Should the shafting instruments of large-scale units be connected to the ESD or to the DCS?

Since ESD points are so expensive, it’s sufficient to incorporate the shutdown or operation signals of a large unit into the ESD; other calculations can be carried out in the DCS. For example, centrifugal compressors usually use ITCC control systems, and DCS is only introduced in a few specific areas; there’s no need to implement it everywhere.

Typical shaft system instruments come equipped with AO and DO outputs; therefore, the most cost-effective approach is to use the DO outputs of these instruments to send high-level interlock signals for shaft vibration and shaft displacement to the ESD system, so that they can be used in the interlock logic. As for analog signals, if the instrument has a 485 communication interface, it can transmit data to the DCS; otherwise, the AO output is used to send the data to the DCS.

It should be the critical signals that go into ESD; ordinary signals need not be included. All shaft system instruments that are involved in interlocking are displayed directly on the ESD, while those that are not part of the interlocking system are displayed directly on the DCS – this is correct

Key points and interlocking points need to be accessed via ETS, while normal monitoring points can be accessed via DCS

Large-scale units generally use ITCC control, which incorporates ESD functions; all monitoring points of the unit are connected to the ITCC system. The shafting instruments are connected to the ITCC system via 3500 converters in order to communicate with the DCS.

The ESD emergency shutdown system is designed to ensure safety during the production process; it is suitable for applications involving continuous production under conditions of high temperature, high pressure, and in environments where materials are flammable or explosive. When unexpected fluctuations occur during the production process or emergencies arise that require certain actions to be taken or the machine to be stopped, this system can monitor the situation accurately and respond in a timely and precise manner, bringing the equipment to a safe level and ensuring the safety of both the equipment and the people involved. ESD and DCS are completely separate. DCS is mainly used for the dynamic control of process industry parameter values. Under normal conditions, the DCS continuously monitors the production process to ensure that high-quality products meeting the requirements are manufactured. ESD, on the other hand, involves continuous monitoring of certain key process and equipment parameters; under normal conditions, ESD remains \"inactive\" and takes no action. However, when the parameters experience abnormal fluctuations or failures, it will take corresponding safety actions according to the established procedure to bring the device to a safe level. Therefore, ESD and DCS play different roles in the process industry; they have distinct responsibilities while also complementing each other. At the same time, ESD is not merely used to establish interlock relationships; it should operate independently of the production process control, which reduces the likelihood of both systems failing simultaneously. The safety level of ESD is higher than that of DCS. So it’s clear now which ones should go into which system!

In the case of large-scale units, although shaft system instrument parameters (such as shaft vibration and shaft displacement) are important parameters of the unit and are involved in the interlocks for its control. But it is not necessarily necessary to go through ESD; the key is to determine whether the start-up and shutdown of the unit will have an impact on the safety of the entire production facility. For example, the dark horse ESD system for the methanol project does not contain parameters for large-scale units (coker gas compression units, syngas compression units).