The health and status of both SLS 1508 Logic Solvers and their channels are

available in the diagnostics explorer.

When one of a redundant pair of SLS 1508 Logic Solversis removed online there

is no disturbance to the process.

When the missing SLS 1508 Logic Solver is replaced with another SLS 1508 Logic Solver,

the new SLS 1508 Logic Solver completes its power-up self-tests before the

active Logic Solver cross-loads the current database.

In safe areas, failed SLS 1508 Logic Solvers can be replaced under power.

In hazardous areas,appropriate installation procedures must be followed.

Automatic proof testing can be selected on a redundant pairof SLS 1508 Logic Solvers.

The desired proof-test interval is set in the configuration and the SLS 1508 Logic Solvers perform

the proof test automatically. A warning is given to the operator before

the automatic proof test is started.

Redundancy

The redundant SLS 1508 Logic Solver modules are connectedto the field at the redundant

terminal block. No control strategy configuration is required to take advantage

of SLS 1508 Logic Solver redundancy, as the system’s auto-sense capability

automatically recognizes the redundant pair of Logic Solvers.

An integrity error alarm in a redundant SLS 1508 Logic Solver pair will notify

the operator of a failure. Both SLS 1508 Logic Solvers in a redundant pair

are monitored for integrity alarms at all times.

Events that can cause integrity alarms include:

• Hardware failure within a SLS 1508 Logic Solver

• Communications failure between a SLS 1508 Logic Solver and the SISNet

• Communications failure between a redundant pair of SLS 1508 Logic Solvers

• Communications failure between a SLS 1508 Logic Solver and an DeltaV Controller

• Removal of a SLS 1508 Logic Solver from the carrier

Unique Redundancy Methodology

Introduction to Redundancy

While the SLS 1508 Logic Solver is rated suitable for use in SIL 3 applications

in simplex mode, it is installed in redundant pairs for increased process availability.

Redundant SLS 1508 Logic Solvers run in parallel at all times.Both read the inputs

from the I/O terminals, both execute the logic and both drive the outputs at the I/O terminals.

There is no concept of primary and backup or master and slave,which is unlike any other SIS.

The only difference between the two is that one communicates with both the engineering

and operator workstations and the dedicated safety network (SISNet);

this is the one with the Active light on the bezel.The other (Standby) is

communicating only on the SISNet.In the event that a failure is detected in

one of the SLS 1508 Logic Solvers, it automatically goes to a failed state. 

In this condition, all its output channels are de-energized;

this has no impact on the other SLS 1508 Logic Solver or the physical

outputs because the other SLS 1508 Logic Solver continuesto read inputs

execute logic and drive outputs. The transition from redundant to simplex

mode is therefore completely bumpless.

Multiple Domains: The simplest implementation of an SLS 1508 network is to have

one SIS Network ring and one SIS Network domain, that includes all of the

logic solvers in the SIS Network ring. In larger applications, the logic solvers

can be split into multiple SIS Network domains. Another approach is to have

multiple SIS Network rings, each on a SIS Network domain.

The SISNet Repeaters can be located anywhere on a local peer bus – between

the DeltaV Controller(s) and the terminated 1-wide carrier.

Remote Peer Ring: SISNet Repeaters hosted by one DeltaV controller communicate

with SISNet Repeaters hosted by a different DeltaV controller over a fiber-optic remote peer ring.

A local SISNet Repeater collects locally generated messages that have

been designated as global variables into a singlemessage and sends it to

the next SISNet Repeater in the ring.

Upon receipt of a message, the receiving SISNet Repeater broadcasts it on its local

peer bus (SISNet) and forwards the message to the next SISNet Repeater in the ring.

A global message is forwarded around the ring once. The primary SISNet Repeaters

form one fiber-optic ring and the secondary form a separate, independent ring.

