UPDATED (scroll to bottom for additions)
In Houston this year I was on the functional safety panel with colleagues from HART Communication Foundation and Fieldbus Foundation plus one user. The 45 or so attendees were mostly interested in hearing from the user and mostly about Foundation Fieldbus. To make up for that, I promised the folks there I would blog about PROFIsafe in more detail, so here it is:
PROFIsafe work was started 11 years ago and there are now more than one million nodes installed in 90,000+ installations. Although PROFIsafe covers discrete, motion control, and process, the vast majority of the installations are in discrete, factory automation applications.
Wireless. Because the PROFIsafe black channel approach ensures safe delivery whatever the media, wireless is just as safe as wired. An interruption of the wireless signal will trigger a go-to-a-safe-state command just like a break in the wire would. Check the application story from 2008 “Machine Building with PROFINET”.
Black Channel? In my system integration days I would occasionally need a “black box” to transform a signal into one I could use, say an incoming Type J thermocouple to 0-10VDC. I didn’t care what was in the black box; it just converted the signal for me. The Black Channel ensures that I don’t have to worry what’s inside, too. (Maybe a more modern analogy is VPN. VPN creates an encrypted tunnel through the communications network and unencrypts it at the other end.) Because of the Black Channel the user does not need safety-rated cable, connectors, Ethernet switches, wireless access points, etc. This is better with pictures; view them in our archived webinar on PROFIsafe (it’s free).
Why do safety over the bus? You get all the advantages of a fieldbus plus diagnostics and reduced testing requirements.
Fieldbus Advantages. The advantages include easier design and configuration, simpler drawings, reduced installation cost, and faster commissioning. We have a good application story you can read, “KUKA Reduces Machine Safety Components”. This company experienced an 85% reduction in the safety components needed and a very fast start up.
Diagnostics. This should be titled “Uptime” because that’s the benefit it brings. PROFIBUS and PROFINET have many diagnostic capabilities available. (We highlighted the PROFINET ones in a webinar: “Diagnostics for PROFINET and other Industrial Ethernets”.) Being able to quickly find problems allows you to get running quicker after a safety event. There’s even more uptime available because of the next item.
Reduced Testing Requirements. Patrick Flanders of Aramco was the user on the panel. He had a really good analogy for the type of constant “testing” that reduces the need to schedule downtime in which to test. When the traffic light unexpectedly turns red and you jam on your car brakes, you are sure it is going to stop… because you are always working the brake in less critical situations. Here in Phoenix the analogy fails because drivers will hit the gas in that situation, but you get the idea.
For further information: There is additional PROFIsafe information in past blog posts and some videos on YouTube, including this demonstration of PROFIsafe in process:
Off-topic reminiscing…
“And what was your impression of ISA Automation Week, Carl” you might ask. Like many, I suppose, who remember the glory days of the ISA Expo, this year’s event was quite a let-down. I can’t help but compare this year’s event with past events. I remember my first ISA Expo was in Philadelphia and I think we arrived in horse drawn carriages – not sure about the last part, it was a long time ago, mid 80’s maybe. Later, in my Wonder Years in the huge booth with 70-seat theater, the crowds were awesome. This year my first impression was not good – finding the venue was a challenge as was finding the registration desk. I already had my badge, but they had run out of lanyards. Lunch was in the exhibit hall from buffet tables, but there was no place to sit. And the exhibit hall was open only briefly: half hour in the morning and again in the afternoon plus for lunch. The big companies have all abandoned the event since they all have their own user meetings. And the low exhibit hall ceiling made me claustrophobic. Ah, for the good old days…
–Carl Henning
UPDATE: For more on ISA Week visit the Readout Instrumentation Signpost blog: “Debacle or basis for development?”