Boiler Omnical  pipe leakage requires a long time and expensive maintenance costs

Abstract. Service Omnical Boiler pipe leakage requires a long time and expensive maintenance costs
the improvement. The generating unit must also be shutdown in its repair Service Omnical Boiler . So that the pipe failure The boiler must be able to be overcome immediately and prevented so that it does not happen. For that it is necessary  known cause of boiler pipe leakage.

Tests conducted include visual observations, tensile tests,composition test, hard test and microstructure. From research on leakage boiler waterwall pipes,it was concluded that the leaky waterwall boiler pipe was caused by oxidation corrosion. In 2019predicted thickness of boiler waterwall pipes stay 71% of the initial thickness, so it needs to be prepared immediatelyfor retubing.Keywords: leakage, pipes, boilers, oxidation.

1. Introduction
1.1 Background
A steam power plant with a capacity of 65 MW has a boiler leak at waterwall pipe. This incident caused the shutdown of the generating unit. These leaks in addition causing looses on the boiler and can endanger the boiler pipes around it. Looses on boiler in the form of wasteful use of water but the resulting steam output is not comparable. Boiler pipe around the location of the leak can also be damaged due to bursts of water from a leaky pipe can hit the pipes around it.

Service Omnical Boiler Failure on the boiler pipe becomes a big problem because it requires a long time and the cost of repairs is expensive, even though the pipe that fails is only one piece. Based on the location of failure, the waterwall pipe occupies the second position that often fails after super heater pipes

[1]. Long time and expensive repair costs caused the incident leakage in boiler pipes must be addressed immediately.

1.2 Formulation of Problems and Research Objectives In this paper, the formulation of the problem taken is how to find out the cause of failure PLTU boiler waterwall pipe material and what recommendations are proposed to minimize and prevent similar failures the next time. The purpose of this study is to find out the cause of failure of PLTU boiler waterwall pipes and to find out recommendations repair / prevention.

1.3 Research Methodology
The object of this study is the PLTU boiler waterwall pipe with a capacity of 65 MW. TimeTh e sampling of this research was in February 2016. Sampling was carried out by cutting a 50 cm boiler waterwall pipe then the cut pipe section is welded with a pipe new so it can be operated. This piece of boiler waterwall pipe will be used as research sample. The instruments in this study were several testing machines, including machines spectometry, tensile testing machines, micro structure testing machines, hard testing machines, and others. Some Tests carried out are run out measurements, composition tests, tensile tests, and microstructure tests.

1.4.1 Literature Review Service Omnical Boiler 
Several studies related to the failure of the boiler pipe have been conducted. Pipeline failure boilers vary greatly. Several variations of the failure mechanism can occur in the boiler because of the boiler operate at high temperatures, high pressures, and thus abrasive environments allows the emergence of variations in failure mechanisms such as overheating, pitting corrosion, creep, erosion, thermal fatigue, corrosion fatigue and stress corrosion cracking

[2].Of the many variations of the failure mechanism, corrosion is one of the causes of failure boiler so that control of contaminants and water hardness becomes important for boiler operation in a safe condition for a long period of time. In addition, inspection of the tube for know the thickness reduction in the tube wall is very important to

1.4.2. Theoretical basis Service Omnical Boiler 
Boilers produce steam at the desired pressure and temperature by burning fuel in the combustion chamber

[4]. One mode of boiler failure is corrosion. Corrosion is destruction or deterioration in the quality of material due to reacting with the environment

[5]. While the decline in quality the result of physical interaction is not called corrosion, but commonly known as erosion and
wear and tear. Corrosion problems in metals, estimated at around 5% of industry revenue, are spent on
finance the prevention of corrosion, maintenance or replacement of equipment as a result of the reaction
corrosion [6].

2. Discussion Service Omnical Boiler 
Several tests were conducted in this study. In this study run out measurements were taken with the results of the inspection as shown in Figure 1. In Figure 1.a is shown that on the side of the pipe is thinning thickness from the outside. In Figure 1.b it is shown that on the leaking side there is a thinning section of the pipe thickness and around the hole, the pipe also undergoes corrosion. Furthermore, the test carried out is the test of material composition. In this composition test, data are obtained as shown in table

1. From table 1 it is shown that the chemical composition of the pipe Service Omnical Boiler
boiler waterwall enters the SA210 grade A1 pipe criteria because the percentage of the elements are in standard SA210 grade A1 pipe. Material grade SA210 A1 is usually made in the form of pipes without seamless joint which is widely used for boiler pipes.

The next test is a tensile test. In this tensile test, the data shown in table 2. From table 2 we get the result that the waterwall pipe has σ Ultimate Tensile Strength (UTS)
and σ yield greater than the standard σ UTS and σ yield SA 210 Grade A1. This matter shows that boiler waterwall pipes fall within SA 210 Grade A1 and not yet experienced a change in tensile strength