SILSafe Data

About SILSafe Data

The use of realistic and application appropriate failure rate data has a significant impact on the validity of SIL verification calculations. Unfortunately there is often conflicting or incomplete information readily available to perform this task.

Origins of SILSafeData How to Use SILSafeData

The impact of poor information can be dangerous under design or expensive overdesign.

Low Bound

3/12

High Bound

11/12

Determining if data is credible for use is a critical first step in SIL verification calculations. The SILSafeData.com website is a listing of upper and lower bounds for various devices commonly used in safety instrumented functions. These bounds were derived from statistical analysis of FMEDA results which represent design variations and application variations in combination with extensive comparisons with realistic field failure data. exida calls this technique “Predictive Analytics.”

The upper and lower bound dangerous undetected failure rate data in SILSafeData is presented to perform a credibility check on any data provided for SIL verification calculations. The data was analyzed using average operating conditions and average maintenance capability (SSI=2). If the dangerous failure rate data presented is not within SILSafeData limits, further analysis and justification is warranted before using the presented data. More specific data may be available from any manufacturer’s exida FMEDA Report. To account for different maintenance / operational situations, refer to exSILentia.

Data Check

Dangerous Undetected Failure Rates for Sensors

(Rates in FITs – 1 failure per billion hours)

Category	Type	Other	DU Low Bound	DU High Bound
Pressure Switch	Mechanical		50	1000
Pressure Transmitter	Analog/Smart		80	500
Pressure Transmitter	Safety Certified		20	150

Temperature Switch	Mechanical		50	1000
Temperature Pyrometer	Smart		200	460
Temperature Transmitter	Analog/Smart		600	1600
Temperature Transmitter	Safety Certified		25	90
Thermocouple	Close Coupled (<1 meter)	excludes open circuit*	5	100
Thermocouple	Extension	excludes open circuit*	100	1000
Two/Three Wire RTD	Close Coupled (<1 meter)	excludes open circuit*	10	200
Two/Three Wire RTD	Extension	excludes open circuit*	110	2000
Four Wire RTD	Close Coupled (<1 meter)	excludes open circuit*	10	150
Four Wire RTD	Extension	excludes open circuit*	80	1800
		* detected by input device
Level Switch	Mechanical		50	1000
Level Transmitter	Analog/Smart	Radar	160	750
Level Transmitter	Safety Certified	Radar	70	750
Level Transmitter	Analog/Smart	Buoyancy	80	330
Level Transmitter	Safety Certified	Buoyancy	50	150
Level Transmitter	Analog/Smart	Capacitance	70	300
Level Transmitter	Safety Certified	Capacitance	50	150
Level Transmitter	Analog/Smart	Vibration	60	300
Level Transmitter	Safety Certified	Vibration	15	150
Level Transmitter	Analog/Smart	Ultrasonic	60	250
Level Transmitter	Safety Certified	Ultrasonic	40	150

Flow Transmitter	Analog/Smart	Magnetic	200	650
Flow Transmitter	Safety Certified	Magnetic	100	400
Flow Transmitter	Analog/Smart	Ultrasonic	400	850
Flow Transmitter	Safety Certified	Ultrasonic	200	700
Flow Transmitter	Analog/Smart	Coriolis	200	650
Flow Transmitter	Safety Certified	Coriolis	100	450
Flow Transmitter	Analog/Smart	Vortex	200	600
Flow Transmitter	Safety Certified	Vortex	100	400
Flow Transmitter	Analog/Smart	Thermal	200	1500
Flow Transmitter	Safety Certified	Thermal	100	800

Current Transmitter	Analog/Smart		80	400
Current Transmitter	Safety Certified		40	250

Dangerous Undetected Failure Rates for Logic Solver Subsystems

(Rates in FITs – 1 failure per billion hours)

Category	Type	Other	DU Low Bound	DU High Bound
Main Processor	PLC/DCS	General Purpose	500	2000
Power Supply	PLC/DCS	General Purpose	10	200
Analog Input Module	PLC/DCS	General Purpose	100	250
Analog Input Channel	PLC/DCS	General Purpose	5	40
Digital Input Module	PLC/DCS	General Purpose	50	150
Digital Input Channel	PLC/DCS	General Purpose	25	100
Digital Output Module	PLC/DCS	General Purpose	50	150
Digital Output Channel	PLC/DCS	General Purpose	25	250

