PID interlock and instrument issues

As shown in the image, XY10601A/B is a pressure transmitter that converts pressure changes in the medium being measured into standard electrical signals for output. It works by using inductive sensors to convert pressure signals into mechanical displacement signals, which are then converted into electrical signals by electronic components for output. This type of instrument is widely used in industrial control systems, playing a particularly important role in PID interlocks. .

This post was last edited by mutianly on 2023-5-24 08:37. Is there an explanation of the design principle for solenoid valves? Using two solenoid valves creates a certain relationship between intake and exhaust ； When the redundancy guarantee signal is set to (s), the valve operates; even if one of the solenoids is damaged, the valve still functions.

I think it’s a three-way solenoid valve, whose function is to lock the air supply to valve xv-10601 based on certain logical relationships.

Yes, two three-way solenoid valves are used in parallel to improve reliability.

When the interlock signal is issued, it is necessary to shut off XV-10601; the signal is sent to solenoid valves A and B. These solenoid valves close, and the air supply is released through solenoid valve A, causing the valve to close as well. If A does not receive a signal while B does during this process, the shut-off valve will not close.

The two solenoid valves operate in interlocked fashion according to fail-safe design. 1. Under normal conditions, the A/B solenoids are powered; air from source IA is supplied to the cylinder valve through solenoid A (not in DE state), and solenoid B is also powered (not in DE state) ； 2. If solenoid valve A is faulty (DE state) and solenoid valve B is functioning properly (not in DE state), the air supply IA passes through solenoid valve B (which is not in DE state) and then reaches the cylinder valve via the faulty solenoid valve A (in DE state) ； 3. If solenoid valve B is faulty (DE state) and solenoid valve A is functioning properly (not in DE state), the air supply IA supplies air to the cylinder valve via solenoid valve A (not in DE state) ； 4. In interlock mode, the interlock signal is sent to both A/B solenoids simultaneously, and if both solenoids are functioning properly, they will both enter the de-energized state (DE state). The cylinder valve has its pressure released (VENT) through solenoid A and solenoid B.

Bro, to be honest, I’m afraid what you’re saying isn’t correct

If this valve operates in the fail-open mode, it can be closed whenever either solenoid valve A or B is powered. The valve will only open when both A and B lose power, which serves to prevent the valve from opening automatically due to a malfunction in the solenoid valves.

XY10601A/B are solenoid valves, providing a degree of redundancy. Working principle: (Assuming the solenoid valves in the diagram are labeled Left 1, Right 2, and Bottom 3.) When the control signal is “1” (power on), the 1-2 connections of solenoid valves A and B become conductive; thus, solenoid valve B is in operation, while solenoid valve A remains in standby mode because there is no connection between 1-3 of solenoid valve B. The instrument air enters the pneumatically controlled valve directly through solenoid valve B, thereby controlling the operation of the actuator. When solenoid valve B fails, its 2-3 connections are established, while at the same time the 1-2 connections of solenoid valve A are intact; therefore, instrument air can still pass through solenoid valve A and then via solenoid valve B to reach the pneumatic control valve in order to activate the actuator. This ensures that the control air supply remains connected even if either of the A or B solenoid valves fails. 　　When the interlock signal is “0” (power loss), contacts 2-3 of solenoids A and B become conductive. The signal air for the pneumatic control valve is discharged to the atmosphere through 2-3 exhaust ports. At this time, a failure in either of solenoids A or B will result in the control air source being unable to be released.

First, let’s talk about the non-standard drawing practices… 1) The symbol for interlock is a diamond shape, but it usually contains the letter “I” inside it; if SS denotes SIS interlock, then one should refer to point 2). 2) In the instrument identification numbers for SIS interlocks, the letter “Z” must be included – for example, XV becomes XZV, and solenoid valves become XZOV, etc. 3) If it’s a SIS system, then all those SIS interlock actions involving XZV may relate to the same scenario and the same IE, meaning that the same valve might be used, which could lead to issues such as common failure points. The same applies to DCS systems; for more details, refer to the requirements outlined in AQT3054/GB. 4) If it’s a SIS valve, why does XV still have a handwheel? This depends on whether the standard HGT20507 or SHT3005 is being used. Generally speaking, there’s no need to equip stop valves with dual solenoid valves; there’s considerable debate regarding whether this is necessary, and different projects adopt different approaches. For specific details, refer to (1) 7.4.5 of GB50770: when high security is required by the system, redundant solenoids valves should adopt an \"OR\" logic structure (in series gas paths) ； When the system requires high availability, redundant solenoids should adopt an \"AND\" logic structure (parallel air paths). Draft for comments: 7.5.2 When high availability is required, control valves or solenoid valves shall have an available redundancy design, such that the operation of a single control valve or solenoid valve will not trigger safety interlocks. (2) The provisions in 4.4.3.2 of GBT50892 relate to the requirements for SIS valves. Installing dual solenoid valves can only improve the safety integrity level of the solenoid valve assembly to a limited extent; this parameter plays a very small role in SIL evaluations (the failure probability of solenoid valves in such evaluations is very low), to the point where it can be ignored. Therefore, if the scope of application and requirements of GBT50892 are not taken into account, there is no need to install dual solenoid valves. Of course, under the condition that SIL verification is met, parallel (or series) solenoid valves can be installed to improve availability (or reliability). It should also be noted that the availability/reliability of the pneumatic system depends not only on solenoid valves but also on components such as pneumatic relays and exhaust systems. Another theory is that one design is used for DCS control and another for SIS control; strictly speaking, this does not comply with the requirement of physical separation of independent systems or independent protection layers. It also goes against the original intention behind the use of dual solenoid valves. In certain scenarios, SIL1 can be handled in this way, but it is not necessary – using logical priority is sufficient. Regarding series and parallel solenoid valves, refer to the installation manual HGT212581, the explanatory notes in GB50770, etc