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An automated sample preparation and testing laboratory for North West Water
Laboratory automation and information management
ELSEVIER
Laboratory Automation and InformationManagement 32 (1996) 103-108
An automated sample preparation and testing laboratory for North West Water A.J. Wyatt The Centralisation of North West Water's, Analytical Testing Laboratories at Lingley Mere, Warrington, Cheshire, UK
Abstract This paper discusses a large robotic automation project implemented by Thumall Plc. on behalf of a major UK water company. The system, which automates the analysis of routine clean and dirty water samples, incorporates 22 individual robots configured into 19 robotic cells together with a transport system to carry samples from the reception area into the analytical cells and then to a wash area for residual sample disposal and bottle washing. Control is performed by 21 local computers coordinated by 5 supervisory control systems which in turn link into a LIMS system for data manipulation and long term storage. This paper discusses the life cycle of the project and examines the following generic issues relating to the integration of large scale automation projects: (a) the factors governing a decision to automate on this scale; (b) the automation to be adopted; (c) risk reduction strategy; (d) the benefits to be achieved from such a scheme. Keywords: Automated sample preparation; Testing laboratory for North West water
1. Introduction North West Water, a major UK utility, originally operated 28 regional laboratories each performing similar analyses on samples taken within their local area. In 1991, a decision was taken to centralise this analytical operation and a purpose built laboratory was constructed to handle all samples taken within the area. Only one of the original regional laboratories now remains, a small facility in Cumbria where microbiological analysis of samples with limited life is carried out. Within the centralisation programme, it was decided that, if economically viable, the facility should be automated utilising a transfer system to route samples around the laboratory and robotic cells performing routine analyses. During 1992, Thurnall PLC carried out a design and feasibility study into the proposed automation
strategy. The company was subsequently awarded a contract to implement and set the system to work.
2. Sample collection Samples are collected by a team of Water Quality Officers who operate to a computer generated collection schedule. All samples are taken to one of three sample reception areas where they are consolidated into crates, any changes to the schedule are logged to the operational computer system and the samples are then shipped to the laboratory by courier.
3. Automation system overview Possibly the largest laboratory robotic automation scheme in the world, the system comprises a total of
0925-5281/96/$15.00 Copyright © 1996 Published by Elsevier Science B.V. All rights reserved. PII S 1381-141X(96)00004-4
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19 sample preparation and analysis cells, a semi automated sample bottle washing facility and two sample transport systems. The main transport system routes crates of sample bottles from sample reception to the robotic cells and then to the sample bottle wash area; the secondary transport system routes containers of sample from cell to cell in the waste water laboratory. Control of the automation system is effected by a hierarchical network of computers comprising the following levels: Cell Level: a dedicated cell controller at each cell, based on Motorola VME bus equipment. This unit provides local control of the cell and primary data acquisition to a schedule downloaded to it. It also controls the local cell operator interface. Control software is written in " C " and runs under the OS9 operating system. Also at this level and analogous to the cell controller, are the transport system controllers. These are based on Allen Bradley PLC5 units, there being one for each individual laboratory area, one to control the routing from sample reception to the laboratories and one for the bottle wash area.
