Request for Wireless Engineering Drawing Standards (P&ID's and Loopsheets)

ANSI/ISA5.1-2009 was issued in September of 2009. It does in fact show the sine wave or the "saw tooth" (with an arrow) as the acceptable symbols for wireless signal transmission. Since the sine wave symbol existed previously for "unguided signal" (e.g. radar, ultrasonic), many people are using at the new saw tooth symbol for wireless.

That said, there are no standards yet to my knowledge, for documenting wireless systems. In other words, instead or point to point wiring drawings, what drawing form should be used to document all of the wireless transmitters in a plant and how they are networked?

Jim F.

I received an email back from one of Emerson's fieldbus consultants, Dan Daugherty (http://bit.ly/dyOnm):

An ISA committee is currently working and will publish guidance on the use of these symbols.

In summary, they say the sideways S (sine wave) symbol or the /\/ sawtooth symbol beside the bubble should be used and some folks are leaning to the sawtooth.

I asked the head of the committee to clarify if the line had to be connected from one bubble to another, and he said yes, but that some people only put the “line” for a ways then show a line break symbol (looks like a vertical S) and then let the line continue at the next bubble.

My personal comment is that engineering companies lately have not been following strict ISA symbology in terms of connecting the lines. The overall trend in real practice is to reduce all symbols to the bare minimum. This usually means no connecting lines at all, but relying upon the tagnames to infer loop connection (e.g. PT-109 and PV-109 are inferred to be in same loop because same loop number).

Beyond that, the traditional loop sketch that shows process equipment, and items in loop plus wire connections plus DCS “logic” are rarely used anymore. These days “loop sketch” is effectively same as hook-up drawing, with one-line representing multiple wires, and terminals shown where wires land. DCS logic is not shown here anymore, because that is considered to be self-documenting in the DCS configuration programming. Since wireless has no communication or power wires, what was the hook-up diagram style “loop sketch” can be accomplished by a simple table (spreadsheet) for each gateway, listing the devices associated with that gateway. It seems that is also just as easily done by adding a column to the instrument database so no separate “drawing” is needed.

On location plans, the typical symbology is a solid black dot. If some want to re-shape the dots to hexagons, etc. for their own purposes, then that is their business. Do wireless devices need to be distinguished on location plan? I say no. The only value in distinguishing is so the designer can guess at location for a gateway based on visual perception of wireless devices’ location. That is better done by using drawing layers, to turn on/off dots for devices on a certain gateway, and then it is easy to locate the gateway.