KF875 and KF UNI Coulometric Karl Fischer Titrators

Transcription

1 KF875 and KF UNI Coulometric Karl Fischer Titrators User Guide MEGGER v.02/03

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3 CONTENTS CONTENTS... 3 PARTS LIST... 4 SPECIFICATIONS & FEATURES... 5 PRINCIPLE OF MEASUREMENT... Error! Bookmark not defined. KEYBOARD INTERFACE... 5 REAR PANEL (Both instruments) SETTING THE DATE AND TIME... 6 OPERATION... 6 TITRATION CELL ASSEMBLY INSTRUCTIONS... 7 TITRATION CELL - DIAGRAM... 7 FILLING AND CHANGING THE REAGENTS... 8 CONNECTION & START UP PROCEDURE... 9 LOADING THE PRINTER PROGRAMME FUNCTIONS MENU LIST RESULT FORMAT CALCULATION MODE PRINTER MODE EXAMPLE APPLICATIONS CRUDE OILS TRANSFORMER/INSULATING OILS TURBINE / LUBRICATING OILS KETONES AND AMINES GAS SAMPLES REAGENT LIFE DRIFT RATE COMPENSATION PRINT-OUTS KF875 PRINT OUT EXPLANATION KF-UNI PRINT OUT EXPLANATION CLEANING GLASSWARE CLEANING GLASSWARE TROUBLESHOOTING OVERTITRATION EXCESS DRIFT LONG PRECONDITIONING TIME PROGRESSIVELY LOWER RESULTS FOR SAME SAMPLE POOR REPEATABILITY FOR SAME SAMPLE Page 3

4 PARTS LIST After unpacking your instrument check that it has been supplied with glassware/accessories pack comprising: - GLASSWARE PACK Item Description Part No. 1 pce Titration Vessel pce Detector electrode pce Generator electrode pce Drying tube pack Injection septa (10) pce 1ml Glass syringe pce Luer needle bottle Molecular sieve pce Stirrer bar pce Funnel pce Paper roll, thermal ACCESSORIES 1 pce Carry Case 1 pce Power pack 1 set Mains leads, UK, USA & Euro 1 pce Car adapter 1 pce User Guide Page 4

5 KEYBOARD INTERFACE KF875 Front Panel KF-UNI Front Panel On both instruments, press START to activate the selected programme, and begin titration MEGGER KF875 Karl Fischer Test Set MEGGER KF-UNI Karl Fischer Test Set START ENTER START PROGRAM Press the left and right arrow keys to move forwards and backwards through the menus. Press the up and down arrow keys to select different program values and parameters Press the Program key to access and quit the menu system Press the Enter key to store selected program parameters. REAR PANEL (Both instruments). RS232C port for connection to a personal computer On / off switch Power in socket Page Amp 20mm fuse. Unscrew to check and replace fuse

6 SETTING THE DATE AND TIME 1. Switch on the instrument and wait for it to display the following: MEGGER KFxxxx Press START 2. Hold down the START key until the display shows: - Set Date / Time: DD/MM/YYYY HH:MM:SS 3. On the KF875 press the START key, on the KF-UNI use the to move the cursor across the screen. 4. On the KF875 use the stirrer speed switch on the lower right front of the instrument to increase or decrease the selected number. On the KF-UNI use the and to increase and decrease the number. 5. After all settings have been completed, hold down the START key for three seconds to save the changes and exit. OPERATION The rear panel of both instruments is identical. There is a mains input socket and a separate power ON/OFF switch. For operation, simply switch ON. Whilst connected to mains power supply, a trickle charge is continuously applied to the battery. It is therefore recommended that the instrument be used from mains power supply whenever possible so that the battery is kept fully charged. Maximum battery operating time is 8 hours continuous use. This may be reduced if repeated high water contents are being determined or if the printer is being continually used. Page 6

7 TITRATION CELL ASSEMBLY INSTRUCTIONS The cell is assembled as shown in the diagram below. Please be sure to assemble correctly every time the cell is cleaned or re-filled. Fill the dry tube with molecular sieve and fit onto cell. Place stirrer bar in the bottom of the titration vessel and check clearance so that the bar does not damage electrodes. TITRATION CELL - Components Page 7

