process control practice renewal 2010 (2010)
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8/12/2019 Process Control Practice Renewal 2010 (2010)
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H P I N CONTROL
PIERRE R LATO UR GUEST COLUMNIST
Process co n trol practice r en e w a l 2 0 1 0Allan Kern, Zak Friedman and I have offered num ero us ideas
to strengthen the practice of process control.' ^ Allan Kern inau-
gurated a fund ame ntal assessment of process con trol en gineer-
ing practice in the HPI since 1990.^ His experience maintaining
control systems in multiple refineries reveals that many challenges
remain . H e offered an excellent sum ma ry of what we have learned.^
He reports the base layer, Field in Fig. 1, is healthy but not suffi-
ciendy functional. It is clearer every year that focus on the b se l yer
is the mos t urgent and promisi ng strategy, and greatest opportunity t
bring ahout undamental improvements in operation and reliability
goingforward. The only way to build is from the bottom up.
Kern may be right, but identifying and curing the root cause of
failure is fund ame ntal. I hope to supplement Kern's recomm enda-
tions with my own, as a consul tant to ma ny refineries for sho rt
periods since 1966.1 see an opportunity to renew the practice of
process control engineering in the new decade by analyzing the
primary causes ofth e disappo inting performance shortfalls across
all layers of Fig. 1 and cor rectin g basic flaws in the enginee ring
approach from the top-layer DSS down.' Kern and I will try to
strengthen our profession and HPI operations.
I place much blame on flawed logic used to quantify the finan-
cial value of all process control and associated operations' IT since
1970 that caused cr ippl ing disconnects between the layers. I
shall pro mo te the view of an architect before constructio n begins
beyond after the house has been lived in, an engineer before a
bridge is built beyond after the bridge is used, a chef before d in-
ner is prepared beyond after guests have dessert. I shall emphasize
identifying, capturing and sustaining significant value from any
process operation tool, technology or solution. The span of Fig.
1 is from basic measurements and actuators to refinery IT eco-
nomics. Proper goals, measurable performance, risks and costs,
includin g manpo wer, will cou nt every step ofth e w ay. Th is is not
quite a top-down approach; i t 's holistic.
Why the base layer has been weak First consider
why rhe base layer has been so weak for so long. Either it adds
DSS
MPC
D S SIS
Field
Decision-support applications
- Performance monitor ing
- Operating target dashboards
- Alarm management, etc.
Mult ivar iable predictive control
Distr ibuted control systems
Safety instnimented systems
Work practices
Process
Equipment
Field devices
F I C Automation layers.
insufficient tangible value (because it costs too m uch to Fix a
mainta in or doesn ' t do much good) or engineers have failed
properly quantify rhat value to justify main tenanc e and improv
men t while piling on m ore layers. W he n the base layer is too f
removed from the DS S to run the plant properly and infiuence
financial performanc e, people ofren resort to simple Faith TTieor
claims that have worn thin long ago. When they do attempt t
relate base-layer activity to process performance, they use fiawe
logic,^ losing credibility. In other words, if the financial case fthe healthy field layer Kern desires is clear and compel l ing
should be made and confirmed regularly.
It's like justifying tires without considering the value ofthe ca
lettuce witho ut co nsidering th e salad and en trée. As Kern affirms
it cannot be done in isolation.
En gine e r ing p rac t i ce renewa l app roa ch . Th e eng inee r i
pract ice renewal approach star ts at the beg inn ing , co mbin i
all layers.
• Agree on how to opera te H PI processes properly. Al l w
can do is select app ropr iate CVIKPÎ response variables, measu
them and modify their means and variances (distribution) to su
our purposes.
• Agree on the purpose of HP I operations: max imu m e xpe a
value profit rate.
• Define th e eco no mic tradeoff sensitivity for every CV/KP
to a l low al ignment wi th the plants econom ic env ironmen t .
• Rela te the main process control funct ions, c om po nen
and layers to CVmean or variance changes, and those changes
average profit rate.
It is clear that focus from the top DSS layer is a promis
strategy to br ing ahou t fundamenta l improvem ent s in ope r
tion an d reliabiiity going forw ard, w ith all layers. Analysis befo
synthesis, always. In the end . Kern a nd I will unite to provi
guidelines for renewing the practice of process control engineeri
durin g refinery g olden ages and struggles. HP
LITERATURE CITE D
' Kern, Allan, More on APC designs or minimum maintenance, HR Dec2009.
^ Kern, Allan, Back co the Furure: A Process Control Strategy for 2010, HFeb. 2010.
^ Laiouf. RR., Demise and keys to the rise of process control, HP, March
2006, p p. 71 -80 and Letters to Editor. Process Control, HP, June 2006, p
42 .
* Latour. PR., Process contro l: CL IFF TEN T shows it's more profitable tha
Expeaed, HP, December 1996, pp. 75-80 . Republished in Kane. Les. E
Advanced Process Control and Information Systems for the Process Industri
Gu lf Publ ishing Co. 1999. p p .31 -37 .
T h e a u t h o r president o f CLIFFTENT Inc., is an independent consulting chemengineer specializing i n identifying, capturing a nd sustaining measurable finan
value from HPI dynamic process control. IT and CIM solutions CLIFFTENT) us
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