RISK BASED MAINTENANCE IMPLEMENTATION OF REGENERATION BOILER AT S.C. SOMES DEJ COMPANY

Transcription

1 RISK BASED MAINTENANCE IMPLEMENTATION OF REGENERATION BOILER AT S.C. SOMES DEJ COMPANY Phd.Eng.Daniela Dorina FULOP, Technical University, Cluj-Napoca, Romania Prof.Dr.Eng.Tiberiu Rusu, Technical University, Cluj-Napoca, Romania Prof.Dr.Eng.Dan Viorel, Technical University, Cluj-Napoca, ROMANIA Dr.Eng.Istvan FULOP, SC Mecsom SA Dej, Romania Abstract: In the paper the authors present some characteristics aspects regarding the implementation of Risk Based maintenance methodology in S.C.Somes Dej company, and their experience in this field. Keywords: maintenance, risk, regeneration boiler, risk assessment 1. Introduction The regeneration boiler is a technological installation of sodium salt waste from concentrate Black Lye, resulted from wood boiling process, resulting dissolving pulp. Boiling the sodium salt are resulting 50 tons vapor at the 40 bar pressure, which is used in the pulp and paper manufacturing process. According the technical directions from the ISCIR collection, the regeneration boiler is considered under pressure installation from A category, with maximum level risk. In the last years, at the pulp and paper S.C. Somes Dej Company, in the field of proactive maintenance, was successfully implemented risk based maintenance of installations with high level risk, such as the regeneration boiler. The implementation stages of risk based maintenance at the regeneration boiler are the following: - identified the component elements and functions of the equipments; - identified the probability that this component element functions not accomplished, and the possible damages of the equipment elements; - the analysis of probability and risk produce at the equipment elements of sodium salt boiler; - identified the causes of damage risk appearance and solutions to avoid the risk appearance; - establish maintenance process for equipments protection avoiding the failure risk appearance and planning the specific demands for avoiding risks. The risk based maintenance and continuous monitory of equipments stage are in close interdependence, which is the only counterwork solution of unexpected breakdowns appearance. The determination produced risk of damage and technical unexpected breakdowns are realized with the risk matrix depending on gravity and probability of damages appearance. The risk matrix is presented in figure

2 SECURITY AND HEALTH OF WORKERS THE PROCESS SAFETY ENVIRONMENT TECHNOLOGICAL ECONOMIC RISK PROBABILITY Huge risk Big risk Medium risk Low risk Fig. 1 The risk matrix The risk analysis of damages is based on equipment analyze and the following components of society integral management: - the security and health of workers; - the process safety of installations equipments; - the actual environment legislation; - the technological aspects; - the economic-financial aspects. 2. Improving the equipment s reliability applying the risk based maintenance at the regeneration boiler 2.1. The black lye pump of regeneration boiler The regeneration boiler is continuous feed with concentrated lye pump type ABS NB , driven by 22 kw/1500 rot/min electric engine. By analyzing the historic of the black lye pump in years, the total duration of the unexpected breakdowns was 280 hours and the main causes were identified, as presented below: - pump bearing deterioration: 48%; - the born of electric engine, because of the excess load, caused by the restriction of the pumping tubing, according with lye pump debit adjusted, which entered into the boiler: 28% ; 266

3 - non-sealing up problems caused by worm sealing destruction from shell and axle pump: 14%; - the breaking of pump hold down screw, through high vibrations caused by non-adequate base of the electric engine and pump in the base of structure: 7%; - other causes: lubricate missing, braking of the rubber blades from the couple, rotor disequilibrium: 3%. The black lye pump is equipped with NU 312ECP bearing, on the rotor side, and a tow 6313NR bearing on the electric engine side. The proposed solution for reducing the deterioration pump bearing was replacing the radial roller bearing 6313 NR with radial-axial roller bearings 7313 BECBP. Meantime we replaced the pump worm sealing with mechanical sealing, a new pump base was fixed in the structure by casting process, proceed from one fixing pump mounting shoe, alignment of the pump electrical engine and laser centre device was made, and the replacement of the manual valve from pump delivery with automatic valve. For protecting the electrical engine from additional load the solution is assembly one frequency converter which adjusts the electrical engine speed by the black lye capacity, barred from operator monitoring board. After functioning of pump from January 2008, the unexpected breakdown decrease with 88%. Fig. 2 Black lye pump 2.2. The cooling water feeding pump of the regeneration boiler The OLT 100 pump with 10 superposed rotors assure regeneration boiler feeding with cooling water, for cooling the tube from furnace boiler. The pump is driven by 250kW and 3000 rot/min electric engine. 267

