Dealing with Process Upsets
• Objectives– Will be able to recognize an Upset
– Will be able to analyze an Upset
• Review Question– Name some causes of “Process Upsets”
Ethernet TCP/IP
Fieldbus
1
Batch
Control
Software
PAM &
CPM
Services
Measurement
Devices
Scales
& Flowmeters
FBM
What is an Upset
• What do we mean by an upset?– Abnormal event that not is not likely to be repeated
– An event which is caused by external action• Operator leaning or stepping on scale• Unbalanced mixer• Sticky valve
– An event that must not affect our working parameter• Adjusting for an event will cause errors during the next feed
– Permanent change in the process that must be fixed• Ie partially blocked pipe
– Long term will show a step change of:• Ave Flow Rate• Spill etc
– Not always detected as could still be within limits!• May require further investigation
Class Exercises A
• Place weight on scale at end of feed before DrainTime Expires• Hint: weight could be a pen or eraser.
– View results
– Be sure to inspect the “Material Transfer Process” Screen
– Make a note of:
– Spill Status, are all three still green ?
– Feed Status; what did it say ?
– There should be some indication that this was an Upset.• Did you see it?
– Do a few more feeds:
– Did the Qi adjust and remove the error
– Hint: it may or may not depending whether you were outside the 100% limits or not
Class Exercises B
• Move scale enough to cause the “StableScale” light to go OFF while trying to start a feed– View results
– Did it start ? (it should not have started)
– Be sure to inspect the “Material Transfer Process” Screen
– What error messages did you get ?
• Increase “Zero Flow Threshold” significantly– Did the feed start?
– Why?
Class Exercises C
• Increase Spill and Flow Limits for a Material Path• Introduce a large spill upset (Repeat Exercise A)
– What happened
– Did the feed complete OK
– What happened to the K1 and K2 parameters?
– Results:
– As long as the upset value fell with the 50%range of the Limits the Qi will accept the result.
• Do a few more feeds without the Upset.– Was the next feed accurate ?
– Why not?