Please advise on the instrument control and DCS control for ammonia synthesis compressors
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Our company’s compressors are intended to operate in a manner that differs from the traditional approach. There are 7 reciprocating compressors, and we plan to install explosion-proof control panels as well as local instruments at the site where the compressors are located. A control room will be used to centrally control these 7 compressors via a DCS system. The electrical actuators will be placed in the low-voltage distribution room beneath the control room. The explosion-proof control panels will have start/stop buttons, and all signals from the local instruments will be sent to the DCS system. Currently, the compressor manufacturers believe that an additional instrument control cabinet is necessary; they argue that if there is a failure in the DCS system, it could lead to the shutdown of the compressors. What troubles me now is whether this additional instrument control cabinet is really needed – after all, wouldn’t it serve as a duplicate of the DCS system? Even with dual protection, will there be no problems with the control cabinet? Can’t control it just by using the DCS system? Isn’t gas production also controlled purely by DCS? Please advise, experts
The failure rate of current DCS systems is now practically negligible! Even as a more precautionary measure to prevent shutdowns caused by DCS failures, we can implement redundant control for the IO signals monitored by the DCS, and that will solve the problem. But I think you have seven compressors; if there’s a malfunction, it’s not possible for all of them to stop at the same time, right? When that person writes the control program, he writes it as: if one compressor stops operating, why should all compressors stop operating as well? Hehe... As LZ said, your company uses reciprocating compressors; such compressors definitely generate a lot of vibration and noise during operation. If they could be replaced with screw compressors, the results would be much better!
For renovation projects like this, the design institute will generally respect the technical requirements; it’s up to you to decide whether to proceed or not.
It is advisable to install a control cabinet with instruments for the compressor
Of course, it is necessary to have manual controls in place at the site
Is it too wasteful to use DCS? A PLC will suffice; there aren’t that many points on the compressor. Our factory has 8 compressors; using a PLC will suffice
It is necessary to set them up, and on-site operation is very important, especially during maintenance
The compressor units do not come equipped with a PLC control system, an ITCC, or an auxiliary control panel – let alone 7 units! For large-scale units like the ones I have experienced, almost all necessary components are required, in addition to a SIS as well. The focus of work then shifts to the communication between various subsystems and the DCS/SIS, as well as signal transmission, rather than focusing on the interlock control of the compressors themselves; this aspect of the work is generally handled by the compressor manufacturers.
For seven compressors, I recommend that the interlock signals be sent to the ESD system for regulation, while the display signals should go to the DCS system. Use a two-way safety barrier; all data should be available in both the ESD and DCS systems, or the signals sent to the ESD system should be communicated directly to that system. All controls are implemented using ESD.
Simple DCS control is sufficient; for more complex cases, ITCC control is more reliable~~