Swan AMI Silitrace Trace Silica Analyzer for Water-Steam Cycles

Automated molybdate blue silica monitoring in high-purity water

The Swan AMI Silitrace is a complete monitoring system for the automatic, continuous measurement of dissolved silica in water-steam cycles or demineralizer plants. The swan.ch page describes a completely automated analyzer for reactive silica at trace concentrations, with a detection limit as low as 0.5 ppb.

Silica is determined photometrically as molybdate blue at 815 nm. Silica and ortho-phosphates react at low pH with ammonium molybdate to form a yellow molybdosilicic acid and a molybdophosphoric acid. Oxalic acid destroys the phosphate complex, and iron(II) ammonium sulfate then reduces the molybdosilicic acid to the blue complex. A thermostatic reaction chamber at 45 C shortens the reaction to about 150 seconds, and the pump speed is adjusted constantly to keep the reaction time exact.

Technical specifications

Values are from the Operator’s Manual A-96.250.811, section 2.2.

Reagents, calibration and sample streams

Four reagents are dosed into the reaction chamber: ammonium molybdate, sulfuric acid, oxalic acid and the reducing agent. A calibration or verification uses a standard bottle, and a zero measurement is made automatically or manually by switching off the reagent that colors the sample. Calibration, verification and zero can run on a programmed schedule. The product page lists a reagent-saving mode that lowers operating cost.

The Dual-Stream variant is identical except for a different flow cell block and a channel selector valve. If more than two streams are needed, the analyzer can be connected to a Sample Sequencer for up to six sample streams. A membrane degassing module is an option for gas-saturated samples and needs an external vacuum pump that is not included.

Selection notes

The AMI Silitrace is intended for trace silica in power plant water-steam cycles and demineralizer monitoring, where breakthrough from ion exchange resin needs early detection. The swan.ch page also lists industrial, semiconductor, green hydrogen and nuclear applications. Silica is measured as reactive silica.

Confirm the number of sample streams, the degassing option, communication option and the reagent supply in the enquiry. Only an AC supply is offered, so check the plant supply. Reagents are consumables.

How the Swan AMI Silitrace works

A small sample of water is mixed with reagents in a reaction chamber. Silica forms a yellow complex with ammonium molybdate, oxalic acid removes the phosphate interference, and the reducing agent turns the silica complex blue. A photometer reads the blue color at 815 nm, and the color depth shows the silica level. The chamber is held at 45 degrees C to speed the reaction, and the cycle repeats every 3 minutes, so the readings follow changes in the water closely.

Where the AMI Silitrace is used

• Power plant water-steam cycles
• Demineralizer and mixed-bed exchanger outlets
• Boiler feed water monitoring
• Condensate polishing plants
• Steam turbine protection against silica deposits

Selection checklist for the AMI Silitrace

• Single stream or the Dual-Stream version
• Measuring range of 0.5 to 1000 ppb
• Sample flow of at least 3 l/h
• Sample temperature of 5 to 50 degrees C
• Sample inlet pressure of 0.15 to 2 bar
• Pressure-free drain
• Supply of 100 to 240 VAC
• Reagent supply and the signal outputs needed

Installation, commissioning and maintenance notes

Mount the panel on a wall near the sample point and keep the sample line short. Connect the inlet with the correct tubing and lead the outlet to a free drain. Fill the reagents, run the start-up routine and then do a zero measurement and a calibration with the standard. Set the schedule for calibration and verification. Replace the reagents and the pump tubing on a regular plan and keep a log of every change.

Requesting a quotation for the Swan AMI Silitrace

Please send the number of sample streams, the output signals and the reagent set needed. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

AMI Silitrace accuracy

Reproducibility is 0.5 ppb or 5 percent, whichever is greater. The detection limit is as low as 0.5 ppb.

AMI Silitrace transmitter

The aluminum housing is rated IP 66 and NEMA 4X. It has a backlit LCD of 75 x 45 mm.

AMI Silitrace panel

The stainless steel panel measures 400 x 850 x 150 mm and weighs 16 kg.

AMI Silitrace reagents

Four reagents are used: ammonium molybdate, sulfuric acid, oxalic acid and a reducing agent.

Analyzer records for AMI Silitrace

Keep the calibration results, the reagent change dates and the zero values with the water chemistry log.

Choosing the right AMI Silitrace stream setup

A single-stream analyzer suits one sample point, for example the demineralizer outlet. The Dual-Stream version adds a channel selector valve so that two sample points can share one analyzer, which lowers reagent use and panel count. Plan the sample lines, the pressure and the temperature of each stream before ordering.

AMI Silitrace schedule

Calibration, verification and zero measurements can run on a programmed schedule, and a reagent-saving mode lowers the running cost of the monitor.

Documents and quotation

The attached Swan Operator’s Manual A-96.250.811 (firmware V6.31 and higher) and the swan.ch product page are the sources for this page. Seven Star LLC supplies Swan products as an independent supplier in Muscat. Send the stream count, options and quantity with your enquiry. More analyzers are listed under liquid analytical systems.