High Performance HMI – Proof Testing in Real-World Trials
Bill Hollifield, PAS Principal Consultant PAS
16055 Space Center Blvd, Suite 600 Houston, TX, USA 77062
(281) 286-6565 e-mail: [email protected]
KEY WORDS High Performance Human Machine Interface, HMI, Operator Effectiveness, Process Graphics, Simulator ABSTRACT: “HIGH PERFORMANCE HMI – PROOF TESTING IN REAL-WORLD TRIALS”
Almost all industrial processes are controlled by operators using dozens of graphic screens. The graphic designs are typically little more than P&IDs covered in hundreds of numbers. This traditional, “low performance” Human Machine Interface (HMI) paradigm is typical in all processes controlled by DCS and SCADA systems, including the water and wastewater sector. It has been shown to be lacking in both providing operator situation awareness and in facilitating proper response to upsets. In many industries, poor HMIs have contributed to major accidents, including fatalities.
HMI improvement has become a hot topic. The knowledge and control capabilities now exist for creating High Performance HMIs. These provide for much improved situation awareness, improved surveillance and control, easier training, and verifiable cost savings. This paper will cover:
HMIs Past and Present
Common but Poor HMI Practices
Justification for HMI Improvement – What Can You Gain?
High Performance HMI Principles and Examples
Depicting Information Rather Than Raw Data
The Power of Analog
Proper and Improper Use of Color
Depicting Alarm Conditions
Trend Deficiencies and Improvements
Display Hierarchy and the Big Picture
The High Performance HMI Development Work Process
Obstacles and Resistance to Improvement
Cost-effective Ways to Make a Major Difference
An Extensive Real-World Trial of These Concepts in a Power Plant Simulator, Sponsored by the Electric Power Research Institute
Implementation of proper graphic principles can greatly enhance operator effectiveness. A High Performance HMI is practical, achievable, and proven.
Hollifield, 2
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
High Performance HMI – Proof Testing in Real-World Trials
Introduction
The human-machine interface (HMI) is the collection of screens, graphic displays, keyboards, switches, and other technologies used by the operator to monitor and interact with the SCADA system. The design of the HMI plays a critical role in determining the operator’s ability to effectively manage the operation, particularly in response to abnormal situations.
For several reasons, the current design and capability of most HMIs are far from optimal for running complicated operations. Most of these consist simply of schematic-style graphics accompanied by numbers. Such displays provide large amounts of raw data and almost no real information. They provide inadequate situation awareness to the operator.
This paper concentrates on proper and effective design of the graphics used in modern SCADA systems.
HMIs Past and Present
Before the advent of sophisticated digital control systems, the operator’s HMI usually consisted of a control wall concept.
The control wall (see Figure 1) had the advantages of providing an overview of the entire operation, many trends, and a limited number of well-defined alarms. A trained operator could see the entire operation almost at-a-glance. Spatial and pattern recognition played a key role in the operator’s ability to detect burgeoning abnormal situations.
Figure 1: Example of a Control Wall
Hollifield, 3
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
The disadvantages of these systems were that they were very difficult to modify. The addition of incremental capability was problematic, and the ability to extract and analyze data from them was almost non-existent. The modern electronic control systems (SCADA & DCS) replaced them for such reasons.
When these systems were introduced, they included the capability to create and display graphics for aiding in the control of the operation.
However, there were no guidelines available as to how to actually create effective graphics. Early adopters created graphics that mimicked schematic drawings, primarily because they were readily available.
Poor graphics such as Figures 2 and 3 were developed over 20 years ago and remain common throughout the industry. This paper deals with the deficiencies of such common depictions. Inertia, not cost, is the primary obstacle to the improvement of HMIs. Engineers and Operators become accustomed to this style of graphic and are resistant to change, until the recommended improvements and principles are clearly presented.
As a result, industries that use modern control systems are now running multi-million dollar operations from primitive HMIs created decades ago, at a time that little knowledge of proper practices and principles was available.
Figure 3: A Typical Crowded, Schematic-Style Graphic
Hollifield, 4
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
As SCADA and DCS system hardware progressed, graphics from the manufacturers began to adopt very flashy design practices. The results were displays that are actually sub-optimal for operators, but operators began deploying these as well.
Figure 4 is an example of flashy design taken from a power generation facility to illustrate the point. The graphic dedicates 90% of the screen space to the depiction of 3-D equipment, vibrantly colored operation lines, cutaway views, and similar elements. However, the information actually used by the operator consists of poorly depicted numerical data which is scattered around the graphic, and only makes up 10% of the available screen area.
Figure 2: An Early Graphic Exhibiting Many Problematic Practices
The limited color palette was used inconsistently and screens began to be little more than crowded displays of numbers.
There are no trends, condition indicators, or key performance elements. You cannot easily tell from this graphic whether the operation is running well or poorly. That situation is true for more than 90% of the graphics used throughout the industry because they were not designed to incorporate such information. Instead, they simply display dozens to hundreds of raw numbers without informative context
Hollifield, 5
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 4: A Flashy Graphic Inappropriate for Actual Operational Control
Justification for HMI Improvement
Poorly performing HMIs have been cited time and again as significant contributing factors to major accidents. Yet our industry, namely process automation in facilities like chemical plants, refineries and wastewater treatment plants, has made no significant change in HMI design in more than a decade. There is another industry that learns from its accidents and has made phenomenal advancement in HMI design based on new technology.
That industry is avionics. Lack of situation awareness is a common factor cited in aviation accident reports. Modern avionics feature fully-integrated electronic displays (See Figure 5). These depict all of the important information, not just raw data, needed by the operator (i.e., pilot). Position, course, route, engine diagnostics, communication frequencies, and automated checklists are displayed on moving maps with built-in terrain proximity awareness. Real-time weather from satellite is overlaid on the map. Detailed database information on airports is available with just a click. Situation awareness and abnormal situation detection is far improved by these advances. This capability – impossible even a dozen years ago in multi-million dollar airliners – is now standard on even the smallest single engine aircraft.
Hollifield, 6
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 5: Garmin G2000® Avionics Package in a Small Plane
Since safety is significantly improved with modern HMIs, it is only logical that we would want all operators to have access to them. Yet most operators have done little to upgrade.
There have been tests involving actual operators running realistic simulations using traditional graphics vs. High Performance ones. The author participated in a major test of these principles sponsored by the Electric Power Research Institute (EPRI) at a large coal-fired power plant. The results were consistent with a similar test run by the ASM® (Abnormal Situation Management) Consortium on an ethylene plant. The test showed the high performance graphics provided significant improvement in the detection of abnormal situations (even before alarms occurred), and significant improvement in the success rate for handling them. In the real world, this translates into a savings of hundreds of thousands of dollars per year.
