Thermo Valve Air Compressor Maintenance and Repair Using the Overall Equipment Effectiveness (OEE) Method in Maintenance

: Production activities carried out every day can interfere with the effectiveness of the machine, one of which is the compressor, so that sometimes problems in the field are still often encountered, such as the piston drive motor not rotating, the compressor does not turn on and off automatically, corrosion (rust), melted capacitors, and many more. things that can happen beyond the operator's control. Due to these constraints, the authors decided to find out more and made direct observations at PT. INKA Multi Solusi Service, as well as studying good and proper machine maintenance so that the company's productivity does not experience a significant decrease. The research was conducted by direct observation and direct interviews with the maintenance department to find out the steps that are usually taken in solving problems. To determine the value of machine effectiveness based on the measurement of three main ratios, namely: availability, performance efficiency, and rate of quality, is carried out using the Overall Equipment Effectiveness (OEE) method. The conclusion that can be drawn from this study is that maintenance on the Ingersoll Rand MM160 type screw air compressor is carried out to maintain the condition of the compressor in a ready state for use in measuring the level of machine effectiveness using the Overall Equipment Effectiveness (OEE) method at PT. IMSS, starting from May – July 2022, where the highest percentage in May 2022 is 94% and the lowest in June 2022 with a percentage is 90%.


PT. INKA Multi Solusi Service is a subsidiary of PT. INKA (Persero) provides "Total Solution
Provider" services in the construction and trade of railway components/spare parts and land transportation products. As a manufacturing company committed to producing the best and highest quality products . Efforts to realize high-quality products and company productivity require periodic machine maintenance, especially repairs to the compressor to extend the life of each component so that it can function properly. The screw compressor is a type of positive displacement compressor classified as a rotary compressor. This compressor compresses (adds energy) the air or gas by rotating simultaneously due to the rotor teeth or gear rotating in the opposite direction and interrelated (Baniasadi et al., 2021;Lim et al., 2020). One of the rotors has a convex groove (male rotor) and the other has a concave groove (female rotor) that interlocks each other, the two rotors are supported at both ends by bearings, one end of which gives an axial bear to resist the axial force arising from the difference in air pressure acting on the two ends of the rotor. It is this synchronous and counter clockwise rotation that moves and exerts pressure on the air along the rotor groove from the inlet to the outlet PT. INKA, compressors are included in production support machines that supply air to pneumatic hoses and production machines have work systems using pneumatics. There are two types of compressors at PT. INKA is called piston compressors and screw compressors, but the existing piston compressors are no longer operational due to high operational costs. There are many brands and types of compressors at PT. INKA, one of them is the Ingersoll Rand type MM160 compressor (Kalairaj et al., 2020).

Procedure of Ingersoll Rand MM160 Compressor
Air compressor brand Ingersoll Rand type air screw compressor type MM160 uses two rotating screws in a screw chamber called the air end. The rotation of the two screw components will cause suction on the intake valve and produce compressed air at the outlet (discharge). Then the compressed air enters the tank separator, which functions are separated oil and air so that the resulting compressed air does not contain oil. The working principle of this tank separator is that in the middle of the tube there is a foam separator, a type of foam that will pass air particles and catch oil particles and then drop the oil to the bottom of the tube. Oil-free air has a fairly high temperature (80-90 °C), so it must pass through a cooler, before being expelled through the air exhaust to enter the external system (Fink & Schlüchtermann, 2018;Jhwueng, 2020 High-temperature oil that collects at the bottom of the separator tube moves to the air filter housing unit. This unit consists of an oil filter which functions to separate impurities and a manifold unit which functions to regulate oil distribution to and from the air cooler (Wu et al., 2023). The oil that has passed through the cooler and the temperature has dropped, returns to the Oil Filter Housing Unit, to be redistributed to the air end or screw chamber. Another system that is no less important is the lubrication of the screw bearings. The Air Filter Housing Unit also supplies oil to lubricate the screw bearings. This system has a very big influence on Over Heating or Over Temperature on the Screw Air Compressor (Cui et al., 2022). The compressor system temperature is detected from the oil temperature. In the separator tank, a temperature sensor/thermostat is installed which will read the oil temperature and send this data directly to the Electronic Processing Unit. Normal working temperature is in the range of 85-95°C. If it's over 100°C, the system keeps running with a warning. Usually, the system is set to automatically shut down at 110°C.

