Mechanised laboratories are gaining increasing popularity in automation of sampling and analysis to reduce sample preparation and analytical errors that can contribute to the total sampling error according to Gy’s Theory Of Sampling. The input sample size to these systems is often specified and requires tight tolerances.
The Multotec Variable Ratio Divider allows a preparation step as part of the mechanical sampling plant where each increment that is deposited into a composite sample container can be controlled allow a composite sample mass with reproducibility to within 1%. The Variable Ratio Dividers also achieve good sampling precision by compliance of the integrated dry Vezin sampler to Gy’s guidelines of radially tapered cutters, linear travel speeds of 0.35-0.6 m/s on the outer radius of the cutter tip and other principles.
The variable ratio divider consist of three main components, namely: the increment receiving hopper to retain a typically fluctuating sample increment mass, the extrusion feeder to present the 3-Dimensional sample increment lot in the hopper to the subsequent Vezin sampler in a controlled, preserved and single dimensional stream and finally the TOS compliant Dry Vezin sampler.
Fluctuating sample increment masses are recorded by the load cells underneath the sample collection hopper. A computer then pre-calculates the Vezin cutter speed and through a Variable Speed Drive energizes the Vezin’s electrical motor to drive the cutter at a fixed speed division ratio and allow the required sample mass to be extracted. The composite sample mass can be controlled to within 1% accuracy.
The retention hopper is rounded as far as practical and polished on the inside to prevent sample retainment that will result in a weighting error. The feeder between the hopper and dry Vezin is sealed to prevent sample contamination and losses, travels at slow speed and can often be VSD controlled for precision feed to the dry Vezin sampler. The dry Vezin’s steep housing allows reliability for even fine, sticky material.
The Variable Ratio Dividers can be tailored to material, application, sampling and robotic laboratory requirements.
Multotec’s Variable Ratio Divider system showing the conical stainless steel primary sample collector ( on load cells ) , the sample dosing feeder and Dry Vezin sampler that will result in composite secondary sample sizes within 1% accuracy.