What's Your Legacy?

InTech, Jun 2006 by Consoli, Richard, Keiser, Ken, Stauffer, Todd

Maximize existing asset value and migrate in a stepwise, incremental fashion

Migration is an important topic in today's industrial marketplace as users confront the life cycle management of their installed control systems.

Sixty-five billion dollars of legacy processcontrol systems have reached the end of their reasonable life cycle. The process automation industry has undergone massive consolidation of both end users and suppliers and has seen significant changes in the life span for distributed control systems (DCS) components spurred by rapidly changing technology.

While the expected life span for input/output (I/O) and wiring is 25 years or more, the life spans for human machine interfaces (HMIs) and workstations are now about five years.

Migration to newer technology presents many challenges to the user and to the supplier.

First, let's assume the decision to migrate from one system to another has already taken place and everyone concerned understands and has researched the advantages of migrating versus not migrating.

Look at the various generic types of products, tools, and services available to help users to extend the life of their existing DCS systems.

* HMI connectivity provides communication channels and HMI elements (such as faceplates) for communication to legacy system controllers via new HMI technology.

* HMI conversion: tool for translating graphics from a legacy HMI to a newer HMI.

* Enhanced batch management provides connectivity for a new Batch Manager to interface directly to an existing controller's phase and recipe sequence logic.

* Engineering library: function blocks, faceplates, and dynamic HMI elements providing equivalent functionality to the existing system, available for use within a new engineering environment.

* Application conversion automatically converts existing process graphics, controller code, or hatch recipes to newer systems, allowing reuse of valuable application code.

* Control network gateways allow peer-to-peer communication between legacy controllers and new controllers.

* I/O gateways connect new I/O technology to existing controllers.

* I/O replacement: Install new I/O modules into existing controller I/O slots. Uses older rack with new I/O technologies.

* I/O interfaces enable an existing I/O subsystem (field devices, racks, terminations, and I/O modules) to be controlled by a new controller.

* Field termination assemblies (FTAs) preserve existing wiring by providing a 1:1 replacement of existing terminations and connection to new I/O modules via a new FTA (with same form/fit and function).

Also, we look at the most common scenarios for DCS migration to see how the generic capabilities described above can be employed to help users maximize the value of their existing assets (such as hardware, application engineering, and process know how) and minimize the cost of change, while providing the flexibility to migrate in a stepwise, incremental fashion. We'll profile some common migration scenarios too.

Migration indispensables

A typical DCS can be migrated to a newer system in a stepwise approach. There are certain points in a system where a new piece can fit naturally. The system can upgrade above or below any of these points. For example, the controller, which is located between I/O and the HMI server, can upgrade without touching any of the other pieces of the system.

In any system, there are pieces that have different life cycle curves and life spans. In a system with the various entities like an HMI, controller, and the like, each part has a different life cycle profile. When a new system debuts, each part will eventually have more functions, features, and benefits than the systems previous parts. Refer to this difference as a technology gap.

The technology gap could occur at different times for different pieces of the system. To maximize the life of existing assets, a stepwise or phased approach to migration is necessary where some older assets remain in place at the same time as other assets are swapping out for newer technology.

Further the life span of these asset classes (HMI, controller, I/O, terminations) are different. Of course, the assets' prices differ as well. Some of these values include both hardware and intellectual property, such as the controller or HMI server. Others, such as the HMI client or terminations, are exclusively hardware assets.

There are two options in any migration of a particular asset: Use the same vendor as the existing asset, or use a different vendor. Additionally, there is an option to migrate part of the system or the total system.

In a total migration, the existing assets all go away, and there is no opportunity to maximize the return on any individual asset.

In most cases, however, a stepwise or phased approach is preferable to a total system migration, as each asset becomes obsolete at a different time.

The first focus of executing a phased migration must be the asset with the shortest life span in the system. This asset will become obsolete first and is prone to the first failures. second, look at the asset with the lower value. This asset tends to be simpler to upgrade and realize a return on that investment. Third, use migration products or tools to maximize the return on existing assets. The migration product or tool itself is the key to a successful project.