Overall Equipment Effectiveness (OEE) method
Overall Equipment Effectiveness (OEE) is a method that can be used to measure machine effectiveness based on the measurement of three main ratios, namely: availability, performance efficiency, and rate of quality (Antônio Mendonça et al., 2022;Ginste et al., 2022). By knowing the value of the effectiveness of the machine, it can be seen how much the loss affects the effectiveness of the machine known as the six big losses of equipment.
Production activities that are carried out every day can interfere with the effectiveness of the compressor so that sometimes problems in the field are still often encountered such as the piston drive motor not rotating, the compressor does not turn on and off automatically, corrosion (rust), melted capacitors, and many other things that can happen beyond the operator's control. Due to these constraints, the authors decided to find out more and made

Research Method
The research will begin with conducting a preliminary study to make observations on the problem of the engine maintenance process on the compressor section and conclude the method that will be used to solve the problem. Furthermore, a literature study is carried out to study the theories needed to achieve the objectives of the research (Dobra & Jósvai, 2021; when conducting research. Data collection was carried out by field surveys to obtain the value of the effectiveness of the compressor engine at PT INKA, and direct interviews with the maintenance department to find out the steps that are usually taken in solving problems. To determine the value of machine effectiveness based on the measurement of three main ratios, namely: availability, performance efficiency, and rate of quality, is carried out using the Overall Equipment Effectiveness (OEE) method (Hung et al., 2022).

Maintenance System
Compressor maintenance is carried out to keep the equipment in reliable condition. Before carrying out repairs, you should do the following:

Damage to the Ingersoll Rand MM160 Compressor
The thermostatic Valve is a spare part that works to open and close the valve (valve) which is controlled by the oil temperature (compressor). When the temperature reaches above 70 (~75) and below 70(~75) degrees, the valve closes so that the oil is directly filtered by the oil filter so that it goes directly into the air end. The way to find out is to measure the temperature (using a tool like a shot used to measure temperature/infra shot) of oil in the pipe from the Thermo valve to the oil filter (towards the air end), the oil from the radiator to the Thermo valve, and the oil from the Thermo valve to the radiator (Picture schematic diagram flow). If it is found that the temperature from the cooler to the air end (after going through the thermostatic valve and the temperature from the oil tank (after going through the Thermo valve) to the air end is random (not the same), then it is certain that this valve is BROKEN. Therefore, repairs must be carried out by paying attention to the oil flow as which is shown in Figure 1

Gas Production Result Data
Below is the production data at PT. INKA presented in Table 1

Working Hours and Machine Delay Data
From the results of observations on the MM160 series Screw Air Compressor machine in the compressor building, the factors that cause delays on the machines are: 1. Schedule Downtime is a planned downtime, which is the time when the machine cannot carry out the production process due to a plane stop of the machine so that it does not produce for a while. Such as the implementation of PM (Preventive Maintenance).
2. Unscheduled Downtime is unplanned downtime, meaning that the machine cannot carry out the production process due to sudden machine damage. Such as damaged spare parts on the machine.   x 100% = 95,79% (1)    Calculation of Rate of Quality Product (RQ) The rate of quality product is a ratio that describes the ability of the equipment to produce products according to standards. To calculate the rate of quality product using Eq. x 100% = 100% (6) Calculation of Overall Equipment Effectiveness (OEE)

Conclusions
The Ingersoll Rand MM160 type screw air compressor uses two rotating screws to produce