Proper Graphic Principles
Ineffectively designed graphics are very easy to find. Simply search the internet for images under the category “HMI”. Problems with these graphics include:
Primarily a schematic representation
Lots of displayed numbers
Few trends
Spinning pumps/compressors, moving conveyors, animated flames, and similar distracting elements
Brightly colored 3-D vessels
Highly detailed equipment depictions
Attempts to color code piping with contents
Large measurement unit callouts
Bright color liquid levels displaying the full width of the vessel
Lots of crossing lines and inconsistent flow direction
Inconsistent color coding
Misuse of alarm-related colors
Limited, haphazard navigation
Hollifield, 7
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
A lack of display hierarchy
Ineffective graphics encourage poor operating practices, such as operating by alarm.
By contrast, High Performance graphics have:
A generally non-schematic depiction except when functionally essential
Limited use of color, where color is used very specifically and consistently
Gray backgrounds to minimize glare
No animation except for specific alarm-related graphic behavior
Embedded, properly-formatted trends of important parameters
Analog representation of important measurements, indicating their value relative to normal, abnormal, and alarm conditions
A proper hierarchy of display content providing for the progressive exposure of detailed information as needed
Low-contrast depictions in 2-D, not 3-D
Logical and consistent navigation methods
Consistent flow depiction and layout to minimize crossing lines
Techniques to minimize operator data entry mistakes
Validation and security measures
Data or Information?
A primary difference of high performance graphics is the underlying principle that, wherever possible, operation values are shown in an informational context and not simply as raw numbers scattered around the screen.
“Information is data in context made useful.”
As an example, consider this depiction of a compressor (see Figure 6). Much money has been spent on the purchase of instrumentation. Yet, unless you are specifically trained and experienced with this compressor, you cannot tell if it is running at peak efficiency or is about to fail.
Figure 6: All Data, No Information
West East
Drive: 232.2 amps
Cooler
W. Vibration: 2.77 E. Vibration: 3.07
2.77
MSCFH
155.2 °F 108.2 °F 166.1 °F55.7 psig
135.1
psig
190.5 psig
Oil 155.2 °F
Oil 85.1 psi
65.1 °F
Hollifield, 8
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
The mental process of comparing each number to a memorized mental map of what is good is a difficult cognitive process. Operators have hundreds of measurements to monitor. Thus the results vary by the experience and memory of the operator, and how many abnormal situations they have experienced with this particular compressor. Training new operators is difficult because the building of these mental maps is a slow process.
Adding more numbers to a screen like this one does not aid in situation awareness; it actually detracts from it.
By contrast, these numbers can be represented in a bank of analog indicators, as in Figure 7. Analog is a very powerful tool because humans intuitively understand analog depictions. We are hard-wired for pattern recognition.
With a single glance at this bank of properly designed analog indicators, the operators can tell if any values are outside of the normal range, by how much, and the proximity of the reading to both alarm ranges and the values at which interlock actions occur.
Figure 7: Analog Depiction of Information
In just a second or two of examination, the operator knows which readings, if any, need further attention. If none do, the operator can continue to survey the other portions of the operation. In a series of short scans, the operator can be fully aware of the current performance of their entire span of control.
The knowledge of what is normal is embedded into the HMI itself, making training easier and facilitating abnormal situation detection – even before alarms occur, which is highly desirable.
Color
Color must be used consistently. There are several types of common color-detection deficiency in people, particularly males (red-green, white-cyan, green-yellow). For this reason, there is a well-known principle for the use of color:
Cool
gpm
RECYCLE COMPRESSOR K43
Alarm Indicator
Desirable Operating Range
AlarmRange
AlarmRange
2
Suct
psig
Inter
psig
Dsch
psig
Suct
degF
Inter
degF
Dsch
degF
E. Vib
mil
N. Vib
mil
W. Vib
mil
Motor
Amps
Oil
psig
Oil
degF
42.7 38.7 93.1 185 95 120 170 12 8 9 170 80 290
Interlock Threshold
Hollifield, 9
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Color, by itself, is not used as the sole differentiator of an important condition or status.
Most graphics throughout the world violate this principle. Redundant coding of information using additional methods other than color is desirable. A color palette must be developed, with a limited number of distinguishable colors used consistently.
Bright colors are primarily used to bring or draw attention to abnormal situations, not normal ones. Screens depicting the operation running normally should not be covered in brightly saturated colors, such as red or green pumps, equipment, valves, etc.
When alarm colors are chosen, such as bright red and yellow, they are used solely for the depiction of an alarm-related condition and functionality and for no other purpose. If color is used inconsistently, then it ceases to have meaning.
So what about the paradigm of using bright green to depict “on” and bright red for “off”, or vice versa if you are in the power industry? This is an improper use of color. The answer is a depiction such as Figure 8.
Figure 8: Depicting Status with Redundant Coding and Proper Color Usage
The relative brightness of the object shows its status, plus a WORD next to it. Things brighter than the background are on (think of a light bulb inside them). Things darker than the background are off.
Alarm Depiction
Proper alarm depiction should also be redundantly coded based upon alarm priority (color / shape / text). Alarm colors should not be used for non-alarm related functionality.
Hollifield, 10
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 9: Depiction of Alarms
When a value comes into alarm, the separate alarm indicator appears next to it (See Figure 9). The indicator flashes while the alarm is unacknowledged (one of the very few proper uses of animation) and ceases flashing after acknowledgement, but remains as long as the alarm condition is in effect. People do not detect color change well in peripheral vision, but movement, such as flashing, is readily detected. Alarms thus readily stand out on a graphic and are detectable at a glance.
It is highly beneficial to include access within the HMI to the alarm rationalization information contained in the Master Alarm Database (See Figure 10). If these terms are unfamiliar, you are advised to become familiar with the 2009 standard, ANSI/ISA–18.2–2009, Management of Alarm Systems for the Process Industries. In the pipeline industry, recent Control Room Management regulations issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA) include an alarm management component. An American Petroleum Institute (API) recommended practice on Pipeline Alarm Management (API RP-1167) was issued in December 2010 and is expected to be incorporated into future PHMSA regulations.
Hollifield, 11
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 10: Linked Alarm Information
Trends
The most glaring deficiency in HMI today is the general lack of properly implemented trends. Every graphic generally has one or two values on it that would be far better understood if presented as trends. However, the graphics rarely incorporate them.
Instead, engineers and managers believe claims that their operators can easily trend any value in the control system on demand with just a click. This is incorrect in practice; a properly scaled and ranged trend may take 10 to 20 clicks/selections to create, and usually disappears into the void if the screen is used for another purpose!
