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©ASCO, L.P. 160 Park Avenue, Florham Park, New Jersey 07932 www.asco.com
I&M No
V 9629 R9
All Ri
hts Rese
ved
1
Introduction
This Operating Manual provides the necessary information to design, install, verify and maintain a
Safety
Instrumented Function (SIF) utilizing an ASCO Solenoid Valve. This manual provides necessary
requirements
for meeting the IEC 61508 or IEC 61511 functional safety
standards.
1.1 Terms and
Abbreviations
•
Process Valve Any valve that is used to control the flow of media being used in a
process.
For the purpose of this document, this is usually a 2-way valve
whose
movement is being controlled by an actuator and pilot
valve.
•
Pilot Valve A 3-way or 4-way valve that is used to send or remove pressurized
media
to and from an actuator for the opening and closing of a process
valve.
•
Direct Acting Refers to a solenoid valves main orifice that is opened and closed as
a
direct result of the solenoid valves electromagnetic movement when
the
coil is energized and
de-energized.
•
Indirect Acting Refers to a solenoid valve’s main orifice that is opened and closed as
a
result of fluid flow being directed from the electromagnetic 3-way
solenoid
pilot.
•
Safety Freedom from unacceptable risk of
harm
•
Functional Safety The ability of a system to carry out the actions necessary to achieve or
to
maintain a defined safe state for the equipment / machinery / plant
/
apparatus under control of the
system
•
Basic Safety The equipment must be designed and manufactured such that it
protects
against risk of damage to persons by electrical shock and other
hazards
and against resulting fire and explosion. The protection must be
effective
under all conditions of the nominal operation and under single
fault
condition
•
Safety Assessment The investigation to arrive at a judgment - based on evidence - of
the
safety achieved by safety-related
systems
•
Fail-Safe State The state where the solenoid is de-energized and its return spring
holds
the pilot in the closed
position.
•
Fail Safe Failure that causes the valve to go to the defined fail-safe state without
a
demand from the
process.
•
Fail Dangerous Failure that does not respond to a demand from the process (i.e.
being
unable to go to the defined fail-safe
state).
•
Fail Dangerous Undetected (DU) Failure that is dangerous and that is not being diagnosed
by
automatic stroke
testing.
•
Fail Dangerous Detected (DD) Failure that is dangerous but is detected by automatic stroke
testing.
•
Fail No Effect Failure of a component that is part of the safety function but that has
no
effect on the safety
function
.
•
Low Demand Mode Mode, where the frequency of demands for operation made on a
safety-
related system is no greater than twice the proof test
frequency.
1.2
Acronyms
•
FMEDA Failure Modes, Effects and Diagnostic
Analysis
•
HFT Hardware Fault
Tolerance
•
MOC Management of Change: These are specific procedures often done
when
performing any work activities in compliance with government
regulatory
authorities
.
•
PFD
AVG
Average Probability of Failure on
Demand
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