ASTM D6923 Standard Test Method for Evaluation of Engine Oils in a High Speed, Single-Cylinder Diesel Engine - Caterpillar 1R Test Procedure
10. Calibration and Standardization
10.1 Test Cell Instrumentation - Calibrate all facility readout instrumentation used for the test immediately prior to stand calibration. Instrumentation calibration following a failed or invalid test is at the discretion of the test laboratory, or as directed by the TMC. Refer to Annex A2 for calibration tolerances and allowable system time constants.

10.2 Instrumentation Standards - Calibrate all temperature, pressure, flow and speed measurement standards on a yearly basis. The calibration of all standards shall be traceable to a national bureau of standards. Maintain all calibration records for a minimum of two years.

10.3 Coolant Flow - Calibrate the coolant flow rate as follows: (1) calibrate the differential pressure transducer as outlined in 10.1 and 10.2, and (2) replace the Barco venturi every two years or calibrate the Barco venturi to a standard. Use the following relationships as conversion factors from the differential pressure across the Barco venturi to determine L/min:
0.75 kPa = 24.3 L/min,
1.76 kPa = 37.8 L/min, and
7 kPa = 75.7 L/min, or use the equation:
L/min = √ΔP 28.848 - 0.5927
where ΔP is measured in kilopascals.

10.4 Fuel Injectors - The fuel injectors are calibrated during the manufacturing process. These fuel injectors can not be re-calibrated in the usual manner and require special test equipment to ensure proper flow, timing response, and spray patterns. Therefore, replace the fuel injector at the start of a calibration test or calibration series. If the fuel injector is replaced on a calibrated stand, re-calibration is not required.

10.5 Air Flow - Install the Sierra Model 780 airflow meter to measure intake airflow. See 6.2.1.5 for calibration information specific to this test method. Measure the intake airflow during the break-in of every calibration test. Record the last value recorded during Step 5 of the break-in as shown in Annex A10.

10.6 Intake Air Barrel - Prior to each stand calibration test, inspect the intake air barrel for rust or debris. This may be done through either of the pipe flanges using a bore scope or some other optical means.

10.7 Fuel Filter - Change the fuel filter before every calibration test.

10.8 Oil Scale Flow Rates - Verify the oil scale flow rates before the start of every calibration test using the procedure listed in Annex A6.

10.9 Test Stand Calibration - Use a blind calibration oil from the TMC to calibrate the engine stand. A stand calibration test is required every twelve months. The calibration period begins on the end date of the acceptable calibration test. A test stand is considered calibrated when the test results are within the acceptability limits as published by TMC in the Lubricant Test Monitoring System (LTMS) manual and the test is operationally valid. The TMC may request stand checks on calibration tests that fail to meet acceptability limits. If the calibration test is operationally valid, send the piston to another calibrated laboratory for a referee rating. In order for the test to be considered valid, report the test data to the TMC within seven days of end-of-test (EOT). The TMC issues the testing laboratory a control chart analysis for each calibration test (see Fig.A7.2). The test stand is not considered calibrated if the calibration test was invalid or uninterpretable. Start any non-reference test prior to the expiration of the calibration period.
10.9.1 Re-calibration Requirements - The calibration status is void if one or more of the following occur:
10.9.1.1 The engine crankcase requires replacing,

10.9.1.2 The engine crankshaft requires replacing or regrinding,

10.9.1.3 The crankshaft is removed for any other purpose besides bearing replacement, and

10.9.1.4 The cylinder head or jug suffer a failure for any reason during the calibration period and a cylinder head/jug not meeting the requirements under 9.7 is used. All other engine components can be replaced at the discretion of the laboratory.

10.9.2 Guidelines for Adjustments to Calibration Periods - Reference oil test frequency may be adjusted for the following reasons:
10.9.2.1 Procedural Deviations - On occasions when a laboratory becomes aware of a significant deviation from the test method, such as might arise during an in-house review or a TMC inspection, the laboratory and the TMC shall agree on an appropriate course of action to remedy the deviation. This action may include the shortening of existing reference oil calibration periods.

10.9.2.2 Parts and Fuel Shortages - Under special circumstances, such as industry-wide parts or fuel shortages, the surveillance panel may direct the TMC to extend the time intervals between reference oil tests. These extensions shall not exceed one regular calibration period.

