CONCRETE PIPES AND MANHOLESProduction of large concrete products with vertical vibration

FEBRUARY

2009 1Concrete Plant Internationalwww.cpi-worldwide.com

SPECIAL PRINTCPI 09/01

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Production of large concrete products with vertical vibration

HawkeyePedershaab, Mediapolis, Iowa, 52637

The demand for larger concrete pipe and box culvert is increasing all over the world and more and more different shapes are used for stormwater drainage, sewers, engineering tunnels and walkways. Traditionally these products have been manufactured by wet casting, whichgives a nice looking product but decreases the production capacity and raises the cost for casting equipment.

The vibration tables produced by HawkeyePedershaab today are from a technologicalpoint of view far beyond from the most well-known types where a steel construction aresuspended by a number of rubber buffersor steel springs, equipped with one or seve-ral unsynchronized motor vibrators.

The HawkeyePedershaab vibration tablesare activated by 2-shaft vibrators perfor-ming a “uniform vibration” in “vertical”direction, a so-called counter revolvingvibrator. This vertical vibration effect isachieved by mounting the swivel weightson 2 parallel shafts with opposite rotatingdirections.

The vibrators are operated by hydraulicmotors mounted directly on the vibrators.Since all vibration tables with the exceptionof small ones are equipped with 2 or seve-ral vibrators, the vibrators are internallyconnected with synchronized shafts to en -sure that the rotation of all vibrators is com-pletely synchronous.

Any “unbalance” can be adjusted on thevibrators within a fixed area to obtain avibration amplitude adjusted to the weightand the shape of the concrete product tobe produced. The adjustment of the un -balance is a manual process whereas theadjustment of the required frequency canbe made regularly during the process.

Within a large working range, it is thus pos-sible to adjust an optimum combination offrequency and amplitude dependent of thecurrent dimension and shape of the con -crete product. The vibration tables are car-ried by a number of air bags whose airpressure is controlled by means of sensorsin such a way that the surface of the vibra-tion is always horizontal no matter whetherthe table is loaded symmetrically or asym-metrically. Thus, there is always a horizon-tal top of the mould, also if the wall thick-ness varies in the product.

An important precondition to obtain opti-mum results with the vibration technology isthat the mould equipment is completely lok-ked to the vibration table during the vibra -tion process so that no uncontrollable reso-nance occurs which can induce a randomand inhomogeneous compaction of theconcrete, and at the same time entail thatthe mould equipment get damaged due tothe uncontrollable power applications thatarise when the mould equipment is expo-sed to resonance.

As regards the mould equipment for thebox culvert or pipe production, the core willbe fastened with bolts and the outer mouldis fastened with hydraulically activatedmould clamps.The vibration tables run with different fre-quency during the production cycle. In

prac tice it runs at approx 2.600 rpm duringthe main filling process, and during fine fil-ling and pressing of the top profile it is spee-ded up to approx 3000 rpm. This way, thevibration tables are working on a very lownoise level which also means minimumwear on the mold equipment.

Vibration tables

Recently HawkeyePedershaab has in closecoorporation with IFF here in Weimar deve-loped a new series of vibration tablenamed VB 40, VB 50, and VB 60.

VB 40Vibration table type VB 40 can carry aload of 26 tonnes, i.e. a total load fromconcrete + mould that doesn’t exceed 26tonnes. VB 40 can produce concrete pro-ducts with maximum outer dimensions of3,2 x 3,2 m in lengths up to 3 m. VB 40 isequipped with 3 vibrators each with anunbalance of 100 kgcm.

VB50Vibration table type VB 40 can carry aload of 26 tonnes, i.e. a total load fromconcrete + mould that doesn’t exceed 26tonnes. VB 40 can produce concrete pro-ducts with maximum outer dimensions of3,2 x 3,2 m in lengths up to 3 m. VB 40 isequipped with 3 vibrators each with anunbalance of 100 kgcm.

Fig. 1: Vibration table V60, size 5.4 x 4.2 m – 60 tons load

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VB60Vibration table type VB 60 can carry a loadof 60 tonnes, i.e. a total load from concrete+ mould that doesn’t exceed 60 tonnes. VB60 can produce concrete products withmaximum outer dimensions of 5,75x3 m inlengths up to 3 m. VB 60 is equipped with 8vi brators each with an unbalance of 100kgcm.

The largest vibration table VB 60 which cancarry a total load of 60 tonnes was newlysold to a customer in Vietnam for the produc-tion of double box culverts that are up to5,75 x 3 m in outer dimension.

The vibration tables are typically includedin a complete semi-automatic casting stationcomprising a vibration table, belt feederand a pressing device – Multicast XL BC360. The machines can be utilized for bothdry and wet cast manufacturing of box cul-verts, pipes etc.

Products

Typical large product types for manufactureon vibration tables are:

• Box culvers with or without flexiblejoint.

• double box culvert. • lined box culvert.• U-channels • large circular pipes• oval-shaped pipes• egg-shaped pipes• gallerias • Large cisterns• large water tanks.• tunnel sections.

The vibration table technology provides avery high degree of freedom as regardsgeometry and shape. Almost no matterwhich product to produce, a uniform andextremely good compaction of the concre-te from the bottom to the top of the productis achievable.

Mould equipment

For the vibration table program, Hawkeye -Pedershaab has developed highly flexiblemodular equipment by which the samemould equipment can manufacture a greatnumber of different product dimensions andtypes.

The mould equipment is built up by a num-ber of modules that all include four cornersection and a number of intermediate pie-ces. Outer mould as well as core, palletsand profile rings can be assembled to a

Fig. 2: Vibration table V60, size 5.4 x 4.2 m – 60 tons load

Fig. 3: Multicast XL BC 300 and Multicast XL BC 360

Fig. 4: Box culverts are typically used for rainwater ducts and for engineer subways (cableand inspection tunnels).

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great number of different dimensions of boxculverts. In a typical set which covers up to3,5x3,5 m you can adjust the rise andspan, and also the wall thickness, whichmeans you can make more than 200 diffe-rent products

Outer mould and core comprise 4 cornerpieces, and the dimen sion will always be

the dimension of the smallest product to beproduced. These can be combined withspaces from 250 to 1500 mm dependenton the product dimension to manufacture.Pallet and profile ring are also modularlyconstructed and manufactured on the basisof the same modular system as outer mouldand core. �

Fig. 5: Modularly constructed mould equipment for boxculvert

FURTHER INFORMATION

The Hawkeye Group506 S. Wapello St.Mediapolis, Iowa, 52637 · USAT +1 319 3943197 · F +1 319 3943977info@hawkeye-pipe.com · www.hawkeye-pipe.com

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