This deficiency is easily provable; simply walk into the control room and count how many trends are displayed. Then pick a value at random and ask an operator to create a trend and watch. Our observations, made in hundreds of control rooms, indicate that trends are vastly underutilized and situation awareness suffers due to that omission.
Trends should be embedded in the graphics and appear, showing proper history, whenever the graphic is called up. This is generally possible, but is a capability often not utilized.
Trends should incorporate elements that depict both the normal and abnormal ranges for the trended value. There are a variety of ways to accomplish this (See Figure 11).
122.1 degC3
Lowered efficiencyOff spec Production
Alarm Consequences:
Priority: 3
Alarm: PVHI
Check feed composition
Feed composition variance
Adjust reflux per
computation; check controller for cascade mode
Insufficient reflux
Check pressure and feed
parameters vs. SOP 468-1
Pressure excursion
Adjust base steam rate
Excess steam
Corrective Actions:
Alarm Causes:
Alarm Consequences:
Response Time: <15 min
Class: Minor Financial
Setting: 320 deg F
TI-468-02 Column Overhead Temperature
Lowered efficiencyOff spec Production
Alarm Consequences:
Priority: 3
Alarm: PVHI
Check feed composition
Feed composition variance
Adjust reflux per
computation; check controller for cascade mode
Insufficient reflux
Check pressure and feed
parameters vs. SOP 468-1
Pressure excursion
Adjust base steam rate
Excess steam
Corrective Actions:
Alarm Causes:
Alarm Consequences:
Response Time: <15 min
Class: Minor Financial
Setting: 320 deg F
TI-468-02 Column Overhead Temperature
Reveal Alarm Rationalization documentation on demand!
Information recalled from your Master Alarm Database
Right-click call-up
Shape and Size of a standard faceplate if possible
Link to Procedures
Hollifield, 12
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 11: Trend Depiction of Desirable Ranges
Level Indication
Vessel levels should not be shown as large blobs of saturated color. A simple strip depiction showing the proximity to alarm limits is better. A combination of trend and analog indicator depictions is even better (See Figure 12).
West Comp Discharge Temp °C
40.0
50.0
-60 -30-90 Hours
44.1West Comp Discharge Temp
40.0
50.0
-60 -30-90 2 Hours
West Comp Flow MSCFH
45.0
55.0
-60 -30-90 2 Hours
49.1West Comp Flow MSCFH
45.0
55.0
-60 -30-90 Hours
49.1
5000
15
1 Hr
Feed
Water
3280
Drum
Level
-0.5
Main
Steam
4150
0
-10
Hollifield, 13
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 12: Vessel Levels
Figure 13: Bars vs. Pointers
Better Vessel Level
Indication
Very Poor Vessel Level
Indication
Crude Feed TK-21
Trend andAnalog Level
Indication
2 Hrs 86.5%
2
0
100
25% 50% 75%
Valve
V-1
V-2
V-3
X-1
X-2
X-3
X-4
S-1
S-2
K-1
K-2
100%
100%
95%
88%
100%
100%
75%
0%
55%
100%
100%
100%0%
Analog Position - Better
25% 50% 75%
100%
100%
95%
88%
100%
100%
75%
0%
55%
100%
100%
100%0%
Analog Position – Poor Bar Graphs
Valve
V-1
V-2
V-3
X-1
X-2
X-3
X-4
S-1
S-2
K-1
K-2
Hollifield, 14
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Bar Charts
Attention to detail is important. It is typical to use bar charts to show relative positions and values. While this may be better than simply showing numbers, it is inferior to the use of moving pointer elements. In a bar chart, it is the end point of the bar that is really the item of interest. “Zero” is often an important condition! But as a bar’s value gets low, the bar simply disappears from view. The human eye is better at detecting the presence of something than its absence. The example in Figure 13 is superior in showing relative values, besides the color improvement.
Tables and Checklists
Even tables and checklists can incorporate proper principles (See Figure 14). Consistent colors and even status indication can be integrated.
Figure 14: Tables and Checklists
Breaker 15 Power
Oil Temp 16-33
Oil Pres Status
Level in TK-8776
Gen System Status
Comp 88 in Auto
Lineup Ready
Sys Status Checks
Bearing Readouts
Comm check
Outlet Temp < 250
Cooling Flow
Internal Circuit Check
Bypass Closed
AFS Function
OK
NOT OK
OK
OK
OK
NOT OK
OK
OK
OK
OK
OK
OK
OK
OK
Startup Permissives
NOT OK
Air
Comp
Status Mode Diag
C #1 RUNNING AUTO OK
C #2 STOPPED MAN OK
C #3 RUNNING AUTO OK
C #4 STOPPED AUTO FAULT 3
Hollifield, 15
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
There are dozens of additional principles like these. See the References section.
Display Hierarchy
Displays should be designed in a hierarchy that provides progressive exposure of detail. Displays designed from a stack of schematic designs will not have this; they will be “flat” – like a computer hard disk with one folder for all the files. This does not provide for optimum situation awareness and control. A four-level hierarchy is desired.
Level 1 –Operation Overview
This is a single display showing the operator’s entire span of control, the big picture. It is an overall indicator as to how the operation is running. It provides clear indication of the current performance of the operation by tracking the Key Performance Indicators (See Figure 15).
Control interactions are not made from this screen.
Figure 15: Example Level 1 Display
Stator
GPM
Turb Oil
°F
Hydrogen
psig
LPT-B
in.hg
LPT-A
in.hgMVARNet MW
Turbine – Generator
Gross MW HZ
702.1 640.1 - 5.2 60.00 0.2 49.1 351 3.1 20.11150.2
HW Lvl
in.H2OB2 BPFT
Condenser–Feed Wtr DA Lvl
in.H2O
3.1 0.0
9.4 775
Econ Gas
Out °F
Boiler BBD
pH
Fans
- 0.5 6.0 7.0
Econ
% O2
Sec Air
in.H2OFurn in.H2O
200
Stack CO
ppm
SO2
#/MMBTU
CEMS/MISC
% OpacNOX
#/MMBTU
0.921.0
05-31-1013:22:07
Total Alarms
Unit 2
Overview
0
1200
600
1200
1 Hr
3000
600
Steam
°F
990
Reheat
°F
1005
Steam
psig
2400
-5
7500
0
1250
1 Hr
5
0
Air
KLBH
7400
Coal
KLBH
1000
Furn
Pres
-0.5
0
5000
0
5000
1 Hr
15
-15
Steam
KLBH
4750
Fd Wtr
KLBH
4580
Drum
Lvl in.
