The High Performance HMI - isawwsymposium.comisawwsymposium.com/.../uploads/...HighPerformanceHMIs-EPRI-stu… · High Performance HMI – Proof Testing in Real-World Trials Bill

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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

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Hollifield, 18


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


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


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

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Valve Positions

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Weyland-Yutani Pipeline Overview

Main MenuLV-426

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Hollifield, 21


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

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High-High Alarm Black Red 1234

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Hollifield, 22


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


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


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


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

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Hollifield, 26


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

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LTR atom air press low

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Sequence Blocked By:

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Hollifield, 27


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


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


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


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


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.

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