Keep process analyzers on-stream

Despite computer operation simplicity, personal skills are still needed to achieve the full benefits of process monitoring.

By Terry McMahon, Steve Walton and Jim Tatera

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Analytical instruments used for online chemical analysis of process streams or plant environments are generally called process analyzers. On-stream analytical data have proven to be crucial to safe and efficient operation in the petroleum, chemical, pharmaceutical, pulp and paper, power and other industries. Historically speaking, these instruments have been complex, even temperamental, systems with relatively unique operational and maintenance needs. If online instrumentation, sample-handling systems and data-analysis software are to realize optimum performance, they will require continual attention from the analyzer support staff.

Increasingly, however, regulatory and high-priority economic concerns such as operator health and safety, emissions control and energy conservation are raising the importance of analyzer reliability to normal operations. Particularly with respect to regulatory and safety uses, the time logged as out-of-limits because of an analyzer outage can result in stiff fines.

In these situations, it’s important to be able to deal with routine maintenance needs, as well as to recognize and characterize maintenance needs that require more specialized skills. Sourcing such specialized skills and an expedited response to an incident frequently become high-priority items.

Looking back

A brief overview of analyzer history can put the current situation into perspective. The technology for on-stream chemical analysis dates back about 70 years. The first nondispersive infrared (NDIR) photometers were developed and deployed in the late 1930s at the Ludwigshafen Research Lab of I.G. Farbenindustrie (German Chemical Trust later broken up by the Allied Occupation Forces into BASF, Bayer and Hoechst). A schematic of UltraRotAbsorptionSchreiber (URAS), the first on-stream analyzer, is shown in Figure 1. The URAS trade name belongs to the original manufacturer, Hartmann & Braun, which is now a unit of ABB, a leading worldwide analyzer supplier. When this work was discovered, its significance was recognized immediately (British Intelligence Operations Subcommittee Report #1007, 12 June 1946). The report states that “I.G. Farbenindustrie’s development in recent years of the infrared absorption meter and the magnetic oxygen recorder represent a great advance.”

Figure 1. This block diagram shows the major components and configuration of the first on-stream analyzer.
Figure 1. This block diagram shows the major components
and configuration of the first on-stream analyzer.

U.S. chemical and petroleum companies began using on-stream analyzers in the 1950s. By 1960, Standard Oil of New Jersey’s (later Exxon) Baton Rouge Refinery had a significant complement of on-stream analyzers (Table 1).

Analyzer Costs and Suppliers (Circa 1960)
Analyzer Installed Cost ($M) Suppliers
Gas chromatograph  10 to 15  Beckman, Consolidated Electrodynamics, Greenbrier, Perkin Elmer
Colorimeter  8 Beckman
Densitometer   8 Precision Thermometer & Instrument
Final boiling point  
9 Hallikainen, Precision Scientific, Technical Oil Tool Co. (TOTCO)
Flash point   10 Precision Scientific
Hydrogen sulfide (Pb acet tape)   11 Minneapolis Honeywell Rubicon
Ionization chamber (ppb gases)   10 Mine Safety Appliances
Initial boiling point   5 to 8 Hallikainen, TOTCO
Infrared (NDIR)  8 to 12  Beckman, Liston-Becker, Mine Safety Appliances
Moisture (electrolytic)  
7 Beckman, Consolidated Electrodynamics, Mfrs Engineering and Equipment
Moisture (heat of adsorption)  
14 Mine Safety Appliances
Differential refractometer  6 to 12  Consolidated Electrodynamics, Greenbrier
Reid vapor pressure (RVP)  
7 Precision Scientific
Viscometer   8 Hallikainen
Ultraviolet  10  Analytic Systems Co.

 

The emergence of real-time digital computers in the 1960s, followed by the microelectronics revolution and the large-scale integration microprocessor in the 1970s, eventually allowed exploitation of highly sophisticated analytical techniques for on-line analysis. These developments required several decades to develop. During the past 10 years or so, the full power of on-stream chemical analysis, combined with modern information technology, has taken hold throughout the process industries and is generating higher productivities, yields, efficiencies and product quality.

Realizing these benefits required highly skilled and experienced technical personnel. The analyzer community evolved into a culture suited to the care and tending of these useful industrial analyzer tools. The question facing plant operations management is: How do you realize the enormous potential benefits of on-stream analysis without the overhead of on-site analyzer specialists?

In the beginning, the computer was a highly specialized tool surrounded by a cadre of expert-practitioners. During the late 1950s, mere mortals never were allowed to approach the computational machines. The high priests who tended the main console, changed magnetic tape drives and otherwise managed the care and feeding of the electronic monster were the only humans allowed to have access to the air-conditioned inner sanctum. These operators accepted your deck of punched cards and, a day later, handed you a printout of your results or, more frequently, a memory-dump to help you with your program fault analysis. What happened between your two visits was known only to the Most High.

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