-0.5
Drum Lvl
in.H2O
-0.5
2
B2 ID
Stall
A2 ID
Stall
A2 FD
Stall
B2 FD
Stall
2
AA-ONPULV
Status
A2 CWP
B2 CWP
B-ON
C-ON
D-ON
E-ON
F-ON
G-OFF
H-ON
Alarms
E
B
F
C
G
D
H
PUMPS
AND
FANS
Pump Status / Alarms
ON
ON
A2 HWP
B2 HWP
ON
OFF
C2 HWP
SUBFP
ON
ON
A2BFPT
B2BFPT
ON
ON
A2 ECW
B2 ECW
ON
ON
Fan Status / Alarms
A2 FDON
ON
B2 FD
B2 ID
ON
ON
A2 PA
B2 PA
ON
ON
A2 ID
C-SBAC
D-SBAC
ON
ON
Hydrogen
°F
104
Econ
pH
9.4
Aux Stm
psig
300
A2 BPFT
400
Cond Hdr
psig
Inst Air
psigA/F Ratio
0.45 907.1
DA Wide
FT.H2O
9.0
2525 2525
0
2
1
8
3 5
AUTO AUTO AUTO AUTO
Hollifield, 16
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Level 2 –Unit Control
Every operation consists of smaller, sectional unit operations. A level 2 graphic exists for each separate major unit operation. It is designed to contain all the information and controls required to perform most operator tasks associated with that section, from a single graphic (See Figure 16).
Figure 16: Example Level 2 Display of a Reactor
Level 3 –Unit Detail
Level 3 graphics provide all of the detail about a single piece of equipment. These are used for a detailed diagnosis of problems. They show all of the instruments, interlock status, and other details. A schematic type of depiction is often desirable for a Level 3 displays (See Figure 17). These display can also contain trend, tables, analog indicators, and proper and consistent color usage as shown, making them superior to the typical “crowded P&ID covered in numbers.” Most of the existing graphics in the world can be considered as “improvable Level 3’s.”
VENT SYS
ThioniteProduct: Mid-Run
5.0 %
PRODUCT
OK
Pumps
Needed 1
SHUT
DOWNM5
VENT
M5
IN OUT
Calc Diff:
-10%
+10%
Hours: 238.1
State:
19707
19301
Material Balance
2.1 %
FREEZE
M5
STOPPED FAULT
Main Menu
80.5
%A
15.5
%B
4.0
%CFeed Composition
76.0
77.5AUTO
33.1%
Feed
MPH
12.0
11.9AUTO
22.3%
ADTV-1
MPH
4.0
4.0AUTO
44.3%
ADTV-2
MPHReserved
Faceplate Zone
When any item on the screen is
selected, the faceplate for that item
appears in this reserved area.
All control manipulation is
accomplished through the standardized
faceplates.
Reactor M5
Analysis: Purity %
32.0-60 -30-90 2 Hrs
40.0
Analysis: Inhibitor Concentration %
4.0-60 -30-90 2 Hrs
6.0
80.5
Coolant:
GPM °C
15.5
Purge
MCFH
4.0
Cat.
Act%
Conv.
Eff. %
80.5 15.5
75.0
75.9AUTO
54.3%
Lvl
%
92.0
Prod
MPH
45.0
45.0AUTO
54.1%
Temp
°C
95.0
97.2AUTO
44.3%
Pres
psig
To Coils
74.3 %
L2 M5 Startup
L2 M5 Scram
M5 Vent Sys
Daystrom Pumps
M5 Agitator
L2 Feed System
L2 Prod Recovery
M5 Interlocks
M5 Cooling Sys
---- Level 3 ----
AgitatorON
4
M5 Circ
Pump A
Pump B
RUNNING
3
ISOLATE
M5
ON-OKRTAM:
Run Plan:
Actual:
Feed
MPH
72.0-60 -30-90 2 Hrs
80.0
OP
Chem
1
MPH
10.0-60 -30-90 2 Hrs
14.0
OP
Chem
2
MPH
2.0-60 -30-90 2 Hrs
6.0
OP
40.0-60 -30-90 2 Hrs
48.0
Temp
°C
OP
L2 Compression
L2 RX Summary
I I-5A I-5B I-5C
I-5D
I I
I I-5EI I-5FI
Feed ADTV-1 ADTV-2
Temp Pres Level
Interlock Actions:
Stop Feed Stop ADTV-1Stop ADTV-2Max CoolingMax Vent
OFFOFFOFFOFFOFF
Reset
0%
Tot. In:
Tot Out:
%DIFF
OPEN OPEN OPEN OPEN OPEN
OPEN
OPENBackup Lvl %75.8
Hollifield, 17
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 17: Example Level 3 Display
Level 4 –Support and Diagnostic Displays
Level 4 displays provide the most detail of subsystems, individual sensors, or components. They show the most detailed possible diagnostic or miscellaneous information. A “point detail” type of diaply would be considered a Level 4. The dividing line between Level 3 and Level 4 displays can be somewhat gray.
Pipeline Network or Distribution Overview Displays
Pipeline networks are used in many industries, including water collection/distribution networks and in the oil/gas sector. Most existing displays that purport to be Overviews of a pipeline network are simply geographical layouts of the network covered in numbers. Figure 18 is a mock-up example of such a typical depiction. For a pipeline network overview display, there are certainly important items related to the geography, but this detail level is distracting and unhelpful to the operator.
PSOAUTO
76.8 MSCFH76.088.5 %
Flow Demand
RUNNING
PSOCAS
90.090.0 %
WC Speed
65.0 °C
West Comp Discharge Temp °C
40.0
50.0
-60 -30-90 2 Hours
1st
Stage
2nd
Stage
CW
32.0 °C
20.0 °C
28.0 °C
WEST
COMP
OH
44.0 °C
90.8 %
48.0 psi
90.0 psi
1 Stg
psi
EAST COMP
Speed
%20.1 psi
EAST COMP
2 Stg
psi
48.0 90.0
CLR IN
°C
FLOW-SPEED
CASCADE
IN EFFECT
CLR OUT
°C
65.0 32.0
Winding
°C
111.0 °C
111.0
West Compressor Interlock Initiators
Comp in Overspeed
Winding Temp is High
Vibration is High
1 Stg Pres is High
2 Stg Pres is High
Suction Pres is Low
Oil Pres is Low
NO
NO
NO
West Comp Flow MSCFH
45.0
55.0
-60 -30-90 2 Hours
48.4 MSCFH
West Comp Speed %
85.0
95.0
-60 -30-90 2 Hours
SHUT
DOWNWESTCOMP
RECOVERY
IDLE
WESTCOMP
ISOLATE
WESTCOMP
West Compressor
90.8
90.0 %90.0CAS
Tot Flow
MSCFH
76.8
88.5 %76.0
AUTO
95.1 Oil psi
Main Menu
Reserved
Faceplate Zone
When any item on the screen is
selected, the faceplate for that item
appears in this reserved area.
All control manipulation is
accomplished through the standardized
faceplates.