Category	Type	Other	DU Low Bound	DU High Bound
Main Processor	Safety PLC	General Purpose	0	300
Power Supply	Safety PLC	General Purpose	0	50
Analog Input Module	Safety PLC	General Purpose	5	150
Analog Input Channel	Safety PLC	General Purpose	1	15
Digital Input Module	Safety PLC	General Purpose	10	30
Digital Input Channel	Safety PLC	General Purpose	3	10
Digital Output Module	Safety PLC	General Purpose	10	30
Digital Output Channel	Safety PLC	General Purpose	2	10

Dangerous Undetected Failure Rates for Final Element Devices

Category	Type	Other	DU Low Bound	DU High Bound
Actuator	Pneumatic Piston	Spring Return	120	700
Actuator	Hydraulic Piston	Spring Return	130	1300
Actuator	Pneumatic Diaphragm	Spring Return	110	910
Actuator	Pneumatic Rack & Pinion	Double Acting	325	1500
Actuator	Pneumatic Rack & Pinion	Spring Return	200	900
Actuator	Hydraulic Scotch Yoke	Double Acting - Single Piston	375	1600
Actuator	Hydraulic Scotch Yoke	Double Acting - Double Piston	525	1600
Actuator	Hydraulic Scotch Yoke	Spring Return	325	1100
Actuator	Pneumatic Scotch Yoke	Double Acting - Single Piston	350	1650
Actuator	Pneumatic Scotch Yoke	Double Acting - Double Piston	500	1650
Actuator	Pneumatic Scotch Yoke	Spring Return	300	1200
Actuator	ESD Hydraulic Scotch Yoke	Spring Return	450	1200
Actuator	Motor Driven		500	2400
Valve	Zero/Single Offset Butterfly	Close on Trip	300	1000
Valve	Zero/Single Offset Butterfly	Tight Shutoff	925	2650
Valve	Zero/Single Offset Butterfly	Open on Trip	150	825
Valve	Double Offset Butterfly	Close on Trip	400	1025
Valve	Double Offset Butterfly	Tight Shutoff	875	2350
Valve	Double Offset Butterfly	Open on Trip	300	750
Valve	Triple Offset Butterfly	Close on Trip	325	1025
Valve	Triple Offset Butterfly	Tight Shutoff	875	2350
Valve	Triple Offset Butterfly	Open on Trip	200	750
Valve	Globe	Close on Trip	350	1800
Valve	Globe	Tight Shutoff	900	2400
Valve	Globe	Open on Trip	250	1000
Valve	Floating Ball	Close on Trip	300	900
Valve	Floating Ball	Tight Shutoff	800	3000
Valve	Floating Ball	Open on Trip	200	800
Valve	Plug	Close on Trip	375	1000
Valve	Plug	Tight Shutoff	725	1900
Valve	Plug	Open on Trip	275	900
Valve	Trunnion Ball	Close on Trip	400	900
Valve	Trunnion Ball	Tight Shutoff	900	3000
Valve	Trunnion Ball	Open on Trip	300	800
Valve	Gate	Close on Trip	300	1000
Valve	Gate	Tight Shutoff	800	2000
Valve	Gate	Open on Trip	200	1000
Quick Exhaust Valve	Diaphram Type		5	80
Quick Exhaust Valve	Pilot Operated		50	200
Volume Booster Valve		DTT - Exhaust on trip	20	350
Poppet Solenoid Valve	Direct Acting 3/2	DTT - Exhaust on trip	40	240
Poppet Solenoid Valve	Pilot Operated 3/2	DTT - Exhaust on trip	60	420
Solenoid Valve Spool	Direct Acting 3/2	DTT - Exhaust on trip	100	650
Solenoid Valve Spool	Pilot Operated 3/2	DTT - Exhaust on trip	150	720
Solenoid Valve Spool	Direct Acting 5/2	DTT - Exhaust on trip	200	900
Solenoid Valve Spool	Pilot Operated 5/2	DTT - Exhaust on trip	250	950
Motor Contactor	0 - 600V	DTT	100	500
Motor Contactor	600V - 15000V	DTT	150	600
Motor Overload Relay	Mechanical		100	400
Motor Overload Relay	Smart		600	2000
VFD Drive		DTT - Electrical Active	400	1000
VFD Safe Torque Off		DTT - Electrical Active	100	400

SERH - The Safety Equipment Reliability Handbook

The SERH provides a collection of failure rate data that is applicable for use in Safety Instrumented System (SIS) conceptual design verification in the process industry. The Safety Equipment Reliability Handbook remains the ultimate reference source for any safety engineer involved in Conceptual Design and Safety Integrity Level verification.

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