Acceptance Test Procedure Research Articles

End item temperature test - an improved line replacement unit (LRU)-level screen

Details the evaluation and implementation of Honeywell's end item temperature test (EITT) process which functionally tests each production LRU at the customer-required temperature extremes. An aircraft system that formerly utilized 100% screening of electronic parts was selected for this process. A fixture was developed to allow the end item to be thoroughly tested while inside an environmental chamber. Using EITT, Honeywell replaced screening with EITT for specifically selected parts. The EITT adds thermal testing in addition to the normal environmental stress screening and acceptance test procedure steps. EITT also provides an effective tool for root cause failure analysis. The EITT-produced units (LRUs) were found to have 47% fewer integrated circuit (IC) removals than the previously built systems that were subjected to the 100% part screening. By reducing the part screening-caused damage, a 42% reduction was observed in mechanical damage such as bent leads. Since production implementation in 1998, only 2 field failures have been observed on the more than 300,000 EITT characterized ICs in the field.

Analysis of the status of X-ray diagnosis in Ghana.

In Ghana's healthcare system there are about 4200 people to each physician. The annual frequency of X-ray examinations during the period 1990 to 1996 ranges from six to 11 per thousand population. Chest radiograph examinations account for 46.5% of the annual frequency. The survey revealed that there are no established acceptance testing procedures for newly installed X-ray equipment. Neither institutional level performance checks following major repairs of faulty equipment, nor routine checks at regular intervals to ensure self-consistency of equipment performance are conducted. The results of the film retake analysis undertaken indicates a need for quality assurance programmes to be taken seriously to avert considerable cost and high patient doses. Radiographers and X-ray-technical officers who physically perform X-ray examinations should receive adequate training in the selection of procedures so as to ensure that doses to patients are as low as reasonably practicable in order to achieve the desired diagnostic objective.

Evaluation of electron-beam uniformity during commissioning of a linear accelerator.

Electron-beam profiles measured during acceptance testing and commissioning of a linear accelerator were analyzed according to manufacturer's specifications and more stringent AAPM TG-25 recommendations. The difference between specifications of the AAPM report and those experienced commercially is discussed. Although all the electron beams met the manufacturer's specifications, the uniformity parameters for some of them were outside the limits suggested by the AAPM report. Profiles acquired at depths larger than dmax were extremely valuable for evaluation and adjustment of the beams. The following suggestions for practical machine commissioning are made: Profiles taken deeper than at dmax are extremely useful indicators of the beam nonuniformity; acquisition of these profiles should be a part of the routine acceptance testing procedure; and beam uniformity should be evaluated against AAPM recommendations, and this should be included in the purchase specifications.

3. Microselectron HDR at SLMC, Philippines

In March, 1991, the first high dose rate remote afterloading brachytherapy machine in the PHILIPPINES was installed at St. Luke's Medical Center in Quezon City. This microselectron system (Ir-192) from Nucletron, Holland requires extensive acceptance testings specific to Nucletron hardware before it can be utilized for actual patient treatment, hence, a system of checks and calibration procedures are performed based on local conditions to verify its basic operational safety, check its mechanical accuracy, measure the dose produced, prepare for patient does calculations, and ensure radiation safety to both patients and workers. Locally fabricated devices are used in the acceptance test procedures. The machine is found to comply with all these requirements and a quality assurance program of routine tests is designed on a daily, weekly, monthly, quarterly, and yearly schedule.

Two stage reliability tests for new series systems

We want to do acceptance testing of newly minted series systems, all of whose component failure distributions are identical Gamma distributions with unknown shape and scale parameters. The criterion is the equilibrium mean time between failure (MTBF) of the systems. We derive a two stage acceptance testing procedure, and show that as the number of systems in the first stage test tends to infinity, the OC-Curve, derived from this two stage testing procedure, tends in probability to the nominal OC-Curve, derived for a single stage procedure assuming the shape parameter to be known. Also, we have performed a simulation study of small first stage test size properties that confirms our limiting results and gives some guidance on how to choose the number of systems for the first stage test.

