Reader David H writes:
Are there pre-defined letter codes for the function aspect like there are for the product aspect?
Yes, the same designators that an electrical engineer or designer would use to identify devices in an electrical system (81346-2) can be used to identify the functional aspects of a design. As a control systems engineer I often use the identifiers found in ISO 81346-2 Table 2 to identify the part aspect (+) of the devices in my projects. However the more generic “parent” identifiers are often used as functional identifiers; see ISO 81346-2 Table 1
ISO 81346-1 was created to help standardize this process; the full name of the document is: “Structuring principles and reference designations for Industrial systems, installations and equipment and industrial products“
The standard (81346-1) does not mandate what designators you should use but it does encourage the use of the standard identifiers found in 81346-2.
The choice of identifiers is left to the design team and in many situations there are other influences that can impact the desired identifiers that include corporate legacy codes, industry standards and common conventions as well as many others.
It should also be mentioned that in certain types of systems the process flow should also be considered. If I were to consider two very different systems; a large boiler and a bottling line for example, in my mind I will quickly see two very different process flow diagrams. The one for the boiler will be very centralized (generic) with many functional sub systems surrounding the central boiler vessel. The bottling line on the other hand will be very sequential, Raw materials at the beginning followed by several process stations and then the end of line packaging.
Since the boiler plant is centralized it would be my inclination to prefer an identification system that uses a letter code from 81346-2 table 1 followed by an incremental counter, the letter code will identify the general function of the sub-system and the incremental counter will allow you to keep track of many functionally similar sub systems. Also the fewer letters the easier it is to remember what it is.
=G1: Electrical Power System
=W1: Material Handling Station 1
=C1: Ingredients Storage system 1
=F1: Fire Suppression system
In the case of the bottling line I would see the very sequential process flow diagram in my mind and I would be inclined to go in a different direction. Since the machine operates in a highly sequential manner I would want to use a numerical identification system. The area where raw materials enter the process flow may be numbered as process stations =100 to =199, the process cells in the middle of the machine might have identifiers such as =500 & =570, and the end of line packaging stations might have identifiers such as =900 & =1500 or whatever makes sense for your machine.
You will also need to consider functional systems that I refer to as infrastructure, these are systems that are part of the building that are also part of your manufacturing line, common examples are; Fire Suppression, Lighting, HVAC, Environmental monitoring, Drainage, Comms Networks and many more. I would also assign identifiers to these systems often using numerals of less than 100 but that’s just my personal preference.
=10: Power Distribution
=30: Building Fire System Circuits
=100: Ingredients Loading
=207: Ingredients Storage system, Hopper Group 7
=403: Bottle Washer; Line #3
=802: Packaging Robot line #2
We have until now been considering system level designs but I often create machine electrical designs using the same principals.
=10: Power Distribution
=101: Motor Circuit 1
=105: Motor Circuit 5
=401: Water Chiller 1
=600: Operations Station
You are free to create your own system that makes the most sense for your application, just remember to document what you decided on and include it early in your design for others to reference.