Valve Magazine - Summer 2008

viewed as a direct replacement for wired instrumentation. Wireless devices are typically slower but can be installed in a matter of minutes. They can often be installed where wired devices cannot— in hard-to-reach locations, in areas hazardous to plant personnel, where power doesn’t exist and where running wires is not allowed or prohibitively expensive, to name a few.

Initially, most wireless devices will be used for monitoring remote but critical sites to improve operational awareness of certain equipment. Wireless transmissions will overlay existing operating architectures at many sites. In such cases, additional wiring is not needed, and existing wired networks are not impacted.

A second stage of wireless development will occur when outdated wired instrumentation is replaced by wireless (Figure 1, page 22). The farther an operation is removed from the control center, the more attractive wireless will become for full control functionality. Driven by lower engineering and installation costs, wireless upgrades will be simpler and easier to implement because new conduit and wires will be eliminated.

Other advantages of wireless technology include:

Reduced project reviews so projects are completed faster

Intrinsic safety, due to low power consumption

Manually operated equipment easily added

An additional layer of assurance in safety-related applications

includes reducing the number of times operators or maintenance personnel must go out to touch equipment and the amount of time needed to take corrective action when necessary. In some cases, regulatory agencies are demanding more information about operating equipment, especially valves. This may include more frequent measurements that use a structured or automated collection process.

A smart wireless solution does not require a large investment in site surveys or an existing wireless infrastructure. An available startup kit includes the gateway and a few field devices to measure or monitor selected sites. A self-organizing mesh network can often be operating in a matter of minutes, and more transmitters can be added easily and seamlessly as budgets evolve.

It’s Here Now

Gaining the benefits of the valve applications outlined above requires a solid

foundation of wireless networks and control infrastructure. To meet this need, the wired and wireless worlds are integrated in a single, scalable infrastructure that helps end-users optimize applications across an entire operation. In effect, the benefits of the digital plant architecture are extended to assets that were previously out of physical and economic reach.

This approach is based wholly on open standards so designers can choose from a variety of wireless solutions without being tied to a specific technology or vendor.

The self-organizing mesh technology that is the basis for WirelessHART has been tested and proved in the field. Each wireless device in a self-organizing network can act as a router for other nearby devices, passing messages along until they reach their destinations. If there is an obstruction, transmissions are simply re-routed along the mesh network until a clear path to the gateway is found.

Motivation for Wireless

The ease and simplicity of implementing wireless technology can be a strong motivator, especially when minimal engineering effort is needed for the important coordination-of-project reviews. As work forces diminish, anything that requires less effort by a smaller and less experienced staff becomes a motivator.