Water treatment in power plants

Electrical Power & Protection

June 2010 Electrical Power & Protection

“With the alignment of Hach and Hach Ultra in South Africa, Hach SA is now able to offer a complete one stop shop for all power plant requirements,” says Hach business development manager, Gary Wilby.

Since 1947, Hach Company has designed, manufactured and distributed instrumentation, test kits and reagents for testing water quality in a variety of power applications, including water treatment, condensate, feedwater, boiler water, cooling water and wastewater applications.

Hach SA offers the following:

* On-line process instrumentation and the related reagents.

* Laboratory equipment reagents and general supplies.

* EPA approved methods.

* Portable test kits and field instruments.

* Automatic samplers and flowmeters.

* Local sales and service support teams.

* Service partnership programmes and customised training schedules.

For example, consider the Orbisphere K1100 optical sensor together with the Orbisphere 410 controller which offer a new way of monitoring oxygen in power plants.

Optical sensor technology for oxygen monitoring

Optical technology eliminates the need for membranes and electrolytes, which means that sensor accuracy is unaffected by process changes such as flow. Sensing is instead based on luminescent measurement technology. An active fluorescent spot is excited with blue light and a red luminescent light is detected. The presence of oxygen changes the rate of fluorescence decay and this directly relates to the oxygen partial pressure value. Maintenance and operating costs are also reduced, since the sensor has been robustly designed to extend operating life and optimise total cost of ownership.

Fast, accurate response

The quick response time comes from the sensors two second measurement frequency. Capable of measuring accurately at this frequency over a 12 month period with no calibration required, the K1100 is designed for minimal drift, resulting in it being one of the most stable sensors with a long calibration interval. This is achieved by its long-life spot and optimised controller software.

This sensor has a precision of 0,8 ppb and a limit of detection of 0,6 ppb. Such accurate measurement readings are essential to control low oxygen levels in AVT power plants. This also allows operators to minimise system maintenance whilst being reassured of the oxygen reading accuracy.

The complete system

The complete system consists of an Orbisphere 410 controller, a flow chamber, and the Orbisphere K1100 luminescent sensor. The sensor is compatible with 28 mm insertion devices and flow chambers, therefore minimising retrofit costs. The installation is fast and easy and does not require special preparation. The 'plug-and-play' sensor is immediately ready for measurement.

Diagnostics

The controller offers diagnostic features that informs users when a sensor service or calibration is due. This supports optimal preventative maintenance planning. It also notifies users of a system or sensor failure. All diagnostic information as well as user programmable measurement alarms can be assigned to one of the three available relays, or to one of the three smart analogue outputs.

For more information contact Gary Wilby, Hach SA, +27 (0)82 876 3390, gwilby@hach.com, www.hach.com

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