How to Operate Online Silica Analyzers for Extended Periods
Because of its tendency to scale, it is critical to monitor silica concentrations in applications such as semiconductor rinse water and steam power generation. Much of the burden in maintaining silica analyzers relates in some way to the required use of reagents and having to calibrate. As such, recent enhancements have targeted the automation of analyzer cleaning and calibration to greatly extend maintenance intervals. These features are particularly beneficial in lean operations where keeping maintenance effort to a minimum is a must. In addition, the specific methods used to transport reagents and standards during operation can also have a significant influence on the frequency and effort needed to maintain the analyzer.
Prevent Clogging with Automatic Cleaning
Online silica analysis is almost exclusively performed using colorimetric analysis. This requires the use of reagents that combine with the sample to ultimately form a blue colour the intensity of which is correlated to silica concentration. A measurement cell is used to pass light of a specific wavelength through the prepared sample and then quantify the amount of light absorbed corresponding to the silica in the sample. Three reagents are needed to react with the sample and each must be drawn accurately from separate bottles. Due to long measurement intervals or planned idle periods, reagent delivery may only be required on an infrequent basis. Without regular movement of silica reagents within the analyzer’s fluidics, crystallization can occur which will clog the tubing necessitating cleaning or tubing replacement. Fortunately, silica analyzers are available that incorporate automatic cleaning routines. These routines may involve moving the fluids or flushing lines to mitigate precipitation when analysis is performed infrequently, or deeper cleaning cycles using a cleaning solution that can be performed at regular intervals.
Improve Accuracy with Automatic Calibration
Similar to automatic cleaning cycles, automatic calibration routines are also available in silica analyzers. By installing calibration standardwithin the analyzer enclosure, the analyzer can be made to run calibration routines on a pre-programmed basis. Single-point and two-point calibrations can be executed automatically as well as analyzer validation. Analyzer validation confirms accuracy against a specific standard and allows the analyzer to be set to continue, re-calibrate or stop should the validation measurement not meet the required tolerance. Overall, automating these tasks reduces maintenance effort and facilitates consistent, documented analyzer calibrations.
Reduce Maintenance with Peristaltic Pumps and Rotary Valve
Delivering reagents and calibration standards can be done in a variety of ways. The use of peristaltic pumps is an accurate and reliable method of moving fluids in an online analyzer. Further, their ability to operate bi-directionally enables the movement of reagents to mitigate clogging without having to consume them. The low pressures exerted by these pumps deliver fluids without the need to pressurize reagent bottles. The use of pressurized lines can lead to leakage within the analyzer enclosure which may expose sensitive electronics to acidic reagent if the enclosure is not designed to isolate these components. As a moving part, a peristaltic pump is something that may ultimately need to be replaced. Through the clever use of clectronic rotary valve technology, however, the number of peristaltic pumps can be kept to a minimum. A rotary valve allows a given pump to access multiple fluid sources thereby reducing the number of pumps required and hence, the effort needed if and when they need to be replaced. The combination of rotary valve and peristaltic pump usage contributes to reducing overall reagent consumption allowing silica analyzers to operate for 100 days without having to replenish reagents (15 minute measurement interval).
Moreover, recent advances in silica analyzers have drastically reduced the required maintenance to be performed. Through optimization of the control and fluidics, what were manual interventions in the past are now performed automatically. As a result, it is possible to operate silica analyzers for extended periods with little to no maintenance.
Related links:
– Thermo Orion 8030cX instructional videos – subscribe to IC Controls youTUBE to be notified when they are uploaded
