What is screen differential control?
This is a control application commonly found at utility plants located on rivers, lakes and other large bodies of water and at industrial facilities where a large amount of cooling water is used. Screen differential control and monitoring is needed to prevent damage to rotating screens caused by excessive pressure being applied by debris collecting on the screens.
Screen Differential Control
Application
A typical cooling system consists of two or more sets of rotating screens. When the differential across a set of screens reaches 15 cm (7 inches), an alarm is activated. If the differential reaches 25 cm (10 inches), the screens start to rotate and backwash pumps are started initiating a backwash procedure to clean the screens of any accumulated debris.
Differential is measured by monitoring the back pressure created by displacing water in sensing lines using regulated air flow. Lines are located upstream and downstream of each screen.
Upstream and downstream pressures are monitored by a recorder set up to read differential flow. Transmitter outputs are fed into the recorder so operators have tide reference, individual screen differentials with alarms and auto start for wash pumps. These contacts are fed into the screen logic by the recorder alarm option.
Solution
DPharp was recently selected for this application by a major Texas electric utility company when they redesigned their screen differential monitoring and control system. The company selected DPharp over their plant standard because of its ability to withstand plant air applied to sensing lines during blowback operation--without having to be taken out of service, and with no shift in calibration after completion of blowback. Transmitters have been in operation since November of 1996, and plant maintenance personnel are very pleased with their performance.
A simplified screen differential monitoring diagram is shown below. Solenoid valves or a timer are used to initiate automatic blowback operation once a day. DPharp monitors the differential across the rotating screens.
Main Features of DPharp
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| DPharp |
EJA110A Digital Solution
- Best-in-class performance
- ±0.03% Overpressure calibration protection
- ±0.1% per 5 years long term stability
- 100:1 turndown
- ±0.065% accuracy
EJX110A Premium Value
- ±0.1% per 10 years long term stability
- 200:1 turndown
- Best-in-class high accuracy, 0.04%
- Multi-sensing output
- Multi-variable transmitter as EJX family line-up
- Safety as standard (IEC 61508)
Industrias
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Agua industrial
El agua industrial se utiliza en todas las plantas industriales, tales como las estaciones de generación de energía, refinerías y plantas petroquímicas. La plataforma de control única de Yokogawa maneja todo el procesamiento integrado del agua y control de las aguas residuales junto con el proceso principal.
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Agua y agua residual
Yokogawa ha estado suministrando soluciones de control para la producción hídrica sostenible desarrollando tecnología con mayor eficiencia energética, ayudando a reducir la huella de carbono de las operaciones y fabricando productos de gran solidez que protegen el ambiente contra los contaminantes. Con nuestra tecnología de vanguardia y amplios conocimientos de las aplicaciones, trabajamos con usted para proveer soluciones hídricas sostenibles que impulsen su negocio y agreguen alto valor a lo largo del ciclo de vida de la planta. Nuestra tecnología y nuestros productos mejoran el desempeño de las plantas y garantiza que puedan operar competitivamente en los mercados del agua de hoy, así como reducir sus costos operativos. Yokogawa brinda apoyo en una amplia gama de aplicaciones para el control del agua en los mercados del agua tanto públicos como privados.
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Tratamiento de aguas
Yokogawa ofrece soluciones óptimas para mejorar el funcionamiento confiable de las plantas de tratamiento de agua. Estas soluciones incluyen tecnologías sofisticadas, una calidad del producto sin igual y la extensiva aplicación de conocimientos a lo largo de todo el ciclo de vida.
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Tratamiento de aguas residuales
Las plantas de tratamiento de aguas residuales utilizan muchos motores, bombas, ventiladores, etc., y es importante reducir su consumo de electricidad con el fin de reducir los costos de operación. Yokogawa ofrece soluciones óptimas de control para mejorar la eficiencia energética.
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