L2 Compression
East Comp
West Interlocks
Logic Diagrams
West Cooling
---- Level 3 ----
I W-1A W-1B W-1CI IMech Flow Pres
Procedures
Sequence Overlay
Startup Overlay
L2 Recovery
PURGE
WESTCOMP
MANUAL ACTIONS
NO
NO
NO
Total Flow is Low
West Compressor Interlock Actions
W. Comp Shutdown
Inlet Block Valve
Outlet Block Valve
Flow Cascade to Manual
Maximum Flow Bypass
Maximum Cooling
E. Comp Override to 100%
NO
OPEN
OPEN
NO
NO
CLOSED
NORM
OFFWinding PurgeNO
NO
Inter-cooler
---- Level 4 ----
OPEN
OPEN
Hollifield, 18
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 18: Typical Low-Performance Pipeline Network Overview
There exists a highly successful technique for depicting geographic networks in a way that strips out all of the nonessential information, leaving what is important to the user and the task at hand. That technique is in the depiction of subway systems.
Early versions of the depiction of the London subway system were confusing to the user (see figure 19.)
Figure 19: Original 1908 Depiction of the London Subway System
11.55
12.44
42.87
21.43
32.17
31.4127.81
40.56
38.33
18.48
60.02
2.34
17.36
29.927
Hollifield, 19
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
In the 1930s, this depiction was modified and has since become a world-famous and universally adopted graphic technique for subway depiction. The key is the depiction of topography, not geography.
Figure 20: Topological London Subway Routing Diagram
In the Figure 20 depiction, all lines (including the Thames river) are horizontal, vertical, or at 45 degrees. The outlying legs are shown as straight lines regardless of the actual routing. This is because the subway rider only needs to know how many stops remain to the destination or terminal, and not the precise direction of travel at any point. Enough geographical cues are shown to identify start points and destinations. While complex and showing a lot of information, the actual use of this drawing for navigation is simple and intuitive. Along with the announcements and labeling on the trains and at the stations, the diagram provides for good situation awareness for the task at hand, even by newcomers to the subway system.
The kinds of geographic information that can be important for depiction of a distribution system (particularly for pipelines carrying hazardous materials) include:
Jurisdictional or regulatory boundaries
Proximity to waterways, residential spaces, or similar areas significantly affected by potential releases
Proximity to response services
Important Status Conditions and Alarms
Significant highway or waterway crossings
A high performance display will incorporate such information along with:
Moving analog indicators indicating performance.
Direction and content indicators
Important trends
Important status and alarms
Hollifield, 20
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Translated to a pipeline network, a conceptual High Performance Overview display might resemble figure 21.
Figure 21: Conceptual High-Performance Pipeline Network Overview
API-RP-1165: Recommended Practice for Pipeline SCADA Displays
In 2006, API issued a document on Pipeline SCADA HMI displays. There are some inconsistencies within that document. This is significant because some parts of API-RP-1165 have been “incorporated” into federal regulations issued by PHMSA.
Overall, the concepts incorporated in the text portion of the document are valid. It mentions several good practices. The examples section, however, provides several depictions that are in direct violation of those very text principles!
For example, Section 8.2.4 properly states that “Color should not be the only indication for information. That is, pertinent information should also be available from some other cue in addition to color such as a symbol or piece of text.”
Yet throughout the remainder of the document, examples are shown that routinely violate this principle. Figure 22 shows only a few of the “recommended practice examples” from API-RP-1165. In many of these examples,
Altair 4
228 660 112 156 302 670 125 212
TX LAAltair 4
Mesklin
Trantor
Minbari
Arrakis
River
Terminus
Gateway
Line Pressure Profiles
Kessel Run
Frostbite Falls
Fra Mauro
Brigadoon
Cannonball
Mayberry
C
Y
C
L
E
665 630 627 615 609 592 560 545 523 481
Leaks
OK
OK
OK
OK
OK
OK
3MCFH psi °F
C1 OK C2 OK
C3 OK C4 OKIC1
IC2
IC3
IC4
3
22
1
2
3
4
1
2
3
4
1
2
3
4
C1 OK C2 OK
C3 Fault C4 OK
C1 OK C2 OK
C3 OK C4 OK
OutletscfhVent
MCFH psi °F Outlet
scfhVentC1 C3
Mesklin
259 635 133 115 202 558 110 108
MCFH psi °F
C1 OK C2 OK
C3 OK C4 OKIC1
IC2
IC3
IC4
OutletscfhVent
MCFH psi °F Outlet
scfhVentC1 C3
Arrakis
238 658 127 116 402 523 114 72
MCFH psi °F
IC1
IC2
IC3
IC4
OutletscfhVent
MCFH psi °F Outlet
scfhVentC2 C4
Trantor
218 675 108 126 302 453 104 61
MCFH psi °F
IC1
IC2
IC3
IC4
OutletscfhVent
MCFH psi °F Outlet
scfhVentC2 C3
Valve Positions
A11
3
A12
A13
A14
B11
B12
B13
B14
J2
J7
R4
R5
R6
R7
Z51
Z52
Z53
Total
Flow
600-60 -30-90 2 Hrs
1000
943MCFH
Weyland-Yutani Pipeline Overview
Main MenuLV-426
Pixley
Cogswell
Raisa
Cernon
Dantooine
Hekate
1
2
3
4
Eddore
Tyrell LV-223
Hooterville
Cannonball
Fra Mauro
Kessel Run
Mayberry
Brigadoon
Frostbite Falls
Green
Acres
Pern
Rama
Chindi
Shady
Rest
Bodine
Armstrong Aldrin
Prod
C57D
JUP2
RV12
V35B
C182
C172
Alarms 32 S1
Total
Un-Ack
0 1 4 2
0 0 1
Additives
Hollifield, 21
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
only subtle color differences, not distinguishable by a substantial fraction of the operator population, are the only means to distinguish a significant status difference.
In one table, API-1165 incorrectly recommends color coding alarms by type. The well-known best practice is that they are redundantly coded by priority, not type (also in Figure 22.)
Users of API-1165 are therefore advised to pay more attention to the principles it contains than to the poor example depictions.
