Analysis of Belt Conveyor Damage in Coal Feeder Units 1-2 Using the Fault Tree Analysis (FTA) Method at PT. PLN
(Persero) UPK Nagan Raya 2x110 MW
Robi Ardiansyaha,1,*, Rita Hartatib, 2
a,bTeuku Umar University, Alue Peunyareng streets, Ujong Tanoh Darat, 23681, Indonesia
1 [email protected]*; 2[email protected]
I. Introduction
In the Sumatra Island area, public consumption on the use of electrical energy every year increases, so the need for an electrical energy plant that aims to meet and serve the needs of electrical energy for the daily community. Steam Power Plant (PLTU) is a plant that relies on kinetic energy from steam to produce electrical energy. The main form of this type of power plant is a generator that is axle as a turbine driven by the kinetic power of hot/dry steam. Steam power plants use a wide range of fuels mainly coal and fuel oil as well as MFO (Marine Fuel Oil) for initial start- ups. MFO is a petroleum refining product, which is produced after residues and before asphalt.
Namely fuel oil which is not a product of distillation but the result of a type of residue that is black.
This type of oil has a high degree of viscosity compared to diesel oil.
In the Steam Power Plant (PLTU) uses several main components that make up the power plant such as steam boilers (boilers), turbines, condensers, generators and others. The steam boiler is one of the main components in the PLTU that functions to change the phase, namely from the liquid phase to the gas phase so as to produce dry steam which will be used to drive the steam turbine.
After the turbine moves, the rotation of the turbine will be used to drive the generator so that it can generate electricity. (Rosyid, 2017)
PT. PLN PLTU Nagan Raya is one of the generation units in the North Sumatra generation section is one of the pillars of electricity supply for the Aceh region and its surroundings. PT. PLN PLTU Nagan Raya has an area of ± 78.4 Ha and is located in Gampong Suak Puntong Village, Geulanggang Meurak Hamlet, Kuala Pesisir District, Jl. Meulaboh-Tapak Tuan km 8.5 Nagan Raya Regency, Aceh Province. At the Nagan Raya power plant, there are several main equipment, one of which is a coal feeder. Coal feeder is one of the main components of pltu that affects the production process.
ARTICLE INFO A B S T R A C T
Article history:
Accepted
This research focuses on conveyor belts on coal feeder units 1-2 located in PT. PLN PLTU Nagan Raya. Belt conveyor is a tool used to move coal from coal feeder to boiler or kiln, belts from conveyor belts are made of various types of materials such as plastic, rubber, leather, metal or other materials depending on the type and nature of the material transported. The purpose of this study is to find out the root cause of the problem of conveyor belt damage in coal feeder units 1-2. The method used is the FTA (Fault Tree Analysis) method and provides a proposed improvement with the 5W + 1H method (what, why, who, when, where and how). Data collection methods are carried out in two ways, namely library studies and elevation directly into the field through interviews with the company's management. The results showed that the better the quality of coal used, the lower the number of damages that occurs on the conveyor belt.
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All rights reserved.
Keywords:
Coal Feeder Belt Conveyor Fault Tree Analysis
PT. PLN (Persero) UPK Nagan Raya
Coal feeder is one of the most important systems in a steam power plant. This tool is used to supply coal fuel from coal bunkers to boilers. This tool is equipped with a Variable Frequency Drive (VFD) which works in accordance with its function, which is to regulate the speed of the belt conveyor drive motor so that the coal that supplies the boiler can be adjusted in quantity, so that the heat formation process in the boiler can run well and efficiently. (Mustaqim, 2020).
Coal feeder serves to regulate the amount of coal that enters the pulverize automatically and under control. Coal feeder output settings can be done in two ways, namely with a drive motor whose rotation can be adjusted (Variable Speed Motor) or a fixed rotation motor equipped with (Variable Speed Drive). (Anthony, 2020)
The coal feeder model used at PLTU Nagan Raya is STOCK EG2490 gravimetric feeder has electronic weighing and STOCK 196 NTR microprocessor controls.