Laboratory Level: a laboratory area controller for each laboratory, again based on Motorola VME bus equipment. The laboratory area controller coordinates the operation of the cell and transport system controllers for a particular laboratory area. It routes crates to cells as required, issues work schedules to the cell controller for each sample in the crate and collates sample data. LIMS Level - daily sample collection schedules are loaded to the LIMS from elsewhere on North West Water's information network. The schedules define the samples, the crates in which they will be received at the laboratory and the analyses to be performed on an individual sample basis. The LIMS uses the schedules to generate work schedules for each laboratory area controller and the transport system. On completion of an analysis, the result together with appropriate supporting information is sent to the LIMS for validation, further processing and storage. The robotic cells fall into two categories: Sample Preparation Cell: this type of cell prepares samples for analysis, but does not itself perform that analysis. The prepared samples are pre-
sented in an appropriate form for manual transfer to the analytical device. An example of such a cell is in metals where the sample is digested by microwave heating, cooled and an aliquot dispensed to an auto sampler tray. When full, the auto sampler tray is manually removed and presented to the instrument (ICP-MS) for analysis. The data output from a sample preparation cell is positional information including, where appropriate, sample, analytical quality control and calibration standard location together with sample preparation details. Analytical Cell: this type of cell prepares samples for analysis, carries out the analysis and generates an analytical measurement. An example of such a cell is the Biochemical Oxygen Demand (BOD) cell in the waste water laboratory. Here, the sample is prepared, initial oxygen content measured, the sample incubated for 5 days and the residual oxygen content measured for the BOD to be calculated. Data output is the sample identification and sample preparation information, e.g., dilution and measured value. The system uses two types of robot, Articulated Robot: a six axis robotic " a r m " manufactured by CRS of Canada, used for localised picking and placing applications and where intricate movement or positioning is required. The system incorporates ten such robots, two of which are mounted on a linear track. Gantry Robot: an overhead carriage supporting a vertically moving mast, capable of flexible positioning within a 3-dimensional rectangular section envelope. The robots, which are from the CROCUS range manufactured by Thumall, enable operations over a greater area than the articulated robot.
4. Crate transport system Sample crates are identified by means of bar code labels and contain up to 12 glass or plastic sample bottles with a total maximum weight of 10 kg. Typically, in the order of 400 crates are received each day. The crate transport system is based on a low level (400 ram) slat band conveyor with low friction plastic slats and a running speed of 10 m/minute. It is designed for use in a laboratory environment being quiet in operation and easy to clean in the event of
A.J. Wyatt~Laboratory Automation and Information Management 32 (1996) 103-108
spillage. As the conveyor speed is relatively low, guarding is not required. However, an emergency stop pull wire runs above the conveyor to halt in an emergency. The crate transport system comprises the following main elements: • Sample reception conveyor onto which crates are manually loaded and which feeds to a main distribution loop. • A main distribution loop with transfer points to the individual laboratory areas and to the bottle wash. • Within each laboratory area, a loop which acts as a temporary buffer store, holds crates until the cell is free to perform the analyses. The loop also has a transfer point to route crates of analysed samples back to the distribution loop. • A bottle wash conveyor which routes the crates to semi automated stations for residual sample disposal and bottle washing. A crate is transferred between sections by a series of pneumatic stops which separate it from the following crates and halt it at a pneumatic pusher. The crates on the receiving conveyor are also halted and the crate pushed onto the conveyor. Each crate transfer station has a barcode reader to identify those crates that are to be transferred. Control is provided by a total of six PLCs each handling a particular section of the transport system as follows: 1. One for each of the four main laboratory areas; microbiology, waste water, metals and organics. 2. One covering sample reception, the main distribution loop and the sludge analysis area. 3. One covering the bottle wash facility. Each PLC receives scheduling information from its own laboratory area controller based on information received by it from LIMS, on the receipt of crates at sample reception. Samples arrive at sample reception and after logging in, the crate is loaded to the transport system. The crate's barcode label is read and immediately passed to LIMS; if the crate is in the day's schedule, it is transferred to the main distribution loop, otherwise the crate is routed to a sample crate rejection area, within sample reception, for manual investigation. From the main distribution loop the crate is routed
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to the appropriate laboratory area where it is held on the buffer loop until the robotic cell is able to process it. Should the laboratory area not be able to accept the crate because, for example of a large backlog, it will remain on the main distribution loop until such time it can be transferred to the laboratory area. Once the crate has arrived at the robotic cell, it remains there until the samples have been processed whence the crate with the residual samples is returned to the buffer loop. The crate remains on the buffer until the cell results have been validated by the LIMS, following which it is routed to the bottle wash area for residual sample disposal and bottle cleaning. Should the LIMS indicate analytical failure, e.g., a measurement validity being exceeded or an AQC fail, the crate, or specified samples from the crate, will be returned to the cell for re-analysis assuming sufficient sample is available.