Figure 22: Sub-optimal Examples from API-RP-1165
T1
V12
L
CLS
V5
T
TI
OPN
V1
T
TI
RUN
U1
T
TI
OPN
V9
T
TI
OPN
V8
T
TI
RUN
T1
T
TO
RUN
U2
T
TI
OPN
V11
T
TI
OPN
V10
T
TI
OPN
V2
T
TI
CLS
V4
T
TIOPN
V3
T
TI
Station ABC
OPN
V6
T
TI
Tank Level
%50.0
Suction
Psi123.4
Case
Psi123.4
Suction SP
Psi123.4
DIscharge
Psi123.4
Discharge SP
Psi123.4
% Open
%123.4
OPN
V17
T
TI
OPN
V16
T
TI
CLS
V15
T
TIOPN
V14
T
TI
OPN
V7
T
TI
OPN
V13
T
TI
To Station BCD To Station DEF
STATE
BACKGROUND
COLOR
Color
FORE-
GROUND
COLOR
Color
EXAMPLE
Normal Black Green 1234
High-High Alarm Black Red 1234
High Alarm Black Yellow 1234
Low Alarm Black Yellow 1234
Low-Low Alarm Black Red 1234
Unknown/Error Black Blue 1234
4 Way Valve Symbols
Comm Failure
Off Scan
Alarm Inhibited
Offscan
Manual
Communication
Failure (Stale)
Alarm Inhibit
Tagged
RIGHT
ABC
T
TI
<- Device State
Data Attribute
<- TagField ID ->
RIGHT
RIGHT
ABC
T
TI
RIGHT
ABC
T
TO
RIGHT
ABC
T
TI
RIGHT
ABC
T
TS
RIGHT
ABC
T
TI
RIGHT
ABC
T
TM
RIGHT
RIGHT
ABC
T
TI
RIGHT
ABC
T
TO
RIGHT
ABC
T
TI
RIGHT
ABC
T
TS
RIGHT
ABC
T
TI
RIGHT
ABC
T
TM
STATIC LEFT
LEFT
ABC
T
TI
LEFT
ABC
T
TO
LEFT
ABC
T
TI
LEFT
ABC
T
TS
LEFT
ABC
T
TI
LEFT
ABC
T
TM
LEFT
LEFT
ABC
T
TI
LEFT
ABC
T
TO
LEFT
ABC
T
TI
LEFT
ABC
T
TS
LEFT
ABC
T
TI
LEFT
ABC
T
TM
TRANSIT
TRN
ABC
T
TI
TRN
ABC
T
TO
TRN
ABC
T
TI
TRN
ABC
T
TS
TRN
ABC
T
TI
TRN
ABC
T
TM
INVALID
INV
ABC
T
TI
INV
ABC
T
TO
INV
ABC
T
TI
INV
ABC
T
TS
INV
ABC
T
TI
INV
ABC
T
TM
Tagged
LEFT
ABC
T
TI
LEFT
ABC
T
TO
LEFT
ABC
T
TS
LEFT
ABC
T
TI
LEFT
ABC
T
TM
UNKNOWN/
ERROR
ERR
ABC
T
TI
ERR
ABC
T
TO
ERR
ABC
T
TI
ERR
ABC
T
TS
ERR
ABC
T
TI
ERR
ABC
T
TM
RUN
ABC
T
TI
Hollifield, 22
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
A Real-World Case Study and Test of HP HMI Concepts
The following section is taken from a study conducted by the Electric Power research Institute (EPRI).
Operator HMI Case Study: The Evaluation of Existing “Traditional” Operator Graphics vs. High Performance Graphics in a Coal Fired Power Plant Simulator , Product ID 1017637
The EPRI study tested these HP HMI concepts at a large, coal-fired power plant. The plant had a full simulator used for operator training. The existing graphics on the simulator (created in the early 1990s) operated the same as those on the actual control system. PAS was retained to prepare several high performance graphics for the simulator. Several operators were then put through several abnormal situations using both the existing and the new high performance graphics.
Four examples of the existing graphics are in Figure 19. They have the following characteristics:
No graphic hierarchy
No Overview
Many controller elements are not shown on any of the existing graphics
Numbers and digital states are presented inconsistently
Poor graphic space utilization
Inconsistent selectability of numbers and elements
Poor color choices, overuse, and inconsistencies. Bright red and yellow are used for normal conditions.
Poor interlock depiction
No trends are implemented, “trend-on-demand” is not used.
Alarm conditions are generally not indicated on graphics – even if the value is a precursor to an automated action.
Hollifield, 23
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 23: 1990s Graphics from the EPRI HP-HMI Test
The operators used dozens of such graphics to control the process.
For the test, several new high performance graphics were created:
Power Plant Overview (Level 1) – see prior figure 15.
Pulverizer Overview Graphic (Level “1.5”) – see Figure 24
Individual Pulverizer Level 2 Control Graphic – see Figure 25
Runback 1 and 2: Special Abnormal Situation Graphics – see Figure 26
The Level 1 Overview (see prior Figure 15)
The Overview graphic shows the key performance indicators of the entire system under the operator’s control. The most important parameters incorporate trends. It is easy to scan these at a glance and detect any non-normal conditions. Status of major equipment is shown. Alarms are easily detected.
The operators found the overview display to be far more useful than the existing graphics in providing overall situation awareness and useful in detecting burgeoning abnormal situations.
• Existing Overview
Hollifield, 24
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
The Level “1.5” Pulverizer Overview Graphic (Figure 24)
The operator controls eight identical, heavily instrumented, and complex pieces of equipment called coal pulverizers. At normal rates, seven are in use and one is on standby in case of a problem. The seven that are running should be showing almost identical performance. It was immediately apparent that an “Overview” graphic of just these eight items would be very useful to the operators, since much of their activity is in monitoring and manipulating them. Being mechanical, they are subject to a variety of problems and abnormal conditions. There were three separate existing graphics needed for monitoring and controlling each pulverizer, 24 in total for them all. Monitoring using 24 graphics was difficult for the operators.
The new Pulverizer Overview in Figure 21 depicts more than 160 measurements on a single graphic! The key to making this understandable is that the devices are supposed to run alike. Instead of blocks of indicators for each pulverizer being grouped together, the same measurement from each pulverizer is grouped together. Any individual unit operating differently than the others stands out. The unit that is in standby service also is easily seen. Air damper positions, a source of problems, are clearly shown.
Note that the trends seemingly violate our recommendation of showing no more than 3 or 4 traces on a single trend. In this case, what the operator is looking for is any trend line that is not “bunched in” with the others. For such a condition, having these 8 traces was acceptable. Note that the standby pulverizer’s trace is normally on the bottom.
Even with such a “dense” information depiction and with so many measurements, the operators found it easy to monitor all eight devices and easily detect burgeoning abnormal situations. It is easy to scan your eye across the screen and spot any elements that are inconsistent. Alarm conditions are also easy to spot.
Note that control actions are not taken on this screen, but rather on the eight individual Level 2 graphics, one for each pulverizer.
Hollifield, 25
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 24: The Level “1.5” Pulverizer Overview
The Level 2 Pulverizer Control Graphic (Figure 25)
Rather than using three separate graphics to control each pulverizer (24 graphics total), a single Level 2 graphic for each pulverizer was created with everything needed to accomplish all typical control manipulations.
