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Author(s): | D. Houpt (362T), X375 (T. Cobb), X376(S.Frazier) |
Reviewer(s): | M. Hastedt |
Management Approval (Name, Title, Date): |
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Audience: | Users of the MAD analysis |
First Release: | 1 March 2009 |
Current Version: | X376 |
Revised: | X376 |
Domain: | Physics |
System: | Moisture and Density |
Contents
Topic | See page… |
Introduction | |
Apparatus, Reagents, & Materials | |
MADMax Software and Procedure | 7 |
Quality Assurance/Quality Control | 30 |
Health, Safety and Environment | 31 |
Technical Information | 32 |
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Introduction
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Method Overview
Core specimens for moisture and density (MAD) analysis are extruded from a section half for:
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- Wet mass
- Dry mass
- Wet volume
- Dry volume
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Method Theory
Phase relationships of mineral density, porosity, void ratio, and water content are basic sediment and rock properties that are found most accurately through mass and volume determinations. The mass or volume of the bulk (wet) material, the dried material, and the extracted water (assumed to be interstitial pore fluid) is corrected for the mass and volume of salt evaporated during the drying process. The mass and volume of the evaporated pore water salts are calculated for standard seawater salinity, seawater density at laboratory conditions, and an average seawater salt density.
Soils can be either 2-phase or 3-phase compositions (i.e., completely dry or partially saturated). For MAD measurements the analyst determines whether the sample contains a 2- or 3-phase system:
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MAD data provide a direct estimate of porosity and void ratio and the average density of constituent minerals. Porosity variations are controlled by consolidation and lithification, composition, alteration, and deformation of the sediments or rocks. MAD data can be used to calibrate high-resolution gamma ray attenuation (GRA) bulk density data, which are sampled at a much higher resolution than is possible with the MAD method. If mineral density can be defined with sufficient precision, GRA bulk density can be expressed as porosity.
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Selecting the Appropriate Analysis Sub-method
The user needs to decide which sub-method (A, B, C, or D) should be used for the MAD analysis. The choice depends primarily on the type of sample material to be measured. In addition, Sub-methods A and B are not recommended from an analytical quality point of view. Therefore, the choice is generally limited to Sub-methods C and D based on the following criteria:
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Analyses in the context of the Laboratory Information Management System (LIMS) are defined based on the data acquisition systems that provide sets of data. The MADMax software application captures the data from all three types of analysis. For the MAD group of analyses, these are as follows.
Caliper analyses (CALIPER)
Volume is calculated after measuring the sample's geometric dimensions using micrometer calipers.
Pycnometer analysis (PYC)
Sample volume is measured using a helium pycnometer.
MAD mass analysis (MAD_MASS)
Wet or dry mass is measured using the motion-compensating dual balance system.
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- "Wet" refers to the saturated (undrained) state of a sediment or rock sample
- "Dry" refers to the state after drying 24 hr at 105°C and holding in the desiccator 2–3 hr.
MAD analysis (MAD)
This set of calculations is applied as appropriate for each sub-method.
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Apparatus, Reagents, & Materials
- Dual balance system
- Hexapycnometer system
- Caliper
- Sample drying equipment
- Sampling tools and sampling containers
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Two Mettler-Toledo XS204 analytical balances compensate for ship's motion while weighing samples (see the Shipboard Analytical Balance User Guide for a detailed description of the mass determination system). In Figure 1 note that the left balance is the REFERENCE balance and the right balance is the UNKNOWN balance.
Anchor
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Six custom-configured Micromeretics AccuPyc 1330TC helium-displacement pycnometers can be run simultaneously (Figure 2). The six cells are mounted in a chassis to protect the electronics and to help provide temperature stability. Although the cells are centrally controlled, they can be started and stopped independently.
Figure 2. Helium-Displacement Hexapycnometer.
Helium Supply and Gauge
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The system depends on a reservoir of helium. Gauges at the gas bottle reservoir ensure no more than 90psi are delivered on the lines. A gauge at the hexapycnometer enables finer pressure control. Conventionally the local gauge is set so no more than 20psi are delivered to the pycnometer cell inlets
The cells are plumbed in
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parallel
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, which while it has no effect on the observation computations, does lead to observable fluctuations in the real-time pressure monitoring provided in software
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.
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Precision Caliper
The caliper (Figure 3) is used to measure the dimensions of cylinder and rectangular prism-shaped samples. The information is entered in the MADMax software, which calculates the volumes of the solid samples.
Figure 3. Precision Digital Caliper for measuring dimensions of certain samples.
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Thermo Scientific HERATHERM AP Oven and Desiccator Boxes
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The desiccator boxes hold samples after they have been dried in order to prevent reintroduction of water weight. The Drierite used on the JR is indicating. The color should be blue, indicating that the desiccant is good. If the desiccant is purple, it is close to being saturated, and once it becomes pink, it should be replaced. !worddav63d948250985687cfb06fc13eb41e2c9.png|height=409,width=480! Figure 4. Thermo Scientific HERATHERM AP 60 L oven, mounted underneath the bench. replaced.