Carrier extender cables and local peer bus extender cablesconnecting a DeltaV

controller and 8-wide carrier with standard DeltaV I/O and SLS 1508 Logic Solver

to a second 8-wide carrier (hosted by the same controller) are installed with

SLS 1508 Logic Solvers, SISNet Repeaters, and a terminated 1-wide carrier.

Communication

Control Network: The DeltaV Control Network provides communication between

the nodes in the DeltaV network.Refer to the Installing Your DeltaV Digital

Automation Systemmanual for complete information on the Control Network.

Local Bus: The Local Bus provides communication between DeltaV controllers

and SLS 1508 Logic Solvers and between DeltaV controllers and SISnet Repeaters.

Local Peer Bus (SISNet): SLS 1508 Logic Solvers communicatewith other SLS 1508

Logic Solvers and with local SISNet Repeaters through the carriers over

a 2 channel local peer bus.

The same message is broadcasted over both channels. The localpeer bus must

be terminated at both ends. The local peer bus is terminated at the left

end through the 2-wide power/controller carrier and at the right end

through a terminated 1-wide carrier.

The SISNet Repeaters can be located anywhere on a local peer bus – between

the DeltaV Controller(s) and the terminated 1-wide carrier.

Remote Peer Ring: SISNet Repeaters hosted by one DeltaV controller communicate

with SISNet Repeaters hosted by a different DeltaV controller over a fiber-optic remote peer ring.

Product Description

This section provides general information on DeltaV SIS hardware. Refer to the Installing

Your DeltaV Distributed Control System manual for more information on DeltaV system hardware.

DeltaV SIS Hardware

The DeltaV SIS process safety system consists of the following hardware:

• Redundant Logic Solvers (SLS 1508) and termination blocks

• SISNet Repeaters (see separate product data sheet)

• Carrier extender cables

• Local peer bus extender cables

• Right 1-wide carrier with termination

Logic Solvers (SLS 1508) contain the logic-solving capability and provide an interface

to 16 I/O channels that can be configured as Discrete Input, Discrete Output, Analog Input

(HART) and HART two-state output channels. Logic Solversand termination blocks

install on the 8-wide carrier.

Logic Solvers communicate with each other through thecarriers over a two-channel,

local peer bus (SISnet) and remotepeer ring. Local Logic Solvers are hosted by the same DeltaV

controller and remote Logic Solvers are hosted by a different DeltaV controller.

Logic Solvers are powered by a 24 V DC power supply that is separate from the

power supply that drives the DeltaV controller and I/O. Logic Solvers install

in odd-numbered slots (1.3.5.7) on the 8-wide carrier.

Easy Compliance with IEC 61511. IEC 61511 demands rigorous user

management and the DeltaV SIS process safety system provides it.

IEC 61511 requires that any changes made from an HMI (e.g. to a trip limit)

be extensively vetted to ensure that the right data is written to the right Logic Solver.

The DeltaV SIS process safety system automatically provides this data verification.

Scales to fit any size application. Whether you have anisolated wellhead

or a large ESD/fire and gas application, the DeltaV SIS process safety system

scales to provide you with the safety coverage you need for your SIL 1. 2 and 3 safety

functions. Each SLS 1508 Logic Solver has dual CPUs and sixteen channels

of I/O built into it. This means that no additional processors will ever be required

to expand the system, since each Logic Solver contains its own CPUs.

Scan rate and memory usage are constant and independent of system size.

SIL 3-rated. DeltaV SLS 1508 Logic Solvers are installed inredundant pairs for

increased process availability of your SIS loops.

Redundant architecture includes:

• Dedicated redundancy link

• Separate power supply to each Logic Solver

• I/O published locally every scan on redundant peer-to-peer link

• Same input data for each Logic Solver

Cybersecurity readiness. In an increasingly connected world,cybersecurity rapidly

became an integral part of every process safety project. Building a defendable

architecture is the basisfor achieving a defendable safety system.

DeltaV SIS when deployed with DeltaV DCS was the first process safety system

to be certified according to ISA System Security Assurance (SSA) Level 1. based on IEC 62443.