4 By analyzing the historic of the boiler feeding pump with cooling water in years, the total duration of the unexpected breakdowns was 280 hours and the main causes were identified: - bearing deterioration because of the working with restriction pump delivery according with water debit adjusted: 41%; - electrical engine bearings deterioration because of lubricate missing; - pump rotors deterioration because of rotors solid particles vibration and penetration getting through. In January 2008 at the planed repairs was made the following modifications: - replacement of the valve from pump delivery with automatic valve; -the assembly of frequency converter which assure the electrical engine functionality at variable speed by the water capacity bared from board; - assembly automat lubrication system on the electric engine bearing; - assembly the sieve filter on pump admission for solid particles storage from the water; - rotor dynamic balance at 3000 rot/min speed in assembly state on pump axle. Until now this pump rotors balance was individual make without rotor-axle assembly balance. - was process from one fixing pump mounting shoe; - alignment of the pump electrical engine and laser center device; - replacement of admission location line and pump delivery, such as the attachment flange to be in parallel with pump attachment flange. After bring into service the regeneration boiler water feeding pump the unexpected breakdowns decrease with 78%. Fig. 3 Water feeding pump 2.3. Installations and electrical equipments inspection Installations and electrical equipments inspection at regeneration boiler is periodic inspect and carefully observed, because is a very complex equipment with high level risk. For optimal working of installations and electrical equipments, the periodic inspections are at exact time based on risk level, using the infrared thermograph process. 268

5 The measured dates are compared with precedent results, following the electrical equipments time evolution, interfering when the equipment state arrive at the critical level for safely functioning, security and health of workers. Fig. 4 Installations and equipments thermograph process 2.4. Vapor tube and pressure lye inspection The 40 bar and16 bar vapor tube, as well as the concentrated black lye are periodic inspected: measuring the tube thickness with the ultrasound equipment, welding inspections using gamers and incisive liquids, analyzing metallographic structure of tube material using non-destructive processes. Pressure tubes are authorized by ISCIR and periodic inspected by IT ISCIR Inspect, for the re-authorized at periods of 4 years. According as the level risk of the pressure tubes is periodic inspect tow times per year, during the planed maintenance. Table 1. No. Section code Pressure [bar] Thickness conform project Minimum admissible thickness Tube pressure sections Measured value Measured value Measured value ,8 13,8 13,8 13, ,8 10,8 10,4 10, ,8 10,1 9,9 9, ,6 7,6 7,5 7, ,6 5,9 5,7 5,6 The pressure tubes and installations inspection has the following stages: a) Detailed documentation realization regarding: - component elements of pressure installations; - breakdowns history and frequency; - repair description of breakdowns; 269

6 - dates regarding the technical state of installation and pressure tubes. b) Measurements and inspections realization at installations and pressure tubes c) Results interpretation and analysis obtained by the measurements d) Proposed solutions for eventually deteriorations at installations and pressure tubes The pressure tubes are divided by sections, marked, counted, inspected and observed in time, regarding the level risk. 3. Conclusions In order to assure a good maintenance of giant industrial equipments it is necessary to prepare one detailed program according the specific rules and experience in this field. ACKNOWLEDGMENT: This paper was supported by the project "Doctoral studies in engineering sciences for developing the knowledge based society-sidoc contract no. POSDRU/88/1.5/S/60078, project co-funded from European Social Fund through Sectorial Operational Program Human Resources Reference [1] Alexandru, I. Metode de evaluare a riscurilor, Universitatea Tehnică Gheorghe Asachi, Iaşi, 2007 [2] Barratt M., Proactive maintenance, SKF Reliabilitz System, San Diego, [3] Nagy I., Müszaki diagnosztika: Termográfia, Delta-3N Kft, [4] Wintle J.B., Kenzie B.W., Best practice for risk based inspection as a part of plant integrity management,twi and Royal&Sun Alliance Engineering, [3] Băbuţ, G. (2007). Metode de evaluare a riscurilor profesionale, Universitatea Petroşani, [4] Fulop, I., Gyenge, Cs., et al., Some practical aspects of Risk Based Maintenance implementation in paper industry, 9 th MTeM International Conference, Cluj-Napoca, [5] Tischuk, J.L., The application of risk based approaches to inspection planning, Tischuk Enterprises, 2002, Aberdeen. [6] ***, Guide to risk assessment requirements, HSE Books, 1996, ISBN