8 FILLING AND CHANGING THE REAGENTS The KF875 and KF-UNI are designed to work with all major coulometric Karl Fischer reagents, either pyridine free or pyridine based. Using the funnel supplied, charge the titration vessel up to the lower line with Anode A reagent (approx 100ml). Also using the funnel, or alternatively by syringe, charge the inner chamber of the generator electrode with Cathode C or CG reagent so that the level is 2-3 mm below that of the Anode reagent. (If the Cathode reagent is higher than Anode reagent when first charging new reagents it may take longer for the instrument to equilibrate.) Cathode Reagent Anode Reagent Page 8

9 CONNECTION & START UP PROCEDURE Both instruments 1. Place the assembled titration cell in the cell clamp and connect the electrode leads to the correct sockets. The generator and detector sockets are clearly marked. When looking at the front of the instrument the cell should be positioned so that the generator electrode is on the left and detector electrode on the right. 2. Attach the power cable (if running from mains). 3. Switch power on. 4. If required adjust the stirrer speed using the black toggle switch on the front of the machine. After being switched on the instruments will display as follows with the KF875 display on the left and KF-UNI on the right: KF875 KF-UNI Press START Press START Press the START key and allow instrument to equilibrate. Microgram count KF875 xxxx µg KF-UNI xxxx µg 4 Precondition 4 Precondition Detector signal Titration speed Battery level / mains indicator At end of the equilibration period the display of either instrument will show: - Dft xxxx µg Drift test After the initial drift has been calculated, in micrograms of water per minute, your instrument is ready for operation. Dft = xx xxxx µg 1 Ready Page 9

10 LOADING THE PRINTER To load the paper into the printer, first open the paper roll holder lid above the print head, remove the old roll and roller. Now load a new paper roll as shown and insert the paper into the slot at the rear of the print head. As soon as the printer sees the paper it will automatically self load the paper. N.B. Make sure the paper being loaded is thermal paper, as the printer will not work with standard till receipt paper. Page 10

11 PROGRAMME FUNCTIONS Your KF875 does not require programming. It is preset for a 1ml sample of insulating oil that has a specific gravity of The only adjustment possible is to increase or decrease the stirrer speed. However, your KF-UNI does require some information before it can be used. When the KF-UNI is ready for operation you must enter the titration parameters, by using PROGRAM, ENTER, and the north/south, east/west keys Key Functions: - PROGRAM - Press PROGRAM key to enter and exit the programming menu. ENTER - Allows parameter values from the displayed menu to be entered into memory. - The east/west key allows you the move through the different menu options. - The north/south keys allow you to scroll through and manipulate the individual parameters in each menu. When required parameter is displayed, press ENTER. MENU LIST There are three menus that control the KF-UNI Result Format Calculation Mode Printer Mode RESULT FORMAT Results can be selected in g, ppm, mg/kg or % water. Display shows: - Result Format ppm If you want to select this format press ENTER and then carry on moving through the menu using the east/west keys. If you want to change format to give results in g, mg/kg or % you can scroll through these options by pressing the north/south keys until the required format is displayed, then press ENTER CALCULATION MODE For your convenience, the KF875 calculation mode is pre programmed into the memory. The instrument calculates the result using set values for the volume and specific gravity (density). By dividing the microgram counts of water by these values, the KF875 can then print out and display the calculated water content in ppm (mg/kg). As the KF875 is specifically intended for transformer oil (mineral oil) the values pre programmed are a volume of 1.00 ml and a specific gravity (density) of Result mg/kg (ppm) = microgram count = microgram count V x SG 1.00 x Where V = volume of sample (ml) and SG = specific gravity of the sample. Page 11

