Designing An Sif Using An Svi Ii Esd; Safety Function; Environmental Limits - GE Masoneilan SVI II ESD Installation And Maintenance Manual

Smart valve interface with sil3 emergency shutdown pst controller

Table of Contents

Designing an SIF Using an SVI II ESD

The following must be taken into consideration when designing a SIF (Safety Instrumented

Function) using the SVI II ESD:

Design Verification

SIL Capability

Connecting the SVI II ESD to the SIS Logic-Solver

General Requirements

Safety Function

When de-energized, the SVI II ESD moves to its fail-safe position. For a single-acting PST

controller the safe state is when the port Actuator 1 is exhausted to a pressure less than 1

PSIG (0.069 bar, 6.9 kPa). The valve actuation must automatically move the valve to the safe

state when the digital valve controller falls in safe state.

The SVI II ESD is intended to be part of final element subsystem, as per IEC 61508, and the

achieved SIL level of the function must be verified by the function designer.

Environmental Limits

The designer of a SIF must check that the product is rated for use within the environmental

limits as stated in Table 13 on page 155.

Application Limits

Listed below are the application limits for the SVI II ESD installed in a SIF:

The application of the SVI II ESD is limited for SIF where the safe state is the

de-energized state (shutdown) of the valve. The PST Controller can be operated with

either one of two control signals: 4 - 20 mA or 0 - 24 VDC.

With a 4 - 20 mA control signal, normal operation is with a 20 mA current loop signal to

the PST controller. A shutdown command is issued by bringing the current to 5.6 mA or

lower.

With a 0 - 24 VDC control signal, normal operation is with a 24 VDC signal applied to

the PST controller. A shutdown command is issued by opening the loop or bringing the

control signal to 3 VDC or lower.

Masoneilan SVI II ESD Installation and Maintenance Manual

| 21

Table of Contents