For a variety of reasons, decreasing resources are causing plant operators in the process and utility industries to look for more efficient ways of monitoring and servicing their instrumentation. The analyzer maintenance department may have been reduced in size, merged with another department or perhaps no longer exists at all, and reassignments and relocation of staff can lead to a loss of experienced process analyzer operation. At the same time, the importance of the analyzer measurements and demands for consistent analyzer performance are increasing. Tighter control limits, higher throughputs and stricter quality reporting can all demand more frequent calibration and less downtime. Much of the routine preventative maintenance work performed on the analyzers may not be required but is performed as part of a fixed schedule rather than a specific need. It would be preferable to have a system of providing maintenance personnel with information that would direct their efforts to those analyzers that do require more frequent attention. There is a growing interest in the possibility of being able to monitor plant instrumentation through any personal computer (PC) on the site's local area network (LAN), or through the DCS system and to be able to do this with no specialized software.
In a modem, multi-unit plant there can be a wide range of communication lines between analyzers and control systems. A typical configuration for a Network Core Protocol (NCP) analyzer maintenance data acquisition system network with typical analyzer shelter connections is shown in Figure 1.
The new LinkBus Remote Instrument Monitoring System (LinkBus RIMS) from AMETEK addresses the limitations of traditional maintenance programs and frees up resources, making them available to give attention where it is most needed. Maintenance and performance personnel now have easy access to all the analyzers' vital signs from their desk computer or through the DCS, not just the measured parameter that is typically delivered to the process control room. Any analyzer can be interrogated from the PC or through the DCS operating under HART™, Fieldbus FOUNDATION™, Modbus™ protocols, and information may be gathered without having to go to the location. This data provides predictive maintenance intelligence and assists the maintenance personnel in effective repair planning. There is no need to climb up to the analyzer, declassify the area, issue work permits, or even visit the shelter to obtain this critical performance data (Figure 2).
Plants are currently examining ways to reduce the operational costs and increase the reliability of instrumentation. However, although analyzer manufacturers continue to strive for greater reliability, every analyzer will still require periodic calibration or verification (a calibration check) and will eventually need service attention. Some components, such as UV lamps or zirconium oxide cells, have a finite lifetime, and will eventually need to be replaced. The type of analyzer and the process and ambient conditions of the application will also affect the mean time between failures. The recent trend towards smart instrumentation began with the high volume devices such as pressure, flow and level transmitters and has gradually shifted to analyzers. Various asset management approaches are now offered using HART™, FOUNDATION™, Modbus™ or other proprietary software protocol based DCS implementations. Many companies are studying the role of information technology in analyzer performance parameters and considering new approaches such as proactive and reliability centered maintenance.
AMETEK's analyzers are equipped with smart electronics able to identify error conditions and report them to the LinkBus gateway. While it is not possible to eliminate attention to analyzers altogether, the LinkBus gateway combined with the ability to automatically initiate and verify analyzer calibration, removes the need for routine visits.