5. Organics laboratory The organics laboratory has a relatively low sample throughput and sample preparation techniques that do not lend themselves to economic low volume automation. As a result, the only automated operation in the laboratory is the transfer of THM samples using a syringe from the sample bottle to an analysis vial contained in an auto sampler tray. When the tray has been filled it is manually taken from the cell for analysis using HPLC. The bottles for other analysis types are simply passed through the cell by the robot for manual collection and preparation. The organics cell is based on a gantry robot.
6. Metals and auto analysis laboratory This laboratory contains three cells, two for the preparation of samples for metals analysis and one for a number of routine chemistry analyses. All cells are based on gantry robots. The two metal preparation cells are essentially the same, one being used for clean water and the other for waste water. Sample bottles are removed from the crate in turn by the gantry robot and decapped
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using a dedicated decapping unit. The sample is then weighed and acidified to a concentration of 10% by the addition of nitric acid. Acidified samples are then placed in one of three fully automatic microwave ovens by the robot, in pairs, and heated to boiling point to digest any metal that may have plated on the container. The sample heating profile and time for which it is held at boiling point are specified in an analytical method defined for the sample. Digested samples are allowed to cool for a short period before being dispensed to an autosampler tray for subsequent analysis on an ICP-MS. The sample bottle is then recapped and returned to the crate. A number of AQC standards are held in containers on the cell and are dispensed to positions in the autosampler tray defined in the analytical method. The routine chemistry cell performs a number of operations, all on clean water samples, as follows: 1. Dispensing of an aliquot of the sample, by syringe, to a sample vial for analysis by ion chromatography. The sample is sealed with a cap, by the robot, after dispensing. 2. Dispensing samples for nutrients analysis on an AQUA 800 multi channel analyser. 3. Dispensing samples for total organic carbon analysis. 4. Performing the analysis of conductivity, colour and turbidity. A sub sample is extracted from the sample bottle and pumped using a precision peristaltic pump, to three individual analytical devices in turn. The cell controller performs device calibration and calculates the required linearised measurement from the voltage response of the device using an appropriate algorithm. In each case AQC standards, located in containers on the cell, are dispensed to positions in the autosampler trays, or analysed in the conductivity, colour, turbidity, sequence, as defined in the analytical method.
7. Waste water laboratory The measurements performed here are Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), suspended solids and pH. Each measurement is made by a separate analytical cell, duplicated for increased throughput and backup in the event of failure. The cells are linked by a sample
conveying loop (the secondary transport system referred to in Section 2) that routes the individual samples from cell to cell for the required analyses. When the system is available to accept new sampies, a crate is transferred to one of two sample decrating cells. The samples are removed from the crate and typically 700 ml dispensed to a reusable plastic beaker on the sample conveyor. The beakers are then transferred in a sequence to the pH, suspended solids, BOD and COD cells. At each cell, if that particular analysis is required on the sample, the beaker is pushed off, an aliquot taken for analysis and the beaker returned to the conveyor. Should the cell be busy, the beaker remains on the conveyor loop for action on the next circuit. For certain sample types, BOD and COD must be performed on a settled sample; to facilitate this the sample is transferred to a slow moving settling conveyor prior to the BOD cell, where it will remain for a time period defined in the method. When all analyses have been performed on a particular sample, the beaker is transferred to one of two beaker wash stations where the residual sample is disposed of and the beaker washed for re-use. The decrate cell utilises a gantry robot and each analytical cell an articulated robot. The cells operate as follows: pH: The pH of the sample is measured. If required by the analytical method, the sample is adjusted to neutrality by the addition of acid or alkali as necessary. Suspended Solids: The cell maintains a stock of filter papers in an oven to ensure dryness. When a sample arrives at the cell, a filter paper is removed from the oven, weighed and placed in a vacuum filtration unit. The sample is filtered and the filter paper then dried at a controlled temperature in a rotating oven. The dried filter paper is weighed and the measurement calculated as difference in weight corrected for sample dilution. BOD: The sample is diluted, as defined in the analytical method, by the addition of aerated water containing a biological seed and nutrients. Dilution is performed by weight. The diluted sample is dispensed to a BOD incubation bottle and the dissolved oxygen content measured. The bottle is capped and placed in a tray for manual loading to an incubator.
