**Abstract**

 For a hydrodynamic journal bearing, it is essential to ensure that the proper dimensional accuracy is maintained during manufacture and also during operation so as to ensure the best performance. In the present work, an application of nuclear reactor feed pump bearing is considered which uses water as a lubricant. Four design procedures are applied to three bearings with different L/D ratio. The bearings and journals are manufactured and checked for the dimensional attributes. The purpose of assessing the geometry is to ensure the hydrodynamic lubrication during its operation. The dimensional checks carried out are: (1) external diameter of journal, (2) internal diameter of bearing, (3) surface roughness measurements, (4) roundness for both journal and bearing. A sample observation for diameters using the optical tool microscope with an accuracy of 1.0 μm for end plane and mid plane is presented. The surface roughness at different locations is measured using TALYSURF with an accuracy of 0.1 μm. The roundness is measured using TALYROND with an accuracy of up to 0.1 μm and is inspected for ovality. A dial comparator with an accuracy up to 1.0 μm is used at different planes axially and circumferentially. The comparison is made with the design specification and actual available dimensions.

**Keywords:** hydrodynamic bearing, water lubrication, metrology, measurement, dimensions

## **1. Introduction**

 In most applications such as pumps, turbines, machine tools and engines, the journal bearings use oil as a lubricant. However, if in applications where the water is a process fluid and if oil lubricated plain bearings are used, then the size of the machine increases due to usage of seals etc. If water i.e. the process fluid itself can be used as the lubricant then the size reduces to a great extent as seals etc. are not required. The advanced boiler reactor is an example of such an application. The feed pumps used here house the bearings which can be water lubricated as the process fluid is water only. The material of the bearing and journal need to be changed and the clearances in such applications are to be maintained accurately.

The materials of the journal and the bearing are required to be changed as corrosion needs to be avoided. Wang et al. [1] and Zhongqian et al. [2] discussed *Proceedings of the 4th International Conference on Innovations in Automation...* 

 the materials to be used and the effect of friction and wear characteristics on the polymer materials. Various researchers [3–8] have experimented with water lubricated bearings used in different applications. The effect of misalignment and other geometrical parameters are studied by Sharma et al. [9] and Elsharkawy [10]. It was emphasized that the performance of the bearing suffers if the dimensions are not maintained in the journal and bearing. Also, the effect of misalignment is discussed resulting in unexpected variation of various variables. The dimensional accuracy of the bearing asks for structured measurements with highly accurate instruments. In this paper, a water lubricated journal bearing of different sizes is considered for the nuclear reactor application. These bearings and journals are designed using (1) ESDU [11], (2) Reason and Narang [12], (3) Cameron [13] and (4) Raimondi and Boyd [14] methods. The methods are applied to three bearings with different L/D ratios. Based on the outcome of designs, the bearings are manufactured and checked for the dimensional attributes. The radial clearance is a critical parameter which directly has an effect of load carrying capacity. As the clearance increases, the capacity decreases. The clearance depends on the outer diameter of the journal and inner diameter of the bearing.
