K Controls 007 K4-20 WirelessHART Valve Position Monitor
07 November 2013
There are many unmonitored manual and actuated isolating valves in industrial process plants, where a cable run from the control room is not available and would be too costly or disruptive to install. To solve this problem K Controls has entered into a partnership with Pepperl and Fuchs to develop the 007 K4-20 WirelessHART Valve Position Monitor to provide frequent, wireless updates about a valve's position and eliminate the need for time consuming and risky visual inspections.
The 007 K4-20 WH is powered by a battery pack with a lifespan of up to 5 years depending on the transmission rate. The rotatable antenna can be adjusted to achieve optimal reception. The unit is easily programmed with a configuration tool (DTM: Device Type Manager or DD: Device Description). The WirelessHART protocol utilizes a time synchronized, self-organizing, and self-healing mesh architecture.
The protocol supports operation in the 2.4 GHz ISM band (Industrial, Scientific and Medical band) that is licence free and used worldwide. Signals from the 007 K4-20 WH and other wireless HART devices are sent to a WirelessHART Gateway which is the interface between the WirelessHART network and the control system or asset management system. The gateway supports up to 250 participants and can be connected to the control system using either an RS485 or Ethernet interface, that can transmit either the MODBUS or HART protocols.
A flat mesh approach is used where all wireless field devices form a network. Every participating field device serves simultaneously as a signal source and a repeater. A message is sent from a field device to its nearest neighbour, that then passes the message on, until the message reaches the WirelessHART Gateway.
The mesh architecture can therefore significantly increase the total area covered way beyond the 75m to 200m range possible between two individual field devices. In addition, alternative routes are set up during in the initialization phase. If the message cannot be transmitted on a particular path, due to an obstacle, interference or a defective field device, the message is automatically sent via an alternative route. So, in addition to extending the range, the flat mesh network provides redundant communication routes to increase reliability. Field devices can be added to the network as required; this will also increase the number of alternative paths available.
WirelessHART employs robust security measures to protect the network and secure the data at all times. The communication in the network is coordinated with TDMA (Time Division Multiple Access), which synchronizes the network participants in 10 ms timeframes. This enables a very reliable (collision-free) network, and reduces the lead and lag times during which a station must be active.
To avoid jamming, WirelessHART also uses FHSS transmission technology, (Frequency Hopping Spread Spectrum). All 15 channels as defined in IEEE802.15.4 are used in parallel and WirelessHART uses FHSS to “hop” across these channels. Channels that are already in use are blacked out to avoid collisions with other wireless communication systems. The combination of 10ms synchronization and 15 channels allows 1500 communications per second.
The 007 K4-20 WH has IP66 rated enclosures manufactured from a combination of engineered plastic and either coated aluminium or stainless steel. For hazardous areas the certification is ATEX and IECEx intrinsically safe Ex ia IIC T4 Gb (-40°C = Ta = +60°C) for hazardous gasses in Zones 1 and 2 and Ex tb IIIC T135°C Db IP6x (-40°C = Ta = +60°C) for combustible dusts in Zones 21 and 22. It is suitable for inclusion in any existing WirelessHART system that uses a true WirelessHART protocol.
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