June 9, 2009 -- When South West Water required level measurement equipment in its wet wells that was compatible with its recently launched new template and control philosophy, it turned to Siemens Automation and Drive Technologies to provide an effective solution.
Since the company was privatized in 1989, South West Water has worked hard to bring its water network up to date, ensuring that the region's drinking water, sewage systems and beaches, fall in line with stringent UK and EU environmental standards.
As part of a recently launched template aimed at its two-pump sewage pumping stations, where possible, South West Water wanted transparency from the supervisory layer (SCADA) to the field instruments. In order to meet this template, South West Water asked Siemens to help find an answer.
The Siemens solution consisted of a Profibus PA system, coupled with a Siemens SITRANS Probe LU, ultrasonic transmitter. The Profibus PA System allows for data to be transferred over a digital network rather than a traditional analogue one, allowing level measurement to be carried out faster and more reliably, with a greater level of accuracy. The ultrasonic transmitter was installed directly in to the wet wells. Using automatic false-echo suppression to eliminate the interference from obstructions, the SITRANS Probe LU is capable of measuring ranges up to 12 meters. In addition the probe offers Sonic Intelligence® Software which has over 1 million proven applications and provides continual reliable measurement. The transmitter is suitable for installation in class II hazardous environments, making it ideal for use in wet wells.
Prior to the early 1980's contact technologies were used for level measurement in wet-well applications to control the simple on/off values of the submersed pumps. This technology was subject to the problems of ragging and build up, meaning it required a great deal of maintenance.
Since the 1980s, non-contact technologies such as the SITRANS Probe LU have been invented. Such technology has proven to be very beneficial to those requiring level measurement in wet-well applications. The technology has a lower risk of ragging which often leads to a need for continuous maintenance. With less ragging and therefore less maintenance required, using non-contact technologies such as the SITRANS Probe LU means that users benefit from significant cost savings, not only from a reduction in the use of resources to carry out the maintenance, but also from reduced downtime.
Furthermore, the Siemens SITRANS Probe LU has been designed to withstand difficult conditions, something which South West Water found particularly beneficial due to the nature of the application.
"We were particularly impressed with the resilience of this device," says Dave Curtis, Senior System Engineer -- SCADA Engineering Services, South West Water.
The SITRANS Probe LU offers easy installation and configuration. It can be configured directly from the Human Machine Interface (HMI) on the control panel, eliminating the need to go into the field in order to carry out programming and diagnostic work. The entire diagnostic configuration set is then retained within data tables on the PLC. The instrument's Profibus node address can be set up using the HMI, where a download can then be initialized. Once this has been completed, the SITRANS Probe LU can be easily swapped, without the need for reprogramming. In addition, the diagnostic information can be viewed by operators at the HMI, through the use of acyclic data retrieval operators, eliminating the need for this data to be collected out in the field.
South West Water's extensive program of environmental improvement has had added benefits for the area. With some of the finest bathing waters in Europe and stunning rivers with extensive wildlife, visitors to the south west region now stands at over 8 million per year.
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