I am a native english speaker and I am sometimes confused about these terms too. Generally speaking these terms are used interchangeably. They all mean about the same thing.
A "shutdown" is a planned or automated plant shutdown i.e. the processes are halted. This may be scheduled for maintenance, or in response to an automated sequence.
"We have a two week shutdown for maintenance in January."
An "outage" is an unplanned event where the plant shuts down in an unexpected manner or for an unexpected reason.
"Thousands of families suffered a power outage in the Florida are as a result of Hurricane IVAN."
I would iuse the term "shut-in" where all the workers (students) decide to shut themselves in i.e. occupy the premises, for a protest...
[/i]"Students in Manchester staged a shut-in today when they occupied University lecture rooms as a protest against cuts in education spending."[/i]
To me a down-turn is where the production is cut back or where the market is in recession. "Thousands of steelworkers were laid of as a result of a downturn in the steel market."
...and...
"Unless there is a turnaround in fuel costs, many in the shipping industry will lose their jobs as companies struge to cut costs."
Others may understand some of these terms differently.
jmv, I think you pretty much gave the definitive definitions!
May want to add "turndown" as another beautiful confusing term beside downturn, turnaround, etc. Turndown being the minimum capacity of a processing unit (in the broadest sense, e.g. a distillation tray) as a percentage of its max capacity.
Epoisses,
"Turndown" is also used to describe the rangability of a flow meter. "The turbine meter typically has a turndown of 20:1 from maximum continuous linear flow."
But this is essentially the same meaning as you have given but applied to a meter rather than a process.
In addition to what JMW explained I could only add (taken from dictionaries):
1. "Outage" in petroleum engineering is the difference between the full or rated capacity of a container (barrel, tank, truck, etc.) as compared to the actual content.
2. "Shut-in" pressure -again in petroleum engineering- is the equilibrated reservoir pressure measured when all the gas or oil outflow has been shut off.
3. "Turnaround" in petroleum refining is the shutdown (i.e., suspension or cessation of operation) of a unit after a normal run for maintenance and repair work, then putting it back in commission.
Experts and english speakers are invited to comment.
Turndown is not just limited to flow meters. Any device that has a finite or limited range of operation has a "turndown" ratio.
A device that can range between 2% and 100% capacity would have a 50:1 turndown ratio. 10% to 100% would be 10:1 turndown ratio.
Desuperheaters come to mind as a device with such a nomenclature.
"Shut-in" is a term that one will hear used many times in the next few days to refer to the oil and gas production platforms in the Gulf of Mexico that will be taken off line while Hurricane Ivan is in the area.
I work in a variety of industries, and have to be careful as to when to use "shutdown" "outage" or "turnaround". They all mean the same thing, but their usage is specific to different industries.
