Vogelsang is known for its range of quality slurry equipment and is seen as a pioneer when it comes to slurry, whether it’s the dribble bar, the trailing shoe, the macerator or lobe pump, it has developed and tested it all. The rotary lobe pump is something that’s very common on the European continent, but Irish manufacturers, farmers and contractors are still sticking to the tried and trusted vane vacuum pump with a directional control valve, which creates a negative pressure within the tanker’s steel tube to load the tanker and vice versa.

The valve is then changed over, which creates a positive pressure to spread on the land.

It’s a simple system, that is reliable when set up and maintained properly. The slurry never actually enters the pump itself as it’s there to move the air within the tanker barrel and therefore create the vacuum.

However, the question is then, why do some of our farming compatriots in Europe have such an affinity towards the positive displacement lobe pump on their slurry tankers.

According to Vogelsang’s David Whelehan, Irish farmers and contractors are starting to see the benefit of optimising their own slurry, and big changes have happened over the last few years.

“Slurry spreading now is becoming more like the silage game, due to closed seasons, weather, field conditions, etc where the gear is very professional and works intensely over a shorter period, farmers and contractors have become more informed about its benefits,” Whelehan says.

Of course, there are additional costs to all this equipment, but the benefits are far outweighing that

“Now they are beginning to talk about cubic metres per hour instead of tanker loads.”

Whelehan notes that the price of chemical fertilisers today, the nitrates directive and the closed season are just some of the main driving factors in why slurry equipment is moving on and becoming bigger, faster and more efficient.

“Of course, there are additional costs to all this equipment, but the benefits are far outweighing that in terms of air and water quality, reducing chemical fertiliser, better utilisation of on farm N, P and K (nitrogen, phosphorus and potassium) and the additional environmental benefits,” he adds.

Why a lobe pump?

Traditionally, in Ireland, most slurry stayed on farm. Now, slurry is moving further and faster than ever before. Some intense livestock farmers today must export slurry compared to before, so a lot more thought is going into being efficient.

“A 3,000-gallon tanker only 70% full of slurry and 30% full of slurry foam is not efficient,” says Whelehan, “that basically means it’s a very expensive 2,000-gallon tanker you’re hauling.”

He highlights that with a vacuum pump — while they are simple — you’re not getting the consistent level of performance as the on-farm slurry tank level is dropping down.

He also notes that what he is seeing on the ground is that, with a traditional vacuum tanker, it will be up to 90% full or thereabouts when the slurry is near the top of the slats, but as the head height of the slurry drops, the tanker rate to fill and its filling capacity drops also.

A rotary lobe pump.

This means, for example, that if there is only two feet of slurry left, it is taking longer to fill, and the tanker is only about 70% full, but the big gain of a lobe pump is it still fills the tanker fast and fills it to 100% capacity all the time, (a typical 3,000-gallon tanker will fill in approximately three minutes).

In Europe, farmers and contractors are often moving slurry greater distances compared to here, so that is one of the major reasons they want the lobe pump.

“As tankers here are getting larger and we are moving slurry greater distances to fields and nurse tanks etc guys are starting to realise it’s much more efficicent to run a lobe pump,” Whelehan says.

False application rates

Another thing Whelehan highlights is people saying they are putting out, for example, 3,000 gallons to the acre as they are using the slurry tanker size to gauge their application rate.

However, if they are filling the tanker less and less throughout the course of the day, it throws this off completely.

“Accurate spreading rates and shut off is difficult with a traditional system, but the lobe pump offers big gains here and works exceptionally well with ISOBUS and variable rate application,” Whelehan points out.

It can also agitate the slurry internally, if desired, while transporting to the field. “If a farmer took, for example, eight hours to spread 18 loads of slurry, he could possibly have achieved this in six hours or thereabouts with 14 loads by fully filling the tanker,” he says. The savings are obvious, and can be seen in fuel, time, tyres, as well as wear and tear on farm equipment.

No priming needed and running dry

Whelehan says that some Irish farmers might have some misconceptions regarding the lobe pump and don’t yet fully understand the technological benefits of it.

Lobe pumps are self-priming and can run dry, “without slurry”. Regarding prepping slurry like agitation, it’s the same for both the vacuum and lobe pump systems. The slurry physically enters this type of pump through the rubber lobes, which is a totally different concept.

An illustration demonstrating the differences in efficiency between a rotary lobe pump system and a vacuum system.

The pump is designed to move slurry, but where foreign objects may be an issue, the option for an inlet macerator/chopper unit and integrated stone box is available. This protects the system, but adds to the overall cost.

“It’s that trade off that customers must balance themselves; of paying out more initially, but be more efficient in their work and with their time.”

He also notes that the Targeted Agriculture Modernisation Scheme (TAMS) is a big incentive too and encourages farmers to do their research.

High ground and stability

Whelehan says when he is talking to farmers on hilly ground or contractors doing a decent amount of tanker road work, they often highlight that the barrel-shape tankers have a high centre of gravity which can sometimes be a safety concern in terms of capsizing.

“With the lobe pump, tanker designers can move from a round tube to a different style completely and hence lower the centre of gravity as the tanker won’t experience the positive/negative pressure it would by a traditional system,” he says.

Lobe pumps are self-priming and can run dry.

“This means not only a safer machine, but the material doesn’t even have to be steel but can be plastic and therefore also lighter.”

Moving away from the vacuum pump can also open up a whole new world with improvements in safety, stability and soil compaction.

Vacuum vs rotary lobe

The running cost of a lobe pump can be less over the life of the tanker system when fuel, wear and time savings are factored into it.

A vacuum pump needs oil and the oiler must be set correctly to lubricate the sliding vanes internally where the lobe pump does not. However, like any pump, a lobe pump has wearing parts such as internal lobes etc, that may need to be replaced over its lifetime pending the application and use. The purchase price is approx three times the cost of a vacuum pump, which is more costly initially.

Those who want fast filling tankers may also need to invest in turbo fillers along with the vacuum pump system to speed up the process.

He says there is no right or wrong way here regarding slurry systems and “it’s a bit like round bale silage vs precision chop pit silage, it’s horses for courses” as both systems have their place in specific applications.