Abstract:
An analyser system including an on-belt analyser having a housing adapted to be positioned across a path of a conveyor belt which carries material to be analysed, wherein the housing defines a tunnel dimensioned to allow the belt to travel therethrough in suspended relation in order to allow analysis of the material without the belt contacting the analyser.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority from Australian Provisional Patent Application No. 2005900951 and U.S. Provisional Patent Application No. 60/658,195, the contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to an on-belt analyser. 
       BACKGROUND OF THE INVENTION 
       [0003]    One form of on-belt analyser, which utilises a thermal neutron capture and gamma ray production technique known as PGNAA (Prompt Gamma Neutron Activation Analysis), is employed to analyse the composition of material such as coal or other mineral product transported on a conveyor belt. The analyser has a C-shaped housing provided with lifting points to allow the analyser to be appropriately positioned across a path of the belt. The weight of the analyser is quite substantial, in the order of 6500 to 9000 kg and the lifting points are necessarily provided at a base of the analyser due to structural load-bearing limitations of the housing. Once positioned, removable side shielding is fitted to close the open side of the C-shaped housing, to thereby define a tunnel in the order of 2 meters long, through which the belt passes. 
         [0004]    The tunnel has a radiation source in its base and sensors in the roof thereof. Tunnel slider panels are provided above the radiation source to support the belt as it passes through the analyser. 
         [0005]    Installation and operating costs of the analyser are relatively high given the analyser generally needs to be installed in a shed or the like for protection from the elements and various component parts such as the slider panels are subject to wear during operation. Also, in order to install the analyser substantial parts of the conveyor belt support structure, such as frame work and stringer or idler wheels, need to be removed. The remaining structure, at either side of the analyser, then needs to be configured in order to ensure an appropriate profile is applied to the conveyor belt, as it enters the analyser, compatible with the shape of the tunnel and the slider panels. 
       OBJECT OF THE INVENTION 
       [0006]    The present invention seeks to provide an improved analyser system. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with the invention, there is provided an analyser system including an on-belt analyser having a housing adapted to be positioned across a path of a conveyor belt which carries material to be analysed, wherein the housing defines a tunnel dimensioned to allow the belt to travel therethrough in suspended relation in order to allow analysis of the material without the belt contacting the analyser. 
         [0008]    In another aspect there is provided an on-belt analyser with a C-shaped housing, to allow the analyser to be positioned across a path of a conveyer belt, wherein an upper arm of the housing includes lifting points. 
         [0009]    In another aspect, there is provided an analyser with a housing adapted to be positioned across a path of a conveyor belt and a canopy for protecting the housing. 
         [0010]    Preferably, the canopy is fitted to lifting points located on an upper arm of the housing. 
         [0011]    Preferably, the housing defines a tunnel through which the conveyor belt passes and has extension panels fitted thereto to provide protection adjacent the analyser and external of the tunnel, from radiation emissions generated from a radiation source within the analyser. 
         [0012]    In another aspect, there is provided an analyser including a housing adapted to be positioned across a path of a conveyor belt, wherein the housing defines a tunnel arranged to receive the belt such that the belt passes through the tunnel without contacting the analyser. 
         [0013]    In another aspect, there is provided an analyser system including an analyser with a housing, which defines a tunnel, and a conveyor assembly with a conveyor belt that passes through the tunnel without contacting the analyser. 
         [0014]    Preferably, the housing has a width dimension in the order of 1 meter to allow the analyser to be positioned between existing adjacent supporting idlers of the conveyor belt. 
         [0015]    Preferably, an under side of the belt has a clearance in the order of 30 mm from a base of the tunnel. 
         [0016]    Preferably, the weight of the analyser is in the order of 2000 kg. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention is described by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1  is a perspective view of an analyser; 
           [0019]      FIG. 2  is a perspective view of the analyser of  FIG. 1 , fitted with extension panels, automatic source drive shield, and canopy; 
           [0020]      FIG. 3  is a cross-sectional view of the analyser; and 
           [0021]      FIG. 4  is a diagrammatic end view of the analyser with a canopy. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    An analyser system  20  is shown in  FIG. 1  as including an analyser  1  and a conveyor assembly  21 . The analyser  1  has a C-shaped housing  2  arranged to be positioned across a path of a conveyor belt  3  of the assembly  21 . The analyser  1  is designed so as to weigh only in the order of 2000 kg which is light enough for the housing  2  to maintain structural integrity even if lifted from lifting points  4  provided by eye-bolts, which are provided on an upper arm  5  of the analyser  1 . For that purpose, the analyser  1  is preferably formed of a steel framed enclosure filled with cast neutron shielding (CNS). The CNS is a dense suspension of 60% high-density polyethylene beads cemented together with a mixture of 20% borax and 20% polyester resin-plus catalyst. This material provides most of the shielding required since it is effective in slowing down and absorbing neutrons. The material is also waterproof, non-corrosive and intrinsically fire resistant. 
