Faults in process industries

Hello,
I a student working on Fault tolerant control in process industries. ("Fault tolerant control" tries to keep process/controller running in
case of faults, by retuning existing controller, reconfiguring/ redesigning controller or replacing measurement from faulty sensors by estimated values)
I am seeing very hi-fi mathematics while reading paper but I don't know what are actual faults in process industry and what is done in such faulty condition.
Can you people please give me some examples of faults. Also, please say me what is done in such cases.
Thank you.
Rahul
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few faults and solution in such case are, 1)connection between controller and actuator fails (solution to it is go for manual mode) 2)if pump fails (and there is no stand by pump) shutdown the plant. 3)If sensor fails (replace it with estimator but to me it seems theoretical concept. I doubt that in industry it is used) I am also student so verify my answer with someone.
Suraj
On May 9, 8:20 pm, snipped-for-privacy@gmail.com wrote:

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On 9 May 2007 17:37:37 -0700, snipped-for-privacy@gmail.com proclaimed to the world:

All these are faults. The third is done in industry. Fault tolerant means that the system keeps the plant running when there is a fault. Fault tolerance can be built into the mechanical design too.
An example of controls fault tolerance - A distributed control system designed to keep a subsystem running even though the supervisory control signal is lost from the main control station. Redundancy in both the sensors and controller aid in designing fault tolerant systems. An aircraft is designed this way. The tradeoff is cost.
A less obvious example would be to program a PID controller so that if system stability became a problem, the controller reverted back to less sensitive settings or even converted into an on off system.
Another example - A lift pump station that used variable speed drives. If a VFD fault is detected, then the system reverted to an on/off system, starting the motors using separated contactors across the line.
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few faults and solution in such case are, 1)connection between controller and actuator fails (solution to it is go for manual mode) 2)if pump fails (and there is no stand by pump) shutdown the plant. 3)If sensor fails (replace it with estimator but to me it seems theoretical concept. I doubt that in industry it is used) I am also novice in the field so verify my answer with someone.
On May 9, 8:20 pm, snipped-for-privacy@gmail.com wrote:

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Hi, there are many faults that can occur in plant. I can see few of them.... (s/d = shutdown)
1. Compressor failure - depending upon the service decision is taken - say H2 compressor - then plant s/d, if recycle gas compressor then partial s/d etc ....
2. Pumps failure - feed pump - then s/d product pump - depending upon level in the column / surge drum and expected time for switch over to a redundant pump , s/d or manual operation can be decided
3. Instrument air - no control, many times auto s/d initiates
4. dcs failure - (power outage / card failure) - emergency trip
5. utility failure - n2/ steam/ colling water / power - many times emergency trip - in some cases for cooling water, power & steam we can pull on for some time
Hope this helps...
Curious
On May 9, 8:39 pm, snipped-for-privacy@gmail.com wrote:

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