12 The KF-UNI has two standard calculation modes in memory. Each of these allows the instrument to divide the microgram count by the gram weight of sample introduced so that the calculated result can be printed out in either ppm (mg/kg) or percentage water. Press the north/south keys to scroll through the options available. Select the calculation mode required and press ENTER. The display will prompt you with the appropriate parameters. Enter the numerical value for each parameter using the north/south keys to increase and decrease numbers, and the east/west keys to move along the decimal places. Press ENTER to confirm you choice and return to the main menu. The standard calculations are: - 1. W/w Result (ppm, mg/kg or %) = microgram count W - w Where W = total weight of sampler + sample (gm) w = tare weight of empty sampler (gm) After entering the total weight (W) the instrument will return to Ready condition. The Tare weight (w) can be entered at any time during the titration by pressing PROGRAM, or at the end of titration. 2. V/SG Result (ppm, mg/kg or %) = microgram count V x SG where V = volume of sample (ml) and SG = specific gravity or density of sample. PRINTER MODE Selecting this programme allows the printer to be turned ON or OFF. Options available: - Off - no result print out Every result - will print result after every titration Page 12

13 EXAMPLE APPLICATIONS The greater the amount of water introduced into the titration cell will cause the titration to take longer and also consume the reagents more quickly. It is recommended that the smallest representative amount of sample be used to ensure fastest titration speed and maximum sample throughput before reagents have to be replenished. This guide may be of assistance: - Expected water content Suggested sample size 1-10 ppm 1 or 2 ml ppm 1 or 2 ml ppm 0 5 or 1 ml ppm 0 5 or 1 ml % 1 or 2 ml % or 2 ml % 0 5 or 1 ml % 0 5 or 1 ml % 0 2 ml above 5 0 % 0 1 ml or less Please note that these volumes are only a guide. You may wish to experiment with sample size to determine the optimum balance between repeatability, reagent depletion and speed of analysis. CRUDE OILS (IP 386, ASTM D4928, API MPMS Chapter 10.9) Most coulometric reagents contain Methanol as the main solvent and as such it is possible that deposits from crude oils can drop out and contaminate the electrodes, requiring more frequent and thorough cleaning of the glassware. Modifying the Anode reagent with 40% volume Xylene can reduce this problem. Mercaptans and sulphides cause the most common interference in crude oil samples. Samples containing alkyl groups will react stoichiometrically so that: 100 ppm Mercaptans would show as approximately 30 ppm water 100 ppm Sulphides would show as approximately 50 ppm water In normal practice oils containing less than 500 ppm mercaptans or sulphides are regarded as having no appreciable effect. Repeatability problems are usually caused by sampling inaccuracies or improper homogenisation. TRANSFORMER/INSULATING OILS Due to the viscosity of these samples, and the fact that typical water content levels are in the range 5 40 ppm (mg/kg), it is usually necessary to inject sample volumes of 1 ml. This means that 50 samples would fill the titration cell. Provided that the other criteria governing reagent life, (total water titrated and reagent age), have not been reached, then it is possible to switch off the titrator and allow the oil to separate from the reagent. The oil can then be syphoned off and the instrument switched on again. After this operation it may take up to 30 minutes before the instrument settles down to a stable baseline. If it takes longer than 30 minutes then it is advisable to clean the cell and recharge with fresh reagents. TURBINE / LUBRICATING OILS For most Lube Oil applications a sample size of 1ml is sufficient. However, if it is suspected that the water content is above 1 %, then sample size of 0 2 to 0 5 ml is suggested. Some lubricating oils contain additives, which can coat the detector electrode or block the glass frit of the generator electrode. Modifying the Anode reagent with % volume Chloroform can reduce these problems. If difficulties continue, contact your reagent supplier for further information. Page 13