A.J. Wyatt~Laboratory Automation and Information Management 32 (1996) 103-108
Samples are incubated for a period of 5 days following which the tray of samples is manually reloaded to the cell where the residual oxygen content is measured. The calculated result is the difference between the two oxygen content measurements, corrected for dilution. Finally, the incubator bottle and cap are washed using a dedicated wash robot contained within the cell and stored for re-use. COD: The sample is dispensed to a reaction vessel together with reagents. The vessel is capped and heated in a rotary oven for a period of time and at a temperature defined by the analytical method. After the prescribed time, the vessel is cooled in a water bath, decapped and the measurement determined by automatic titration. The cell incorporates 3 reagent addition stations and 3 titrators.
8. Sludge The sludge cell, which is based on a gantry robot, measures the pH and dry weight content of sewage sludge and dispenses a sub sample for metals content analysis. Having removed the sample bottle from the crate and decapped it, the robot places the bottle beneath a linear slide on which is mounted a homogeniser, pH measurement probe and sample syringe. The sample is first homogenised, its pH measurement taken and a sub sample extracted by the syringe into a disposable tip. The sub sample is then dispensed into a previously weighed dish which is again weighed to determine the quantity of sample. Six dishes containing samples are then placed into an automated microwave oven on a tray and are then heated to dryness by a controlled programme to prevent the sample splattering. The dried samples are again weighed and the dry weight percentage calculated. The final operation on a sample is to dispense an aliquot into a reaction vessel which is transferred from the cell for acid digestion and metals content analysis off line.
9. Microbiology The microbiology cells prepare routine samples for colony count and analysis for E. coli and total
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coliforms. In each case, the cells prepare petri dishes which are placed onto trays ready for incubation. Subsequent operations of loading to incubators and inspection of the incubated plates are performed manually. There are two identical sets of three cells, each set consisting of: 1. A decrate cell to remove sample containers from the crate and decap them ready for dispensing. 2. A colony count preparation cell to dispense a small amount of sample into a petri dish containing agar. 3. A membrane filtration cell to filter the sample through a membrane which is then placed in a petri dish containing a growth medium. A particular requirement of these cells is that they should operate under strict aseptic conditions. Specialised design ensures that there is no possibility of cross contamination, that all units within the cell coming into contact with the sample are sterilised between samples and that all consumables held on the cell are kept sterile until used.
10. Bottle wash On completion of analysis and confirmation by the LIMS system that the analysis was successful, sample bottles are routed to the bottle wash area. Bottles are washed or treated as appropriate, i.e., microbiology bottles are sterilised, metals sample bottles rinsed with acid, etc. The bottle wash area comprises a number of manual wash stations, each fed by conveyors routing the bottles to the correct station.
11. Design philosophy The design phase was carried out in two distinct stages:
• Design and feasibility study This concentrated on conceptual matters and provided the client a basis on which to make a decision as to how, or indeed if, to proceed. Carried out as a joint exercise by the client and Thurnall; the client provided the science and methodology input, Thurnall the robotic application expertise.
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The study phase delivered the following items: User Requirement Specification defining the analytical methodology and automation requirements. Feasibility study report providing a number of options for automation together with recommendations regarding the way forward. Implementation strategy plan for the implementation and post installation phases. Design proposal documents defining conceptually the cell structure and control strategy. • Detailed design This commenced post contract and delivered the following items on an individual system module basis (i.e., cells and transport system): Functional design specification detailing the scope, operation, functions and control. • Detailed design drawings of mechanical and electrical aspects. Software system specification defining the software structure. • Detailed item specification for each individual software module from which code could be directly written.
12. Implementation
Key elements of the implementation strategy were: Systems integration to, wherever possible, utilise proprietary equipment to meet the requirements. • Choice of industrial standard robots and equipment, recognising the required duty cycle and reliability needs. Well defined user requirements definitions and design specifications, discussed with and agreed with, the client. Strong project management supported by appropriate tools. A properly defined testing strategy and acceptance criteria. Post installation support plans. Acknowledgements
The author, employed by the Robotic Automation Business Unit of Thurnall PLC, would like to thank all staff at North West Water, also all suppliers to Thurnall and Thurnall staff involved in the project.
