New Gear Pump Design Keeps Compactor Quiet

Sept. 9, 2013
Noise protection means higher quality of life, because noise is acoustic waste. In spite of EU directives for noise limits, there is still a great need to act in industry. One company has tackled this problem with their waste compactors — using the Quiet Plus pump from Bosch Rexroth.
Husmann's model SPB 20 SEL self-compacting bins have a large opening, which makes them fast and convenient to use. They've also become popular due to their long service life and maintenance-free operation.

Along with increased industrialization and automation comes greater noise load both on operators and anyone within range. According to calculations by the German Federal Environment Agency around 16% of the population is subjected to continuous noise levels of more than 65 dBA per day from vehicle traffic alone — with additional noise sources to boot. The most recent findings point to increased risk of heart and circulatory system disease from continuously exceeding this noise level. EU directives have accordingly specified noise limit values. Still, there is a need to act, because noise disturbs, stresses, and makes people ill — in increasing numbers.

Technical noise reduction measures and developments by industrial companies are in demand. Husmann Umwelt Technik offers the new Silence Plus external gear pump from Rexroth as an option on their waste compactors, lowering the noise level by an average of 15 dBA compared with conventional external gear pumps.

Economical and environmentally friendly

Especially in areas with direct-vicinity customer contact such as supermarkets and hotels, noise reduction is an important consideration. Wherever people gather you will find corresponding amounts of trash — which is precisely where Husmann’s containers are designed to be placed. Waste compactors are suitable for many types of materials. In commercial kitchens, hotels and hospitals the compactors often compress material with higher moisture content.

Waste compactors are made in various configurations depending on where they will be used. They compact the waste to around 1/5 of its original volume, enabling economical transport while reducing CO2 emissions. The self-compacting bins are simple to use. The operator fills the compactor and presses a button to start it up. In continuous operation the ram plate presses the material directly into the container and then returns. This sequence is automatically repeated until a built-in timer shuts the machine off .

The process duration can be set from 0 to 12 min and can be repeated at the push of a button. During the compaction phases the unit can still be continually filled. After the maximum allowable quantity of material in the container has been reached, the full container is hauled away.

Quiet pump reduces noise

Bosch Rexroth's Silence Plus external gear pump makes secondary noise suppression measures unnecessary in many applications.

Husmann Umwelt Technik is a manufacturer of technical equipment for the waste disposal industry and environmental technology. Husmann has been one of the leading partners for private and municipal waste collection and disposal for more than 50 years. Husmann has made it their priority to support their customers with technically refined products of high quality. “In addition to user-friendliness, we focus on reducing the noises level for the machine operator as well as those in the immediate vicinity,” explains Gerhard Husmann, owner and CEO of Husmann Umwelt Technik. Husmann has used Silence pumps from Rexroth as their standard since 1999.

Silence pumps are somewhat quieter than conventional external gear pumps. The reduced flow pulsation results in fewer pressure fluctuations in the hydraulic system, thereby indirectly ensuring less noise from the waste compactor. Still, this pump does give off audible intrinsic noise. It is with this problem that the product engineers at Bosch Rexroth have given their attention to. The result is the new, significantly quieter Silence Plus external gear pump.

Waste compactors from Husmann in rear loader format for various container sizes.

“At low pressure ranges the Silence Plus pump increases the noise emission of the electric motor almost imperceptibly by just a few decibels,” explains Christian Bohmcker, Product Manager for external gear pumps at Bosch Rexroth. In the working range of 10 bar, the airborne sound increases by just 3 dBA — from 52 dBA to 55 dBA. And by shifting the noise to a 35% lower frequency range the slight noise contribution lies closer to the range of the electric motor. “This is how we achieve a sonorous and, compared to other external gear pumps, significantly more pleasant sound,” continues Bohmcker.

The design of the Silence Plus external gear pump prevents trapped oil formation. The non-involute rounded tooth profile of the Silence Plus creates a closed line of engagement in the form of a figure 8. This reduces intrinsic noise drastically. The Silence Plus also reduces pressure pulsations in the system by around 75% and reduces the structure-borne noise of the entire hydraulic circuit. The external gear pump ensures full, permanent contact on the flank as well as in the top and bottom area of the gears. The first product configuration includes nominal sizes with a displacement from 12 to 28 cm3 per revolution.

Self-compacting container with attached lift-tilt mechanism. Ideal for collection,compacting and transport of waste and recyclable materials.

“The self-compacting containers with the especially quiet Silence Plus external gear pump are ideal for locations such as camping sites, recreational facilities, in residential areas and pedestrian zones,” explains Gerhard Husmann. There is where the reduced noise level will especially benefit both operators and other people in the vicinity.  

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