Online filter monitoring avoids downtime

Emerson Process Management Smart Wireless technology is enabling INEOS to monitor filters within polyethylene pellet transportation tubes.

The polyethylene pellets are passed through the transportation tubes using compressed air.

The in-coming air is filtered to prevent any pollution of final product.

The filters become blocked over time and lose their efficiency, which in turn affects the quality of the end product.

A liquid column (U-tube) was installed across the filter, indicating the differential pressure.

An increase in the pressure suggests that the filters are blocking.

Identifying a blocked filter did, however, depend on the operator making his rounds at the moment the blockage was becoming noticeable.

An automated alternative to operator visual inspection was to measure the differential pressure across the filter.

An increase in differential pressure above a pre-determined point would indicate that the filter is becoming blocked.

However, because of the location of the filters, connecting the required measurement points back to the control system using a wired solution was not feasible.

'The filters are very hard to reach and the high cost of installing cabling to connect the devices prevented us from installing the online condition monitoring points we wanted,' said Frank Mehlkopf, maintenance engineer, INEOS Koln.

'In addition, using wired transmitters could have meant lengthy installation times, something that was not possible with our production schedule,' he added.

Ineos looked at a number of wireless technologies for this task, but found that line-of-sight solutions could not provide the reliability of connection or the robustness they required.

The transmitters are positioned in a very dense working environment with many metal obstructions that can cause interference.

There is also a large amount of moving equipment that could cause temporary loss of signal for line-of-sight wireless solutions.

Therefore, Ineos elected to install an Emerson Smart Wireless solution.

Eight Rosemount 3051S DP wireless transmitters were installed as well as a single Emerson Smart Wireless gateway.

The eight wireless transmitters send the pressure data back to the Ineos control system where the condition of the filters can be constantly monitored.

The transmitters are positioned up to 150m from the gateway.

With Emerson self-organising technology, each wireless device can act as a router for other nearby devices, passing messages along until they reach their destination.

If there is an obstruction, transmissions are simply re-routed along the network until a clear path to the Smart Wireless gateway is found.

As conditions change or new obstacles are encountered in a plant, these wireless networks simply reorganise and find a way to get their signals through.

All of this happens automatically, without any involvement by the user, providing redundant communication paths and better reliability than direct, line-of-sight communications between individual devices and a receiver.

This self-organising technology optimises data reliability while minimising power consumption.

It also reduces the effort and infrastructure necessary to set up a successful wireless network.

'We found Smart Wireless easy to use and we are currently testing it at eight filters in our logistic area,' said Mehlkopf.

'One of the main attractions of the solution is the ease in which you can expand the network.

'It is possible to add additional transmitters to the existing wireless network without having to add additional gateways,' he added.

Emerson AMS Suite predictive maintenance software was used to manage the Smart Wireless devices, enabling the technicians to configure the devices, run diagnostic checks and monitor alarms and alerts.

The wireless network has been up and running without any problems for eight months.

Ineos intends to further expand the wireless installation with the introduction of vibration monitoring.

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