ELSEVIER
Laboratory Automation and InformationManagement 32 (1996) 103-108
An automated sample preparation and testing laboratory for North West Water A.J. Wyatt The Centralisation of North West Water's, Analytical Testing Laboratories at Lingley Mere, Warrington, Cheshire, UK
Abstract This paper discusses a large robotic automation project implemented by Thumall Plc. on behalf of a major UK water company. The system, which automates the analysis of routine clean and dirty water samples, incorporates 22 individual robots configured into 19 robotic cells together with a transport system to carry samples from the reception area into the analytical cells and then to a wash area for residual sample disposal and bottle washing. Control is performed by 21 local computers coordinated by 5 supervisory control systems which in turn link into a LIMS system for data manipulation and long term storage. This paper discusses the life cycle of the project and examines the following generic issues relating to the integration of large scale automation projects: (a) the factors governing a decision to automate on this scale; (b) the automation to be adopted; (c) risk reduction strategy; (d) the benefits to be achieved from such a scheme. Keywords: Automated sample preparation; Testing laboratory for North West water
1. Introduction North West Water, a major UK utility, originally operated 28 regional laboratories each performing similar analyses on samples taken within their local area. In 1991, a decision was taken to centralise this analytical operation and a purpose built laboratory was constructed to handle all samples taken within the area. Only one of the original regional laboratories now remains, a small facility in Cumbria where microbiological analysis of samples with limited life is carried out. Within the centralisation programme, it was decided that, if economically viable, the facility should be automated utilising a transfer system to route samples around the laboratory and robotic cells performing routine analyses. During 1992, Thurnall PLC carried out a design and feasibility study into the proposed automation
strategy. The company was subsequently awarded a contract to implement and set the system to work.
2. Sample collection Samples are collected by a team of Water Quality Officers who operate to a computer generated collection schedule. All samples are taken to one of three sample reception areas where they are consolidated into crates, any changes to the schedule are logged to the operational computer system and the samples are then shipped to the laboratory by courier.
3. Automation system overview Possibly the largest laboratory robotic automation scheme in the world, the system comprises a total of
0925-5281/96/$15.00 Copyright © 1996 Published by Elsevier Science B.V. All rights reserved. PII S 1381-141X(96)00004-4
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A.J. Wyatt/Laboratory Automation and Information Management 32 (1996) 103-108
19 sample preparation and analysis cells, a semi automated sample bottle washing facility and two sample transport systems. The main transport system routes crates of sample bottles from sample reception to the robotic cells and then to the sample bottle wash area; the secondary transport system routes containers of sample from cell to cell in the waste water laboratory. Control of the automation system is effected by a hierarchical network of computers comprising the following levels: Cell Level: a dedicated cell controller at each cell, based on Motorola VME bus equipment. This unit provides local control of the cell and primary data acquisition to a schedule downloaded to it. It also controls the local cell operator interface. Control software is written in " C " and runs under the OS9 operating system. Also at this level and analogous to the cell controller, are the transport system controllers. These are based on Allen Bradley PLC5 units, there being one for each individual laboratory area, one to control the routing from sample reception to the laboratories and one for the bottle wash area.