         [0023]    Once the analyser  1  is positioned in the manner shown, side shield  8  is fastened in place so that the analyser defines a tunnel  9  through which the belt  3  passes. A width dimension “w” of the analyser is preferably in the order of  1  metre to allow the analyser to be positioned between existing supporting structure, such as idlers  10 , of the conveyor assembly  21 , which are conventionally spaced at between 1.2 and 1.5 metres apart. 
         [0024]    In some circumstances, it may be necessary to provide additional shielding for radiation protection and, in that case, a further side shield  6  may be provided and extension panels  11  may be fitted either side of the tunnel, as shown in  FIG. 2 . The extension panels are preferably formed of LTV stabilised polyethylene or like material, which is suitable for absorbing radiation from, for example, a Cf-252 source. The panels  11  may be dimensioned so as to provide protection for an additional length “L” of, say, 1 metre either side of the analyser  1 . 
         [0025]      FIG. 2  also shows the system  20  as including an optional microwave moisture content analyser  7  positioned above the belt  3 . 
         [0026]    Referring now to  FIG. 3 , a cross-section of the analyser  1  is shown in detail with the side shielding  8  attached to the housing  2 , so as to define the tunnel  9 . A radiation source  12  is provided in a base  13  of the tunnel and detectors  14  are appropriately located above the tunnel  9 . The tunnel  9  is positioned and dimensioned so as to receive the conveyor belt  3  in an elevated position relative to the base  13  of the tunnel  9 . The clearance is preferably in the order of 30 mm to allow for a slight droop in the belt  3  between its supporting idlers  10 . Previously, it was considered critical to minimise the distance between the Cf-252 source and material to be analysed in order to maximise absorption of neutrons in the material. Accordingly, the prior-art analyser was designed to have contact between the belt and the analyser using 25 mm thick slider panels. The geometry of the analyser illustrated in  FIG. 3 , however, has been investigated using a program called MCNP (Monte Carlo N-particle) and it has been found that replacing the slider panels with air made little difference. Accordingly, a clearance is provided between the belt  3  and the base  13  of the tunnel  9 , which allows the previous slider panels to be dispensed with, thereby reducing construction and maintenance costs. The tunnel  9  is shaped to accommodate conveyor belts  3  from 600 mm to 1400 mm wide with trough angles from 30° to 45° with no modification to belt  3  or tunnel  9 . As a result of the relative clearance, an additional advantage is realised in that belt clips and staples (not shown) can not damage analyser  1 . 
         [0027]    Turning now to  FIG. 4 , the analyser  1  is shown with a canopy  15  supported on struts  16  fixed to the lifting points  4 . The canopy  15  is preferably formed of 3 mm thick steel or fibreglass and stands approximately 400 mm above the analyser  1 , leaving an approximate clearing of 50 mm above the 350 mm high air conditioners  17 . The canopy  15  provides protection to the top  18  of the analyser  1  from direct sunlight, rain and snow. The canopy  15  should also minimise dust build-up on and around the air conditioner  17 . Provision of the canopy  15  additionally allows the analyser to be installed in an external environment at any desired location along the length of the conveyor belt  3 , as compared to the prior art analyser, which needed to be installed within a shed. As such, the analyser  1  provides for further reduction in installation costs. 
         [0028]    In addition to the above, the prior-art analyser used proprietary analogue electronics and NaI (sodium iodide crystal) detectors. The present analyser  1 , on the other hand, uses off-the-shelf digital multi-channel analysers and bismuth germinate crystal (BGO) detectors. 
         [0029]    The digital multi-channel analysers provide more consistent, linear, stable spectra and are more reliable as compared to the previous analyser electronics, for which components are becoming obsolete. The BGO detectors capture more gamma rays and have better photo-peak fraction due to higher crystal density, have better peak to background ratio (ie better signal-to-noise ratio) and better linearity. The detectors  14  and associated multi-channel analyser electronics are preferably located within a single common air-conditioned, temperature-controlled detector enclosure  22  to simplify operational and construction requirements. The remaining electronics such as an analyser computer and other electronics modules are likewise located within a single air-conditioned, temperature-controlled electronics cabinet  23 , which has a sealed and locked door  24 . 
         [0030]    As such, the above-described analyser  1  provides a number of advantages over the prior-art analyser, which result from internal componentry, reduced weight and dimensions, as well as the provision of a canopy and the clearance between the analyser and a conveyor belt passing through the analyser tunnel. As may be appreciated then, the analyser may be installed on an existing conveyor assembly with minimal modification or removal of steel work of the belt support structure since the analyser is of a width sufficient to fit between pre-existing idlers and does not contact the belt so the supporting structure does not need to be configured in any particular fashion necessary to form a specific belt profile suitable for the tunnel, as compared to the prior-art analyser arrangement. 
         [0031]    Further and more particular details of a preferred form of analyser are provided in Applicant&#39;s publications “On Belt Analyser Operation &amp; Maintenance Manual” Version 1.3, September 2005; “On Belt Analyser-5 Health &amp; Safety Review” Version 1.6, February 2006; and “On Belt Analyser Installation Manual” Version 7.3, October 2005, the contents of which are incorporated herein by reference. 
         [0032]    The invention has been described, by way of non-limiting example only, and many modifications and variations may be made thereto, without departing from the spirit and scope of the invention, as described.