Differences between process valves and instrument valves
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How to distinguish between process and instrument valves! Encountered an interesting issue (in a foreign company): The pressure in the ethylene tank was 9 MPa. The pressure gauge was damaged, so the instrumentation technician shut down the root valve and used a detector to confirm that there was no leakage; afterwards, the gauge was removed and replaced! OK! But this assignment requires discussion – to whom does this root valve belong? In my understanding, only one valve should belong to the instrumentation system. However, if the pressure in the tank is high and there is a leak, it can be dangerous; so maybe another valve should be added for process control purposes. This should be taken into account during the design phase, or the tank could be emptied (but that’s not practical). Please help with the discussion! Difference: This post was last edited by hw197358 on 2009-4-7 14:38.]
For one-way valves, the instrumentation department is responsible; design, installation, and maintenance are all handled by this same department. In the case of ultra-high voltage systems, two additional pressure-taking valves are used, but both of these valves are also under the responsibility of the instrumentation department.
The calibration of pressure gauges is the responsibility of the instrumentation department, while everything else falls under the responsibility of the process department.
Aren’t the answers on floors 2 and 3 contradictory? What is the basis?
Petrochemical companies’ maintenance departments all have equipment management systems (regulations), which should contain detailed provisions regarding the classification of process and instrumentation devices. Generally, in CNPC and Sinopec*, instruments with local displays such as pressure gauges, bimetallic thermometers, and glass panels are classified under process piping； Remote (cable-equipped) and base-type control valves are classified under instrument piping. However, during the capital construction phase, all instruments were designed and installed by the automation team
This root valve falls under process management in our unit.
I think it’s best for someone who is familiar with both the manufacturing processes and the instruments to make these decisions, so that accurate solutions can be found; after all, these two aspects are inseparable
Valve maintenance should fall under the category of instrumentation; as for whether an additional valve is needed, that is a process-related decision.
For purely mechanical pressure gauges, in our unit, the operators on duty are responsible for disassembling, assembling, and replacing them, as well as sending them for regular inspection. The instrument operators don’t need to worry about it.
Root valves should be under the control of instrumentation, especially those used with pressure gauges; they should not fall under process management.
You can refer to the instrumentation installation manual for chemical industry standards, which outlines the responsibilities.
If we have to be precise, the root valve should be part of the process control system, and both isolation and restoration operations should be carried out by the personnel in charge of the process. We’ve had problems because of this here
Since it refers to tanks, the valves should first be provided by the equipment supplier; generally, the process department is responsible for their procurement and management. But if this interface is determined to be a thread or a flange, it becomes a bit more complicated: the first thread or flange interface can serve as a boundary, and the valves that follow could belong either to the process side or to the instrumentation side. If it is welded, it mostly falls under process pipes. Of course, if one insists on installing a root valve for the instrument, it definitely falls under the instrument piping. There are also configurations like this: one process valve + one process valve, or one process valve + one instrument valve. It belongs to whoever is in charge, as the name implies.
According to foreign design practices, root valves are considered part of the pipeline design scope. Now, chemical engineering design institutes are also adopting these foreign practices; however, production management is a separate matter. The maintenance of root valves should fall under the purview of process engineering, while their operation should be handled by the instrumentation department. Otherwise, process engineers will have to assist the instrumentation maintenance staff, which is unnecessary for simple operations in order to save manpower.
The management structure varies from one unit to another; sometimes the process and instrumentation teams argue over responsibility, with the supervisor deciding whose responsibility it is.
The management of each company is different, and the scope of division may also vary. So it still depends on the situation of your own company; you can sit down with the relevant team members to decide this matter – it doesn’t matter who is in charge. Doing your job well should be your top priority; otherwise, your year-end bonus might be reduced. Hehe.
Refer to \"Design Division of Automation and Piping Specialties\" – the root valves for instruments fall under the responsibility of the piping specialty.
All the root valves in our plant are part of the process piping. When dealing with instrument issues, a process engineer must be present, as it is explicitly stipulated in our factory’s rules. Personally, I think it is very necessary to do this; after all, the instruments are not as familiar with the manufacturing process as the operators themselves. When process-related issues arise, it is possible to communicate and exchange ideas at any time, as well as supervise and remind one another, thereby preventing accidents from escalating and ensuring that faults can be resolved safely and effectively.
The valve at the root of the instrument pressure guide tube is the primary valve, which is under the maintenance responsibility of the process department; all valves located after the primary valve fall under the responsibility of the instrumentation department.