Figure 4. Thermo Scientific HERATHERM AP 60 L oven, mounted underneath the bench. Back-vented,
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the
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oven
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does
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not
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warm
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the
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benchtop
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results
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from
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the
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analytical
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balances.
Figure 5. Exhaust tubing and the butterfly valve control (circled in green). The butterfly is completely closed; this is the correct position! Enough air flow goes around the valve blades to exhaust the oven. Do not open the butterfly valve. The desiccator boxes are to the left of the exhaust tubing.
Electronics and Control System
The software control system is a mixed language tool. MADMax is a C#/.NET application providing sample management, mass measurement, and methods computation. The C#/.NET component integrates with a LabVIEW component to manage volumetric measurement.
Masses are obtained via serial communication (RS232) with dual Mettler Toledo balances. The pycnometer control system supplies the control signals to manage helium flow for the duration of experiments and acquires the resulting !worddav5cef11ca5dda30b2529b6707e968509a.png|height=336,width=253! Figure 5. Exhaust tubing and the butterfly valve control (circled in green). The butterfly is completely closed; this is the correct position! Enough air flow goes around the valve blades to exhaust the oven. Do not open the butterfly valve. The desiccator boxes are to the left of the exhaust tubing. \\ Electronics and Control System \[proposed inclusion df\] The software control system is a mixed language tool. MADMax is a C#/.NET application providing sample management, mass measurement, and methods computation. The C#/.NET component integrates with a LabVIEW component to manage volumetric measurement. Masses are obtained via serial communication (RS232) with dual Mettler Toledo balances. The pycnometer control system supplies the control signals to manage helium flow for the duration of experiments and acquires the resulting data.
Sampling Tools and Sample Containers
Sampling Tools
- For soft materials, syringes/plugs are used to extract sediment samples with a nominal volume of 10 cm3 from the section halves.
- For hard materials, it is necessary to use drills and saws to cut cylindrical and rectangular prism-shaped rock samples; this is done in the core splitting room.
Sample Containers
Sample containers for the MAD analysis are either glass Wheaton vials or anodized aluminum cups (Figure 6). Each of them has a numeric identifier that is used to track the container and its sample throughout the process. Each container's mass and volume are recorded in the database and the MADMax program uses these values to subtract the container mass and volume from the sample values.
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- Wheaton type 800 vials are used for soft to indurated sediment samples; basically if it fits in the glass vial, use a glass vial. The glass vials have a density of 2.48-2.50 g/cm3 and their volume has been calculated from the mass determined on shore prior to shipment; their mass is approximately 21 grams and volume is about 8.3 cm3.
- Anodized aluminum sample cups are used for igneous or consolidated sedimentary samples. The mass of each of the cups was determined experimentally (approximately 14.8 g) and the volume of 5.842 cm3 was estimated from the dimensions and confirmed by experiment.
Figure 6. Sampling tool (left), aluminum cup, and Wheaton vial for MAD measurements.
MADMax Software and Procedure
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MADMax is a C# application that controls all of the measurements used in the MAD process. It can be found on the applications web page. Due to browser compatibility issues, MADMax must be installed from Microsoft Internet Explorer; any other browser is unlikely to install properly.
Login
Users must authenticate to the database in order to use the MADMax application. Upon starting the application, the user will see the login screen (Figure 7). If a new version of MADMax is available, the user will be prompted to install it.
Figure 7. MADMax login screen. Note that the application is aimed at the SHIP database.
If the user cannot login, please see a technician to ensure that the appropriate database authorization has been granted to the user account.
Main Screen
The main screen of the application (Figure 8) is the central command center for the entire process. Various actions on this screen initiate the balance measurements, the pycnometer measurements, the entry of caliper data, and the calculation of the derived MAD results.
Figure 8. MADMax main screen. Note the pycnometer display screens below the main application window.
It is recommended to click the "Display ON" button to turn the live pycnometer monitoring off unless troubleshooting a problem. The live display is memory-intensive and will slow down the functioning of the software.
Once a sample has been assigned to a MAD vial using the Sample Master program, it will be available to the MADMax application. Click the "Refresh Sample List" button to cause the sample to appear in the table.
IMPORTANT! Note that once the samples are in the MAD vials, they are tracked solely by their vial number. Care should be taken not to confuse the samples at any point in the process.
PRO TIP! Keep good logs!
MAD Method C is the most common one used on the JOIDES Resolution, so the MADMax application defaults to the "Method C" mode. The method indicator is a pull-down menu to switch between the four methods A, B, C, and D. Again, Method A and Method B are not recommended.
Regardless of method, the user can make up to five discrete types of measurements:
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Depending on the method selected, different actions will be available by double-clicking on the color-coded section of the main screen appropriate to the method. For example, to make a wet mass measurement on a sample, double-click on the left-hand yellow cell as shown in Figure 9. This action will invoke the balance control software portion of MADMax.
Figure 9. Activating a wet mass measurement.
Order of Actions by Method
For each method, the measurements should be done in a specific order, as given below. Note that the MADMax interface does not sort these columns by this order, but the columns can be rearranged to do so if the user wishes.
