Alarm Management with zenon: Save Time and Money with an ergonomic System in place
COPA-DATA has more than 100,000 zenon HMI/SCADA installations worldwide. The one zenon feature which is used in nearly every installation is the alarm concept. As a native part of the zenon Runtime, the core zenon alarm functionality is available for all users and all licenses. This article will explain how companies can improve productivity, efficiency, and safety by utilizing zenon HMI/SCADA solutions in combination with international alarm management standards such as ISA 18.2 or IEC 62682.
The task of implementing and maintaining an effective alarm management system compliant to the International Society of Automation (ISA) ISA 18.2-2009 or the International Electrotechnical Commission (IEC) IEC 62682 is by no means a simple one. A successful implementation requires input from plant management, engineering, facilities, information technology and operators. To start a successful alarm management project, we show you which aspects one should consider according to ISA 18.2 / IEC 62682.
Alarming has been a crucial and important topic for manufacturers since the days of giant control rooms with massive annunciator panels. In the early days of Human Machine Interfaces (HMI), the annunciator panel offered a limited amount of space to give plant operators only the most crucial information to maintain safety and productive operations. Since the inception of PC-based HMI systems, the amount of alarms which can be configured and shown on HMI screens with relative ease has escalated at Moore‘s Law proportions. This influx of storage and processing capabilities eventually led to one of the biggest problems facing a typical plant operator: the overwhelming amount of information presented by the modern alarm system.
Let’s have a closer look at how engineers can cope with this and some other challenges:
Alarm Management Challenge 1: Too many Alarms
The test of a good alarm management system does not occur when the plant is running smoothly, but instead when there are disruptions in the process. According to the IEC, an average rate of 288 alarms per day or twelve alarms per hour or two alarms per ten minutes is maximum which is manageable. The ISA classifies an alarm flood as more than ten alarms, per ten minute period, per operator. The target alarm volume, over a 30-day monitoring period should be in the range of one alarm, per ten-minute period, per operator.
zenon’s Alarm Management Solution 1: Delay Time, Threshold, and dynamic Alarm Limits
zenon offers features and functionalities to reduce unnecessary alarms. For example, in zenon each variable when activated as an alarm has both a delay time and dead band property. Here we offer a short technical description of each method:
- Delay Time Example:
A pressure transmitter is monitored by zenon and is set to alarm when the value reaches or exceeds 350 psi. If the normal operating condition and ideal pressure is 349 psi, the operator may encounter many chattering alarms which takes focus away from more serious alarms. In this case, one is able to define a delay time of 15 seconds. This means that alarm conditions will only be triggered if the pressure transmitter has a value > 350 psi lasting for at least 15 seconds. If the 15 second period has lapsed and the value is still > 350 psi, then zenon will generate the alarm with the timestamp when the limit violation originally occurred. If any time before the 15 seconds the value drops below 350 psi, the alarm will not be generated.
- Alarm Threshold Example:
A threshold value can be defined that will be used for clearing a limit violation so unwanted reactions for chattering analog values can be avoided. If an alarm threshold of 5 for the pressure transmitter is set on the limit, which still alarms at > 350 psi, then the alarm will occur as normal at 350 psi or greater. However, now the alarm condition will only clear if the threshold value of 5 has been reached. In our example, this means the alarm will be only cleared if the value returns to < 345 psi.
- Dynamic Alarm Limits:
zenon also allows for Runtime-based alarm set point tuning through a functionality called dynamic alarm limit. This can be implemented for any numeric variable, regardless of the PLC. The alarm set point tag can come from the PLC or can even be an internal zenon variable. In Runtime, if we find that the pressure transmitter alarm limit of > 350 psi is too low, the operator or supervisor with appropriate user rights can push the limit up to 355 psi, without changing the engineered configuration or project. Of course, this change will be logged in the zenon Chronological Event List.
In the next blog post you will read about the Alarm Management Challenge 2: Managing a diverse Infrastructure.
Tags: Alarm Management