. If it is modified, turning off the positioner is only a temporary measure.

Currently in the petrochemical industry, DCS performs BPCS tasks； SIS performs interlocking action, and its quick shut-off valve is additionally set.

1. HGT-20507 stipulates that the selection of 11.9.3 solenoid valves should meet the following requirements: Used in remote control, program control, interlocking systems, to realize automatic closing of gas lines, to open or close control valves. 2. SHT3005 In remote control, process control, interlocking systems, to realize automatic closing of gas lines, to realize automatic closing of regulating valves, etc., low-power (less than 4W) three-way or four-way solenoid valves should be used. Special regulating valves may not be suitable for low-power solenoid valves. 3. In the company’s corporate standards: If the control valve, as the final component of the SIS interlock, has SIL level requirements, the solenoid valve needs to be activated, and the corresponding controller needs to be manually turned on to give the corresponding output. Under normal circumstances, control valves with DCS interlock action without SIL level requirements do not require solenoid valves. When operating, the corresponding controller is manually turned on and the corresponding output is given. Combining specifications and company requirements, and comparing with P&ID practices, the configuration recommendations for solenoid valves are as follows:: 1) Regulating valves participating in IPL (whether DCS or SIS) interlocking should be equipped with solenoid valves ； 2) There is no shut-off valve in the pipeline of the regulating valve, and the process considers that the interlocking requirements for this operation are relatively high (the solenoid valve can be understood as the hard switch of the light, and 4/20mA is the knob of the light), so a solenoid valve can be considered.

If a solenoid valve is equipped, it is recommended to equip it with valve position feedback (HART protocol can feedback position) A: 1. HGT20507 11.9.4 Valves used in interlocking systems (operating interlocking, safety interlocking) and sequence control, and where feedback of valve position is required, a valve position switch should be equipped. 2. It is stipulated in 10.1.2 of SHT3005 that when e) indicating the open and closed status of the regulating valve, a limit switch should be used. The limit switch type should be proximity dry contact type or NUMAR type. Regulating valves with solenoid valves must have at least one limit switch with interlocking position indication. f) When it is necessary to monitor the precise valve position of the regulating valve, a valve position transmitter should be used. 3. In HGT20511, the final component in 4.4.1 should have feedback output for interlocking action (Note: For control valves, the feedback output position is the interlocking position of the valve. ； For the motor, the feedback output is the interlocking status of the motor) From the above specifications, combined with the actual situation of the company, it is recommended that the IPL regulating valve be equipped with a solenoid valve and also equipped with position feedback of the interlocking position. For regulating valves that participate in SIL2 and the owner thinks there is a need or requirement, they are equipped with a valve position transmitter.