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1 Functional safety

VEGACAL series 60 • Two-wire 4 … 20 mA/HART

35593-EN-181129

 

– Functional safety - safety instrumented systems for the process 

industry sector - Part 1: Framework, definitions, system, hard-

ware and software requirements

Failure limit values for a safety function, depending on the SIL class 

(of IEC 61508-1, 7.6.2)

Safety integrity level

Low demand mode

High demand mode

SIL

PFD

avg

PFH

4

≥ 10

-5

 … < 10

-4

≥ 10

-9

 … < 10

-8

3

≥ 10

-4

 … < 10

-3

≥ 10

-8

 … < 10

-7

2

≥ 10

-3

 … < 10

-2

≥ 10

-7

 … < 10

-6

1

≥ 10

-2

 … < 10

-1

≥ 10

-6

 … < 10

-5

Safety integrity of hardware for safety-related subsystems of type B 

(IEC 61508-2, 7.4.3)

Safe failure fraction

Hardware fault tolerance

SFF

HFT = 0

HFT = 1 

(0)

HFT = 2

< 60 %

not permit-

ted

SIL1

SIL2

60 % … < 90 %

SIL1

SIL2

SIL3

90 % … < 99 %

SIL2

SIL3

(SIL4)

≥ 99 %

SIL3

(SIL4)

(SIL4)

According to IEC 61511-1, paragraph 11.4.4, the failure tolerance 

HFT can be reduced by one for service-proven subsystems if the fol-

lowing conditions are met:

• 

The instrument is service proven

• 

Only process-relevant parameters can be modified on the instru-

ment (e. g. measuring range, current output in case of failure …)

• 

These process-relevant parameters are protected (e.g. password, 

…)

• 

The safety function requires less than SIL4

The assessment by change management staff was a part of the 

"service proven" verification.

1.2 Planning

The measuring system generates on the current output a signal be-

tween 3.8 mA and 20.5 mA corresponding to the level.
This analogue signal is transmitted to a connected processing unit to 

monitor the following conditions:

• 

Exceeding a preset level

• 

Falling below a preset level

When the switching point set on the processing unit is reached, a 

signal is output.

Safety requirements

Service proven

Safety function

Содержание VEGACAL 60 Series

Страница 1: ...Safety Manual VEGACAL series 60 Two wire 4 20 mA HART Document ID 35593...

Страница 2: ...1 Functional safety 3 1 1 General information 3 1 2 Planning 4 1 3 Instrument parameter adjustment 6 1 4 Setup 7 1 5 Reaction during operation and in case of failure 7 1 6 Recurring function test 8 1...

Страница 3: ...ant architecture is excluded The SIL conformity is confirmed by the verification documents in the appendix SIL Safety Integrity Level HFT Hardware Fault Tolerance SFF Safe Failure Fraction PFDavg Aver...

Страница 4: ...According to IEC 61511 1 paragraph 11 4 4 the failure tolerance HFT can be reduced by one for service proven subsystems if the fol lowing conditions are met The instrument is service proven Only proce...

Страница 5: ...responding portions of the failure rates must be assigned to the dangerous failures The stated values in chapter Safety relevant characteristics can thus worsen The processing unit must correspond to...

Страница 6: ...s e g HART I C Bus are not used for transmission of safety relevant information The measuring system should be used appropriately taking pressure temperature density dielectric value and chemical prop...

Страница 7: ...rized modification the set parameters must be protected against unintentional access Activate the password protection in the adjustment software Activate the PIN on the display and adjustment module A...

Страница 8: ...hitectures it is a good idea to verify the effect of the redundancy through recurring function tests at appropriate intervals Please carry out the test in such a way that the correct safety function i...

Страница 9: ...F MTTF MTTR 0 93 x 106 h E013 no measured value available 10 sek E036 E037 no executable sensor software 1 h Single channel architecture SIL SIL2 HFT 0 Instrument type Type B Applies to overfill and d...

Страница 10: ...years Multiple channel architecture If the measuring system is used in a multiple channel architecture the safety relevant characteristics of the selected structure of the meas chain must be calculat...

Страница 11: ...11 2 Supplement VEGACAL series 60 Two wire 4 20 mA HART 35593 EN 181129 2 Supplement...

Страница 12: ...12 2 Supplement VEGACAL series 60 Two wire 4 20 mA HART 35593 EN 181129...

Страница 13: ...13 Notes VEGACAL series 60 Two wire 4 20 mA HART 35593 EN 181129...

Страница 14: ...14 Notes VEGACAL series 60 Two wire 4 20 mA HART 35593 EN 181129...

Страница 15: ...15 Notes VEGACAL series 60 Two wire 4 20 mA HART 35593 EN 181129...

Страница 16: ...of delivery application practical use and operat ing conditions of the sensors and processing systems correspond to the information available at the time of printing Subject to change without prior n...

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