BS ISO 13939 pdf free download
BS ISO 13939-2019 pdf free download.Foil bearings — Guidelines for testing of the performance of foil journal bearings — Testing of load capacity, friction coefficient and lifetime.
This International Standard describes a method of comparing the performance test results of foil journal bearings, which are lubricated by air (gas) and supported by hydrodynamic force generated by the rotation of the rotating shaft. The test procedure proposed in this International Standard aims to predict and evaluate the static load capacity, friction coeffcient and lifetime of the foil journal bearing, and compare the results with those occurring under different test conditions, i.e. dimensions of a foil bearing, rotational speed of a shaft, pressure and humidity of surroundings and so on. The magnitude of the static load capacity can change according to the test setting, as the test conditions can be changed.
The test method described in this International Standard has the following application coverage:
a) the criterion of the static load capacity is the steady-state, i.e. it is applied in a limited operating condition with a uniform magnitude, load direction and rotational speed;
b) the evaluation procedure can be applied only if the foil journal bearing is under a uniform rotating inertia at an arbitrary rotational speed;
c) the dynamic load with a time-variant magnitude and direction is not taken into consideration;
d) for the purposes of this International Standard (these guidelines), the confguration of a typical foil journal bearing is presented in Annex A.
2 Symbols
For the purposes of this document, the following symbols apply.
3 Purpose of test The primary purpose of the test is to measure and evaluate the static load capacity, friction coeffcients and lifetime of the foil journal bearing. These are the primary performance metrics of the foil journal bearing as a mechanical element with a specifc dimension. These are closely related to the performance of the mechanical systems to which the bearings are applied. 4 Test conditions
4.1 General In order to compare the static load capacity, the test should be performed after the ambient pressure, temperature and humidity of the environment in which the bearing operates have reached a state of equilibrium. The bearing performance is obtained by measuring the bearing torque and the rotational speed of the shaft. In this case, the take-off speed, at which the shaft foats on the top foil without contact, may be observed. Bearing performance should be measured and compared at a rotational speed which is higher than the take-off speed. 4.2 Design of test facility The bearing test facility should be designed to control the relative position of the bearing in relation to the shaft. The bearing housing may be connected to a separate supporter, such as a spring or springs. Otherwise, a vibration-proof facility may be applied in order to prevent perturbation, which can have a severe effect on the test results. Also, excessive friction can have a severe effect on the test results due to misalignment of the bearing. 4
.3 Installation of sensors The equipment to measure the bearing torque and static load capacity of the foil journal bearings may be installed as shown in Figure 1. Using the measurement system clarifed in Figure 1, the bearing torque and applied load may be measured and calculated as explained in 4.4. As shown in Figure 2, the displacement sensors are installed at right angles to each other at both ends of the bearing housing. The displacement of the shaft centre may be observed by measuring and comparing the values arrived at. The rotational speed of the shaft may be obtained by applying a fast Fourier transform (FFT) algorithm to the measured displacement data or by the use of a rotational speed meter. A thermocouple is installed inside the bearing housing to measure the temperatures of surrounding air (gas). To measure the surface temperature of a top foil, the thermocouple should be welded to the top foil surface.BS ISO 13939 pdf download.
