CA2069029C - Decay detection in wood - Google Patents
Decay detection in woodInfo
- Publication number
- CA2069029C CA2069029C CA002069029A CA2069029A CA2069029C CA 2069029 C CA2069029 C CA 2069029C CA 002069029 A CA002069029 A CA 002069029A CA 2069029 A CA2069029 A CA 2069029A CA 2069029 C CA2069029 C CA 2069029C
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- Canada
- Prior art keywords
- wood
- decay
- sample
- analytes
- determining
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/622—Ion mobility spectrometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/46—Wood
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/24—Nuclear magnetic resonance, electron spin resonance or other spin effects or mass spectrometry
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Pathology (AREA)
- Electrochemistry (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Wood Science & Technology (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
The presence of decay is determined in wood by testing a sample. The wood tested may be standing timber, cut timber or when coated in building structures.
The testing occurs in very short time intervals so that tests can be carried out on timber in mills and the like.
The method of testing includes heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes within the ionizing chamber at a temperature in the range of about 220 to 350°C, generating an ion drift time signature in the detector, and comparing the signature with predetermined signatures representing decay in wood.
The testing occurs in very short time intervals so that tests can be carried out on timber in mills and the like.
The method of testing includes heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes within the ionizing chamber at a temperature in the range of about 220 to 350°C, generating an ion drift time signature in the detector, and comparing the signature with predetermined signatures representing decay in wood.
Description
2069~29 DECAY DETECTION IN WOOD
TECHNICAL FIELD
The present invention relates to sampling wood and dete_ ;n;ng if decay i8 present. More specifically, the present invention can determine the species of a wood sample and dete ;ne if decay is present in the sample.
BACKGROUND ART
Decayed wood i8 often not initially visible on the wood surface. For instance in the case of utility poles, decay often occurs in the portion of the pole below the ground. This makes it difficult to dete ine visually whether decay is present in the wood, particularly when decay generally occurs in the heartwood at the center of the pole and cannot be dete ;ne~ from the outside without drilling a hole into the wood. In present day examination of utility poles, it is no_ -l to drill a hole downwards from above the ground line into the center of the wood 80 that a sample of the wood from the heart or core i8 extracted. In some cases decay i~ visible, however if the decay is incipient, then it is difficult to detect.
Vibration techn;ques have been suggested for dete i ni ng decay in poles. Shaw in U.S. patent 3,877,294 disclosed a vibration techn;que. Heath et al U.S. patent 3,531, 983 related to Sonic testing. Miller et al in V.S. 3,521,483 and Shigo in U.S. patent 3,864,627 utilize electrical signals to detect the presence of decay.
There is also a need to determine if decay is present in st~n~; ng trees, logs, and lumber being processed in sawmills, pulpmills or other manufacturing 206~029 plants, as well as wood in use. Decay is often not visible from the exterior of trees, boards, or othex wood products. Detection of decay in these situations would allow manufacturers to select the highest value processing option for individual pieces. In the case of wood in use, decay detection would allow engineers, or others responsible for the maintenance of structures, to determine when and if r ~ 1 steps are necessary. Some indication of the severity of decay or residual strength of the wood member would also be useful.
In our U.S. patent 5,071,771 is di~closed a method of producing an ion mobility signature representing a wood sample and then comparing the signature with known signatures of wood species to determine the species of the sample. There is a need to dete ; ne not only the species but also to detect decay in a log or board at the same time that the ~pecies is determined. The time that is available for detecting decay at a sawmill is about one half to ten seconds per sample.
DISCLOSURE OF lNV~ ~ lON
It is an aim of the present invention to detect decay in wood products or detect fungi in other natural products by utilizing an ion mobility spectrometer, and conduct the tests in a short time generally within ten seconds. It is a further aim to combine identification of species of a wood sample that has little or no decay present, or to identify decay present in a wood sample.
A further aim of the present invention is to detect incipient decay in sapwood or heartwood O r a log, cut lumber, st~n~i ng structure or tree regardless of moisture content of the wood, and regardless of external conditions, namely temperature and h ;~;ty.
2069~29 A still further aim of the pre~ent invention is to use ion mobility spectrometry to determine the stage to which decay has progressed in wood, and to determine if the wood is suitable for it's intended use based on the severity of decay present.
By producing an ion mobility signature for a wood sample having decay therein, one is able to determine certain peaks in the signature representing ch~ ic~ls resulting from the decayed wood or fungi present in the wood. At the same time by knowing the species of wood being tested, one can compare a sample of a par icular species without decay and one that has decay therein.
The peaks representing decay are clearly vi~ible and by comparing IMS signatures from samples of known wood species with and without decay, one is able to detect whether decay is present in a wood sample. One cannot nece~sarily detect the wood species in a sample having extensive decay therein, but one can detect the severity of the decay ~epen~; ng on the number, position and intensity of the peaks representing decay.
The present invention provides a method of determining the presence of decay in wood, comprising the steps of:- heating a portion of a wood sample at a temperature in the range of about 220 to 350~C to evaporate analytes from the wood sample, conveying the trace analytes in a sample gas flow into an ionizing ch~ ~?r of an ion mobility spectrometer detector, ionizing the analytes within the ionizing ch~ '-er at a temperature in the range of a~out 220 to 350~C, generating an ion drift time signature in the detector, and comparing the signature with predete ;ne~ signatures representing decay in wood.
In another : 'o~; -nt of the present invention there is provided an apparatus for determining presence of . ~
2069~29 . . .
