Safety Considerations Guide for Trident v2 Systems - TUV ...

Hazard and Risk Analysis
Hazard and Risk Analysis 5
In the United States, OSHA Process Safety Management (PSM) and EPA Risk Management
Program (RMP) regulations dictate that a Process Hazard Analysis (PHA) be used to identify
potential hazards in the operation of a chemical process and to determine the protective
measures necessary to protect workers, the community, and the environment. The scope of a
PHA may range from a very simple screening analysis to a complex hazard and operability
study (HAZOP).
A HAZOP is a systematic, methodical examination of a process design that uses a multidisciplinary
team to identify hazards or operability problems that could result in an accident. A
HAZOP provides a prioritized basis for the implementation of risk mitigation strategies, such
as SISs or ESDs.
If a PHA determines that the mechanical integrity of a process and the process control are
insufficient to mitigate the potential hazard, an SIS is required. An SIS consists of the
instrumentation or controls that are installed for the purpose of mitigating a hazard or bringing
a process to a safe state in the event of a process disruption.
A compliant program incorporates “good engineering practice.” This means that the program
follows the codes and standards published by such organizations as the American Society of
Mechanical Engineers, American Petroleum Institute, American National Standards Institute,
National Fire Protection Association, American Society for Testing and Materials, and National
Board of Boiler and Pressure Vessel Inspectors. Other countries have similar requirements.
Safety Integrity Levels
This figure shows the relationship of DIN V 19250 classes and SILs (safety integrity levels).
R
I
S
K
R
E
D
U
C
T
I
O
N
99.999
99.99
99.90
99.00
90.00
Percent
Availability
0.00001
0.0001
0.001
0.01
0.1
PFD avg
Risk Measures
>10,000
10,000–
1,000
1,000–
100
100–
10
RRF
Figure 2 Standards and Risk Measures
SIL 3
SIL 4
SIL 3
SIL 2 SIL 2
SIL 1
ANSI/ISA
S84.01
SIL 1
IEC
61508
Risk Standards
Safety Considerations Guide for Trident v2 Systems