By Jeff Gould, AlarmManagement Insider Contributor
OPERATORS CONTROL how a plant operates from hour to hour (or even minute to minute). Their job is to run the physical assets at target production rates safely and within environmental constraints. When conditions change or equipment runs abnormally, their job is to avoid downtime, or at least prevent costly damage, and to prevent environmental releases, all while protecting the safety of the staff.
DCS alarms are a key part of this effort, and are intended to provide operators with the information they need to achieve these goals. However, since adding new alarms to a DCS costs nothing, new alarms are often configured without following a rigorous engineering process. As a result, over time most facilities have alarmed virtually every reading, creating alarm floods that overwhelm operators and prevent them from effectively assessing the root cause of problems. For this reason, many plants today have either implemented an Alarm Management solution or are in the process of doing so.
Nevertheless, most of the literature concerning Alarm Management refers to existing facilities: an alarm system exists, and we can measure its performance and rationalize the alarms.
The benefits of rationalizing alarm systems (running into tens of billions of dollars annually) are well documented by the EEMUA and the ASM consortium. While these organizations and some operating companies have proven methods to increase the effectiveness of alarm systems at existing facilities, little has been done to apply these methods to new facilities. What follows will address the latter issue: delivering effective alarm systems for new operations.
The alarm system is the primary means to identify abnormal operations and target the operator's attention. If the operator takes timely, appropriate action, then the plant can usually be kept operating and quickly brought back to target operation. At worst, the operator will be able to safely shut down equipment in order to avoid more serious damage, environmental releases, and to protect the safety of staff.
In short, the more effective the alarm system, the more effective the operator. Moreover, the operator has more abnormal operation while lining out the facility than at any other time in its operating life. Since new facilities commonly take months to line out, and very large facilities can take well over a year, there is clearly a lot to gain.
The first step is to define the objectives and risks inherent to a facility to determine our target alarm system performance.
Second, configure the alarm systems so that they possess the known characteristics common to highly effective alarm systems (this information is available from alarm management companies or through industrial standards and literature).
Since effective alarm settings are different from what has been practiced in the past by EPC (Engineering, Procurement, and Construction) firms and even by in-house staff, this is a serious change management issue. Change takes time, yet with new facilities, we run under the constraints of a project schedule. It is therefore imperative to initiate the alarm effectiveness program early in the project - at least before P&IDs are finalized.
The change management program includes development of a project-specific alarm philosophy, including a methodology and rules for setting alarms, training for process engineers and operations representatives, a P&ID alarm review to build commitment from both in-house and EPC engineers (and to consolidate training), as well as an audit process to ensure that the philosophy is consistently applied by EPC firms and contractors.
Every methodology used to ensure a highly effective alarm system identifies the possible causes of alarms and the appropriate actions the operator should take. In fact, alarm reviews ensure that all aspects are documented, including the equipment, the process, operational constraints and instrument & control. This is critical information for operator procedures and training. In today's world, this information must be recorded electronically for easy review by operators during training and when they are actually operating the facility.
While it might be nice to believe that our designs are perfect, startup identifies many discrepancies, and the alarm system is no exception, unfortunately. We can very quickly identify which alarms are hindering operator effectiveness and correct them by measuring the key performance indicators - the average alarm rate and the peak alarm rate - and by profiling individual alarms to identify the causes of poor performance.
Poor alarm performance and abnormal profiles can be caused in two ways: either by inappropriate configuration of alarms, or because there are underlying problems in the process or equipment. The former are generally simple to fix by changing alarm settings in control or data acquisition systems, although more advanced alarm schemes may be needed to avoid alarm floods and other poor alarm profiles. The latter is an added benefit since an unusual alarm profile for a system that appears to be running within design guidelines generally indicates other potentially serious problems that need to be addressed by engineering or maintenance.
Thus the process of building an effective alarm system has many benefits to the project team and to operations. First and most important, it reduces our risk and the costs incurred during line-out of new facilities. Furthermore it documents critical engineering information for operations and provides another tool to identify process and equipment problems while lining out the operation.
Providing operators with enough information to prevent abnormal situations and to diminish the impact of unpreventable abnormal situations is the key to an effective alarm management solution. Although such solutions can be implemented in existing facilities, the construction of a new plant provides a unique opportunity to put an effective system in place. Moreover, a properly designed alarm system can even help reduce problems during the critical startup process and can be a key driver in getting your plant fully operational, on time.
Four Key Advantages of an Alarm Management Solution
- Automatic controls keep the plant running where it should.
- Safety systems shut the plant down when damage could occur.
- An interface into the operation displays how the plant is operating and when it may be shifting away from target operation.
- An alarm system tells operations that action must be taken.
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