Figure 1 View from the outside (Coal Feeder)
Figure 2 Coal feeder components
Stock of coal supplies in PT. PLN PLTU Nagan Raya uses Dome Shelter. The Dome Shelter used is a type of open Dome Shelter located in the coal yard. Coal at the Dome Shelter is channeled to units through several belt conveyors and transfer houses to coal feeders. The obstacle faced when using coal from the Dome Shelter is the quality of the coal that is not maintained moisture, which has an impact on the disruption of the coal distribution process to the combustion chamber or boiler due to damage to the belt conveyor on the coal feeder. Measurements can be taken from the time of unloading coal at the pier to when coal flows in the coal feeder to the boiler. Quality measurement is not only based on one parameter but must be carried out comprehensively. Failures in the boiler are not only affected by the operations that occur inside the boiler, but also by other supporting operations such as handling coal during the flow from the stock yard to enter the boiler. Based on reports of disturbances and performance of units 1-2 in PT. PLN PLTU Nagan Raya found that the
disturbances originating from the belt conveyor were disturbances in the belt conveyor which resulted in the inhibition of the optimal production system in the boiler and the belt damage often occurred in coal feeder units 1-2.
Conveyor Belt Recapitulation Table In 2021/2022
No Tool Units (U) Date Description
1 Coal feeder A U2 20 April 2022 Conveyor Belt on fire
2 Coal feeder A U1 11 April 2022 Tilt Conveyor Belt
3 Coal feeder A U1 11 April 2022 Tilt Conveyor Belt
4 Coal feeder D U2 21 April 2022 slip Belt Conveyor
5 Coal feeder A U2 22 January 2021 Belt Conveyor does not rotate 6 Coal feeder A U1 23 February 2022 Belt Conveyor does not rotate
7 Coal feeder D U1 04 April 2022 Tilt Conveyor Belt
8 Coal feeder C U2 04 April 2022 Torn Conveyor Belt
Source : PT PLN (Persero) UPK Nagan Raya
Damage to the belt conveyor caused operational activities at PT. PLN PLTU becomes inefficient and the production system is hampered. The purpose of this study is to determine the root cause of the problem of belt conveyor damage to coal feeder equipment at PT. PLN PLTU by using the FTA (Fault Tree Analysis) method and providing proposed improvements with the 5W + 1 H method (what, why, who, when, where and how) so that operational activities at PT. PLN PLTU. PLN PLTU becomes efficient and effective so that the operation of the coal feeder into the boiler runs smoothly according to standards.
According to Papadopoulos (2004) Fault Tree Analysis (FTA) is a deductive analysis method to identify the occurrence of damage to the system by describing alternative events in a structured diagram block. FTA is an analytical tool that translates graphically combinations of errors that cause system failures. This technique is useful in describing and assessing events in the system (Ferdiana, 2015).
An FTA is an analytical tool that makes a combination of definite errors or failures to a system.
This technique is useful for creating or describing and assessing events in a system. Thus the events can be normal or not, but the sequence and combination are very important. The FTA shows the possible causes of system failures from several events and various problems. The FTA was used for reliability, maintainability, and safety analysis which was used in 1961 in the Bell Laboratory to evaluate the minuteman launch control system to avoid accidental negligence. (Nikolaos. 2007).
According to the results of Kurniawan's research (2022) which analyzes the risk management of the PT. SWABINA GATRA uses the FTA Method, the cause of failure in the compressor system is caused by unstable electric current / short circuit, corrosion occurs in the main tank of air storage, looseness of bolts on the main tank, pressure regulation in the engine, damage to the Pressure Indicator, damage that occurs by several system circuits (Cooler Failure.Cooling Fan Failure.indicator.oil line), and damage that occurs by several series of systems (Cooler Failure.Cooling Fan Failure.indicator.oil pump). Based on the cut-set results obtained by the prevention stage, the nailed stage is the earth-leakage circuit breaker (ELCB) on the electrical panel of the compressor system, Carry out periodic pressure vessel calibration testing no later than once every 5 years, Work in accordance with SOPs or work instructions that have been set by the
Company, and conduct inspections or inspections periodically and make scheduling repairs and maintenance.
