Emerson DeltaV™ Digital Automation System Concepts

DeltaV System Concepts

The DeltaV system helps users create process control systems that are easy to set up,

easy to operate, consistent, and secure. To accomplish these goals, the DeltaV system

uses the following:

Plug-and-play technology for hardware configuration

A library of reusable control modules to simplify the initial configuration effort

Techniques like drag-and-drop to simplify system configuration and modification

Consistent graphical interface similar to that of the Microsoft Windows operating

environment

Integrated, context-sensitive help and online documentation

Hardware and software approaches to ensure system security and integrity

A Configuration Assistant that steps you through the configuration process,

configuring the system while teaching you the fundamentals

Terminology

Control strategies in the DeltaV system are configured in modules. A module, which

is the smallest logical control entity in the system, contains algorithms, conditions,

alarms, displays, historical information, and other characteristics that define the

process equipment. Algorithms are the logical steps that define how the module

behaves. The DeltaV system provides control, equipment, and unit modules.

Generally, a control module contains one uniquely tagged control entity, such as a

control loop or motor, with its associated logic. Defining a module around a single

field device and its related control logic makes it easy to create, download, operate,

debug, and take a single module out of service without affecting other modules.

Equipment modules coordinate the operation of control modules and other

equipment modules that work together to control related equipment. The algorithm

for the containing equipment module manages the operation of the contained

modules.

Unit modules can be used in non-batch applications to group control modules and

equipment modules for alarm management purposes. For example, alarms for a

specific unit, such as a boiler, can be combined. All control and equipment modules

associated with the unit will be contained within the unit module.

Function blocks are building blocks for creating the continuous and discrete

algorithms that perform the control or monitoring for the process. The DeltaV

Library contains function block templates for analog control (bias/gain, lead/lag,

PID, etc.), Logical, I/O (analog and discrete input/output), and other basic functions.

Each function block contains parameters that can be modified to customize the

algorithm. Algorithms range from simple input conversions to complex control

strategies. Function blocks can be combined into composite function blocks to build

complex algorithms.

In addition to Function Block algorithms, the DeltaV system supports Sequential

Function Charts (SFCs) as well as Command-driven and State-driven algorithms

for control tasks requiring sequencing strategies.

Parameters are the user-defined data used within a module’s algorithm to perform its

calculations and logic. Parameters can be described by the type of information they

provide, such as input or output. Tables listing the parameters and their properties are

included in the Books Online information.

The DeltaV system includes a library of pre-engineered module templates with basic

characteristics. You can customize these library modules or create your own modules

from scratch. Your customized modules can be added to the library, making them

available for reuse in the development of your control strategy.

Modules that work closely together to perform a specific process control function are

typically grouped in an area. An area is a logical division of a plant. Areas typically

represent plant locations or main processing functions. The configuration engineer

determines how to logically divide the plant into areas.

Nodes are physical pieces of equipment on the control network, such as a controller

or a workstation. You control your process by downloading modules in the controller

nodes. The configuration tells the node how to act and what information to receive or

save from the process.

Device Tags represent the instruments, valves, and other field devices. A Device

Signal Tag consists of a specific signal from a device.

Alarms alert the operator that an event has occurred. (Alarms are assigned to

modules.) Typically, you want the operator to perform some action and respond to the

alarm. Alarms can be both visible and audible.

The database contains configuration information and lets you make off-line changes

without affecting the process. Online control algorithm monitoring and modification

are also available.

Following is a diagram showing the DeltaV system’s hierarchical structure.