Chemical Engineering March 2016 - 60

Alarms per day likely to have been missed
Alarms per day before and after rationalization
1200
1000
800
600
400
200
Week 1: 3,885
Week 2: 2,281
Week 3: 2,728
Week 4: 1,903
Week 5: 2,173
Week 6: 1,443
Week 7: 2,253
Week 8: 4,260
Total: 20,926
8 weeks
Figure 5. Despite sound averages for alarm rates, it can still
be the case that many alarms could be missed during alarm
flood periods
alarm system is rationalized, its configuration
must not change without authorization.
because DCS systems can be easily
changed by a variety of sources, they often
require mechanisms that frequently audit
(and enforce) the approved configuration.
Step 6: Implement advanced alarm management.
Certain advanced alarm capabilities
may be needed on some systems to
address specific issues. For example, statebased
alarming monitors the current process
state, and alarm settings are dynamically altered
in predetermined ways to match the
alarming requirements of that process state.
Alarm flood suppression temporarily eliminates
the expected and distracting alarms
from a unit trip, leaving the relevant alarms
that assist the operator in managing that
post-trip situation. Such advanced methods
can ensure that the alarm system is effective
even in abnormal situations.
Step 7: Control and maintain the improved
system. An effective alarm system
requires an ongoing and typically automated
Alarm
count
35,000
30,000
25,000
20,000
15,000
10,000
5,000
Most frequent annunciated alarms
30 days
Cumulative %
Ten alarms make
up 76% of the total
alarm loading
100
90
80
70
60
50
40
30
20
10
8000
7000
6000
5000
4000
3000
2000
1000
Average before: 2,417
Average after: 249
An 89% reducation
31 days
Figure 7. Alarm rates can usually be brought into target limits
by alarm rationalization and bad-actor reduction steps
program of system analyses that may include
KPI monitoring and the correction of
problems as they occur.
Concluding remarks
The various problems with alarm systems are
well recognized and there are proven solutions
to these problems. The principles from these
solutions have been successfully applied to
thousands of alarm systems worldwide. The
alarm management body of knowledge is mature.
Solving alarm-system problems simply
requires the will and effort to do so.
n
Edited by Scott Jenkins
References
1. Hollifield, B. and Perez, H. Maximize Operator Effectiveness: High
Performance HMI Principles and Best Practices, Part 1 of 2. PAS
Inc., Houston, 2015.
2. Hollifield, B. and Perez, H. Maximize Operator Effectiveness: High
Performance HMI Case Studies, Recommendations, and Standards,
Part 2 of 2. PAS Inc., Houston 2015.
3. Hollifield, B. and Habibi, E. The Alarm Management Handbook, 2nd
Ed., PAS Inc., Houston 2010.
4. Hollifield, B. Understanding and Applying the ANSI/ISA 18.2 Alarm
Management Standard. PAS Inc., Houston 2010.
Author
Bill Hollifield is the principal consultant at
PAS Inc. (16055 Space Center Blvd., Suite
600, Houston, TX 77062; Phone: 281-2866565;
Email: bhollifield@pas.com). He is responsible
for alarm management and highperformance
HMI. He is a member of the
ISA-18 Alarm Management committee, the
ISA-101 HMI committee, and is a co-author of
the Electric Power Research Institute's (EPRI)
Alarm Management Guidelines. Hollifield is
Figure 6. In many cases, the most frequently occurring
alarms make up the bulk of the total alarm load
60
also coauthor of the Alarm Management Handbook and The High
Performance HMI Handbook, along with many articles on these topics.
Hollifield has a dozen years of international, multi-company experience
in all aspects of alarm management and effective HMI
design consulting for PAS, coupled with 40 years overall of industry
experience focusing on project management, chemical production
and control systems. Hollifield holds a B.S.M.E. from Louisiana Tech
University and an MBA from the University of Houston. He's a pilot
and has built his own plane (with a high-performance HMI).
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