Basics of Condition Based Maintenance (CBM)-Definition, Types & Examples.

Condition Based Maintenance (CBM) at SgTPP-Case Studies by Mechwix Technology.

CBM

Preludes: I am Md Kamaluddin, author of this article presenting some of the practical aspects acquiring as a maintenance planning engineer in West Bengal Power Development Corporation (WBPDCL) at it's Sagardighi Thermal Power Plant (SgTPP). This facility was put into commercial operation since 2007 with 2*300 MW Thermal Power generating units. Later from 2016 this station was commissioned to additional 2*500MW units. Again this station was added another 660MW super critical thermal power unit till date under construction. Likely it will to be commissioned in 2025. Thus this power station will be equipped with 2260 MW capacity soon. There are lot of equipments and machineries within and outside of this plant premises. Operation of these machineries at maximum availability is very vital for plant performance. The goal of generating power at most economic and competitive way is key factors for survival in the power industries. So we are continuously improving every point of Operation & Maintenance (O&M) aspects. Very starting of the installation of this facility, there was no such distinct feature for co-ordination of operation & maintenance activities. The Equipments ran until breakdown. To eradicate the inconveniences, management had decided to establish the Maintenance Planning cell. As a planning engineering we enforce the implementation of  the condition based maintenance(CBM) or predictive maintenance along with preventive maintenance. Thus we are savings crores of money and achieving to generate power in competitive price. Also we success to achieve national level PLF based ranking in the financial year 2022-23 in Indian Power Industry.   

Aspects of CBM: Industrialization was started in the seventeenth century. Mechanized system was incorporated starting from small handloom to power loom. Wheels were running till it breaks into pieces. Then machine put into service after a catastrophic recovery.  This is uncertain and non predictive circumstances. This incurs a huge loss of materials resulting in productivity loss. It is not only impacted on the operating cost but also in reliabilities to downstream customer to whom a concern is committed to timely delivery of products or service. Thus breakdown failures impact brand values of any entity. Researchers were developing many more approaches to reach out this bad patch in the industries. It was eliminated through routine and preventive maintenance. But this practice incurs cost of unnecessary replacement of spares. These rejected materials may work more. The researchers emphasize on the Condition Based Maintenance (CBM). It is a dynamic approach to monitor the health of equipments vide different parameters related to mechanical conditions such as bearing temperature, vibration, cooling water follow, debris contamination, acidity and moisture ingression. CBM helps to determine whether the equipments are in bad or good condition. Thus the condition based maintenance approach can insist the requirement of maintenance before it undergoes to catastrophic failure.

Advantages & Challenges of CBM: The implementation of CBM offers several advantages along with some of drawbacks: These are depicted below as follows:

1) It reduces Maintenance cost by avoiding unnecessary maintenance. Organization can save on labor and spare parts. In roller Mill installed at stage-I, SgTPP equipped with vibration monitoring probe installed since commissioning. Due to these vibration monitor we were informed the catastrophic failure due to foreign materials ingression in mill inside. Thus we avoided a huge failure in 2010 while rollers run out.

2) It extends the equipment life though proper & timely maintenance, repair & replace wear parts. Through CBM we insist management to timely shut down of load bearing equipments to avoid premature failure of equipments like Air Preheater, Boiler feed pumps, etc.

3) Early detection of potential failures enhance the safety of operation and maintenance activities. Thus we achieve the target of zero accidents in the preceding Financial Year.

4) CBM minimizes unplanned downtime, subsequently it leads to more consistent production and service delivery. Uninterrupted power generation is being maintained through out the year. This makes WBPDCL to be nation wide (India) rank holder as highest PLF achiever in FY 2022-23.

Challenges & Considerations: Though there are several benefits for CBM, there are several challenges that organization must consider the following aspects:

Initial Investment: Presently most of the organizations allot cost to setup of CBM system including investment in sensors, monitoring equipments and data analysis tools.

Skill Requirement: We have four Technicians whom were trained to interpret CBM accurately. Annually they are sent for advance training in this field.

Data Management: Large volume of data generated by CBM is required to be effectively managed and analyzed. So sufficient soft and hard storage space are required. Consequently anti virus and anti malware are to be updated.