~ 4 -decay in wood, comprising means for heating at least a portion of a wood sample at a temperature in the range of about 220 to 350~C to evaporate analytes from the wood sample, an ion mobility spectrometer detector adapted to generate an ion drift time signature from the analytes admitted into an ionizing chamber of the detector, the chamber having a temperature in the range of about 220 to 350~C, and comparison means to compare peak patterns on the ion drift time signature with known peak patterns representing decay in wood.
BRIEF DESCRIPTION OF DRAWINGS
In drawings which illustrate embo~; -ntS of the present invention, Figure 1 is a schematic diagram showing an ion mobility spectrometer suitable for analyzing a wood sample according to the present invention.
Figures 2 to 5 show ion mobility signatures for samples of balsam fir heartwood for 30und, incipient decay, moderate decay and heavy decay, 2~ Figures 6 to 8 show ion mobility signatures for samples of spruce heartwood for sound, ;nC;p;ent decay and heavy decay, Figures 9 to 11 show ion -hil;ty signatures for samples of douglas fir heartwood for sound, incipient decay and heavy decay, Figures 12 to 14 show ion mobility signatures for samples of red pine heartwood for sound, incipient decay and heavy decay, , .
Figures 15 and 16 show ion mobility signatures for samples of jack pine heartwood for sound and heavy decay, Figures 17 and 18 show ion mobility signatures for ~amples of western cedar heartwood for sound and heavy decay.
BEST MODES FOR CARRYING OUT THE lNV~ lON
An ion mobility spectrometer (IMS) detector 12 is illustrated in Figure 1. A desorber heater 10 is positioned at one end of the detector 12 and a wood sample 14 re~ts on top of the filter above the desorber heater 10. A passage 16 from the desorber heater 10 leads through a repelling ring 18 to an ionizing ch~ 'er 20 which includes a weak radioactive source. An electronic gate 24 separates the ionizing chamber 20 from a drift region 26. ~he drift region 26 is a drift tube ~8 with a series of stacked cylindrical metal rings 30 to produce a uniform electric field throughout the drift region 26. An ion 32 passes an electric current through an amplifier 34 into a computer 36 where the signal is averaged and an ion drift time signature is produced.
This ion drift time signature i8 then compared with a programmed time signature representing different species of wood, or different stages of decay in the wood, and sample identification then takes place. The ion drift time signature can be displayed in real time and stored in the computer 36 for p~ -ne~t records from which a hard copy can be obt~ine~.
A sampling gas flow 40 entrains analytes from the heated wood sample 14, and conveys the analytes through a transfer line 16 into the ionizing ch~ '-?r 20 of the detector. The transfer line 16 cont~; n; ng the analytes is maintained at a high temperature to prevent co~e~ation of the analytes. The drift region 26 and .- . .
2069~29 the ionizing chamber 29 are at atmospheric pressure. The ionizing source in one embodiment is 63Ni, a radioactive isotope emitting beta particles. These beta particles collide with oxygen and nitrogen molecules in the sampling gas flow 40 forming both positive and negative ions. These ions undergo fast ion molecule reactions with reactant molecules. The reactant ions ionize the analytes introduced into the sampling gas flow. As a result of complex ion molecule reactions that take place in the ionizing chamber 20, the molecules of some analytes form stable ions while others do not. These ions are prevented from entering the drift region 26 by the electronic gate 24 and cannot return to the passageway 16 because of the repelling ring 18. When the gate 24 i8 open, the ions accelerate under the influence of a strong electric field through the drift region 26 towards the collector 32. The gate 24 is repetitively opened at brief intervals (typically 0.2 i~ econds) emitting pul~es of mixed ions into the drift region 26.
A typical time between pul~es is 20 milliseconds. As the ions drift against the counter current drift gas flow, the ions in any particular pulse separate into their individual chemical species based upon their differing intrinsic propertie~. The arrival of the individual ion pulses at the collector 32 produces a characteri~tic ion arrival time spectrum. This ionic signal in the form of a weak electric current from the collector 32 i8 amplified by the amplifier 34 and then fed to a computer 36 where it is filtered, digitized and st~cke~ to increase signal to noise ratio. The _ ~er of sweeps or cycles can be varied and an average signal generated or stored. ~his average signal can be viewed on a computer monitor or in real time on an appropriate display.
Because each ion travels at different velocities, the ions are separated in drift time as they arrive at the collector 32. A plot of ion inten~ity as a function o~
drift time i~ referred to as a pla~magram or signature.
, - ' ' 20~9~29 A drift gas flow 42 was maintained in the drift xegion 26 against the ion travel direction and exited at an exhaust 44 together with the sampling gas 40. A
typical time between pulses is 20 ill;~econds~ this represents an analysis time for one pulse of the gate 24.
The wood sample is obtained in a number of different ways either by taking out a small wood sample with a drill or core borer or removing a vapor sample through a heated hollow needle. In the case of cut lumber, the sample may be taken internally or from the surface, or alternatively a portion of the lumber heated, either by remote or contact methods, to evaporate an analyte, and the analyte drawn into the ionizing chamber of the analyzer. In the case of a utility pole, a core borer may be used to L. ve a plug, and a series of samples along the length of the plug may be analyzed to create a decay profile through the pole.
The sample or at least a part of the sample is heated to a temperature in the range of about 220 to 350~C
and the analyte conveyed to the ionizing chamber 20. The -nner of producing the signature is similar to that shown in U.S. patent 5,071,771. Temperature in the ionizing chamber is in the range of about 220 to 350~C and the same polarity is provided in the zone to retain the same polarity ion~ for production of ionic signals and a subsequent drift time signatures that enable wood species to be determined, and decay to be detected. For each detection at least a portion of the wood sample is heated to within the desired desorption temperature range, the analyte is carried to the ionizing chamber and a n ~er of pulses occur in each detection cycle. The complete detection cycle occurs in less than a second preferably less than one half second from entry of the analytes into the ioni~ing chA '-qr. For the tests to obtain the IMS
signatures in the figures, each signature was taken in a .
