Construction News - International Construction Industry
International
Construction News
UmweltBau GalaBau Bau Magazin

EXCON Special: High-Quality Compression with Stehr Machines

SCHWALMTAL/GERMANY, November 12, 2013 - At the Bauma show in 1989, on what was then the Gehl stand, a few people looked astonished as Jürgen Stehr revealed his first SBV 55 H1 hydraulic plate compactor as a mounted device on a small skid steer loader.  What was then regarded as a novelty was also the start of the Stehr Story. 

The cornerstone for series production had been laid. What followed was mostly in line with direct customer requests: Double and triple plate compactors were produced; usually for installation on wheel loaders.  They were subsequently mounted on tractors, diggers, rollers, snow groomers, mining machines etc. Nowadays Stehr plate compactors can be found at construction sites throughout the world, where they are used to solve familiar compacting problems. 

Stehr SBV 240/2 plate contractor

Stehr SBV 240/2 plate contractor with a Bobcat T 870 H tracked loader. | photo: Stehr

The new Stehr SBV 240 / 2 mounted compactor with a width of 2114 mm has been developed in order to compact large areas sparingly and with a low level of energy consumption, if possible with just one passage.  Given that several manufacturers of wheel loaders equip them with high-performance hydraulics, Stehr also constructs high-performance compactor equipment for these devices. To do so, a new eccentric gear drive has been developed which allows for speeds of up to 5000 rpm.  The high axial pressure hydraulic motors are responsible for actuation.  At a speed of 4200 revolutions an oscillation frequency of 70 Hz is achieved with amplitude of 1.5 mm.  Four opposed shafts generate directed oscillation which hits the material being compacted 100% vertically downwards with a centrifugal force of 240 KN.  This makes for the best conditions for optimum compacting of sandy, gravelly material.  The mounting has been engineered so that almost no vibrations are transferred onto the carrier device or into the surrounding area, meaning that work can often be carried out in residential areas with listed buildings.

SBV 160-2 City

Confirming a story of success and innovation: Stehr products like the SBV 160-2 City. | photo: Stehr

The SBV 240/2 is the most powerful mounted compactor on the market. Compacting values on problematic surfaces, such as gravel, sand, frost protection layers, mineral aggregate or recycled material, are often achieved with just one passage with a dumping height of up to 0.5 metres. Oscillations which are directed 100% vertically downwards direct the force to the areas where it is required and not into the environment. It is even suitable for use in the vicinity of listed buildings. Newly developed connection kinematics with inclined carrying handles mean that almost no vibrations are transferred to the carrier device or the environment.  These unwanted vibrations cost force and represent an enormous loss of energy. A roller with 100 kW of power consumes approximately 20 litres of fuel/hour.  Several passages are required in order to achieve anywhere near the required level of compacting. Thus approximately 360 - 720 m³ per hours are possible (source: Bomag Handbuch der Verdichtung).  With the Stehr SBV 240/2 plate compactor the required compacting values are often achieved with one passage with triple or quadruple the performance.  Compared directly to other compacting devices, this saves enormous amounts of energy and thus fuel.

The largest SBV 240/2 plate compactor with a Bobcat T 870H tracked loader has now been shown at Korz Alsenborn/Palatinate, where 3 Bobcat T 250 tracked loaders are already being used with smaller Stehr SBV 55 H3 . Mr Korz, who attended the demonstration in person, confirmed that the Bobcat machines with Stehr plate compactors are now amongst the most important devices in his comprehensive fleet of state-of-the-art machines.  At the construction site at the Alsenborn railway station material comprising a sand and gravel mixture had to be installed behind a supporting wall.  A large wheel loader dumped the material behind the wall, the Bobcat installed it and subsequently compacted it with the largest Stehr compactor. The customer was convinced and ordered a complete machine unit from the Bobcat subsidiary in Kaiserslautern. The benefits were evident: high compacting performance with hardly any perceivable vibrations in the surrounding area.  "The ideal machine for residential construction sites", the company owner stated. In order to meet the high demands for compacting in the future and to keep standards as high as possible constantly a test track for compacting devices has been installed on Stehr's premises.  The topsoil has been solidified with binding agent so that any situation which can be encountered on construction sites can be played out. The set-up which is equipped with state-of-the-art measuring technology has already led to a few discoveries.  Competitors' devices are tested in order to be ready for the future. In a direct head-to-head test between an SBV 240/2 plate compactor and a 13.5-tonne roller an independent testing body - Baugrundlabor Fulda - carried out numerous plate pressing trials as per DIN 18134 and established that with a dumping height of 50 cm frost protection with a grain of 0>32 compacting values of 148 MN/m² with a deformation modulus of 2.05 could be achieved with just one passage.  Even after 3 passages of the 13.5-tonne roller the values achieved were not even close to these results. The next step was a combination with a working width of 3 a 4 metres. So the Stehr Story will be written further on, confirming a tale of success and innovation.
bi