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Wireless transmitters prove effective leak detectors

11 February 2013

Barking Power has installed smart wireless technology to help identify potential problems, improving plant availability and the efficiency of its combined cycle gas turbine (CCGT) power station in London. 

Wireless acoustic transmitters are helping maintenance staff to identify failed steam traps, leaking valves and boiler tube leaks, avoiding substantial costs for lost steam and feed water as well as lost revenue from plant downtime.

Barking Power Station, operated by Thames Power Services, is one of the largest independently-owned generating plants in the UK, capable of generating 1,000MW of electricity - about 2% of the peak electricity demand in England and Wales.

To remain competitive in the deregulated UK power generation market, the plant makes continual improvements to increase plant availability and efficiency, which in turn help reduce overall unit generating cost. Ian MacDonald, senior control systems engineer  for Barking Power, takes up the story:

"Improving process performance is all about understanding what is happening around the plant and being able to respond quickly to any problems. Emerson's Smart Wireless technology enables us to introduce additional measurement points quickly and cost effectively at any location, so we can gather additional information to identify potential faults."

To improve identification of failed steam traps and problem valves, the company initially installed 35 of these wireless acoustic transmitters across the plant. Should a steam trap fail or a small leak begin, an acoustic device transmits changes in sound and temperature which are configured to alert operators to the source of a potential problem.

Indeed, the plant gained benefit from the new devices from the outset, as a leak from a high pressure super heater steam trap was identified that would have cost £1,400 for every 24 hours of lost operation, had it not been detected and attended to. 

A additional 15 acoustic transmitters were subsequently installed to monitor other 'problem' areas, including vent valves that can stick during start-up and pressure relief valves that don't seat correctly. Previous manual monitoring was not only time-consuming but also failed to indicate when or why a release occurred, increasing the chances of a safety, regulatory, or environmental incident. The wireless devices alert operators when valves have opened for as little as a single second. 

Rosemount 708 wireless acoustic transmitters have also been installed to identify leaking boiler tubes. These leaks not only reduce performance but also waste large amounts of costly is de-mineralised and chemically treated boiler feed water. The data from these acoustic transmitters are fed into the plant's existing Emerson Ovation control system, where noise levels can be trended to identify gradual changes. Repairs can then be scheduled during normal off-times to maintain maximum plant availability and avoid forced downtime.

Using the wireless networks already in place, additional devices can be added at much lower cost than if they had to be wired-in individually. This provides Barking Power with additional opportunities where monitoring was previously cost prohibitive - for example, identifying blockages in venturi eductors. Ian MacDonald again:

"Having already installed Emerson's Smart Wireless THUM adaptors for access to stranded HART diagnostic data in traditional field devices, we were very familiar with Smart Wireless technology and confident about using it in other applications. The mobility and flexibility of the battery powered wireless devices also allow us to run trials and move devices to different areas without having to lay temporary cables. As a result, we can spot early problems and improve response to malfunctioning equipment, enabling better planning and utilisation of maintenance resources."

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