.
2~69~29 time of about 0.3 to 4.5 seconds from c~~ -ncement of heating the sample. In the tests conducted, a negative polarity was provided in the ionizing GhA ~cr 20 and the drift region 26, and the negative ions were measured for the drift time signatures.
Signatures were obtained for a number of different wood species having varying stages of decay in accordance with the method disclosed in U.S. patent 5,071,771. The signatureg indicate the drift time and the reduced mobility which i8 det~ ;ne~ by referring the measured ion drift time to the drift time and reduced -hility of a calibrant ion. These are shown by a number of peak patterns which represents the analysis of the trace vapor.
Figures 2 to 5 show the progression from sound to heavy decay for balsam fir heartwood. In Figure 2 the sound sample, the only peak present i8 at reduced mobility of 1.847. The re~uce~ mobilities referred to are all in cm2 V~1S~1. This peak is u~ed to identify the wood species. Incipient decay is shown in Figure 3 and peaks with reduced mobility of 1.953, 1.807, 1.663 and 1.449 are now present. In Figure 4 these ~ame peaks are present, but the intensity of the species peak, reduced mobility of 1.847, is much lower. Figure 4 is a sample of moderate decay, whereas Figure 5, which is a heavy decay sample, shows a completely different set of peaks with reduced ~b;lities of 1.698, 1.521 and 1.371 representing decay. The species peak of 1.847 can no longer be seen.
A similar pattern occurs for spruce heartwood in Figures 6, 7 and 8. As can be seen the relative intensity of the peaks with reduced mobilities representing species decrease whereas the relative intensities of the peaks representing decay change. In , ~ ~
' ~ '- ' ' ' ' Figure 7, the incipien~ decay ~ample, the peak with reduced mobility of 1.337, representing decay, is prominent but is almost undetectable in Figure 8 when the decay was heavy.
Figures 9, 10 and 11 show douglas fir heartwood and the pattern i8 repeated as the decay increases. The peaks with reduced -hilities of 1.700, 1.573 and 1.475 shown in Figure 9 representing wood species decrease in Figure 10 and almost disappear in Figure 11, however the peaks representing decay change. The reduced ~b;l;ty peak of 1.885 increases while the re~nce~ mobility peak of 1.350 decreases from Figure 10 to Figure 11.
The red pine heartwood samples shown in Figures 12, 13 and 14 show decreases in the peaks representing species (1.737, 1.591 and 1.100) and the peaks representing decay tend to increase and change in relative intensity. The jack pine heartwood samples ~hown in Figures 15 and 16 and the western cedar heartwood samples ~hown in Figures 17 and 18 also follow the same pattern.
The peaks representing species decrease as the stages of decay increase. The peaks representing decay change as the levels of decay change. This is characteristic of the intensity of the deterioration. As the peaks which identify species disappear, it becomes more difficult to identify species. However, knowing that certain peak represent decay, and comparing signatures with known signatures one can identify decay and even the level of decay in the wood.
In certain cases by comparing decayed wood signatures, one is able to identify the species of the decayed wood.
.
IIOOD SPECIES
IIEDUCED .~.-.... ,,,,,,,,, ,_ ~IOBILITr SPRUCE J~Cit PIIIE BALSAN FIR DOUCL~S FIR RED PINE ~1. RED CED~R
Ito ~ ~ ) SOUND DEC~/ED SOURD DEc~l'Eo SCUND tNClPlEllT HEI~vr SOUND DEC~YED SOUND DE~lED SaUND DECArED
DECAl' DECA~' .. . . ............. _ _ .. ~ ...... . .. -- ............................. _ _ .. _ .. _ .. _ 2.002 XXXXXXXXX
l.ff9 XXxXXXXxX
1 ~53 XXXXXXXXX
~ 933 XXXXXXXXX
1 ~85 xXXXxxxXX
l.a~7 XXXXXXXXX
1.807 XXXXXXXXX
1.788 XXXXXXXXX XXXXXXXXX
~.765 XXXXXXXXX
1.737 XXXXXXXXX XXXXXXXXX XXXXXXXXX
1.66~ XXXXXXXXX
1.591 XXXXXXXXX
1.57~ XXXXXXXXX XXXXXXXXX xxxx1aXXX
1.537 XXXXXXXXX
1~520 XXXXXXXXX XXXXXXXXX
1.~ 75 ~ xxXXXX XXXXXXXXX X~OOOflOtXX XXXXXXXXX
~ .9 XXXXXXXXX
1.~21 XXXXXXXXX
1.371 XXXXXXXXX
350 XXXXXXXXX XXX10t~XXX
1.337 XXXXXXXXX x~xxXXxXX
1.265 XXXtUtXXXX
1.160 XXXXXXXXX
1 108 xxxxxxxxx ~a .,,,,,,,, .. ,, .. , .. _ .. _ .. . .............. _ ......................... , _ _ ... . C~
CD
2069~29 The table summarizes results from figures 2 ~o 18 showing reduced mobilities for ions representing sound and decayed wood for different species.
It has been found that moisture in the wood has little effect on the signatures. For the specific tests carried out to produce the signatures shown in Figures 2 to 18 desorption temperature was 300~C. The ionizing temperature was 260~C.
Comparison of the signatures produced by testing stAn~;ng timber or cut timber may be compared -n~lAlly by checking the peak patterns representing the wood sample.