14 KETONES AND AMINES These samples react with the Methanol contained in the standard coulometric reagents resulting in inaccurate results and, in extreme conditions, titration end point being unattainable. For samples containing ketones, amines or aldehydes the use of specially formulated coulometric reagents for ketone samples is recommended e.g. Hydranal Coulomat AK and CGK. GAS SAMPLES 1. Replace the injection septa with the gas analysis inlet & outlet adapters. Contact your supplier for details. 2. Remove the drying tube and fit the blanking disc on top of the generator electrode. 3. Connect outlet tube to wet gas flow meter. 4. Flush the sample lines and allow instrument to stabilise. 5. Press RUN and allow gas sample to flow through the cell at an approximate flow rate of 0 5 litres/minute. 6. Turn off gas flow and allow titration to reach end point. Calculation W= G x (273 + t) x 22 4 where V x 273 x 18 W = moisture content G = microgram count V = gas volume, litres t = water temperature of wet gas flow meter ( C) Page 14

15 REAGENT LIFE There are three main factors that govern the life of reagents, and therefore, the frequency of cleaning and recharging the titration cell: 1. The physical size of the titration cell allows for mls of sample to be added. As the KF875 requires a 1 ml injection the reagent should be changed after approximately every sample injections. 2. The total amount of water that can be analysed before saturation of the reagents varies slightly from manufacturer to manufacturer. Typically a 100 ml charge of Anode reagent will analyse up to 1 gram water, whilst a 5 ml charge of Cathode reagent will analyse upto 250 mg water. Considering that the injected sample volume is normally small, and also that the analysis is usually for the determination of low levels of water, these water capacity values should not normally become a limiting factor. 3. Similar to all other Karl Fischer reagents, coulometric reagents will deteriorate when exposed to sunlight and with increases in temperature. Placing the instrument in direct sunlight or near to a heat duct can decrease the reagent life. Typical life expectancy of one charge of reagents (Anode and Cathode), when left in the titration cell on the laboratory bench, is of the order of 3 4 weeks. This is also obviously dependent on the total amount of sample injected and the total amount of water titrated. DRIFT RATE COMPENSATION At the start of any titration the displayed drift value, on the top left side of the screen (in micrograms per minute), is stored in memory. This ensures that the displayed result is corrected for any ingress of atmospheric moisture during the titration period. Whilst in READY condition the KF875 and KF-UNI continually compensates for any drift caused by atmospheric moisture ingress or reagent decomposition and displays this information, which is updated every 10 seconds. If the drift value is above 60 g per minute the display will read EXCESS DRIFT. Most common causes of excess drift are: 1. Titration vessel not properly sealed (check septa & fittings). 2. Reagent life almost depleted (clean & recharge the cell). 3. Sample introduced before pressing RUN key. 4. Trace moisture on cell walls. If excess drift occurs, switch the instrument off, remove titration cell from clamp, gently swirl the anode reagent around the cell walls, replace cell in clamp, switch instrument on and allow to precondition. Page 15

16 PRINT-OUTS KF875 PRINT OUT EXPLANATION. The KF875 prints the calculated results in ppm (mg/kg) along with time and date of the titration and run number. The KF875 automatically increments the next run number every time you press the start button. The run counter is reset to zero when power is switched off and back on again. A duplicate set of results can be printed out simply by holding down the Start button for 3 seconds. Results memory is cleared after duplicate print out or when power is switched off. Run number Pre programmed result format, calculation mode, volume and density. MEGGER KF875 vx.xx DD MM YY Run 1 HH:MM:SS Count xx g Result Format mg/kg (ppm) Calc Mode V / SG Volume ml Density Res: x.x mg/kg Software version & Date Start time of the titration Micro-gram counts of water Reminder that mg/kg is the same as ppm Run 2 Count Res: HH:MM:SS xx g x.x mg/kg Final result Run 3 Count Res: HH:MM:SS xx g x.x mg/kg Etc.. Page 16

