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Analytical Instrumentation
A More Reliable Way of Recording and Archiving Jet Fuel Oxidation Test Results
Larry Spino, PAC 8824 Fallbrook Dr. Houston, TX USA Tel: 1.800.444.TEST • Email:
pacsales@paclp.com • Web:
www.paclp.com
Te jet fuel thermal oxidation test is a procedure used to evaluate the thermal stability of a fuel to ensure it can withstand the maximum temperatures that jet fuel experiences during operation and does no damage to the critical metal parts it contacts. Tis is accomplished by assessing the fuel's resistance to undergoing any chemical changes with increased thermal oxidative stress, until a thermal breakpoint temperature is reached. In practice, the fuel is pumped isocratically past a precision machined aluminum heater tube, located in the heater tube section on a jet fuel thermal oxidation instrument, at a fixed temperature and duration (See Image 1). Deposits may adhere to the heater tube; the operator then visually compares these deposits to a reference colour scale to decide if the sample passed or failed.
Standards Compliance
Due to the sensitive nature of this test, jet fuel thermal oxidation testing has always been strictly regulated. Originally, ASTM D1660 (Method of Test for Thermal Stability of Aviation Turbine Fuels) was the standard written for this test. It required a large amount of sample (5 gallons) and took around 7 hours to run including set up and tear down. This test standard was formally withdrawn in 1992.
The current jet fuel thermal oxidation test consumes less than a litre of sample and takes 150 minutes (2.5 hours) in length to complete. It is described in jet fuel reference standards DEFSTAN 91-91, ASTM D1655, and ASTM D7566. These references list the acceptable limits for temperature, visual rating, and pressure differential across the test filter. These references also list the approved standards used to determine the quality of aviation turbine fuels, which are ASTM D3241 and IP323. In these tests, the specification and use of the instruments and heater tubes are clearly defined.
Record and Archive Concerns
The jet fuel thermal oxidation standards describe how the test should be run in terms of fuel flow and duration. However, they impart little information about the best practice to record or archive the heater tube deposit results. The general laboratory practice is to keep a paper copy of the test results, with some labs using LIMS to record final deposit data. In some cases, the heater tube is
Reducing Data Matching Errors
To reduce data matching errors, companies must be able to store the results data and the heater tube together. The ideal solution for this would be to include a recording device on the heater tube that would electronically store results so that the heater tube and test data are inseparable (See Image 2). One such recording device is the radio frequency identification device (RFID). It is a relatively simple technology to use and is commonly used across all industries. Its data is secure while being easy to program and read. Since the jet fuel thermal oxidation standards have recently included the use of electronic data storage onto heater tubes, the RFID could be used for this solution and would still be in compliance.
With the RFID, although time may degrade the deposit on the heater tube, the data on the IHT will always stay with the heater tube for quick and easy access which is advantageous for audits. This saves laboratories time and money due to fewer errors and less time finding and correcting those errors. It also provides several other significant benefits:
• Improves traceability
• Increases analysis integrity by minimising risk of data transcription errors
• Ensures smoother audits of jet thermal oxidation test results
• Promotes laboratory process and procedure discipline
• Aids in preventing the reuse of heater tubes which is a requirement of the standard methods
• Helps ensure the correct heater tube is used based on individual company requirements
• Saves storage space since only the heater tube needs to be kept
Image 1: Typical Assembly of Heater Tube Section on Jet Fuel Thermal Oxidation Instrument
To address these issues faced by end users, PAC developed the Alcor Intelligent Heater Tube™
Image 2: Heater Tube with RFID Assembly
retained with a printed copy. On average, labs run 10 tests per week so this can lead to storage problems. It is also not efficient to store heater tubes taped to full size or even folded print outs. Labs that retain their used heater tubes need a simpler process.
The standards have long mentioned that the heater tube may be physically identified with a unique serial number for traceability. Recently, digitally recording data directly on the heater tube was approved for use. Radio-frequency identification (RFID) equipment has been shown to be an efficient way to digitally record test and deposit data. The standards do not require that the heater tubes be kept or discarded, only that they be used once. Therefore, laboratories have developed their own procedures for keeping or discarding heater tubes. When audited by quality standard accreditation organisations, which can be based on regularly scheduled events, spot audits, or associated with specific projects or events, companies may be required to match reported data along with the heater tube. It is standard for laboratories to keep heater tubes and data separate, which can be a real issue for laboratories that are subjected to frequent audits. Audits can turn up mismatched data due to poor record keeping or simple transcription errors, which can result in audit findings or perhaps more severe consequences.
APRIL / MAY 2013 •
WWW.PETRO-ONLINE.COM
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