ASTM D7097 Standard Test Method for Determination of Moderately High Temperature Piston Deposits by Thermo-Oxidation Engine Oil Simulation Test - TEOST MHT
13. Procedure - Startup
13.1 Using the manufacturer's Instruction Manual, check the program's PID settings (see 8.1) and the temperature profile to ensure that no settings have been changed.

13.2 While the depositor rod is still at room temperature, start the pump at maximum flow rate on the pump control and run until the test oil flows out of the pump outlet tubing and into the sample flask with no bubbles.

13.3 At this point, temporarily turn the pump setting to zero flow rate and return the pump outlet tubing into the upper end cap.

13.4 Snap the special sample flask mantis clip shown in Fig. 2 around the neck of the sample flask as shown in Fig. 6.
13.4.1 Place the air flow restrictor over the opening of the sample flask, and then insert this assembly over the oil outlet of the lower end-cap and simultaneously snap the open jaws of the mantis clip around the juncture of the mantle and the lower end-cap.

13.4.2 If not already aligned, rotate the sample flask so that the flask sidearm is directly below the flask (see Fig. 6.)

13.5 Place the volatiles collector vial in position on the volatiles delivery tube from the mantle and carefully snap on the volatiles vial clip (see Fig. 4).

13.6 Make sure that the volatiles collector vial does not block air flow from the mantle's volatiles delivery tube and that the volatiles delivery tube outlet is well within the vial (see Fig. 4).

13.7 If desired, turn on the recording device for continuously recording depositor rod temperature indicated by the controlling thermocouple.

13.8 Install the operator poly(methylmethacrylate) shield for safety and test consistency.

NOTE 16 - The shield not only protects the operator but also allows a constant temperature within the rod area by keeping passing room or hood airflow to a minimum.

13.9 Turn on the heater switch.

13.10 Start the program on the temperature controller but leave the pump speed at zero.

13.11 When the depositor rod temperature controller shows rod temperature between 200 and 250°C, increase the pump speed from zero to the value determined during calibration for sample delivery of 0.25 +/- 0.02 g/min (see 9.2). Make sure that oil circulation is functioning with no leaks and the oil is flowing down the depositor rod.

13.12 After any initial temperature overshoot and stabilization of the temperature, temperature control shall remain at 285 +/- 2°C. If, after an hour, the temperature is still not stable, abort the test and contact the manufacturer.

13.13 Run the test for the required 24 h +/- 10 min test time.

NOTE 17 - If desired, a timer can be placed between the instruments power cord and the wall socket to shut off the instrument when the test is completed.

13.14 The instrument will indicate that the test is finished by either showing the word off on the temperature controller or, in older models, by the temperature dropping to room temperature (see respective Instrument Manuals).

14. Preparation and Disassembly for Weighing
14.1 Preparation:
14.1.1 Prepare the three test tubes for extracting any remaining oil from the depositor rod by filling the test tubes with hydrocarbon solvent, enough to cover at least 3/4 of the rod. If desired, one test tube may be used and simply rinsed into the material to be filtered.

14.1.2 Bring out the depositor rod weighing boat from 11.3.9 but keep it under a cover to prevent contamination from airborne particles.

14.2 Disassembly:
14.2.1 Remove the volatiles collector vial from the depositor rod assembly and cap the vial.

14.2.2 Disconnect the air supply line from the upper end-cap.

14.2.3 Carefully remove the temperature control thermocouple from the depositor rod to avoid bending it.

14.2.4 Remove the oil feed tube inlet nut and withdraw the oil feed tube from the upper end-cap.

14.2.5 Place the beveled tip of the oil feed tube into a 10-mL recovered end-of-test oil vial held securely in a clamp or vial stand.

14.2.6 Use the pump to drain the remaining end-of-test oil in the flask, pump, and lines into the clean residual oil vial by turning the pump on at maximum speed until no more end-of-test oil is recoverable (approximately 5 min). If there is a desire to measure the mass of this material, allow at least 10 to 15 min for the remnant oil to flow off the rod into the flask.

NOTE 18 - Save these oils for further information and analysis if desired.

14.2.7 When as much of the end-of-test oil is removed as possible, remove the tip of the pump outlet tubing from the end-of-test vial, cap the vial, and turn off the pump.

NOTE 19 - If the operator has elected to determine the mantle mass, mass of volatiles, or recovered end-of-test oil mass collected during the test, record the final mass of the mantle to the nearest 0.0001 g and the mass of the vials to the nearest 0.01 g or less. Subtract the initial masses of the mantle and vials from the final masses and report the resulting values.

14.2.8 After pumping out all recoverable residual oil, place the tip of the pump outlet tubing onto a vacuum source that is connected to a vacuum flask. After cleaning the sample flask, reconnect to the pump inlet tubing and turn on the vacuum and fill the sample flask with a hydrocarbon solvent and use the pump at maximum speed to flush the hydrocarbon solvent through the pump.