17 KF-UNI PRINT OUT EXPLANATION The KF-UNI allows you to select whether you would like the printer either on or off. If you choose to have the printer on, you will receive a hard copy of the result obtained, together with the selected parameters for that particular titration every time a titration is performed. The KF-UNI automatically increments the next run number every time you press the start button. The run counter is reset to zero when power is switched off and back on again.. A duplicate set of results can be printed out simply by holding down the Start button for 3 seconds. Results memory is cleared after duplicate print out or when power is switched off. KF-UNI vx.xx Software version KF-UNI vx.xx DD MM YY & date DD MM YY Run 1 HH:MM:SS Run number, & Run 1 HH:MM:SS Count x.x g start time of the titiration Count x.x g Result Format ppm Result Format % Calc Mode V/SG Micro-gram counts Calc Mode W/w Volume x.xxxml of water Total wt x.xxxxg Density x,xxxx Tare wt x.xxxxg Selected result format Sample wt x.xxxxg Res: x.xx ppm Res: x.xxxx% Run 2 HH:MM:SS Selected calculation mode Count x.x g Run 2 HH:MM:SS Result Format ppm Count x.x g Calc Mode V/SG Calculation parameters Result Format % Volume x.xxxml Calc Mode W/w Density x,xxxx Final Result Total wt x.xxxxg Tare wt x.xxxxg Res: x.xx ppm Sample wt x.xxxxg Run 3 HH:MM:SS Res: x.xxxx% Count x.x g Result Format ppm Run 3 HH:MM:SS Calc Mode V/SG Count x.x g Volume x.xxxml Result Format % Density x,xxxx Calc Mode W/w Total wt x.xxxxg Res: x.xx ppm Tare wt x.xxxxg Sample wt x.xxxxg Res: x.xxxx% Etc. Etc. Page 17

18 CLEANING GLASSWARE IMPORTANT The platinum mesh and wires of the electrodes are fragile and can be easily bent or broken. Extreme care MUST be taken when disassembling, cleaning and reassembling the titration cell. The generator electrode is the most expensive part of the titrator. Under normal circumstances the titration cell can be used for a large number of samples before having to replenish the reagents. Once the reagents have been exhausted, or when the titration cell maximum volume has been reached, it should simply be necessary to: - 1. DISASSEMBLE titration cell 2. EMPTY the titration cell and generator electrode 3. RINSE all parts with methanol. 4. DRY all parts. 5. REASSEMBLE and RECHARGE with fresh reagents. If the cell is heavily contaminated then it may be necessary to clean it more thoroughly. For oil samples cleaning with chloroform or xylene is suggested, whilst for salt deposits a water wash may be required. The titration vessel can be cleaned with hot soapy water and a bottlebrush. After cleaning with suitable solvent, all glassware parts MUST be rinsed inside and out with methanol. They can then be dried with a warm air blower, such as a domestic hair dryer, placed in a low temperature oven at C, or left in a desiccator. After being fully dried, reassemble the titration cell and charge with fresh reagents. THE MORE THOROUGHLY THAT THE TITRATION CELL IS CLEANED AND DRIED THE FASTER THE INSTRUMENT WILL STABILISE READY FOR OPERATION AFTER RECHARGING REAGENTS. Under normal conditions, the titrator should be ready for operation within 5 10 minutes after reassembly, however it could take up to 20 minutes before to completely stabilise if the drying procedure has not been properly carried out. Page 18

19 TROUBLESHOOTING OVERTITRATION Detector senses too much iodine. Usually caused by old reagents or stirrer switched off. Check stirrer speed. Add 3-5 micro litres of water until detector bars activated. Allow to precondition. EXCESS DRIFT Indicates excess moisture ingress or condensation on cell walls. Switch OFF. Remove titration cell from clamp and gently swirl anode reagent around the cell walls. Reconnect and switch ON. Allow to Precondition. LONG PRECONDITIONING TIME Normally caused by glassware not being sufficiently dried before assembly. Re-clean glassware and electrodes, dry thoroughly and charge with fresh reagents. PROGRESSIVELY LOWER RESULTS FOR SAME SAMPLE The syringe is contaminated by moisture. Flush syringe and needle with sample several times before beginning new test. POOR REPEATABILITY FOR SAME SAMPLE The sample size is probably too small or moisture is contaminating the syringe. Increase sample size and flush syringe and needle several times before beginning new test. WARNING LETTERS ON PRINT OUT Warning letters will be printed after time of each analysis to signify the following:- U Uncalibrated, E Calibration expired, B Battery level low, A ACE system active Page 19