Radar measures wood dust silo levels reliably

Vega radar is reliably monitoring the silo level of wood waste at a furniture plant, providing instant silo contents display and Ethernet transmission of the data for improved plant efficiency

Since 1963, William Ball and the Ball family has manufactured high quality fitted furniture and are one of the UK's premier manufacturers of fitted kitchens, bedrooms and bathrooms.

They combine quality craftsmanship with 'high tech' manufacturing lines, which cut and shape the furniture.

This also means they get significant volumes of waste wood dust, which is collected from the different manufacturing units via a pneumatic extraction system and collected in a large central silo.

The wood dust is used as a fuel for a newly installed high efficiency 'low ash' boiler system to provide both steam and heat for the whole plant.

Keeping an accurate reading of the available 'fuel' capacity in the silo is critical, to ensure the boiler system does not run out, and that cooling fans are used efficiently for expelling any excess heat generated.

If there is over-supply of wood waste, then arrangements for costly disposal to land fill need to be made: if the silo were full then production would have to stop.

So, optimum control of the throughput is essential to maximise the boiler system investment and keep disposal costs to a minimum.

Silo contents were previously measured manually, but this method proved difficult.

The main drawbacks were the limited visibility inside, due to the high dust levels and a time consuming and a potentially hazardous climb to the silo top in all weathers.

There was also a likelihood of dust emissions, however small, released into the local environment every time the lid was raised to measure the level.

A Vega vibrating rod level switch was already in use for high and low level alarms.

This had proven reliable, so the engineer decided to seek a continuous measurement solution for indication and so consulted Vega.

During the site survey of the application, the high levels of dust, the filling and the poor reflective properties of the material were taken into account.

The customer also expressed a preference for a non-contact measurement, as this would avoid the risk of any cable-based device damaging the discharge mechanisms in the unlikely event of a breakage.

A Vega level radar for solids, which handles dust, continuous filling and angles of repose was recommended.

It was also identified that the silo capacity information needed to be shared with production, disposal and the facilities departments across the site.

So the radar was teamed up with a 'signal-conditioner', which can provide power to the device, give a local display, relay and signal output (4-20mA), and distribute information over the computer network, using two-way Ethernet connectivity.

There is also an integral webpage server for wider global information transmission.

The complete solution was provided in the form of a Vega 2-wire solids radar connected to a signal conditioner with network connectivity built in.

Tony Rogers, The site engineer said, "It was easy to get set up, the radar device worked 'straight out of the box...' - I had expected it to be much more complex to set up!".

It is now delivering accurate inventory of the waste wood silo, operating with the very high dust levels, despite the light bulk density of the waste, the continuous filling and the surface angles of the product.

The engineer also commented, "I am pleased with how representative it was of the level, even with an uneven surface profile and continuous filling and emptying".

The system provides real-time data across the network for all departments so they can anticipate and control needs.

The result is an efficient boiler system feed, with very low waste and optimised heat output all year round.

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