18 August 1995

Booms outfire rainguns, says manufacturer

By Andy Collings

BOOM-type irrigators are better than rainguns, claims Boston-based John Pett Irrigation. Water is applied more gently, more evenly and soil does not become capped, says the company.

Such conviction has led to the introduction of a £28,000, 64m boom system capable of applying between 4-125mm of water to over 3ha (7.5 acres) between moves.

Imported from Italian manufacturer, Turbocipa, the 110 GT 450, complete with its Series 10 boom, is reputed to be one of the largest of its type in the country. Boom feed is via a 450m x 110mm pipe and working width when sprinklers are used on the outer sections is an impressive 72m.

The boom is built from aluminium and is equipped with a series of upward facing nozzles. To compensate for the pressure loss which occurs as the water flows through the boom – and ensure even application – the nozzles become progressively larger towards the boom-ends. Boom height can be set from 1.5m to 3m through the use of a hydraulic ram primed at the start of proceedings from a tractor.

Reel design is, on the face of it, fairly conventional – the reel can be rotated through 90 degrees and speed of the wind-in mechanism can be adjusted to allow different application rates to be achieved – up to 150m/hr, if required.

But there are some interesting features which should appeal to growers concerned about the time it takes to move boom-type irrigators.

When the boom has completed its run, a trip switch automatically turns off the water supply. The operator then winds in the boom close enough to the reel to enable two lift arms to bodily lift the boom and its carriage clear of the land. With the water supply disconnected, the whole irrigation plant is towed along the headland to line up for the next area.

In practice, such a manoeuvre, although clearly quicker than many other systems, is not without its teasing problems. Maintaining boom balance so it remains level during transport requires the boom to be drained of water, and the units all-up weight could conceivably cause problems when travelling on soft terrain, despite the machines tandem axles.

Folding the boom for transport is a reasonably speedy affair. The boom is attached to the reel unit as before, and the end sections removed and clipped along side the second sections. Hydraulically powered winches then concertina the sections into a vertical stacked position – wheels on the boom ensuring section ends remain clear of the ground during this "gathering" operation.

Once stacked and secured, the reel complete with boom, is rotated through 90 degrees into the transport position. Machine height is reduced slightly by lowering the boom sections onto a support cradle, but care still needs to be taken when passing under trees or power lines.

&#8226 John Pett Irrigation estimates boom irrigators currently account for about 25%of UK sales.

So what argument does John Pett Irrigation put forward to convince growers to choose a machine significantly more expensive than a raingun?

"Boom irrigators can work on much less pressure than rainguns," says sales manager Chris Pett. "This means pumps are not working so hard and they last longer – typical boom pressure for the Series 10 is about 1.5bar while a raingun usually operates at about 5bar.

"But the main adantages are to be had in the field. Water droplets from a boom are much smaller and treat delicate crops gently; more water can be applied at any one time without risk of soil capping. And applications are even and predictable."

Mr Pett estimates boom-type irrigators currently account for about 25% of sales in the UK but predicts this ratio could change in years to come.