instrumentation control pilosophy

[Lancie1]

i want a standard form for wiriting instrumentation control pilosophy

Back to the original want, I have never seen a standard form for writing any type of control philosophy. A control philosophy is by nature dependent on each plant or system. There are some common items, but listing things that are common for all systems is just rehashing the hash, chewing your tobacco twice, or restating the obvious.

It is the things that are going to be different or special that you need to mention in your Instrumentation Control Philosophy for ______ (the blank is where you fill in for WHAT it is going to be used).

 

[V0N_hydro]

- ultrasonic level technology for open channel flow only, no covered tanks or pressure vessels

Can you elaborate on why?

Usually I see pressure transducers used for measuring water level but my last project they used vega brand ultrasonic in an 8" diameter tube. Tube may be air tight and that might be one issue.

Two out of three of the stilling well tubes are outdoors and temps are down to -20, and the two which are outdoors are erroneously reading 100% scale for days at a time.

Curious what experience you have with ultrasonic for non open channel.

 

[harryting]

Just guessing, but I had issue with ultrasonic in tanks due to steam. Radar works better in those situation.

 

[V0N_hydro]

I think I actually have radar sensors not ultrasonic. Now I see there is a difference between them. I have been told they poured some type of bio-oil in the stilling well to prevent the water from freezing. That would create an air-oil interface as well as oil-water interface which might confuse the sensor.

 

[danw]

To me, the concept of an instrumentation philosophy is expressed not as a written document of a company's philosophy, but as requirements for instrumentation, either written or verbal. Those requirements generally come from site experience.

For example, "We got a treatment skid in and it had a couple Profibus devices on it. We couldn't do anything with those. From now on, no Profibus, no matter what". The experience gets translated into a philosophy expressed as a requirement on an RFQ, "level transmitter output must be 4-20mA analog with HART, not Profibus, Foundation Fieldbus, nor Modbus".

In the example for ultrasonics, there are people who want to do all top mounted non-contact level measurement with radar because they've had a bad experience with ultrasonics. Radar has its problems, too, but it generally isn't as fault prone as the first 2 or 3 generations of ultrasonics were in the 80's and early '90's.

Banning ultrasonics is not my philosophy; it still works very well in many applications. I just listed it as an example, like all the others, because it's something I hear when I talk to customers or read their RFQs.

Dan

 

[dginbuffalo]

OK now I have to ask. Did Badger really give dginbuffalo a yacht? and what's the ETA from the UK to Buffalo, via the pond, St. Lawrence then to Lake Erie I guess

My yacht just arrived!!

 

[Nova5]

2+2=5.
It'll work fine.