08-15-2009 14:22:09PULVERIZER OVERVIEW
Coal Flow Trend
Coal
Flow
KLB/HR
2 Hrs1
140
PULV A PULV B PULV C PULV D PULV E PULV F PULV G PULV HL1 OVERVIEW RUNBACK 1 RUNBACK 2
E
F
G
H
75
74
78
45
76
74
75
74
51
50
50
5075
65
55
51
A A A A M A A A
113113
112113
0113
112112
A B C D E F G H
Mill Amps Trend
A A A A M A A A
4243
4244
043
4343
A B C D E F G H
Diff Pres Trend
A A A A M A A A
8.09.8
10.09.5
0.69.8
9.59.0
A B C D E F G H
Pri. Air Flow Trend
A A A A M A A A
204205
204205
0205
204205
A B C D E F G H
A A A A M A A A
A B C D E F G H
H H
75
74
78
77
78
78
75
74
0
0
50
5075
76
55
51
S. Air Flow Trend
A A A A M A A A
204205
204205
0205
204205
A B C D E F G H
A A A A M A A A
A B C D E F G H
Primary Damper
75
74
78
77
78
78
75
74
30
30
50
5075
73
55
51
A A A A M A A A
A B C D E F G H
North Damper South Damper
75
74
78
77
78
78
75
74
40
40
50
5075
65
55
51
C/A Temp Trend
A A A A M A A A
135135
135135
277135
135135
A B C D E F G H
A A A A M A A A
A B C D E F G H
H
75
74
78
77
78
78
75
74
50
50
50
5075
73
55
51
A A A A M A A A
A B C D E F G H
Hot Damper Cold Damper
ON
Pulverizer Status
G
E
C
A
B
D
H
F
ON
ON
ON
ON
ON
ON
ON
Diag
Burn
Maint
A
B
C
D
Diff
PresPSI
2 Hrs0
16
E
F
G
H
A
B
C
D8
OPENOPENSWG Valves
NORMNORMFlm Mnt Mod
OFFOFF
ON
M1Flame
Main
Flame
Igniter
Flame
Fuel Type
Gas -1
Flm Mnt Mod
90 90
30
M2
S
S
OFF
30
ON
SS
L
Hollifield, 26
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Figure 25: Level 2 Pulverizer Control
While complex in appearance to the layman, the trained operator had no difficulty in understanding and accessing everything they needed for pulverizer startup, shutdown, and swap situations that arose during the test. Much of the text on the screen has to do with the status of automated sequences that sometimes require operator intervention. Everything on the screen is selectable, and when selected the standard faceplate for the element appears in a reserved “faceplate zone” rather than floating around the screen obscuring the graphic. Element manipulation is made via the faceplate.
Abnormal Situation Response Graphics
The operator response for many abnormal plant situations is to cut rates by half, from 700MW to 350MW. Called a “Runback,” this is a complicated and stressful procedure that takes about 20 minutes to accomplish. If done incorrectly or if important parameters are missed, the plant can fall to zero output, a very undesirable situation. One of the main purposes of the simulator was to regularly train the operators for this situation. The operators have to use more than a dozen of the existing graphics to accomplish the task, involving much navigation, screen callups and dismissals, and control manipulation.
PULV B
14:22:09PULVERIZER A – Level 2
PULV OVERVIEW PULV C PULV D PULV E PULV F PULV G PULV H
5.9
AUTO
10.0
82%
GAS PSI
Open Swg Valves
40
140
“A” Coal Flow KLB/HR
2 Hrs
“A” C/A Temperature
135
AUTO
130
71.2%0
200
2 Hrs
“A” Primary Air Flow KLB/HR
120
220
2 Hrs
“A” Sec. Air Flow (Total)
400
900
2 Hrs
Any Seal Air blower stopped
No coal on feeder belt
Any Pulv group trip not reset
Lube oil press low
Flame det clg air press lo
Flame detected
Min boiler A.F. required
LTR atom air press low
Pulv seal air dif f press low
Feeder inlet gate not open
LTR oil press low or HDR VLV not open
All PA fans stopped or PAH stopped
Sequence Blocked By:
Diff-P
72.1%
AUTO
70.0%
70.1%
H. DmpAmps
50.0
CAS
49.0%
48.0%
Damper
31.0%
AUTO
30.0%
27.8%
C.Dmp
Start Pulv
Start Feeder
Pulv Tmp to Auto
Rel Sec Air
Stop Ltrs
Rel Pul DmdReady
Ready
Open Swg Vlvs
PULV “A”
TRIP VALVES
IG HDR VENT
10.7 45
PULV “A”
Group Trip
50%
CAS
50%
56%
N Damp S. Damp
STOP“A” PULVERIZER
Start Sequence
Ready
Ready
Ready
Ready
DoneStatus
Begin Sequence
Sec Air to L.O.
Start Ltrs.
Pulv Grp Dmd
Start PA Flow
STARTING
OPENOPENOPENOPENOPENOPENSWG Valves
NORMMNT-BNORMNORMNORMNORMMaint Mode
OFFOFFOFFOFFOFFOFF
ON
A7A6A5A3A2A1Flame
Main
Flame
Igniter
Flame
Fuel Type:
Gas
90
30 30 30 30 30 30
DoneStatus
Air-N Air-S
X
X
X
Face
Plate
Zone
50%
CAS
50%
42%
312 312
88 90 91 91 94ON ON ON ON ON
113.0
AUTO
115.0
75.0%
Flow
205.0
AUTO
200.0
65.0%
615.2
AUTO
600.0
60.0%
Flow
X
Ready
HOLD
PTR Status OK
Reset
Flame Status OK
Reset
Trip Status OK
Reset
CLOSED
IG GAS TRIP CLOSED
IG OIL TRIP CLOSED
BURNER VENT CLOSED
L3 Feeder L3 Flame L3 GAS Main Menu
Hollifield, 27
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
However, in more than a decade of such training, it had never occurred to anyone to design special graphics specifically designed to assist in this task! This demonstrates the power of inertia in dealing with our HMIs. Specific Abnormal Situation Detection and Response graphics are an important element of an HP HMI.
PAS created two “Runback” graphics designed specifically to assist in this task. Every element that the operator needed to effectively monitor and control the runback situation was included on them. In use, the operators placed them on adjacent physical screens. Figure 26 shows “Runback 1,” Runback 2 was similar. The reserved faceplate zone is on the lower right.
Figure 26: Abnormal Situation Graphics – Runback 1
As a simple example of providing information rather than data, consider the trend graph at the upper left of Runback 1. To be successful, the rate of power reduction must not be too slow or too fast. The existing graphics had no trend of this, simply showing the current power megawatt number. This new trend graph had the “sloped-line” element placed next to it, indicating the ideal rate of power reduction, the full load zone, and the target half-rate zone. On the figure, the actual rate of drop is exceeding the desired rate, and that condition is easily seen. (Note: It would have been more desirable to have the sloped lines on the background of the trend area itself, but the DCS could not accomplish such a depiction. This is a compromise, but one the operators still found very useful.)
