See a list of references at ControlGlobal.com/0802_nichols.html
By Gary D. Nichols, PE
Analyzer engineers’ and technicians’ jobs are not just about installing and maintaining process analyzer systems. A survey of recent literature show that other issues also require our time and attention. (See ControlGlobal.com/0802_nichols.html for a list of references.)
The New Sample System Iniative (NeSSI) is probably the most immediate current issue that analyzer engineers and analyzer technicians have to address. We are likely to have less of a leadership role, but definitely will participate in and contribute to discussions about alarm management, wireless communications, security and SIS/SIL decisions at the corporate and plant levels.
NeSSI has been available for several years, but is now beginning to find a home, or homes, in process plants. NeSSI is a modular method for assembling sample conditioning systems, especially complex one. NeSSI has been likened to children’s Lego blocks because of the size of some of the modules and the way they are assembled.
When implemented, NeSSI is reported to have shrunk the sample conditioning system footprint by 50% (for an offgas analyzer system installation), with accompanying reduced maintenance. The footprint for an optical measurement system was reportedly reduced to 1.6 in. x 7.75 in; the original footprint was not revealed, but few are the sample handling systems that do not require considerable more space.
The ISA/ANSI standard that was promulgated several years ago provided the base dimensions for the devices (valves, meters, tube fittings, etc.) that would be integrated into the NeSSI system. Since that time, well-known firms such as Swagelok, Parker and Circor have been proponents of NeSSI systems; more and more suppliers are adopting sample conditioning system components and analyzer components to fit the NeSSI standard.
We already tacitly identified one reason for NeSSI not being implemented earlier: Suppliers needed time to adapt their manufacturing to meet the NeSSI standard. They also needed time to design sample conditioning system components to accommodate unusual tubing geometries, sealing systems to accommodate corrosive samples and a customer education system to let users know of NeSSI’s availability and benefits.
But other reasons may have played a part in potential NeSSI users’ decision to stick with conventional sample conditioning systems. Conventional components have an established track record. NeSSI components for some applications might not have been available. Analyzer engineers and technicians may have been looking for the ideal application for NeSSI to ensure that it would demonstrate distinct benefits when first implemented. Finally, analyzer system integrators and other in the analyzer community may not have been familiar with the NeSSI components and systems.
“The essence of alarm management is to supply operators with enough information to prevent abnormal situations, and to prevent abnormal situations from escalating into unpreventable situations,” says a recent article on the subject. That is a nice theory, or “alarm strategy,” but why is it necessary to develop the theory, and how can the theory be implemented?
Though analyzer engineers and technicians are not likely to drive alarm management, we need to be aware of the ongoing process of alarm management and be prepared to understand and influence the process.
First we must answer, “Why has alarm management become an issue?” With the proliferation of microprocessors, DCSs, PLCs, PCs and other easy and inexpensive ways to add alarms, almost “for free,” to the myriad operator responsibilities, it is almost a given that there might come a time when operators became overwhelmed with alarms at the expense of acknowledging and responding to them and to the potential neglect of other operator responsibilities (3,4).
This affects analyzers because most modern analyzers come from the factory equipped not only with the analytical measurement, but with analyzer condition alarms which signal that the analyzer is malfunctioning in various combinations or ways or indicate that the analyzer is deliberately out of service for maintenance. This can lead to alarm proliferation.
The current philosophy is to configure an alarm only when operator action is needed and clearly identified. For analyzers, this can mean to (1) obtain agreement between the analyzer technician and the operator as to the criticality of the alarm, (2) alarm only the analyzer signals that are immediately critical to safety, loss prevention, and the environment, (3) and perhaps to “daisy chain” alarms that do not justify individual alarms.
Readers who must know more about alarm management are encouraged to consult the referenced articles, the EEMUA document (5), and other articles, standards, and recommended practices on the subject, and to become active in their site’s or corporation’s alarm management committee or group.
Wireless control systems communications is one of the leading topics of 2007; in retrospect, it would seem inevitable that process industries which progressed from pneumatics to 4-20 mAdc to field buses in a few years would eventually want to go wireless as the broadcast bands became available and technology became feasible. Actually, wireless telephony grew from the aerospace and defense industries in the 1950s and 1960s (6).