   

Types of CBMS We introduced : At SgTPP, different types of CBM are incorporated and maintained such as Temperature, Thermography, Vibration analysis, Oil Analysis, Wear Debris Analysis(WDA), Dissolve Gas Analysis (DGA). Some Non destructive tests are performed to detect the internal strength of  some critical equipments like Turbine, Generator, Transformer, Fans and Pumps shafts, impeller, Motors and Generators, etc. 

1) Oil Analysis: Lubrication oil is used to minimize friction losses between moving & non moving parts of the machineries. The lubrication oil is an important source of information of earlier failure of the equipments. Lubrication oil Analysis (LOA) can give the ten times earlier warning of the machine health. Lubrication oil analysis is based on property analysis (fluid viscosity, additive level and specific gravity), fluid contamination analysis (include moisture, metallic particles, coolant, air,) and wear debris analysis. Fluid properties analysis is performed to evaluate the the condition of oil in engine and machineries weather it is deteriorated itself. WDA is used to analyse the contamination, wear particles in the lubrication. Particle filtering methods, spectrographic oil analysis, analytical ferrography and radioactive tracer methods, etc. are used to study the chemical composition of oil. In this context we are placing a typical example of oil analysis at SgTPP. 

Oil Analysis.

2) Temperature Monitoring: At Sagardighi thermal power plant there are several RTDs installed to monitor the real time temperatures of bearings and friction parts. Besides collecting the online data, some off-line datas are also collected for analyzing the temperature mapping of the high energy drain valves downstream. It helps us to determine the erosion of the valves sheet.

3) Vibration Analysis & Monitoring: There are several probes installed to monitor vibration of different rotating equipments and machineries. These instruments help to detect misalignment, unbalances, mechanical looseness, bending in the shaft and turbulences. At SgTPP, SKF make CMSS6155W Optical Phase Reference Sensor is used for condition monitoring. It is basically a portable accessory to the microlog data collector. It is used to monitor speed and phase angle of any operating machine by triggering off or reflective tape attached on the shaft surface.

4) Thermal Imaging or Thermography: Infrared thermography is one of the most common indicators of the structural and functional health of the equipment and components. IRT is the process of using thermal images to capture infrared radiation emitted by any abnormal heat pattern. It can detect possible fault, defects, damaged material in a  system. It can detect heat anomalies in electrical systems, mechanical components and building envelops.

5) Non-Destructive Testing: Besides continuous monitoring through IR Thermography, Oil analysis and vibration analysis, there are several approaches of non destructive testing like Ultrasonic testing of tubes and pipe thickness. Radiography of welding joints are performed to distinguish the healthiness of welding joints. Eddy current testing is done to ensure the thickness of condenser tube thickness. MPI of the Turbine blades is performed to ensure the continuity of blades and shafts of turbine and fans. Fluorescent test is performed to detect condenser tube leakage d cracks. 

Case Study of CBM Practices: A practical example of CBM can be seen in the monitoring of Boiler Feed Cycle Monitoring system in thermal power plant as SgTPP. By using sensors to track temperature, pressure, water flow, storage tank levels, maintenance teams can identify the inefficiencies or potential failures before they escalate into costly repair.

Case Study-1

Vibration Analysis in Seal Air Fan:

Seal Air Fan (SAF) is an integral part of Boiler Accessories. It is used for supplying air for sealing mill gearbox. Seal air prevents to dust ingression in Mill gear box. On 28.06.2024 it is observed that this fan is running with high vibration shown in the figure. The velocity components shows defects in bearing segment.  

SAF 1

Accordingly bearing is checked and found micro cracks in inner race. Bearing is replaced and vibration was taken. It was vibration profile is within normal as shown in figure.

SAF-2

By continuously monitoring of the vibration, technician or operational engineer can detect the abnormal pattern. It may indicate wear or misalignment. It prompts for timely maintenance.

Conclusion:

    Condition Based Maintenance represents a significant leap forward in management, offering a more intelligent, efficient, and cost effective approach to asset care. By leveraging advance technology and data analysis CBM enables organization to make informed decisions that enhance the reliability.

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Author: Er. Md Kamaluddin

Mentors & Team Members: 

1) Nitai Chandra Saha. DGM (Engineering). 2) Er. Manoj Debnath, (HOD & Sr. Manager). 3)Soumik Sarkar (Sr. Manager. 4) Anup Mondal (Sr. Manager). 5) Trina Mukherjee (Sr. Manager). 6) Pinaki Sen (Manager) 7) Mr. Ashim Bhattacharyya, Vibration Analyst /SgTPP/WBPDCL.

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