Laboratory Level: a laboratory area controller for each laboratory, again based on Motorola VME bus equipment. The laboratory area controller coordinates the operation of the cell and transport system controllers for a particular laboratory area. It routes crates to cells as required, issues work schedules to the cell controller for each sample in the crate and collates sample data. LIMS Level - daily sample collection schedules are loaded to the LIMS from elsewhere on North West Water's information network. The schedules define the samples, the crates in which they will be received at the laboratory and the analyses to be performed on an individual sample basis. The LIMS uses the schedules to generate work schedules for each laboratory area controller and the transport system. On completion of an analysis, the result together with appropriate supporting information is sent to the LIMS for validation, further processing and storage. The robotic cells fall into two categories: Sample Preparation Cell: this type of cell prepares samples for analysis, but does not itself perform that analysis. The prepared samples are pre-
sented in an appropriate form for manual transfer to the analytical device. An example of such a cell is in metals where the sample is digested by microwave heating, cooled and an aliquot dispensed to an auto sampler tray. When full, the auto sampler tray is manually removed and presented to the instrument (ICP-MS) for analysis. The data output from a sample preparation cell is positional information including, where appropriate, sample, analytical quality control and calibration standard location together with sample preparation details. Analytical Cell: this type of cell prepares samples for analysis, carries out the analysis and generates an analytical measurement. An example of such a cell is the Biochemical Oxygen Demand (BOD) cell in the waste water laboratory. Here, the sample is prepared, initial oxygen content measured, the sample incubated for 5 days and the residual oxygen content measured for the BOD to be calculated. Data output is the sample identification and sample preparation information, e.g., dilution and measured value. The system uses two types of robot, Articulated Robot: a six axis robotic " a r m " manufactured by CRS of Canada, used for localised picking and placing applications and where intricate movement or positioning is required. The system incorporates ten such robots, two of which are mounted on a linear track. Gantry Robot: an overhead carriage supporting a vertically moving mast, capable of flexible positioning within a 3-dimensional rectangular section envelope. The robots, which are from the CROCUS range manufactured by Thumall, enable operations over a greater area than the articulated robot.
4. Crate transport system Sample crates are identified by means of bar code labels and contain up to 12 glass or plastic sample bottles with a total maximum weight of 10 kg. Typically, in the order of 400 crates are received each day. The crate transport system is based on a low level (400 ram) slat band conveyor with low friction plastic slats and a running speed of 10 m/minute. It is designed for use in a laboratory environment being quiet in operation and easy to clean in the event of
A.J. Wyatt~Laboratory Automation and Information Management 32 (1996) 103-108
spillage. As the conveyor speed is relatively low, guarding is not required. However, an emergency stop pull wire runs above the conveyor to halt in an emergency. The crate transport system comprises the following main elements: • Sample reception conveyor onto which crates are manually loaded and which feeds to a main distribution loop. • A main distribution loop with transfer points to the individual laboratory areas and to the bottle wash. • Within each laboratory area, a loop which acts as a temporary buffer store, holds crates until the cell is free to perform the analyses. The loop also has a transfer point to route crates of analysed samples back to the distribution loop. • A bottle wash conveyor which routes the crates to semi automated stations for residual sample disposal and bottle washing. A crate is transferred between sections by a series of pneumatic stops which separate it from the following crates and halt it at a pneumatic pusher. The crates on the receiving conveyor are also halted and the crate pushed onto the conveyor. Each crate transfer station has a barcode reader to identify those crates that are to be transferred. Control is provided by a total of six PLCs each handling a particular section of the transport system as follows: 1. One for each of the four main laboratory areas; microbiology, waste water, metals and organics. 2. One covering sample reception, the main distribution loop and the sludge analysis area. 3. One covering the bottle wash facility. Each PLC receives scheduling information from its own laboratory area controller based on information received by it from LIMS, on the receipt of crates at sample reception. Samples arrive at sample reception and after logging in, the crate is loaded to the transport system. The crate's barcode label is read and immediately passed to LIMS; if the crate is in the day's schedule, it is transferred to the main distribution loop, otherwise the crate is routed to a sample crate rejection area, within sample reception, for manual investigation. From the main distribution loop the crate is routed
105
to the appropriate laboratory area where it is held on the buffer loop until the robotic cell is able to process it. Should the laboratory area not be able to accept the crate because, for example of a large backlog, it will remain on the main distribution loop until such time it can be transferred to the laboratory area. Once the crate has arrived at the robotic cell, it remains there until the samples have been processed whence the crate with the residual samples is returned to the buffer loop. The crate remains on the buffer until the cell results have been validated by the LIMS, following which it is routed to the bottle wash area for residual sample disposal and bottle cleaning. Should the LIMS indicate analytical failure, e.g., a measurement validity being exceeded or an AQC fail, the crate, or specified samples from the crate, will be returned to the cell for re-analysis assuming sufficient sample is available.
5. Organics laboratory The organics laboratory has a relatively low sample throughput and sample preparation techniques that do not lend themselves to economic low volume automation. As a result, the only automated operation in the laboratory is the transfer of THM samples using a syringe from the sample bottle to an analysis vial contained in an auto sampler tray. When the tray has been filled it is manually taken from the cell for analysis using HPLC. The bottles for other analysis types are simply passed through the cell by the robot for manual collection and preparation. The organics cell is based on a gantry robot.
