Meaning of "high high" alarm 2

[skuntz]

How does a "high high" alarm differ from a "high" alarm?

 

[zdas04]

"High high" is physically higher in the vessel than the "high" alarm. The only reason for two set points is that they do different stuff. Most often in my experience, the high level gives you an alarm, but no process changes. The high-high is often connected to a shutdown or some other major process change.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist

 

[danw2]

Agreed. Lots of people use the terms high, high-high, low, or low-low for process values that are not level elevation, but for any process: flow, temperature, pressure, whatever.

 

[phteven]

Really the difference is dependant on what you do with them, like having 2 switchs in one. A "high" and "high high" can be the same as "low" and "high'. But generally the "high high" is of greater magnitude than high.
Example: you might have a system monitoring vibration on an agitator that allows 4 alarms to be set for each probe. "low' "low low" "high" and "high high". the high is set at .25 in/pk s and the high high at .4 in/pk s. The high would be an "alert" however the high high would be a "trip".
Note: a high high alarm could be on any variable like a temperature were "high" is 100degrees and "high high" is 50degrees counter-intuitive
Basically the idea is that High High is of greater significance than "high" and therefore represents a greater response ie high - alerts or warning "high high" - trips and Dangers.

 

[wde0665]

In a hopper filling application - the low and high can be used as the signals to start and to stop filling. The low-low and high-high can be used to stop the process to avoid either running the hopper empty and upsetting the recipe, or to prevent overfilling the hopper. During typical operations, the low-low and high-high serve as protection in the event of failure of either the low or high signals - the process is stopped and one can see that the extreme signal came in without the normal signal first.

 

[mcgyvr]

clearly the controls industry isn't too creative.

"well what are we going to call the alarm higher than the high alarm"...
"well the high-high alarm of course"..

"ok.. well whats greater than that.."
"The high-high-high alarm obviously"

 

[PeterKsiazek]

I guessing the "Oh Sh*t" alarm was already taken.

 

[ScottyUK]

That one occurs right before the "Run like f*ck" alarm. :-D

 

[Gadgit]

My current system uses 'Warning' which just notifies the user, and then 'Critical' which causes the process to shut down. Some of these may be literal high alarms, and others are low values.