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In Method D's case, "wet volume" is better stated as "bulk volume," because the method is used only for samples with such high porosity that the water cannot be kept inside the sample (e.g., vesicular basalt or corals). Figure 10 shows all of the methods and the required measurements for each one.
Figure 10. All of the MADMax methods shown in cascade style.
In Figure 10, note that the colored columns for the measurements (yellow for balance, green for pycnometer, and blue for caliper) are slightly different for each method. The pink Methods Completed column is the same for each method and will be discussed later in the MAD Calculations section.
Wet Mass Determination by Analytical Balance
As shown in Figure 9, above, double-click on the "Mass Wet (g)" column in the field adjacent to the sample to be analyzed. This will invoke the Balance Measurement dialog box as shown in Figure 11. The container number and the full Label ID of the sample will be displayed to ensure the correct sample was selected. Select the number of measurements to average (at least 300 is recommended, more if the sea state is high) and click "Measure." The measurement speed of the XS-204 balances is 5 Hz, so 300 measurements will take 60 seconds.
Figure 11. Balance Measurement dialog box. A typical expedition Label ID would be formatted as follows: 360-U1473A-21R-2-W 10/12-20127.
The next screen will appear in a minimal size with some detail hidden. If the window is expanded as shown in Figure 12, additional information can been seen.
Taring the Balances
The first step to be taken is to tare the balances; measure the tare with empty pans. This step measures the differential tare between the two balances and is used to create a motion-compensated tare value. Do not try to tare the balances by using the Tare button on the keypad; the balances must be tared using the software. The window header will show the Text ID of the sample, what measurement is being done (e.g, "Mass Wet (g)"), and the container number.
Activate the tare function by clicking the "Tare" button on the upper left-hand corner of the screen (circled in green) and the tare will begin. The reference balance trace is green, the unknown balance trace is red, and the corrected mass (in this case the tare value) is a blue trace.
The balances should be tared relatively often as many things can affect the balance reading. The most common causes of these changes are:
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It is recommended that the user tare no less frequently than six hours, but certainly if the user suspects anything may have changed on either balance.
Figure 12. Taring the paired balances at 300 measurements.
Making the Measurement
Once the tare is complete, place the sample container on the unknown balance and close the sliding door. Place counterweights from the standard box as close to the mass of the unknown as possible and close the reference balance door. It may be useful to look at the balance LCD screens; the circle shows the rough load on the balance and masses can be roughly equalized by using them. It is important to get the masses within 5 grams. If the red and green traces are more than 5 grams apart after the measurement is started, then press the "Stop" button, add or subtract reference masses, and start the measurement over.
The "Reference Mass" field should be filled with the total mass of the reference masses before the measurement is started. Figure 13 shows the Reference Mass (circled in blue) and the traces of the two balances and their corrected result mass. Note that the reference mass balance began at a value of just under 19 grams and the unknown balance started close to 21 grams; the difference between them is ≤5 grams, so this measurement could be allowed to continue.
Figure 13. Mass measurement on a sample.
Once the analysis is completed (Figure 14), the mass determined by the measurement process will be displayed (in this case 22.120 grams). The Tare button is active again, but it not appropriate to use it at this time without removing the sample and reference masses. The user has three choices: accept the result and send it to the main screen display and the LIMS database by clicking the "Accept" button, reweigh the mass by clicking the "Weigh" button again, or completely cancel the measurement and discard all results by clicking the "Cancel" button.
The user should note that the instantaneous values of the balances varied by more than 20 grams in this example because of ship's heave, but the measured mass (22.110 grams of known masses) was accurate to within 0.010 grams.
Note: At the time of writing this manual, the Std Deviation field is recording the standard deviation of the unknown mass measurement (which obviously varies highly). An upcoming upgrade will switch this to the corrected mass value.
Figure 14. Completed measurement.
Once the "Accept" button is pressed, the user is returned to the main MADMax screen.
Reassigning Results
The result should be in the appropriate field, but in case the user double-clicked the wrong mass measurement, MADMax provides the capability to switch the mass measurement from "wet" to "dry" and vice-versa. As shown in Figure 15, right-click the mass cell and select the "Swap the result with Mass Dry (g)" option. If two masses are already present, this option will instead state "Swap Mass Dry (g) and Mass Wet (g)" to swap the mass measurements.
Figure 15. Right-click options for the mass measurement.
Once the user clicks the "Swap" options, a window will pop up to confirm the action as shown in Figure 16; the window for moving a result from wet-to-dry or dry-to-wet is very similar.
Figure 16. Reassign Result window. It is important to be able to do this as the drying step is irreversible and the wet mass cannot be repeated without taking a new sample.
Cancel Mass Result
The user can also cancel a result using the same right-click option, with a confirmation window as shown in Figure 17. A developer or technician can uncancel the result if this was done in error.
Figure 17. Cancel mass result pop-up window.
Review Results
If the user wishes, they can also look at the details of the mass results as shown in Figure 18. This is a summary of all of the parameters used to determine both the wet and dry masses with the parameters labeled by their database names.
Figure 18. Review wet mass results window.
The mass_dry and mass_wet components are the mass of the sample. The mass_dry_container and mass_wet_container components are the mass of the sample and the container together.
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