DECAY DETECTION
Assessment of tree hollowness and quantification of decay using microdrills (Resistograph) and sonic tomography (PICUS). Our reports clearly display results alongside management recommendations to allow the client to make an informed decision.
Internal decay can lead to a loss of strength within the wood that may result in tree failure. Indicators of decay include the presence of a pathogenic fungal species, an open cavity or a trunk bulge.
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We use the specialised tools below to better quantify and locate the internal decay. The information gathered, along with our knowledge of specific tree/pathogen relationships and biomechanics, allow us to provide our clients with reasoned, informed management options.
MICRODRILLS
The specific microdrill we use is the IML-RESI F400. It has a 400mm long drill bit with a 3mm diameter needle tip that drives into the wood with a constant drive. The drilling resistance at the needle tip is transferred by the use of two gearboxes (speed selected is species dependent) to a pointer at the top of the device. This pointer scratches the drilling profile onto bespoke wax paper strips that tracks and records 1:1 as it passes through the tree. This information is also computerised via the bluetooth link attached to the device. The drilling resistance recorded is a function of the mechanical wood quality. The great advantage of the Resistograph is the efficiency with which results can be gathered and the reliability with which it picks up advanced decay. It is often used in conjunction with a sonic tomograph to confirm the results from that test.
SONIC TOMOGRAPHY
The specific device we use is the PICUS Sonic Tomograph. Sensors (usually between 8-16) are attached by nails around the circumferance of the suspected area of decay. In turn, each of these sensors are sequentially tapped with a special mallet generating a sonic impulse through the wood that is detected by the other sensors. Once all the sensors have been tapped the data is interpreted by the connected on-site laptop and reconstructed into a colour-coded graphic. Four colours are used to differentiate between wood of different states of degradation. The system works on the basis that sound travels faster through dense, solid wood compared to decayed wood. Where cavities are present, sound cannot pass directly through them resulting in longer travel times as the sound wave circumnavigates the void. The great advantage of this device is how clearly the extent and location can be conveyed to the client.
