Are tasks such as drying/fluidization/packaging required on-site, necessitating a PLC, or is a DCS sufficient?

When there are many digital inputs and independent control is required, PLCs are generally used, as they are inexpensive; there are few compact versions of DCS.

It depends on the conditions of your company as well as the safety level of the production environment; if Siemens 400 is used, there’s basically no difference from using a DCS

Count the analog points and digital points. If there are very few analog points, use a PLC. It mainly depends on whether the temperature, pressure, and liquid level you control change frequently and drastically, and whether such changes affect your operations. If these analog parameters are important and there are many of them, then use a DCS

If drying/fluidization/packaging are all part of a complete set of equipment, then if you want to use a DCS to handle the control procedures, the supplier of that complete set of equipment will be unhappy, as such equipment may also involve matters related to trade secrets.

In short, it depends on the importance of the control points. If redundancy is required, then DCS is the only option; PLCs cannot provide redundancy. If redundancy isn’t needed, then choosing a PLC is a more cost-effective solution. Generally speaking, DCS is more expensive

1. Maintenance and usage perspective: Most of these systems are available as complete sets of equipment, and the manufacturers of such sets usually have their own programs, which are quite mature and allow for smooth operation. However, considering future maintenance, it is important to avoid situations where the manufacturer locks down the programs and prevents access to them. Moreover, if there are no people familiar with this aspect, maintenance will become dependent on others. Therefore, when choosing a PLC, it is essential to ensure that the manufacturer provides the source code along with backup cards for the programs； 2. Investment cost: Taking Siemens PLC as an example, for large-scale complete sets of equipment with around 400 I/O points, a CPU with 400 channels is sufficient; the 414 model will also work. Additional 300 series cards and the ET200M can be used for further configuration. For smaller systems with around 200 points and a high proportion of digital inputs, a 200 series PIC is adequate ； If DCS is chosen, there is a framework available for the entire plant; it’s from the same manufacturer, and the price is quite reasonable. Installing it separately isn’t appropriate; instead, program transplantation and custom configuration are required, which is time-consuming and labor-intensive. The advantage, however, is that it facilitates maintenance and management ； In summary, each option has its advantages and disadvantages; small chemical plants should consider the PLC solution, while large-scale chemical plants, with their need for comprehensive planning, are advised to opt for DCS. For your reference!

There are countless explanations online about the differences between PLCs and DCSes, so I won’t go into detail. The key point is that DCS facilitates changes by the owner, while PLC facilitates encryption by the supplier.

The most important thing here is to look at the wallet. I’ve seen a fuel depot that uses Yokogawa DCS: lol

PLCs can now also be made redundant; the Siemens 400 will do

Siemens’ DCS is PCS7; although many of the cards used are those from the 300PLC