6. Metals and auto analysis laboratory This laboratory contains three cells, two for the preparation of samples for metals analysis and one for a number of routine chemistry analyses. All cells are based on gantry robots. The two metal preparation cells are essentially the same, one being used for clean water and the other for waste water. Sample bottles are removed from the crate in turn by the gantry robot and decapped
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using a dedicated decapping unit. The sample is then weighed and acidified to a concentration of 10% by the addition of nitric acid. Acidified samples are then placed in one of three fully automatic microwave ovens by the robot, in pairs, and heated to boiling point to digest any metal that may have plated on the container. The sample heating profile and time for which it is held at boiling point are specified in an analytical method defined for the sample. Digested samples are allowed to cool for a short period before being dispensed to an autosampler tray for subsequent analysis on an ICP-MS. The sample bottle is then recapped and returned to the crate. A number of AQC standards are held in containers on the cell and are dispensed to positions in the autosampler tray defined in the analytical method. The routine chemistry cell performs a number of operations, all on clean water samples, as follows: 1. Dispensing of an aliquot of the sample, by syringe, to a sample vial for analysis by ion chromatography. The sample is sealed with a cap, by the robot, after dispensing. 2. Dispensing samples for nutrients analysis on an AQUA 800 multi channel analyser. 3. Dispensing samples for total organic carbon analysis. 4. Performing the analysis of conductivity, colour and turbidity. A sub sample is extracted from the sample bottle and pumped using a precision peristaltic pump, to three individual analytical devices in turn. The cell controller performs device calibration and calculates the required linearised measurement from the voltage response of the device using an appropriate algorithm. In each case AQC standards, located in containers on the cell, are dispensed to positions in the autosampler trays, or analysed in the conductivity, colour, turbidity, sequence, as defined in the analytical method.
7. Waste water laboratory The measurements performed here are Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), suspended solids and pH. Each measurement is made by a separate analytical cell, duplicated for increased throughput and backup in the event of failure. The cells are linked by a sample
conveying loop (the secondary transport system referred to in Section 2) that routes the individual samples from cell to cell for the required analyses. When the system is available to accept new sampies, a crate is transferred to one of two sample decrating cells. The samples are removed from the crate and typically 700 ml dispensed to a reusable plastic beaker on the sample conveyor. The beakers are then transferred in a sequence to the pH, suspended solids, BOD and COD cells. At each cell, if that particular analysis is required on the sample, the beaker is pushed off, an aliquot taken for analysis and the beaker returned to the conveyor. Should the cell be busy, the beaker remains on the conveyor loop for action on the next circuit. For certain sample types, BOD and COD must be performed on a settled sample; to facilitate this the sample is transferred to a slow moving settling conveyor prior to the BOD cell, where it will remain for a time period defined in the method. When all analyses have been performed on a particular sample, the beaker is transferred to one of two beaker wash stations where the residual sample is disposed of and the beaker washed for re-use. The decrate cell utilises a gantry robot and each analytical cell an articulated robot. The cells operate as follows: pH: The pH of the sample is measured. If required by the analytical method, the sample is adjusted to neutrality by the addition of acid or alkali as necessary. Suspended Solids: The cell maintains a stock of filter papers in an oven to ensure dryness. When a sample arrives at the cell, a filter paper is removed from the oven, weighed and placed in a vacuum filtration unit. The sample is filtered and the filter paper then dried at a controlled temperature in a rotating oven. The dried filter paper is weighed and the measurement calculated as difference in weight corrected for sample dilution. BOD: The sample is diluted, as defined in the analytical method, by the addition of aerated water containing a biological seed and nutrients. Dilution is performed by weight. The diluted sample is dispensed to a BOD incubation bottle and the dissolved oxygen content measured. The bottle is capped and placed in a tray for manual loading to an incubator.