Alternatively the signatures may be computerized for ct -ring the peaks with those of known signatures for specific wood species and decay in those ~pecies. The sampling of the analyte is preferably carried out in the range of about 0.3 to 5 second~. The time of 0.5 to 2 seconds is all that is needed for desorbing the wood sample, even in severe cold, thus this permits wood sample~ to be desorbed on cut timber moving in a sawmill.
Determining species and presence of decay in timber is dete ;ne~ within a short time from the initial sample being desorbed.
Whereas the tests described herein have all referred to heartwood of different wood species, the method of detecting decay is not limited to heartwood but can apply to sapwood and other lignocellulosic materials.
Initially tests are run to produce IMS signatures of different types of material that have decay therein.
Comparisons may then be made with tests on samples to compare signatures with Xnown signaturea. From this information a dete_ ;nAtion of species and/or decay may be made.
' -206~029 Tests to determine the presence of decay may be carried out on all lignocellulosic materials, for instance standing structures such as buildings, which have wood or beams that are coated with paint, stain or other types of coating. A wood sample must be taken from under the coating. The sample may be sapwood or heartwood, but the presence of decay can be determined and in some cases when decay is not at an advanced stage, the species of the wood determined. In the case where there is advanced decay, and the wood species cannot be identified, another sample of structurally sound wood with little or no decay present should be tested in order to identify wood species.
Railway ties and utility poles can also be tested but the sample should be taken beneath the weathered surface. If a preservative or other ch ic~l is present in high concentrations, the signature will not allow one to dete ine if decay is present, or the sample wood species. ~c.!e~er in most cases, and particularly when decay is present, the concentration of the preservative is such that it does not effect deteation of the decay.
Various changes may be made to the ~ ntS shown herein without departing from the scope of the present invention which is limited only by the following claims.
TECHNICAL FIELD
The present invention relates to sampling wood and dete_ ;n;ng if decay i8 present. More specifically, the present invention can determine the species of a wood sample and dete ;ne if decay is present in the sample.
BACKGROUND ART
Decayed wood i8 often not initially visible on the wood surface. For instance in the case of utility poles, decay often occurs in the portion of the pole below the ground. This makes it difficult to dete ine visually whether decay is present in the wood, particularly when decay generally occurs in the heartwood at the center of the pole and cannot be dete ;ne~ from the outside without drilling a hole into the wood. In present day examination of utility poles, it is no_ -l to drill a hole downwards from above the ground line into the center of the wood 80 that a sample of the wood from the heart or core i8 extracted. In some cases decay i~ visible, however if the decay is incipient, then it is difficult to detect.
Vibration techn;ques have been suggested for dete i ni ng decay in poles. Shaw in U.S. patent 3,877,294 disclosed a vibration techn;que. Heath et al U.S. patent 3,531, 983 related to Sonic testing. Miller et al in V.S. 3,521,483 and Shigo in U.S. patent 3,864,627 utilize electrical signals to detect the presence of decay.
There is also a need to determine if decay is present in st~n~; ng trees, logs, and lumber being processed in sawmills, pulpmills or other manufacturing 206~029 plants, as well as wood in use. Decay is often not visible from the exterior of trees, boards, or othex wood products. Detection of decay in these situations would allow manufacturers to select the highest value processing option for individual pieces. In the case of wood in use, decay detection would allow engineers, or others responsible for the maintenance of structures, to determine when and if r ~ 1 steps are necessary. Some indication of the severity of decay or residual strength of the wood member would also be useful.
In our U.S. patent 5,071,771 is di~closed a method of producing an ion mobility signature representing a wood sample and then comparing the signature with known signatures of wood species to determine the species of the sample. There is a need to dete ; ne not only the species but also to detect decay in a log or board at the same time that the ~pecies is determined. The time that is available for detecting decay at a sawmill is about one half to ten seconds per sample.
DISCLOSURE OF lNV~ ~ lON
It is an aim of the present invention to detect decay in wood products or detect fungi in other natural products by utilizing an ion mobility spectrometer, and conduct the tests in a short time generally within ten seconds. It is a further aim to combine identification of species of a wood sample that has little or no decay present, or to identify decay present in a wood sample.
A further aim of the present invention is to detect incipient decay in sapwood or heartwood O r a log, cut lumber, st~n~i ng structure or tree regardless of moisture content of the wood, and regardless of external conditions, namely temperature and h ;~;ty.
2069~29 A still further aim of the pre~ent invention is to use ion mobility spectrometry to determine the stage to which decay has progressed in wood, and to determine if the wood is suitable for it's intended use based on the severity of decay present.
By producing an ion mobility signature for a wood sample having decay therein, one is able to determine certain peaks in the signature representing ch~ ic~ls resulting from the decayed wood or fungi present in the wood. At the same time by knowing the species of wood being tested, one can compare a sample of a par icular species without decay and one that has decay therein.
The peaks representing decay are clearly vi~ible and by comparing IMS signatures from samples of known wood species with and without decay, one is able to detect whether decay is present in a wood sample. One cannot nece~sarily detect the wood species in a sample having extensive decay therein, but one can detect the severity of the decay ~epen~; ng on the number, position and intensity of the peaks representing decay.
The present invention provides a method of determining the presence of decay in wood, comprising the steps of:- heating a portion of a wood sample at a temperature in the range of about 220 to 350~C to evaporate analytes from the wood sample, conveying the trace analytes in a sample gas flow into an ionizing ch~ ~?r of an ion mobility spectrometer detector, ionizing the analytes within the ionizing ch~ '-er at a temperature in the range of a~out 220 to 350~C, generating an ion drift time signature in the detector, and comparing the signature with predete ;ne~ signatures representing decay in wood.