Therefore, it is necessary to conduct this study to find the root cause of the problem in order to reduce or even eliminate the variation in the causes of the problem so as to improve the production process. The method that can be done to find out the root cause of belt conveyor damage is to use Fault Tree Analysis (FTA). FTA is an analysis used to determine the root cause of potential damage to the belt conveyor that occurs in the system so that efforts can be made to reduce damage in the production process.
II. The Proposed Method
This research was conducted at PT. PLN PLTU Nagan Raya which is engaged in steam power generation. The object of this study focuses on the belt conveyor on the coal feeder in PT. PLN PLTU Nagan Raya. Data collection was carried out in two ways, namely literature studies and direct observation to the field through interviews with the company's management and several PT workers.
PLN PLTU for 4 (four) months, namely February 26 to May 26, 2022.
Figure 3 Flowchart of research stages
Fault Tree Analysis is an analytical tool that translates graphically the combinations of errors that cause system failures. This technique is useful in describing and assessing events in the system (Foster, 2004).
This Fault Tree Analysis method is effective in finding the core of the problem because it ensures that an unwanted event or the loss caused does not originate at one point of failure. Fault Tree Analysis identifies the relationship between causal factors and is displayed in the form of an error tree involving simple logic gates.
Start
Preliminary Research Identification Of Problems
Identificationi & Problem Formulation and Research Objectives
Field observation
Literature review
Data collection
Data processing
Analysis and Discussion
Conclusions and recommendations
Done Analysis With Fault
Tree Analysis (FTA) Method
Recommended Use (5W+1H)
System failure analysis using the FTA method is made using a failure tree or fault tree from a system that is analyzed first. Fault tree is a graphical model of failures in a system and their combinations resulting in undesired events. Failures that exist in the system can be due to failures in its components, failures in the humans who operate it (human errors) and events outside the system that can lead to the occurrence of undesired events.
The FTA graphic model contains several symbols, namely the event symbol, the gate symbol and the transfer symbol. Event symbols are symbols that contain events in the system that can be depicted in the form of circles, squares and others that have their respective meanings. Examples of event symbols are intermediate events and basic events. As for the gate symbol, it states the relationship of the input event that leads to the output event.
Logic gates describe the conditions that trigger failures, both single conditions and a set of various conditions. The construction of Fault Tree Analysis includes logic gates namely AND gates and OR gates. Each failure that occurs can be described into a form of failure analysis tree by transferring or moving the failure components into the form of symbols (Logic Transfer Components) and Fault Tree Analysis.
Table 1 Symbols in FTA (Fault Tree Analysis) Symbols Description
Top Event Logic Event OR Logic Event AND Transferred Event Undeveloped Event
Basic Event
The benefits of the Fault Tree Analysis method are as follows:
1. Can determine the causative factors that are most likely to cause failure.
2. Find the stage of the event that is most likely to be the cause of the failure.
3. Analyze possible sources of risk before failure arises.
4. Investigating a failure
According to Priyanta (2000: 113), there are 5 stages to conduct analysis with Fault Tree Analysis (FTA), namely as follows:
1. Defining the problems and limit conditions of a system under review 2. Fault Tree graphic model depiction
3. Looking for a minimum cut set of Fault Tree analysis 4. Conducting a qualitative analysis of the Fault Tree 5. Conducting quantitative analysis of the Fault Tree
The first step above aims to find the top event which is a definition of the failure of a system, determined first in determining an FTA graphics model, The second stage, creating a fault tree graphic model. The rules in creating an FTA are:
a) Describe fault events b) Evaluate fault events c) Complete all logical gates
The graphical model of the FTA contains several symbols, namely the event symbol, the gate symbol and the transfer symbol. Event symbols are symbols that contain events in the system that can be depicted in the form of circles, squares, and others that have their own meanings. Examples of event symbols are intermediate events and basic events. As for the gate symbol, it states the relationship of the input event that leads to the output event. The relationship starts from the top event to the most basic event. Examples of gate symbols are AND and OR.