14.2.9 Repeat the flush by again filling the sample flask with a hydrocarbon solvent and continue to vacuum. If the hydrocarbon solvent is colored at the end of this second flush, repeat the flushing until the hydrocarbon solvent is clear.

14.2.10 When clear hydrocarbon solvent emerges from the pump, continue to vacuum for 10 min.
14.2.10.1 This flush is done to avoid a sludge buildup in the pump. If the oil residue is allowed to sit in the pump longer than several hours, perform an initial flush with about 10 mL of fresh SAE 50 engine oil in the same manner prior to the hydrocarbon solvent flush and then follow by the hydrocarbon solvent flush as needed.

14.2.10.2 For more effective cleaning, periodically remove the metal pump inlet/outlet tubing connectors from the pump and place in a sonic bath containing varnish remover for 20 min.

14.2.11 Remove the sample flask, mantis clip, and tubing to the pump. Thoroughly rinse the sample flask and magnetic stir bar with the hydrocarbon solvent. Remove the bar, and dry both the flask and bar for reuse.

14.2.12 If needed, place the sample flask in a plastic beaker for protection against breakage. Cover the flask with varnish remover and let soak until the flask washes clean with warm water.

14.3 Disassembly of Depositor Rod Casing Assembly:
14.3.1 Loosen the hex screws on the busbars and carefully remove the depositor rod casing assembly.

NOTE 20 - In lifting the depositor rod casing assembly off the bottom over-temperature thermocouple, exercise care not to bend the thermocouple.

14.3.2 Place the entire depositor rod assembly in a clean and dry rinse container such as a 600-mL beaker or other suitable container.

14.3.3 Hereinafter, use a plastic squeeze bottle containing the hydrocarbon solvent for carefully cleaning the assembly and its components so as to not lose any deposits except into the rinse container.

14.3.4 Refer to the manual for further cleaning details.

14.3.5 Carefully place the mantle and lower end-cap in the container for later washing and drying. Do not use a sonic bath to clean the glassware.

14.3.6 Hold the end of the depositor rod with the thumb and index finger and gently rinse the inside and outside of the rod with the hydrocarbon solvent, while allowing the residue to fall into the container.

14.4 Washing, Drying, and Weighing the Depositor Rod:
14.4.1 Place the depositor rod immediately into the first of the three test tubes previously filled with hydrocarbon solvent (see 14.1.1) for 10 min progressively in each of the three test tubes to soak the rod deposits and extract any residual oil. If the deposit is heavy, longer soak times may be required. Again, one test tube may be used as long as it is rinsed into the deposit rinse container.

14.4.2 Thoroughly rinse the depositor rod with hydrocarbon solvent over the chosen container. Use a vacuum hose to dry the inside bore of the rod thoroughly but do not bring the vacuum hose near the deposit area of the depositor rod. Do not use any air source to dry the rod because this will blow some of the deposits off the rod and spoil the test.

14.4.3 Immediately set the depositor rod onto the pre-weighed weighing boat (see Fig. 3 and 14.1.2) and allow about 10 min for the hydrocarbon solvent residue to evaporate.

14.4.4 After placing the depositor rod in the weighing boat, do not remove the rod from the weighing boat until the weighing process is completed.

NOTE 21 - Deposits may fall off the rod during the weighing period but will be caught by the boat.

14.4.5 Weigh the rod and boat to the nearest 0.0001 g. Reweigh after 10 min to determine if all of the hydrocarbon solvent has evaporated. If not, continue to redetermine the mass of the rod and boat every 10 min until it reaches constant mass of +/- 0.0001 g. Subtract the empty mass of the boat (determined in 11.3.1) from this value and record the difference as the final mass of the rod.

NOTE 22 - If fluctuations are seen on the balance, touch some part of the boat containing the depositor rod momentarily to a grounding mat, grounding wire, or equivalent technique to discharge the static.

14.5 Collecting the Mass of Depositor Rod Deposits into the Container of Hydrocarbon Solvent:
14.5.1 Pick up the lower end-cap from the container and rinse it with hydrocarbon solvent into the container and set the lower end-cap aside.

14.5.2 Pick up and rinse the glass mantle with hydrocarbon solvent into the container and set it aside.

14.5.3 Add and rinse the contents of the three test tubes from 14.4.1 into the container. Rinse thoroughly to ensure that no depositor rod deposits are lost.

14.6 Filtering the Contents of the Wash Hydrocarbon Container:
14.6.1 Select a filter cartridge, determine, and record its mass on a balance to the nearest 0.0001 g.