In another : 'o~; -nt of the present invention there is provided an apparatus for determining presence of . ~
2069~29 . . .
~ 4 -decay in wood, comprising means for heating at least a portion of a wood sample at a temperature in the range of about 220 to 350~C to evaporate analytes from the wood sample, an ion mobility spectrometer detector adapted to generate an ion drift time signature from the analytes admitted into an ionizing chamber of the detector, the chamber having a temperature in the range of about 220 to 350~C, and comparison means to compare peak patterns on the ion drift time signature with known peak patterns representing decay in wood.
BRIEF DESCRIPTION OF DRAWINGS
In drawings which illustrate embo~; -ntS of the present invention, Figure 1 is a schematic diagram showing an ion mobility spectrometer suitable for analyzing a wood sample according to the present invention.
Figures 2 to 5 show ion mobility signatures for samples of balsam fir heartwood for 30und, incipient decay, moderate decay and heavy decay, 2~ Figures 6 to 8 show ion mobility signatures for samples of spruce heartwood for sound, ;nC;p;ent decay and heavy decay, Figures 9 to 11 show ion -hil;ty signatures for samples of douglas fir heartwood for sound, incipient decay and heavy decay, Figures 12 to 14 show ion mobility signatures for samples of red pine heartwood for sound, incipient decay and heavy decay, , .
Figures 15 and 16 show ion mobility signatures for samples of jack pine heartwood for sound and heavy decay, Figures 17 and 18 show ion mobility signatures for ~amples of western cedar heartwood for sound and heavy decay.
BEST MODES FOR CARRYING OUT THE lNV~ lON
An ion mobility spectrometer (IMS) detector 12 is illustrated in Figure 1. A desorber heater 10 is positioned at one end of the detector 12 and a wood sample 14 re~ts on top of the filter above the desorber heater 10. A passage 16 from the desorber heater 10 leads through a repelling ring 18 to an ionizing ch~ 'er 20 which includes a weak radioactive source. An electronic gate 24 separates the ionizing chamber 20 from a drift region 26. ~he drift region 26 is a drift tube ~8 with a series of stacked cylindrical metal rings 30 to produce a uniform electric field throughout the drift region 26. An ion 32 passes an electric current through an amplifier 34 into a computer 36 where the signal is averaged and an ion drift time signature is produced.
This ion drift time signature i8 then compared with a programmed time signature representing different species of wood, or different stages of decay in the wood, and sample identification then takes place. The ion drift time signature can be displayed in real time and stored in the computer 36 for p~ -ne~t records from which a hard copy can be obt~ine~.
A sampling gas flow 40 entrains analytes from the heated wood sample 14, and conveys the analytes through a transfer line 16 into the ionizing ch~ '-?r 20 of the detector. The transfer line 16 cont~; n; ng the analytes is maintained at a high temperature to prevent co~e~ation of the analytes. The drift region 26 and .- . .
2069~29 the ionizing chamber 29 are at atmospheric pressure. The ionizing source in one embodiment is 63Ni, a radioactive isotope emitting beta particles. These beta particles collide with oxygen and nitrogen molecules in the sampling gas flow 40 forming both positive and negative ions. These ions undergo fast ion molecule reactions with reactant molecules. The reactant ions ionize the analytes introduced into the sampling gas flow. As a result of complex ion molecule reactions that take place in the ionizing chamber 20, the molecules of some analytes form stable ions while others do not. These ions are prevented from entering the drift region 26 by the electronic gate 24 and cannot return to the passageway 16 because of the repelling ring 18. When the gate 24 i8 open, the ions accelerate under the influence of a strong electric field through the drift region 26 towards the collector 32. The gate 24 is repetitively opened at brief intervals (typically 0.2 i~ econds) emitting pul~es of mixed ions into the drift region 26.
A typical time between pul~es is 20 milliseconds. As the ions drift against the counter current drift gas flow, the ions in any particular pulse separate into their individual chemical species based upon their differing intrinsic propertie~. The arrival of the individual ion pulses at the collector 32 produces a characteri~tic ion arrival time spectrum. This ionic signal in the form of a weak electric current from the collector 32 i8 amplified by the amplifier 34 and then fed to a computer 36 where it is filtered, digitized and st~cke~ to increase signal to noise ratio. The _ ~er of sweeps or cycles can be varied and an average signal generated or stored. ~his average signal can be viewed on a computer monitor or in real time on an appropriate display.
Because each ion travels at different velocities, the ions are separated in drift time as they arrive at the collector 32. A plot of ion inten~ity as a function o~
drift time i~ referred to as a pla~magram or signature.
, - ' ' 20~9~29 A drift gas flow 42 was maintained in the drift xegion 26 against the ion travel direction and exited at an exhaust 44 together with the sampling gas 40. A
typical time between pulses is 20 ill;~econds~ this represents an analysis time for one pulse of the gate 24.
The wood sample is obtained in a number of different ways either by taking out a small wood sample with a drill or core borer or removing a vapor sample through a heated hollow needle. In the case of cut lumber, the sample may be taken internally or from the surface, or alternatively a portion of the lumber heated, either by remote or contact methods, to evaporate an analyte, and the analyte drawn into the ionizing chamber of the analyzer. In the case of a utility pole, a core borer may be used to L. ve a plug, and a series of samples along the length of the plug may be analyzed to create a decay profile through the pole.
