Detailed Product Description
Coal gasifier units crush raw coal in a vertical rotating shell, powered by a pinion drive coupled to the Prime mover. The abrasive coal particles and fly ash corrode the moving parts in due course, and offer more resistance to movement. In extreme cases the pinion is over loaded in one segment leading to eccentric wear of the tooth profile, and if not noticed may lead to non-contact with the bull gear rotating the vertical shell. During initial trials, the coal gasifier unit encountered frequent shut downs mainly because of seal failure, and over heating of the pinion shaft. The design of the rotating system was studied.
It was felt that an alternative Centering and Sealing Retrofit may provide the necessary safeguards for the pinion shaft. A on-line heat transfer of the pinion shaft, through rotor- cooling, by a coolant- passage through the neutral axis, will reduce the surface temperature to enable positioning of anti- friction bearings to take the axial and radial loads of the coal gasifier. Because of this provision, the drive became more energy-efficient, besides offering scope for introducing multi layer sealing at the driving end of the pinion shaft. Three types of contact-sealing were designed to suit the axial and radial space limitations. Proven high temperature contact-sealing materials like graph oil, was chosen in one seal, to provide a contacting mechanical seal for the system. Because of effective three- tier sealing at the pinion end, lubrication of anti friction bearings became easy. Through a combination of on line shaft-cooling, anti-friction bearings to share thrust and radial loads, three- tier sealing of the pinion shaft, the Retrofit for centering and sealing the pinion shaft of the coal gasifier, was finalized. The design was discussed with the operational staff of the CCDP unit, at BHEL, Tiruchi. They agreed to implement the design, and the retrofit was manufactured and installed in the gasifier unit of CCDP, BHEL Tiruchi.
It is proposed to gather feed back information on the performance of this retrofit for further course correction. The drive arrangement of the coal pulveriser of the gasifier drive is shown in figure 1, giving the location details of driving pinion, bush bearing and gland rope seal. Shaft centering and sealing arrangement before retrofitting is given in Figure2. Figure 3 gives the complete details of the modified centering and sealing arrangement provided for the pinion shaft of the coal gasifier unit, at CCDP, BHEL, Tiruchi