Getting more from OPC A&E white paper

Getting More from OPC A&E

Easily access OPC A&E from multiple network sources, or convert it to OPC DA, UA and other protocols using the Cogent DataHub.

OPC Alarms and Events (OPC A&E) is a data communications protocol for conveying information about process alarms and events. A&E data can be used to notify operators and management of system problems and convey sequences of events to optimize operations. Such information is invaluable for scheduling maintenance and predicting equipment failure. However, A&E data is often hidden away on the plant floor, in multiple locations, making it hard to access from an IT department or central office where it could provide valuable insights for corporate management.

To get the most out of OPC A&E, you need secure, convenient and reliable access to the data. This is more challenging than you might think, because unlike OPC DA, there are not many tools available for networking or integrating OPC A&E. The Cogent DataHub stands out as one of the few widely-used and field-tested OPC A&E integration products, offering networking, aggregation, redundancy, and conversion of the OPC A&E protocol itself.

For example, the recently-completed 1850-kilometer Trans-Anatolian Natural Gas Pipeline (TANAP) in Turkey uses the DataHub to support highly redundant, secure communications of OPC A&E data.  This case study describes how every aspect of operation is successfully coordinated between remote stations and central control.

Networking

OPC A&E is a COM-based technology, developed in the 1990s, that relies on DCOM (Distributed COM) for networking. Although it is now widely used, DCOM was never designed for real-time industrial applications. It is not as robust or secure as these mission-critical systems increasingly require, and it is notoriously difficult to configure. To make matters worse, there are very few diagnostic tools available for debugging A&E DCOM problems, so trouble-shooting becomes an arduous task.  Because of these problems, OPC A&E is often the weak link when trying to secure an industrial control system.

Getting More from OPC A&E diagram 1

To overcome these limitations, the Cogent DataHub offers A&E tunnelling to connect OPC A&E clients and servers over a network, avoiding DCOM altogether. This uses the same proven DHTP technology that the DataHub uses for tunnelling OPC DA and OPC UA. DataHub tunnelling is unique in that it never blocks OPC or drops the local OPC connection. It detects network breaks in seconds, and recovers from them smoothly, without breaking the OPC A&E server or client connection.

The secure-by-design architecture of the DataHub allows it to make outbound connections from behind plant firewalls, keeping all inbound firewall ports closed. It supports seamless connectivity through proxy servers and DMZs, giving it high marks from IT departments responsible for corporate network security.

The DataHub’s modular design means that the OPC A&E tunneling can be integrated with other DataHub features, supporting aggregation of A&E servers, redundant A&E tunnels, and A&E data conversions to OPC DA and UA.

Aggregation

Seeing the big picture and locating the weak points and potential trouble spots in a system often requires pulling together alarm and event data from multiple sources. As systems grow in complexity, and as demand grows for more remote monitoring of alarms and events, it can help to simplify incoming OPC A&E data streams by consolidating them. Aggregating A&E data also helps reduce network traffic and free up bandwidth on busy systems.

Getting More from OPC A&E diagram 2

The Cogent DataHub connects to any number of OPC A&E servers, and collects their current alarm and event data. All of this data can then be accessed by one or more local A&E clients, or tunnelled across the network to any number of remote A&E clients. Whenever any client acknowledges an alarm, the server retransmits that to all connected clients. In this way, you can have multiple OPC A&E servers communicating bidirectionally with multiple A&E clients.

Redundancy

System integrators and plant engineers often use redundant data paths to ensure the effectiveness of OPC A&E. After all, if an alarm message doesn’t reach its destination, it’s useless. Since networks are never 100% reliable, adding redundancy for A&E connections significantly improves the chances of alarms being received and acted upon.

Getting More from OPC A&E diagram 3

Implementing OPC A&E redundancy typically means configuring two OPC A&E servers to connect to the same data source and then tunnelling the data from each A&E server to a redundancy broker on the client side.  The redundancy broker monitors both tunnel connections and sends the data to the OPC A&E client (or clients).  Should one of the connections fail, the redundancy broker immediately switches over to the other tunnel connection and the client continues to operate with the current data.

The DataHub’s Redundancy feature lets it act as a redundancy broker. It channels the incoming data from the two tunnels into two identical input data domains.  One of those domains is used to feed a third (output) domain for the client. Switchover logic configured in the DataHub determines how and when a data stream is considered invalid, and triggers a switchover to the second, identical data stream. This switchover happens in a matter of milliseconds, which allows the client to continue uninterrupted.

Protocol Conversion

The value of alarm and event data generated by OPC A&E servers often goes beyond the immediate context of an A&E client.  Many people find it useful to expose this A&E information to systems that don’t support the A&E protocol at all, such as reporting packages and SCADA systems.

Getting More from OPC A&E diagram 4

Again, the DataHub’s unique architecture plays an important role here, enabling protocol conversion. Internally, all of the data points in the DataHub are maintained as a single, unified data set.  Whenever it receives a change to a data point value, it immediately updates the data set, and then forwards the new value to every application subscribed to that point, in that application’s own protocol. In this way, incoming OPC A&E data can be passed to OPC UA or DA clients. This architecture also provides the ability to write A&E data to SQL databases, Excel spreadsheets, custom programs, and more.

With the advent of Industrie 4.0 and the Industrial IoT, plant engineers and managers are receiving more and more requests from management for production data of all kinds. Having proven its worth for on-site, day-to-day operations, OPC A&E is now attracting attention from analysts and upper management who envision applying it in broader, large-scale planning and efficiency initiatives. The Cogent DataHub can play an important role in turning this vision into reality. All over the world companies are using the DataHub to aggregate OPC A&E data, send it across redundant networks, and convert it to OPC DA, UA, and other protocols.  Maybe yours will be next.