A.J. Wyatt~Laboratory Automation and Information Management 32 (1996) 103-108
Samples are incubated for a period of 5 days following which the tray of samples is manually reloaded to the cell where the residual oxygen content is measured. The calculated result is the difference between the two oxygen content measurements, corrected for dilution. Finally, the incubator bottle and cap are washed using a dedicated wash robot contained within the cell and stored for re-use. COD: The sample is dispensed to a reaction vessel together with reagents. The vessel is capped and heated in a rotary oven for a period of time and at a temperature defined by the analytical method. After the prescribed time, the vessel is cooled in a water bath, decapped and the measurement determined by automatic titration. The cell incorporates 3 reagent addition stations and 3 titrators.
8. Sludge The sludge cell, which is based on a gantry robot, measures the pH and dry weight content of sewage sludge and dispenses a sub sample for metals content analysis. Having removed the sample bottle from the crate and decapped it, the robot places the bottle beneath a linear slide on which is mounted a homogeniser, pH measurement probe and sample syringe. The sample is first homogenised, its pH measurement taken and a sub sample extracted by the syringe into a disposable tip. The sub sample is then dispensed into a previously weighed dish which is again weighed to determine the quantity of sample. Six dishes containing samples are then placed into an automated microwave oven on a tray and are then heated to dryness by a controlled programme to prevent the sample splattering. The dried samples are again weighed and the dry weight percentage calculated. The final operation on a sample is to dispense an aliquot into a reaction vessel which is transferred from the cell for acid digestion and metals content analysis off line.
9. Microbiology The microbiology cells prepare routine samples for colony count and analysis for E. coli and total
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coliforms. In each case, the cells prepare petri dishes which are placed onto trays ready for incubation. Subsequent operations of loading to incubators and inspection of the incubated plates are performed manually. There are two identical sets of three cells, each set consisting of: 1. A decrate cell to remove sample containers from the crate and decap them ready for dispensing. 2. A colony count preparation cell to dispense a small amount of sample into a petri dish containing agar. 3. A membrane filtration cell to filter the sample through a membrane which is then placed in a petri dish containing a growth medium. A particular requirement of these cells is that they should operate under strict aseptic conditions. Specialised design ensures that there is no possibility of cross contamination, that all units within the cell coming into contact with the sample are sterilised between samples and that all consumables held on the cell are kept sterile until used.
10. Bottle wash On completion of analysis and confirmation by the LIMS system that the analysis was successful, sample bottles are routed to the bottle wash area. Bottles are washed or treated as appropriate, i.e., microbiology bottles are sterilised, metals sample bottles rinsed with acid, etc. The bottle wash area comprises a number of manual wash stations, each fed by conveyors routing the bottles to the correct station.
11. Design philosophy The design phase was carried out in two distinct stages:
• Design and feasibility study This concentrated on conceptual matters and provided the client a basis on which to make a decision as to how, or indeed if, to proceed. Carried out as a joint exercise by the client and Thurnall; the client provided the science and methodology input, Thurnall the robotic application expertise.
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A.J. Wyatt~Laboratory Automation and Information Management 32 (1996) 103-108
The study phase delivered the following items: User Requirement Specification defining the analytical methodology and automation requirements. Feasibility study report providing a number of options for automation together with recommendations regarding the way forward. Implementation strategy plan for the implementation and post installation phases. Design proposal documents defining conceptually the cell structure and control strategy. • Detailed design This commenced post contract and delivered the following items on an individual system module basis (i.e., cells and transport system): Functional design specification detailing the scope, operation, functions and control. • Detailed design drawings of mechanical and electrical aspects. Software system specification defining the software structure. • Detailed item specification for each individual software module from which code could be directly written.
12. Implementation
Key elements of the implementation strategy were: Systems integration to, wherever possible, utilise proprietary equipment to meet the requirements. • Choice of industrial standard robots and equipment, recognising the required duty cycle and reliability needs. Well defined user requirements definitions and design specifications, discussed with and agreed with, the client. Strong project management supported by appropriate tools. A properly defined testing strategy and acceptance criteria. Post installation support plans. Acknowledgements
The author, employed by the Robotic Automation Business Unit of Thurnall PLC, would like to thank all staff at North West Water, also all suppliers to Thurnall and Thurnall staff involved in the project.