Figure 4 Example of FTA (Fault Tree Analysis) Method
III. Results and Discussion
Belt conveyor is a tool used to assist in completing the work. This tool can be used to transport large quantities of units. Part of this tool consists of a belt-shaped machine that can withstand a wide range of transports of solid objects. These belts can be made of various types of materials. For example, from plastic, rubber, leather, metal, or other materials depending on the type and also the nature of the material transported using a conveyor belt. The belt conveyor on the coal feeder serves to move coal from the coal feeder to the boiler or kiln. Belt conveyors are used in various industries as transportation of various materials as a means of moving materials (Sochib, 2018).
Figure 5. Broken conveyor belt
In PT. PLN PLTU Nagan Raya has 2 generator units, each unit of which has 4 coal feeders. Belt conveyor specifications are as follows :
Table 2 Belt conveyor specifications
No Description
1 2 3 4 5 6 7
Coal feeder Belt Type V Center Guide Spesifikasi : Belt Width : 835 mm Belt Length : 28500 mm
Thickness : 10 mm, 4Ply EP 500 Top Cover : 3 mm
Bottom Cover : 2,5 mm Kapasitas : 45 t/h
Tensile Strenght : 400-500 kN/m
Figure 6. FTA (Fault Tree Analysis) Diagram
Damage to the Conveyor Belt in the
Coal Feeder
Coal Factor
Human Factor
Tool Factor
Coal capacity
Coal size Lack of Patrol Check
No Equipment Backup Duration
Usage Belt
Coal Quality Lack of
Preventive Maintenance
Operating Pattern
Continuously Operating Machine
Proposed improvements to reduce and even eliminate the risks that occur in coal feeder machines after FTA is carried out using the 5W +1H concept can be seen in Table 3 below:
Table 3 Recommendations for improvement with 5W+1H
What Why Who When Where How
Coal Factor (Material)
Excessive coal capacity makes the belt conveyor at any time can tilt, tear, not rotate, slip and burn the size of coal that is too large and the quality of coal that does not comply with the SOP
Manager 2021 Boiler
combustion chamber
Analyze the good quality of coal so that there is no damage to the belt conveyor.
Human Factors
Lack of regular Patrol checks on belt conveyors and coal feeder operating patterns
Supervisors and operators
2021 Coal feeder Carry out changes in routine maintenance scheduling at least per week, so that it is effective and efficient.
Tool Factor (machine)
machines that are
continuously operating, making the duration or life of the tool less and the lack of routine
maintenance
Supervisors and Manager
2021 Coal feeder Analyze the use of the machine so that it does not operate continuously and
simultaneously, so that the production process can run normally.
IV. Conclusion
Based on the evaluation and analysis of the belt conveyor on the coal feeder that has been carried out at PT. PLN PLTU can be concluded, namely the occurrence of belt conveyor damage to the coal feeder due to excessive coal capacity which causes the belt conveyor to tilt and tear. It can be seen from the analysis obtained, that the better the quality of coal used, the lower the number of damage
that occurs to the belt conveyor, this is estimated that the quality of coal is very influential in the production system.
Acknowledgment (HEADING 5)
The author would like to thank you ladies and gentlemen from Teuku Umar University and PT.
PLN PLTU Nagan Raya which is willing to provide an opportunity for writers to gain knowledge in terms of the world of work that I did not get at Teuku Umar University.
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