Hollifield, 28
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
The Testing
Eight Operators, averaging 8 years console operating experience each, were used in the test. They received only one hour’s familiarity with the new graphics prior to the start of testing. They were tested on four increasingly complex situations, lasting about 20 minutes each.
Coal Pulverizer Swap Under Load
Pulverizer Trip and Load Reduction
Manual Load Drop with Malfunctions
Total Plant Load Runback
All operators did all scenarios twice, using the old graphics alone, and the HP HMI graphics. Half used the old graphics first, and half used the HP HMI graphics first).
Quantitative and qualitative measurements were made on the performance of each scenario (e.g. detection of the abnormal condition, time to respond, correct and successful response).
The Results
The high performance graphics were significantly better in assisting the operator in:
maintaining situational awareness
recognizing abnormal situations
Recognizing equipment malfunctions
dealing with abnormal situations
embedding knowledge into the control system
Operators highly rated the Overview screen, agreeing that it provided highly useful “big picture” situation awareness. Even with only a few hours total with the new graphics, operators had no difficulties in operating the unit. The High Performance graphics are designed to have intuitive depictions.
Very positive Operator comments were received on the analog depictions, alarm depictions, and embedded trends. There were consistent positive comments on how “obvious” the HP HMI made the various process situations. Values moving towards a unit trip were clearly shown and noticed by the operators.
The operators commented that HP HMI would enable faster and more effective training of new operations personnel. The negative operator comments generally had to do with lack of familiarity with the graphics prior to the test.
The best summary quote was this one:
“Once you got used to these new graphics, going back to the old ones would be hell.”
The effect of inertia being the controlling factor for HMI change was once more confirmed. The existing HMI had been in use since the early 1990s, with simulator training for more than a decade. Despite clear deficiencies, almost no change to the existing HMI had been made since inception.
Hollifield, 29
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Operators using the existing graphics first in the test were then asked “What improvements would you make on the existing graphics to help in these situations? In response, there were very few or no suggestions!
However, operators using the existing graphics after they used the HP HMI graphics had many suggestions for improvement, namely analog depictions, embedded trends, consistent navigation, etc!
So, people get “used to” what they have – and do not complain or know what they are missing if they are unfamiliar with these HP HMI concepts.
A lack of complaints does not indicate that you have a good HMI!
The Seven Step Work Process
There is a seven step methodology for the development of a high performance HMI.
Step 1: Adopt a high performance HMI philosophy and style guide. A written set of principles detailing the proper way to construct and implement a high performance HMI is required.
Step 2: Assess and benchmark existing graphics against the HMI philosophy. It is necessary to know your starting point and have a gap analysis.
Step 3: Determine specific performance and goal objectives for the control of the operation and for all modes of operation. These are such factors as:
Safety parameters/limits
Production rate
Run length
Equipment health
Environmental (i.e. Emission control)
Production cost
Quality
Reliability
It is important to document these, along with their goals and targets. This is rarely done and is one reason for the current state of most HMIs.
Step 4: Perform task analysis to determine the control manipulations needed to achieve the performance and goal objectives. This is a simple step involving the determination of which specific controls and measurements are needed to accomplish the operation’s goal objectives. The answer determines the content of each Level 2, 3, and 4 graphic.
Step 5: Design high performance graphics, using the design principles in the HMI philosophy and elements from the style guide to address the identified tasks.
Step 6: Install, commission, and provide training on the new HMI.
Step 7: Control, maintain, and periodically reassess the HMI performance.
Hollifield, 30
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
Conclusion
Sophisticated, capable, computer-based control systems are currently operated via ineffective and problematic HMIs, which were designed without adequate knowledge. In many cases, guidelines did not exist at the time of graphic creation and the resistance to change has kept those graphics in commission for two or more decades.
The functionality and effectiveness of these systems can be greatly enhanced if redesigned in accordance with proper principles. A published test of these concepts proves their superior performance. A High Performance HMI is practical, achievable, and proven.
References
Hollifield, B., Oliver, D., Habibi, E., & Nimmo, I. (2008). The High Performance HMI Handbook.
Hollifield,B., Perez, H., Crawford, W., (2009), Electric Power Research Institute (EPRI), Operator HMI Case Study: The Evaluation of Existing “Traditional” Operator Graphics vs. High Performance Graphics in a Coal Fired Power Plant Simulator, Product ID 1017637, Note: currently available only to EPRI members
Acronyms
API American Petroleum Institute
ASM® Consortium Abnormal Situation Management Consortium
DCS Distributed Control System
EPRI Electric Power Research Institute
HMI Human-Machine Interface
PHMSA Pipeline and Hazardous Materials Safety Administration
SCADA Supervisory Control and Data Acquisition
Hollifield, 31
Presented at the 2013 ISA Water & Wastewater and Automatic Controls Symposium Aug 6-8, 2013 – Orlando, Florida, USA – www.isawwsymposium.com
About the Author
Bill Hollifield is the PAS Principal Alarm Management and HMI Consultant. He is a voting member of the ISA SP-18 Alarm Management committee, the ISA-101 HMI committee, and the American Petroleum Institute’s committee for API-1167 Recommended Practices for Alarm Management of Pipeline Systems.
Bill is also the coauthor of The Alarm Management Handbook, The High-Performance HMI Handbook, and the Electric Power Research Institute’s Alarm Management and Annunicator Application Guidelines. Bill has international, multi-company experience in all aspects of Alarm Management and HMI, along with many years of chemical industry experience with focus in project management, chemical production, and control systems.
Bill has authored several papers on Alarm Management and HMI, and is a regular presenter on such topics in such venues as API, ISA, and Electric Power symposiums. He has a BSME from Louisiana Tech University and an MBA from the University of Houston. He’s a pilot, built his own aircraft (a Van’s RV-12, with a High Performance HMI!), and builds furniture (and the occasional log home in the Ozarks) as a hobby.
Bill and “Sweetie”
About PAS
PAS (www.pas.com) improves the automation and operational effectiveness of power and process plants worldwide by aggregating, contextualizing, and simplifying relevant information and making it universally accessible and useful. We provide software and services that ensure safe running operations, maximize situation awareness, and reduce plant vulnerabilities. Our comprehensive portfolio includes solutions for Alarm Management, Automation Genome Mapping, Control Loop Performance Optimization, and High-Performance Human-Machine Interfaces. PAS solutions are installed in over 1,000 industrial plants worldwide.