COMMUNICATING WITH VALVES imtex valvescan monitoring & control is Higher Level Bus Networks () Lower Level Bus Networks a manufacturing and marketing company Field based communication networks are A field proven standard such as Actuator established in 1990 specialising in the available for interconnecting controllers – Sensor Interface (AS-i) originally supply of advanced valve monitoring and complex instruments in the plant developed for applications which require and communication systems. environment and are ideally suited for on-off or “binary” feedback, has proved With the increasing implementation of continuous (0 to 100%) or critical duty ideally suited for discrete (on/off) valve fieldbus networks which form part of the discrete (on/off) valve applications. In the applications operating with end of travel process plant intranet system, process process industries, , HART, limit switches / sensors and solenoid control valves supplied with imtex Foundation Fieldbus and DeviceNet have valves. However, with the latest revision valvescan communication system established a strong base of user of the protocol specification, AS-i is now devices offer many advantages and support whereas other protocols such as optimised for use with both binary and benefits to process users. and Interbus have had traditional analogue (4 to 20mA) control devices imtex valvescan devices incorporate an support for interconnecting remote I/O. and as such is also suited for use with input/output (I/O) card which integrates imtex valvescan devices are available to continuous (0 to 100%) valve with the bus network and can either be work directly with the following higher applications. AS-i was designed to be a used for continuous feedback (0 to 100%) level protocols: lower cost but complementary system to or discrete (on/off) valve applications the higher-level bus networks and as with the following advantages: • Profibus PA - Continuous such gateways very conveniently to the (0 to 100%) Feedback higher-level bus protocols. Simplified Electrical Wiring • imtex AS-i valvescan devices are Using 2 or 4 wires for all the HART - Continuous • available to gateway* with the following valves in the valve network (0 to 100%) Feedback higher level protocols: eliminates the wiring ‘spaghetti’ Foundation Fieldbus of conventional systems. • Profibus DP - Continuous (0 to 100%) • • Reduced Installation Costs Feedback or Discrete (on/off) • Modbus and Modbus Plus By reducing the number of wires used in the valve network, the • DeviceNet - Discrete (on/off) • LON electrical set-up becomes much simpler and installation time • Interbus is reduced. • Ethernet (TCP/IP) Increased System Reliability • DeviceNet Using solid-state circuitry and • micro-chip technology, maintenance CC-Link downtime is reduced, system • diagnostic functions are enhanced • CANopen and CANrho and system reliability is increased. *Note : Imtex can offer a full range • Standard Bus Technology of AS-i gateways as well as power By integrating with the leading supplies, repeaters and ancillary bus technology protocols, systems components are supported by almost all of the leading manufacturers of process equipment. Overview of Main Protocols

Profibus and Foundation Fieldbus DeviceNet AS-Interface (AS-i)

Designed as a digital replacement of the The DeviceNet protocol is based on CAN AS-i networks up to 62 I/O or 31 4 to 20mA standard in the process (Controller Area Network) technology and analogue modules onto a single pair of industries, the Profibus and Foundation dramatically reduces costs by integrating wires which delivers both signal and Fieldbus protocols are a Local Area up to 64 devices on a 4-wire trunk power and is ideally suited for discrete Network (LAN) for instruments offering network. Communication data is carried on/off and continuous control multi-drop capabilities with up to 32 over two wires with a second pair of applications. devices per network. The physical wiring wires carrying the power. Both analog Benefits for both protocols are fully compatible and discrete devices may be connected with intrinsic safety standards and may into the DeviceNet protocol. • Ideally suited for batch be used in hazardous as well as general Benefits process duties. purpose areas. Capability to install up to Benefits • More than 30% savings in installation • costs over conventional systems. 62 discrete and 31 analogue • Reduction in field wiring costs. devices per network • Capability to handle both analogue master/gateway. • Intrinsic safety wiring option and discrete valve and instrument available for further cost reductions applications. • Simple electronics providing in hazardous environments. economical and robust • supplied over the 4-wire bus. performance. • Same bus used for continuous and discrete applications. • Capability to install up to 64 • Transfer medium unshielded devices on the same bus network. 2-wire cable for both data • Control may reside in the field and power supply. devices freeing up space in • Hot insertion of the field devices central controllers. without dropping power. • Signal transmission has high tolerance to EMI. • Provides greater control • Message prioritising to enable functionality and process fast throughput rate for critical • Easy to install providing the information. information. greatest cost saving with the least complexity. • Standardised function blocks • Bus lengths up to 500 metres representing control and I/O (dependent on data baud rate). • Highly effective fault correction. speed set-up. • Technology with proven reliability • Bus lengths up to 100 metres • Bus lengths up to 1900 metres in millions of mission critical which can be extended to 500 and spurs up to 120 metres applications. metres with repeaters. span most process systems. HART • Free choice of network topology Supported by over 8% of the (line, ring, star or tree) allows • HART (Highway Addressable Remote World’s process instrumentation optimised wiring network. Transducer) is a digital communication suppliers. protocol which operates on top of a • Variety of gateways available conventional 4 to 20mA analogue current to seamlessly tie into high loop signal from a measurement device level bus networks. such as a valve feedback transmitter.

Benefits

• Allows remote configuration, adjustment and diagnostics of the field device.

• Compatible with existing analogue connections on most control systems. COMMUNICATING WITH VALVES

Bus Networks and Valvescan Standardised bus networks are able to link intelligent field devices to enterprise systems to offer unparalleled benefits to the process industries. Benefits include dramatic reductions in installation costs, reduced maintenance & commissioning costs and improved process performance. Valvescan, process networking solutions and support services, facilitates the implementation of the plant process bus network.

Optimized Process Bus Architecture An optimised network may consist of two or three buses which seamlessly and economically link sophisticated process instruments and simple, discrete devices into the process control architecture. Figure 1 illustrates a fieldbus and sensor bus being directly attached to the process control/enterprise system. Although one higher level bus network may be capable of directly connecting all of the field devices with the control architecture, area classifications, reliability, and economic considerations make the layered approach preferable.

Enterprise Networks Ethernet with TCP/IP is the de facto standard for linking computer control and business systems together. Field level bus networks are now being plugged into the enterprise networks by sliding the application protocol from theFieldbus onto the Ethernet network. As a result, the following Ethernet based protocols have emerged at the control system level: • Profinet - Ethernet with Profibus • Ethernet IP - Ethernet with ControlNet/DeviceNet • HSE - Ethernet with Foundation Fieldbus • Modbus TCP - Ethernet with Modbus

Ethernet with OPC (OLE for Process Control) clients/servers promises to offer universal translation for each of the different protocols’ application layers to seamlessly interact with windows-based software.

Figure 1 AS-Interface Type of Control

Enterprise Enterprise Control Networks Full Function • HSE Fieldbus • EthernetIP Ethernet Device Buses • Foundation Fieldbus H1 • Modbus TCP Field • WorldFIP Control • DeviceNet Sensor/Actuator • Modbus • ControlNet Buses • Interbus-S • AS-Interface • LonWorks Foundation Fieldbus H1 • Seriplex • Profibus-DP & PA Discrete Control Optimized Process Bus Architecture Simple Devices Complex Devices

Device Functionality/Cost

Imtex Controls Limited Tonbridge - UK Tel +44 (0)8700-340002 Fax +44 (0)1732-852133 Email [email protected] www.imtex-controls.com