Efficiency Calculation and Sensor Fault Detection in a Large Scale Plant

With the sale of large-scale chemical plants, the plant constructor undertakes to fulfil certain guaranteed values. For a nitric acid plant one of the essential guarantee figures is the acid yield. Consequently, a check of this value is a central item during the plant acceptance test procedure (test and guarantee runs). Until now stationary material balances have been used to determine the yield. However, the result may be falsified for two major reasons. First the measurements entering the calculation may exhibit systematic errors where the investigation is difficult. Another source of error is the time lag in the measurements caused by the plant dynamics. In the present report the material balances were determined with the plat dynamics taken into account, in addition the measurements made during the process were monitored. This was done on the one hand by utilizing the redundancy of the available measurements by so-called voters (which form weighted means) and on the other hand by the use of mathematical models (input-variable, output-variable and parameter observers). In order to design the observers mathematical models of the various sources of error (error hypotheses) were introduced and the size of the postulated error was estimated. In order to establish the dynamic model of the overall plant the process was shared into subsystems. Through correlation of the individual subsystems and utilization of hardware redundancy it was possible to recognize faulty measurements and obtain an improved material balance.

Present practices and future plans for MIL‐STD‐781

AbstractMIL‐STD‐781 specifies reliability acceptance test procedures based on both fixed‐length tests and probability ratio sequential tests. The assumption underlying MIL‐STD‐781 is a constant mean time between failures (MTBF) and typical practice applies MIL‐STD‐781 to electrical, electronic, and mechanical equipment. This article discusses some of the difficulties that have prompted the C and D revisions of MIL‐STD‐781. In addition, it discusses the relationship of MIL‐STD‐781 with MIL‐STD‐1635(EC) which deals with reliability growth testing. The article concludes with a discussion of needed research in reliability growth testing, in support of MIL‐STD‐781, and in the area of stress and its impact of MTBF.

A Simulation Study of Maneuverability of Vehicle

In the field of vehicle handling research many and various investigations have been devoted to evaluate driver-vehicle system performance. However, no generally accepted test procedures have been evolved from the past research efforts. This paper proposes a method for evaluating objective and fundamental maneuverability of the vehicle by a simulation study of lane-change maneuvers. As the most important handling qualities of the vehicle in cruising on the roads, there could be considered three aspects; (1) keeping the vehicle with ease on the centerline of the road in fast straight running, (2) conducting lane-changing maneuvers quickly and safely and (3) making a rapid 90 degree turn smoothly at the corners. No doubt the first of them is mainly concerned with the directional stability and both the second and the third are closely related to the controllability of the vehicle. In this paper, the second aspect of vehicle handling, that is, a double lane-change maneuver is selected to evaluate the maneuverability of a motor vehicle.

Acceptance Testing of Concrete: Various Plans

A method of evaluating various acceptance test plans for concrete is presented. This method uses operating characteristic curves and a definition of what is good concrete and what is an acceptable level of consumer’s risk. The results presented in the paper are intended to illustrate the behaviour of various acceptance testing procedures with a standard deviation of 500 psi (3.5 MPa). What is good or bad is not a part of the test but a criteria that all parties involved with concrete production have agreed to use. Once this agreement is reached, the operating characteristics for various testing plans should be evaluated to determine which tests provide the best balance between consumer and producer risk.

A Simplified ASME Acceptance Test Procedure for Steam Turbines

A simplified procedure is proposed, which reduces the cost of steam turbine acceptance testing without significantly affecting testing accuracy. This simplified acceptance test procedure is applicable to both fossil and nuclear power plants. It involves only the measurements required to calculate heat rate and required to compare the test value to guarantee. The object is to simplify the acceptance test and to reduce its cost to the extent that a no-tolerance acceptance test is conducted on every new, large steam turine-generator unit. While maintaining the traditional high level of testing accuracy, this method also facilitates periodic testing. The results of such tests can provide the information required for scheduling plant outages for maintenance or repair thus ensuring efficient operation of the steam turbine/feedwater cycle throughout the life of the turbine.