Major improvement in boiler water quality

Demonstrating new levels of accuracy and reliability, the new Solartron Mobrey Total Dissolved Solids Control System, the TDS 880, offers a significant advance in boiler blow-down management

Demonstrating new levels of accuracy and reliability, the new Solartron Mobrey Total Dissolved Solids Control System, the TDS 880, offers a significant advance in boiler blow-down management.

Benefits to steam boiler operators include more efficient use of fuel, savings in water treatment chemicals, and less water carryover in steam.

Key to the superior performance of the TDS 880 is an innovative design for the self-contained probe, which functions independently of any boiler components and eliminates a major cause of measurement drift.

Integral temperature compensation further improves measurement accuracy and stability.

The total amount of dissolved solids (TDS) in boiler water is assessed from the conductivity of the water.

Uniquely, the TDS 880 performs this measurement entirely within the calibrated probe tip.

This yields excellent long-term accuracy and stability by avoiding the problems associated with using part of the boiler structure as the second electrode, such as unpredictable changes in the electrical circuit through scaling and oxide build-up.

Measurement integrity is enhanced further by the use of titanium and a high frequency AC signal to minimise electrode contamination.

The probe tip is also equipped with an integral platinum resistance thermometer (PRT) to ensure close tracking of any changes to water temperature, enabling accurate conductivity readings to be made from a cold start up to 300C.

Manufactured using techniques and materials developed over 25 years for the Solartron Mobrey renowned Hydrastep and Hydratect products, the TDS 880 probe is designed to provide unsurpassed reliability in the highly aggressive environment of a steam boilers.

The glandless, all-welded construction uses zirconia, titanium and stainless steel components which negates the use of glands and any possible leak.

The probe is also fully adjustable during installation and can be mounted both horizontally and vertically.

A separate microprocessor-based control unit provides full configuration facilities and control outputs for blow-down systems.

The unit, which is available for panel mounting or within an IP66 enclosure, provides a direct, high visibility readout of TDS or water conductivity.

Readings of water temperature, TDS set-point, alarm points and mA output are available via a secondary display, and LEDs are used to indicate current alarm conditions and blow-down valve status.

The unit is easy to set up using the intuitive, menu-based configuration facility, which is password protected for security.

Two fully independent TDS set-points can be configured to operate volt-free relay contacts for blow-down valve control, using on/off, time proportioning, pulse proportioning or band operating modes.

A separate 4-20mA output can be allocated to either TDS (configurable for neutralised or raw water) or to water temperature, enabling the TDS 880 to be easily incorporated into a plant DCS or SCADA system.

Blow-down is an essential process for maintaining the efficiency of steam boilers.

As boiler water evaporates, the concentration of suspended and dissolved solids increases.

This can lead to adverse conditions such as sludge build-up, surface foaming, and increased water carryover into the steam, resulting in damage to turbine blades and inline instruments or damage to valves and process equipment through water hammer.

Blow-down is the controlled drainage of water containing dissolved solids and sludge; the introduction of cleaner top-up water consequently reduces the level of contaminants.

Draining water from the bottom of the boiler at regular intervals reduces sludge deposits, and dissolved solids are normally removed by taking water from near the surface in a continuous blow-down process.

This can result in unnecessary loss of both energy (from the discarded hot water) and expensive water treatment chemicals if the process is not carefully and accurately controlled.

The TDS 880 system, with its enhanced accuracy and stability, enables blow-down to be optimised to maintain TDS at an acceptable level while minimising wastage.

Solartron Mobrey can supply all the components necessary to implement a TDS Control System, including blow-down valves and a dedicated T-piece that provides a boiler attachment for the probe with the blow-down connection in a single unit.

Alternatively, the TDS 880 system can be used to enhance existing installations.

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