10.9.2.3 Reference Oil Test Data Flow - To ensure continuous severity and precision monitoring, calibration tests are conducted periodically throughout the year. There may be occasions when laboratories conduct a large portion of calibration tests in a short period of time. This could result in an unacceptably large time frame when very few calibration tests are conducted. The TMC can shorten or extend calibration periods as needed to provide a consistent flow of reference oil test data. Adjustments to calibration periods are made such that laboratories incur no net loss (or gain) in calibration status.

10.9.2.4 Special Use of the Reference Oil Calibration System - The surveillance panel has the option to use the reference oil system to evaluate changes that have potential impact on test severity and precision. This option is only taken when a program of donated tests is not feasible. The surveillance panel and the TMC shall develop a detailed plan for the test program. This plan requires all reference oil tests in the program to be completed as close to the same time as possible, so that no laboratory/stand calibration is left in an excessively long pending status. In order to maintain the integrity of the reference oil monitoring system, each reference oil test is conducted so as to be interpretable for stand calibration. To facilitate the required test scheduling, the surveillance panel may direct the TMC to lengthen and shorten reference oil calibration periods within laboratories such that the laboratories incur no net loss (or gain) in calibration status.

10.9.3 Donated Reference Oil Test Programs - The Surveillance Panel is charged with maintaining effective reference oil test severity and precision monitoring. During times of new parts introductions, new or re-blended reference oil additions, and procedural revisions, it may be necessary to evaluate the possible effects on severity and precision levels. The surveillance panel may choose to conduct a program of donated reference oil tests in those laboratories participating in the monitoring system, in order to quantify the effect of a particular change on severity and precision. Typically, the surveillance panel requests its panel members to volunteer enough reference oil test results to create a robust data set. Broad laboratory participation is needed to provide a representative sampling of the industry. To ensure the quality of the data obtained, donated tests are conducted on calibrated test stands. The surveillance panel shall arrange an appropriate number of donated tests and ensure completion of the test program in a timely manner.

10.10 Test Run Numbering - Number each test to identify the test stand number and the test run number. Number all runs sequentially. Append repeat calibration runs with a letter that is also sequential (that is, number the first re-run of test 45 as 46A, the second as 47B, and so forth). Maintain the letter suffix sequencing for each calibration test until the calibration has been accepted. Increment the run number for any test start.

10.11 Humidity Calibration Requirements - The accuracy of the laboratory's primary humidity measurement system shall be within +/- 0.6 g of the humidity measuring chilled mirror dew point hygrometer or equivalent.
10.11.1 Calibrate the primary laboratory humidity measurement system within 48 h before the start of each stand calibration test or during the stand calibration test using a chilled mirror dew point hygrometer or equivalent with an accuracy of at least +/- 0.55 °C at dew point of 24 °C.

10.11.2 The calibration consists of a series of paired comparison measurements between the primary system and the chilled mirror dew point hygrometer or equivalent. The comparison period lasts from 20 min to 2 h with measurements taken at 1 min to 6 min intervals, for a total of 20 paired measurements. The measurement interval should be appropriate for the time constant of the humidity measuring instruments.

10.11.3 Ensure that the flow rate is within the equipment manufacturer's specification.

10.11.4 Take all measurements made with the dew point hygrometer or equivalent at atmospheric pressure and correct them to standard pressure conditions (101.12 kPa). Compute the difference between each pair of measurements and calculate the mean and standard deviation of the differences.

10.11.5 The absolute value of the mean difference shall not exceed 0.6 g and the standard deviation shall be less than or equal to 0.3 g. The primary humidity measurement system is deemed calibrated only if both of these requirements are met. Ifeither of these requirements is not met, investigate the cause, make repairs, and recalibrate. Maintain the calibration data for a minimum of two years.

10.12 Calibration of Piston Deposit Raters - Train each piston deposit rater by the TMC Rating Task Force and each rater shall maintain rating expertise by attending at least one of the rating seminars annually. Each rater shall rate a minimum of six diesel pistons. If this schedule is not suitable to a particular rater or test laboratory, make alternative arrangements by contacting the TMC as soon as possible to have the rater calibrated.
10.12.1 Failure to attend a rating seminar results in the loss of calibration status for that rater.