NOTE 23 - Do not permit the hydrocarbon solvent to remain in contact with the filter cartridge any longer than needed for flushing the hydrocarbon solvent through the filter since the plastic of the filter cartridge may adsorb some mass from the hydrocarbon solvent if the two are left in contact for an extended time of 20 min or more.

14.6.2 Connect the filter cartridge to the filter system shown in Fig. 8, turn on the vacuum source and slowly pour the contents of the container into the glass filter funnel and draw these contents into and through the filter cartridge where the solid contents are trapped and the liquid contents pass into the vacuum flask connected to the vacuum source. To ensure that no stray deposits are lost, rinse the inside of the container with hydrocarbon solvent into the funnel and through the filter cartridge.
14.6.2.1 If larger deposits from the depositor rod are lodged in the neck of the funnel above the filter, use a wire rod (see 6.1.3.6) extended down from the top of the funnel to break up and dislodge any deposits that may collect. Wash off any deposits adhering to the wire into the filter. To avoid puncturing the layered filters, do not push the wire rod into the filter cartridge.

NOTE 24 - Deposits often adhere to the funnel outlet because of the influence of static electrification and the wire rod also helps to dissipate this charge and permit the particles to travel on to the filter when washed.

14.6.3 Rinse the sides of the funnel with about 10 mL of hydrocarbon solvent, and then add about 90 mL of the hydrocarbon solvent through the filter in three 30 mL aliquots, to allow the hydrocarbon solvent to percolate slowly through the filter and solubilize any oil remaining in the deposit.

NOTE 25 - On rare occasions the filter may become clogged because of both numerous and very fine deposits. Under these conditions, a second or possibly even third pre-weighed filter cartridge shall be used.

14.6.4 When filtering is completed, allow the filter cartridge(s) to dry under vacuum for 30 min and weigh. Continue drying until the cartridge(s) come to constant mass as indicated by agreement of two weighings taken 10 min apart to within +/- 0.0001 g.

NOTE 26 - If the drying time becomes lengthy, draw the pre-warmed air by vacuum through the filter to obtain complete drying. This avoids the use of air circulating ovens, which prolong the time of bringing the filter cartridge to constant mass because of the added time to bring the filter back to ambient temperature.

14.7 Cleaning the Reusable Components:

NOTE 27 - Since this is a 24-h test, depending on the operator's interest in quickly starting another test, it is helpful to have two complete sets of casing components (upper and lower end-caps and mantle) so that following tests can be initiated quickly.

14.7.1 Place end-caps in a glass or plastic container and place the mantle in a separate plastic container for protection against breakage. Cover both contents with varnish cleaning material that does not etch glass or adversely affect metal, and let soak until the various components wash clean with warm water.

14.7.2 Soak all depositor rod-casing components in acetone to take up water and other hydrocarbon insoluble materials. Remove the O-rings and discard.

NOTE 28 - After soaking in acetone for about 1 h, the end-cap O-rings will swell and usually dislodge themselves from the end-caps.

14.7.3 Rinse the depositor rod casing components with hydrocarbon solvent and store for next use.
14.7.3.1 Inspect the mantle for any chips or cracks. If the mass of the cleaned mantle is less than its mass obtained at the initiation of the test, this is an indication that some chipping has occurred. Replace the mantle if chipping or breakage does not permit air flow control (see 11.8.4).

15. Test of Instrument Functionality
15.1 After setting up the TEOST MHT instrument for analysis according to Sections 10 through 12, first test the instrument and supporting equipments to determine if it will produce acceptable results.
15.1.1 Chose one or more of the three certified reference fluids available (see 7.4) and run such oil or oils through the test sequence of Sections 13 and 14.

15.1.2 Determine the mass of combined depositor rod and filter deposits (see Section 16) and compare this mass to the acceptable range for the chosen certified reference fluid(s).

15.1.3 If the value(s) obtained is within the acceptable calibration range, proceed to test oils.

15.1.4 If the value obtained is not within the acceptable calibration range, recheck and verify control thermocouple depth, air flow rate, and oil circulation rate. If these are acceptable, contact the manufacturer. If not, reset these conditions and rerun the reference fluid(s).

16. Calculations
16.1 Calculate the following to the nearest 0.0001 g by subtracting the pretest mass of each item from the post-test mass:
16.1.1 Depositor rod deposits equals final rod mass (see 14.4.5) minus initial rod mass (see 11.3.8).

16.1.2 Filter deposits equals final filter mass (see 14.6.4) minus clean filter mass (see 14.6.1).

NOTE 29 - If the mass of mantle deposits, volatiles and recovered oil are desired, calculate by subtracting the initial mass from the final mass of the mantle and vials, respectively. Report mantle deposits in milligrams. However, volatile material and recovered end-of-test oil are normally reported in grams.

16.2 Convert results in 16.1.1 and 16.1.2 to milligrams (g x 1000 = mg).