The sample or at least a part of the sample is heated to a temperature in the range of about 220 to 350~C
and the analyte conveyed to the ionizing chamber 20. The -nner of producing the signature is similar to that shown in U.S. patent 5,071,771. Temperature in the ionizing chamber is in the range of about 220 to 350~C and the same polarity is provided in the zone to retain the same polarity ion~ for production of ionic signals and a subsequent drift time signatures that enable wood species to be determined, and decay to be detected. For each detection at least a portion of the wood sample is heated to within the desired desorption temperature range, the analyte is carried to the ionizing chamber and a n ~er of pulses occur in each detection cycle. The complete detection cycle occurs in less than a second preferably less than one half second from entry of the analytes into the ioni~ing chA '-qr. For the tests to obtain the IMS
signatures in the figures, each signature was taken in a .
.
2~69~29 time of about 0.3 to 4.5 seconds from c~~ -ncement of heating the sample. In the tests conducted, a negative polarity was provided in the ionizing GhA ~cr 20 and the drift region 26, and the negative ions were measured for the drift time signatures.
Signatures were obtained for a number of different wood species having varying stages of decay in accordance with the method disclosed in U.S. patent 5,071,771. The signatureg indicate the drift time and the reduced mobility which i8 det~ ;ne~ by referring the measured ion drift time to the drift time and reduced -hility of a calibrant ion. These are shown by a number of peak patterns which represents the analysis of the trace vapor.
Figures 2 to 5 show the progression from sound to heavy decay for balsam fir heartwood. In Figure 2 the sound sample, the only peak present i8 at reduced mobility of 1.847. The re~uce~ mobilities referred to are all in cm2 V~1S~1. This peak is u~ed to identify the wood species. Incipient decay is shown in Figure 3 and peaks with reduced mobility of 1.953, 1.807, 1.663 and 1.449 are now present. In Figure 4 these ~ame peaks are present, but the intensity of the species peak, reduced mobility of 1.847, is much lower. Figure 4 is a sample of moderate decay, whereas Figure 5, which is a heavy decay sample, shows a completely different set of peaks with reduced ~b;lities of 1.698, 1.521 and 1.371 representing decay. The species peak of 1.847 can no longer be seen.
A similar pattern occurs for spruce heartwood in Figures 6, 7 and 8. As can be seen the relative intensity of the peaks with reduced mobilities representing species decrease whereas the relative intensities of the peaks representing decay change. In , ~ ~
' ~ '- ' ' ' ' Figure 7, the incipien~ decay ~ample, the peak with reduced mobility of 1.337, representing decay, is prominent but is almost undetectable in Figure 8 when the decay was heavy.
Figures 9, 10 and 11 show douglas fir heartwood and the pattern i8 repeated as the decay increases. The peaks with reduced -hilities of 1.700, 1.573 and 1.475 shown in Figure 9 representing wood species decrease in Figure 10 and almost disappear in Figure 11, however the peaks representing decay change. The reduced ~b;l;ty peak of 1.885 increases while the re~nce~ mobility peak of 1.350 decreases from Figure 10 to Figure 11.
The red pine heartwood samples shown in Figures 12, 13 and 14 show decreases in the peaks representing species (1.737, 1.591 and 1.100) and the peaks representing decay tend to increase and change in relative intensity. The jack pine heartwood samples ~hown in Figures 15 and 16 and the western cedar heartwood samples ~hown in Figures 17 and 18 also follow the same pattern.
The peaks representing species decrease as the stages of decay increase. The peaks representing decay change as the levels of decay change. This is characteristic of the intensity of the deterioration. As the peaks which identify species disappear, it becomes more difficult to identify species. However, knowing that certain peak represent decay, and comparing signatures with known signatures one can identify decay and even the level of decay in the wood.
In certain cases by comparing decayed wood signatures, one is able to identify the species of the decayed wood.
.
IIOOD SPECIES
IIEDUCED .~.-.... ,,,,,,,,, ,_ ~IOBILITr SPRUCE J~Cit PIIIE BALSAN FIR DOUCL~S FIR RED PINE ~1. RED CED~R
Ito ~ ~ ) SOUND DEC~/ED SOURD DEc~l'Eo SCUND tNClPlEllT HEI~vr SOUND DEC~YED SOUND DE~lED SaUND DECArED
DECAl' DECA~' .. . . ............. _ _ .. ~ ...... . .. -- ............................. _ _ .. _ .. _ .. _ 2.002 XXXXXXXXX
l.ff9 XXxXXXXxX
1 ~53 XXXXXXXXX
~ 933 XXXXXXXXX
1 ~85 xXXXxxxXX
l.a~7 XXXXXXXXX
1.807 XXXXXXXXX
1.788 XXXXXXXXX XXXXXXXXX
~.765 XXXXXXXXX
1.737 XXXXXXXXX XXXXXXXXX XXXXXXXXX
1.66~ XXXXXXXXX
1.591 XXXXXXXXX
1.57~ XXXXXXXXX XXXXXXXXX xxxx1aXXX
1.537 XXXXXXXXX
1~520 XXXXXXXXX XXXXXXXXX
1.~ 75 ~ xxXXXX XXXXXXXXX X~OOOflOtXX XXXXXXXXX
~ .9 XXXXXXXXX
1.~21 XXXXXXXXX
1.371 XXXXXXXXX
350 XXXXXXXXX XXX10t~XXX
1.337 XXXXXXXXX x~xxXXxXX
1.265 XXXtUtXXXX
1.160 XXXXXXXXX
1 108 xxxxxxxxx ~a .,,,,,,,, .. ,, .. , .. _ .. _ .. . .............. _ ......................... , _ _ ... . C~
CD
2069~29 The table summarizes results from figures 2 ~o 18 showing reduced mobilities for ions representing sound and decayed wood for different species.
It has been found that moisture in the wood has little effect on the signatures. For the specific tests carried out to produce the signatures shown in Figures 2 to 18 desorption temperature was 300~C. The ionizing temperature was 260~C.
