Why you should use 81346 for your reference designations
Many engineers are tempted to design their own tagging systems. I’ll make it intuitive, they think. I won’t make the same mistakes that I’ve seen on all the other tagging systems. I’ll make it flexible, yet consistent across everything across this system.
They will most likely assign letter codes first. M
for motors, PU for pump, FN
for fans, XV for on/off valves, SN for
solenoid, R for relay, CB
for circuit breaker, CP for compressor
etc. Numbers are then assigned, often with meanings: 100 for
line 1, 200 for line 2, etc.
It starts off great. 100PU01 for the
first pump in line 1. 200PU01 for the first pump in
line 2. There are only 5 lines, so the other numbers
are used for other systems. There are no free numbers. The
a pump is added between lines 1 and 2. What number do
you give it? There are more than 50 items in line 1, so you
can't use 150 as a number.
Suppose something else happens. The tag system links the
motor to the pump
In desperation they might assign the compressor to be CP101, so that they can make CB100 go to PU100, and then CB101 go to CP101. But this means that the pumps start at 100, while the compressors start at 101. Then they want to assign a letter to a control panel. ”How about CP?” No, that’s already assigned as a compressor. Add in a few last minute design changes, and the system is no longer intuitive.
The tag system is broken, and it will only get messier over time. You eventually need an extra document that tells you what the exceptions are.
Everyday usage
You probably use a great reference designation system every
day without thinking about it. If you are telling someone
where to find you, you probably are using the postal address
system. If they are in the same city, you'll give them the
suburb, street, number, and maybe a unit number. If they are
in the same suburb, you'll just give the street and house
number. If they are in another country, you'll give the
country, state, and postcode, along with the other
information. You can make more designations. If you are both
in the same house, you can tell someone where to find a roll
of cling wrap. In the kitchen, third drawer down, on the right
hand side.
You could use latitude and longitude, Melways reference, or
What Three words, but under most circumstances, the system
described above is convenient and accurate.
IEC/ISO 81346 uses the same principles. Tags or Reference Designations have the same tree like structure, with the implied part of the branch omitted. For example, a relay might be physically labelled K1. There will be many relays marked as K1, the same as there are many houses marked as No 10. However, since the panel that they are located within have different tags, the same as streets have different names, an unambiguous reference designation is achieved. Yes, there are may be duplicate streets, but these will be in different suburbs. The same is true for control panels. You can have more than one U1 control panel, as long as the reference designation above it is different
Where IEC/ISO 81346 differs from the postal address system is
that it allows different aspects. Addresses only use locations
and sub locations to designate a place. IEC/ISO 81346 uses
three aspects.
The Three Aspects
IEC/ISO 81346 uses three prefixes allow you to split your
system by function, location or product type.
- = Function: What the object does.
- + Location: Where the object is physically located.
- - Product: What the object is (the specific component).
The reason for this is that an industrial system is different
to an addressing system. Items that may be physically in close
proximity to one another may not be related functionally, or
items that are functionally related may be physically
separated. You also care more about what the item you're
referring to physically is. In the postal address system, we
don't really need to differentiate between a unit, house, or
empty block of land. In an industrial installation you do want
to know the function of a device (=), and whether an item is
part of the cooling system, or safety circuit.
You also care about what type of device it is (-), whether
it's a circuit breaker, contactor, etc.
Going back to the house example, while the power points
(GPOs) in the electrical system can be related neatly to the
location (room), the cables cannot. For the wiring system, it
makes more sense to break it up by function rather than
location.