ASTM D524 method for Ramsbottom carbon residue of petroleum products
6. Apparatus
6.1 Glass Coking Bulb, of heat-resistant glass conforming to the dimensions and tolerances shown in Fig. 1. Prior to use, check the diameter of the capillary to see that the opening is greater than 1.5 and not more than 2.0 mm. Pass a 1.5-mm diameter drill rod through the capillary and into the bulb; attempt to pass a 2.0-mm diameter drill rod through the capillary. Reject bulbs that do not permit the insertion of the smaller rod and those whose capillaries are larger than the larger rod.
6.2 Control Bulb, stainless steel, containing a thermocouple and conforming to the dimensions and tolerances shown in Fig. 2, for use in determining compliance of furnace characteristics with the performance requirements (Section 7). The control bulb shall be provided with a dull finish, as specified in Fig. 2, and must not be polished thereafter. A polished bulb has different heating characteristics from one with a dull finish. A suitable thermocouple pyrometer for observing true temperature within +/- 1°C is also required.
6.3 Sample Charging Syringe, 5 or 10-mL glass hypodermic (Note 5), fitted with a No. 17 needle (1.5 mm in outside diameter) or No. 0 serum needle (1.45 to 1.47 mm in outside diameter) for transfer of the sample to the glass coking bulb.
NOTE 5 - A syringe having a needle that fits on the ground-glass tip of the syringe is not recommended, as it may be blown off when pressure is applied to the syringe plunger. The Luer-Lok type syringes are more satisfactory, as the needle locks on the bottom of the syringe barrel, and cannot be blown off by pressure.
6.4 Metal Coking Furnace of solid metal, having coking bulb wells 25.45 +/- 0.1 mm in internal diameter and 76 mm deep to the center of the well bottom, with suitable arrangements for heating to a uniform temperature of 550°C. The bottom of the well shall be hemispherical to accommodate the bottom of the glass coking bulb. Do not cast or otherwise form the furnace with unnecessary voids which will impede heat transfer. If a molten metal furnace is used, provide it with a suitable number of bulb wells, the internal dimensions of which correspond to the internal dimensions of holes in the solid metal furnace. The bulb wells shall be immersed in the molten metal to leave not more than 3 mm of the bulb well exposed above the molten metal at operating temperatures.
NOTE 6 - Ramsbottom coke furnaces now in use can have dimensional differences from those given in 6.4; however, it is essential that new furnaces obtained after the adoption of this test method conform to the requirements outlined in 6.4. A description of one type of furnace which has been found to be satisfactory is given in Appendix X1.
6.5 Temperature-Measuring Devices - A removable iron-constantan thermocouple with a sensitive pyrometer, or other suitable temperature-indicating device, located centrally near the bottom portion of the furnace and arranged to measure the temperature of the furnace so that the performance tests specified in Section 7 can be obtained. It is desirable to protect the temperature-indicating device with a quartz or thin metal sheath when a molten bath is used.
NOTE 7 - It is good practice to calibrate the thermocouple or other temperature-measuring device against a standard thermocouple or reference standards about once a week, when the furnace is in constant use, the actual frequency depending on experience.
7. Checking Performance of Apparatus
7.1 Periodically check the performance of the furnace and temperature-measuring devices as described in 7.1.1-7.1.3 to make certain that as used they conform to the requirements of the method. Consider the furnace as having standard performance, and use it with any degree of loading, when the operating requirements described for each coking bulb well are met, while the bath is fully loaded as well as singly loaded. Use only a furnace that has successfully passed the performance or control tests given in this section.
7.1.1 Thermocouple - At least once every 50 h of use of the control bulb, calibrate the thermocouple in the control bulb against a standard thermocouple.
NOTE 8 - In use at the high temperature of the test, iron-constantan thermocouples oxidize and their calibration curves change.
7.1.2 Fully Loaded Furnace - When the furnace temperature is within a previously chosen 2°C temperature range (which range is to be used thereafter with that particular furnace for both standardization and routine operation) and within the general range 550 +/- 5°C, insert the control bulb in one well and, within 15 s, insert in each of the other wells a glass coking bulb containing 4 +/- 0.1 g of a viscous neutral petroleum lubricating oil with a viscosity within the SAE 30 range or 60 to 100 mm2/s (cSt) at 40°C. With a suitably accurate potentiometer or millivoltmeter (sensitive to 1°C or less), observe the temperature rise in the control bulb at 1-min intervals for 20 min. If the temperature in the control bulb reaches 547°C in not less than 4 and not more than 6 min from the instant of its insertion in the furnace, and remains within the range 550 +/- 3°C for the remaining portion of the 20-min test, consider that particular coking bulb well suitable for use as a standard performance well when the furnace is used fully loaded. Inspect each well in similar fashion with the furnace fully loaded each time.
7.1.3 Singly Loaded Furnace - When the furnace temperature is within a previously chosen 2°C temperature range (which range is to be used thereafter with that particular furnace for both standardization and routine operation) and within the general range 550 +/- 5°C, insert the control bulb in one well, with the remaining wells unoccupied. With a suitably accurate potentiometer or millivoltmeter (sensitive to 1°C or less), observe the temperature rise in the control bulb at 1-min intervals for 20 min. If the temperature in the control bulb reaches 547°C in not less than 4 and not more than 6 min from the instant of its insertion in the furnace, and remains within the range 550 +/- 3°C for the remaining portion of the 20-min test, consider that particular coking bulb well suitable for use as a standard performance well when only a single test is made. Inspect each well in similar fashion with the furnace singly loaded each time.
NOTE 9 - It is possible that not all of the wells in old furnaces will meet the requirements when fully loaded and singly loaded; and, when this is the case, inspect each well for any degree of furnace loading which may be used. For example, when not more than three wells of a six-well furnace can be used at any one time, the three wells to be used should be chosen from the performance data obtained with fully loaded and singly loaded furnaces. Then each of the three wells should be inspected for triple loading, two of the wells for double loading, and one for single loading. Use the wells tested and no others in applying the test procedure.
NOTE 10 - In sampling oils containing sediment (for example, used oils), it is important to make the transfer of sample in the shortest possible time to avoid segregation of the sediment. Samples containing sediment which settles quickly after stirring can be placed in the coking bulbs more expeditiously by using an arrangement such as that shown in Fig. 3. This sampling device consists of a three-way 2-mm stopcock to which have been fused two lengths of capillary tubing (1.5 mm in inside diameter). Connect the third leg of the stopcock by means of pressure tubing to a vacuum line. Secure the glass coking bulb to the short arm of capillary tubing by a 25-mm length of rubber hose, taking care that the capillary of the glass bulb is butted up against the capillary tubing. Immerse the long end of the capillary tubing in the sample. After evacuating the coking bulb, manipulate the stopcock to cause the stirred sample to flow freely into the bulb through the two lengths of capillary tubing. It is necessary to use tubing with the same size capillary as that in the neck of the coking bulb to prevent accumulation of any sediment during transfer.
8. Sampling
8.1 For sampling techniques see Practice D4057 or Practice D4177.