Comparison of the signatures produced by testing stAn~;ng timber or cut timber may be compared -n~lAlly by checking the peak patterns representing the wood sample.
Alternatively the signatures may be computerized for ct -ring the peaks with those of known signatures for specific wood species and decay in those ~pecies. The sampling of the analyte is preferably carried out in the range of about 0.3 to 5 second~. The time of 0.5 to 2 seconds is all that is needed for desorbing the wood sample, even in severe cold, thus this permits wood sample~ to be desorbed on cut timber moving in a sawmill.
Determining species and presence of decay in timber is dete ;ne~ within a short time from the initial sample being desorbed.
Whereas the tests described herein have all referred to heartwood of different wood species, the method of detecting decay is not limited to heartwood but can apply to sapwood and other lignocellulosic materials.
Initially tests are run to produce IMS signatures of different types of material that have decay therein.
Comparisons may then be made with tests on samples to compare signatures with Xnown signaturea. From this information a dete_ ;nAtion of species and/or decay may be made.
' -206~029 Tests to determine the presence of decay may be carried out on all lignocellulosic materials, for instance standing structures such as buildings, which have wood or beams that are coated with paint, stain or other types of coating. A wood sample must be taken from under the coating. The sample may be sapwood or heartwood, but the presence of decay can be determined and in some cases when decay is not at an advanced stage, the species of the wood determined. In the case where there is advanced decay, and the wood species cannot be identified, another sample of structurally sound wood with little or no decay present should be tested in order to identify wood species.
Railway ties and utility poles can also be tested but the sample should be taken beneath the weathered surface. If a preservative or other ch ic~l is present in high concentrations, the signature will not allow one to dete ine if decay is present, or the sample wood species. ~c.!e~er in most cases, and particularly when decay is present, the concentration of the preservative is such that it does not effect deteation of the decay.
Various changes may be made to the ~ ntS shown herein without departing from the scope of the present invention which is limited only by the following claims.
Claims (14)
1. A method of determining the presence of decay in wood, comprising the steps of:
heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes within the ionizing chamber at a temperature in the range of about 220 to 350°C, generating an ion drift time signature of the wood sample in the detector, and comparing the signature of the wood sample with predetermined signatures representing decay in wood to determine presence of decay in the wood sample.
heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes within the ionizing chamber at a temperature in the range of about 220 to 350°C, generating an ion drift time signature of the wood sample in the detector, and comparing the signature of the wood sample with predetermined signatures representing decay in wood to determine presence of decay in the wood sample.
2. The method of determining the presence of decay in wood according to Claim 1 wherein peak patterns on the ion drift time signature are compared with known peak patterns representing decay in known species of wood.
3. A method of determining the presence of decay in a known species of wood, comprising the steps of:
heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, generating an ion drift time signature of the wood sample in the detector wherein the analytes are ionized in the ionizing chamber at a temperature in the range of about 220 to 350°C maintained in the chamber, and comparing peak patterns on the ion drift time signature of the wood sample with known peak patterns representing decay in the known species of wood to determine presence of decay in the wood sample.
heating a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, generating an ion drift time signature of the wood sample in the detector wherein the analytes are ionized in the ionizing chamber at a temperature in the range of about 220 to 350°C maintained in the chamber, and comparing peak patterns on the ion drift time signature of the wood sample with known peak patterns representing decay in the known species of wood to determine presence of decay in the wood sample.
4. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein a negative polarity is maintained in the ion mobility spectrometer detector.
5. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the wood sample is taken from standing timber.
6. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the wood sample is taken from cut timber.
7. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the wood sample is taken from heartwood.
8. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the wood sample is taken from sapwood.
9. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the ion drift time signature is taken within a time of about 0.3 to 4.5 seconds from entry of the analytes into the ionizing chamber.
10. The method of determining the presence of decay in wood according to Claim 1 or Claim 3 wherein the ion drift time signature is produced within the time of about 0.3 to 5 seconds from commencement of heating the wood sample.
11. A method of determining the presence of decay in a known species of wood, comprising the steps of:
heating at least a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes in the ionizing chamber at a temperature in the range of about 220 to 350°C, pulsing ions from the ionizing chamber through a gate means into a drift region, measuring a time of arrival of the ions and the ion flux for each pulse with a collector electrode located at the end of the drift region to produce an ionic signal, amplifying and averaging the ionic signal to generate an ion drift time signature of the wood sample having peak patterns at different ion drift times, and comparing the signature of the wood sample with the known species of wood having decay therein with peak patterns representing decay in the known species of wood, to determine presence of decay in the wood sample.
heating at least a portion of a wood sample at a temperature in the range of about 220 to 350°C to evaporate analytes from the wood sample, conveying the analytes in a sample gas flow into an ionizing chamber of an ion mobility spectrometer detector, ionizing the analytes in the ionizing chamber at a temperature in the range of about 220 to 350°C, pulsing ions from the ionizing chamber through a gate means into a drift region, measuring a time of arrival of the ions and the ion flux for each pulse with a collector electrode located at the end of the drift region to produce an ionic signal, amplifying and averaging the ionic signal to generate an ion drift time signature of the wood sample having peak patterns at different ion drift times, and comparing the signature of the wood sample with the known species of wood having decay therein with peak patterns representing decay in the known species of wood, to determine presence of decay in the wood sample.
12. The method of determining the presence of decay in wood according to Claim 11 wherein the drift region has a negative polarity.
