Impact Extractors
These are air powered impact extractors, and so are directly related to APE’s air hammer range. They offer a simply and rugged design ideal for sheet extraction. In recent years, this design has lost favour, when compared to vibrators, as the means by which the unit grips the pile, is somewhat more cumbersome. Further these products can only extract sheets, hence are typically used for temporary applications, in as a standby product if sheets have been miss driven, using an air hammer.
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Overview
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These are dedicated sheet extractors that operate in a similar way to an inverted air hammer, and so the impact generated acts to thrust the sheet upward.
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All units use a friction grip, as opposed to a clamping mechanism, the strength of the grip is directly related to the pulling force and requires an opposing reaction force.
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These extractors need to operate as close to the maximum pull as possible, if held loose substantial damage can occur.
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These are design to extract sheets, but not to lift them out of the ground.
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Ideally designed for use with crawler cranes, although some small models can be used with excavators. |
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Advantages
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Provides the only alternative to vibratory extraction, therefore its impact mechanism can prove better at extracting in certain soils.
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With only an upward force applied, ground vibration tends to be lower, and there is little chance of settlement problems.
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If site is equipped with the correct compressor size, then these units are a good complement to air power impact hammers.
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These are ‘suspended’ products and so will not tie-up the excavator.
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Slender design enables extractor to be used closer to obstructions. |
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Disadvantages
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Can only extract sheets – single use.
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Friction grip can fail to release or can slip off pile.
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Its use will not be permitted with mobile cranes.
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Not as fast as a vibrator for sheet extraction.
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Typically requires a larger compressor than impact hammer equivalents.
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High noise levels.
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Site needs to work a panel; rarely will a single sheet be removed in first operation, site need to use on several sheets until movement seen.
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Cannot lift sheets out.
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Cannot be used on Domex sheets |
Environmental
- High Noise levels
- Open Lubrication system – pollution/COSHH
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