IN-SITU RECONDITIONING OF RAW MILL FAN SHAFT

摘要

Jaipraksh Associates Ltd. is a well diversified infrastructural conglomerate in India having business interests in: - Engineering & Construction, Cement, Power, Real Estate, Hospitality, Express Ways, Sports & Education. Jaipraksh Associates Ltd is the 3rd largest cement producer in the country having total 29 MTPA capacity spread at various location in India and produces a special blend of Portland Pozzolana Cement (PPC) & Portland Slag Cement (PSC) under brand name Jaypee Cement. Jaiprakash Associates Ltd. acquired sick Dalla Cement Factory from U.P. Cement Corporation Ltd. in the year 2006 and implemented a comprehensive rehabilitation & modernization program to revive the Plant which had been out of operation for last 10 years. The existing Kiln K#4 1200 TPD capacity with 4 stage suspension Preheater, Ball Mills upgraded to 1700 TPD with installation of RPS-10 Roll Press for Raw material grinding and Installed a new 4500 TPD brown field clinkerization unit K#5 with 6 stage Preheater, Calciner & Vertical Mills, new generation Polytrack Cooler supplied by M/s Polysius Germany / ThyssenKrupp Industries Ltd. India In new clinkerization K#5 Unit II for Raw material grinding M/s Polysius Germany (O.E.M.) has supplied Vertical Roller Mill RM-54/27/460 & Raw Mill Cyclone Fan of the following specifications. Raw Mill � VRM-RM-54/27/460 VRM Size - RMR 54 / 27 Separator Size - RMR 470 Mill Capacity - 330 TPH @ 15% R ON 90 Micron OR @ 2.5% R ON 212 Micron Sieve Raw Mill Cyclone Fan Fan type - Backward curved Make - Venti-Oelde Model - DHRVS 45-1800/K Volume handled (cu.m/hr) - 7,40,000 Static pressure (mbar) - -105 Temperature oC - 110 Fan static efficiency (%) - 81.46 Fan total efficiency (%) - 81.46 Theoretical power at shaft (kw) - 2785.29 Motor rating (kW / rpm) - 3300/600-1000 Speed of fan (rpm) - 984 Critical speed (rpm) - 1485 GD2 value (Provisional) (kgm2) 28000 Both the clinkerization Units K4-1500 TPD & K5-4500 TPD have been operating more than rated capacity at production level of 1700 TPD & 4800 TPD on sustained basis. The fan had been operating at Rated capacity & R.P.M with vibration level of 1.4 mm/sec DE & 1.35 mm/sec NDE bearings. In the month of June 2012 fan tripped two times due to High Vibration during operation. The fan was stopped and detailed visual inspection of Impeller shaft, bearings, coupling & Drive motor has been carried out, also Checked the dynamic balancing of impeller & no abnormality was observed. Being a major critical process fan & to keep the plant running, operated the fan at lower RPM 911 to 931. Maintaining the vibration level 3mm/sec well below the permissible tripping limits 7.1 mm/sec recommended by (O.E.M.) for the safety of the equipment. During Major shutdown detailed inspection of both the bearings was carried out & found the DE bearing (22244 W-33, CC/C-3) inner race loose on the fan shaft due to inadequate interference fit between shaft & bearing. After detailed discussions, it was decided to adopt In-situ cold repair methodology with metal Putty & to fit new bearing. Loctite superior Metal Putty-40025 applied on the worn out surface uniformly after preparing the worn out shaft area with fine dot punch to get knurling type rough surface on the shaft for better interference fit, new bearing heated up to 100�c & pushed on the shaft. Spillover Metal Putty in sides cleaned & Left for 4 Hrs curing to get proper interference fit between bearing inner race & shaft. After reassembly of the components, HT motor & alignment, dynamic balancing of impeller the fan was put back into operation and observed fan vibration at DE & NDE bearings in the range 2.5 � 4.00mm/sec. at 931RPM. Finally In-situ repair was organized during next major shutdown in February 2013. For this preheating shafts and stress reliving by use of equipments as well as grinding of critical shafts in stationary condition of DG and Set Crank Shaft was carried out. In Situ-Reconditioning of Raw Mill cyclone fan shaft adopting build up heat treatment machining, grinding with special grinding machine on stationary shaft achieved minimum vibration level 1.20mm/sec. & 1.15mm/sec.