13. An apparatus for determining presence of decay in wood, comprising:
means for heating at least a portion of a wood sample at a temperature in the range of about 220 to 350°C
to evaporate analytes from the wood sample, means for transferring the analytes to an ion mobility spectrometer detector, the ion mobility spectrometer detector adapted to generate an ion drift time signature of the wood sample from the analytes admitted into an ionizing chamber of the detector, the chamber having a temperature in the range of about 220 to 350°C, and computer means for comparing peak patterns on the ion drift time signature of the wood sample with known peak patterns representing decay in known species of wood to determine presence of decay in the wood sample.
means for heating at least a portion of a wood sample at a temperature in the range of about 220 to 350°C
to evaporate analytes from the wood sample, means for transferring the analytes to an ion mobility spectrometer detector, the ion mobility spectrometer detector adapted to generate an ion drift time signature of the wood sample from the analytes admitted into an ionizing chamber of the detector, the chamber having a temperature in the range of about 220 to 350°C, and computer means for comparing peak patterns on the ion drift time signature of the wood sample with known peak patterns representing decay in known species of wood to determine presence of decay in the wood sample.
14. The apparatus for determining presence of decay in wood according to Claim 13 wherein the ionizing chamber has a negative polarity.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US703,116 | 1991-05-20 | ||
| US07/703,116 US5244814A (en) | 1991-05-20 | 1991-05-20 | Decay detection in wood |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2069029A1 CA2069029A1 (en) | 1992-11-21 |
| CA2069029C true CA2069029C (en) | 1998-04-14 |
Family
ID=24824080
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002069029A Expired - Fee Related CA2069029C (en) | 1991-05-20 | 1992-05-20 | Decay detection in wood |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5244814A (en) |
| CA (1) | CA2069029C (en) |
| GB (1) | GB2256054B (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2297381A (en) * | 1995-01-30 | 1996-07-31 | Eastern Group Plc | Detecting decay in wood |
| EP1669738A3 (en) * | 1996-10-09 | 2007-12-12 | Symyx Technologies, Inc. | Infrared spectroscopy and imaging of libraries |
| DE19941124B4 (en) * | 1999-08-25 | 2007-01-18 | IUT Institut für Umwelttechnologien GmbH | Method and device for the patterning of waste wood |
| US6229143B1 (en) * | 2000-09-07 | 2001-05-08 | Saes Getters S.P.A. | Ion mobility spectrometer with improved drift region and method for making same |
| RU2217738C2 (en) * | 2001-08-03 | 2003-11-27 | Конструкторско-технологический институт геофизического и экологического приборостроения СО РАН | Ionization detector |
| ATE556309T1 (en) * | 2007-08-20 | 2012-05-15 | Bea Electrics Energietechnik Gmbh | METHOD FOR EXAMINING AND ASSESSING THE STABILITY OF WOODEN POLES |
| WO2010135246A1 (en) * | 2009-05-18 | 2010-11-25 | Jeol Usa, Inc. | Method of surface ionization with solvent spray and excited-state neutrals |
| DE102011017280A1 (en) * | 2011-04-15 | 2012-10-18 | Fagus-Grecon Greten Gmbh & Co Kg | Method of measuring wood material emitting volatiles and apparatus for measuring the emission of volatile materials from wood-based materials |
| CN104345086B (en) | 2013-08-01 | 2017-02-08 | 同方威视技术股份有限公司 | Method for rapidly detecting volatile substances of high concern in textiles |
| GB2521753B (en) * | 2013-11-21 | 2020-12-30 | Hamilton Sundstrand Corp | High temperature differential ion mobility spectroscopy |
| CN105805779B (en) * | 2016-05-11 | 2018-06-29 | 公安部四川消防研究所 | Grillage igniter and grillage ignition method |
| US11162869B2 (en) | 2019-09-30 | 2021-11-02 | King Fahd University Of Petroleum And Minerals | Double force two sensor vibration method |
| CN112698016A (en) * | 2020-12-11 | 2021-04-23 | 西安建筑科技大学 | Method for detecting mechanical property degradation of decayed wood |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3531983A (en) * | 1967-10-06 | 1970-10-06 | Heath Intern Inc | Sonic pole testing apparatus |
| US3521483A (en) * | 1968-02-28 | 1970-07-21 | Detroit Edison Co | Pole testing apparatus |
| AU471299B2 (en) * | 1972-04-11 | 1976-04-15 | Fanner Mfg. Co., The | Vibration technique for rot detection inwood poles and trees |
| US3864627A (en) * | 1973-12-03 | 1975-02-04 | Northeast Electronic Corp | Probing for detection of decay in wood |
| FI63835C (en) * | 1981-02-10 | 1983-08-10 | Altim Control Ky | FOERFARANDE FOER IDENTIFIERING AV ETT VIRKES YTEGENSKAPER |
| WO1987001205A1 (en) * | 1985-08-24 | 1987-02-26 | Analytical Security Systems Limited | Method and apparatus for detecting dangerous substances |
| US4797554A (en) * | 1987-12-24 | 1989-01-10 | Allied-Signal Inc. | Ion mobility spectrometer |
| US5071771A (en) * | 1989-12-04 | 1991-12-10 | Forintek Canada Corporation | Identification of wood species |
-
1991
- 1991-05-20 US US07/703,116 patent/US5244814A/en not_active Expired - Fee Related
-
1992
- 1992-05-13 GB GB9210257A patent/GB2256054B/en not_active Expired - Fee Related
- 1992-05-20 CA CA002069029A patent/CA2069029C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2069029A1 (en) | 1992-11-21 |
| GB9210257D0 (en) | 1992-07-01 |
| GB2256054B (en) | 1994-11-16 |
| US5244814A (en) | 1993-09-14 |
| GB2256054A (en) | 1992-11-25 |
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