Centrifugal Pump Shaft Coupling Durability Material S45C in the Water Treatment Plant Unit with the Destructive Test
Method (Impact)
Fransnazoan Sitorus a,1,*, Muhammad Fajar Lubis b,2, Nuzuli Fitriadi c,3
a,b Mechanical Engineering, Politeknik Teknologi Kimia Industri Medan
c Mechanical Engineering, Politeknik Aceh Selatan, Tapaktuan, Aceh, Indonesia, 23711
1[email protected]*, 2[email protected], 3[email protected]
I. Introduction
A centrifugal pump (centrifugal pump) has the main element in the form of a motor with impeller blades that rotate at high speed. The working principle is to convert the mechanical energy of the propulsion device into the kinetic energy of the fluid (speed). Then the fluid is directed to the exhaust channel using pressure (the kinetic energy of some of the fluid is converted into pressure energy) using an impeller rotating in the casing. The casing is connected to the suction and discharge channels. To ensure that the casing is always filled with liquid, the suction line must be equipped with a foot valve. The centrifugal pump itself has a shaft to transmit rotation from the electromotor which is connected via a coupling [1].
The shaft is one of the main parts that functions as a medium to transmit power and rotation from the driving motor to the pump impeller. Where the link between the electromotor and the pump is connected using a clutch which then the power and rotation are forwarded by the shaft [1]. To bond between the shaft and the clutch, a peg is used as a binder between the two components, to help transmit power and rotation. When operating under load conditions that do not comply with the provisions, the pin on the shaft breaks in a position above the bearing from the direction of the pump housing. In the broken position, it appears that there is a flawed hole on the surface of the peg.
Some devices on automotive and transmission as well as parts on trains as well as pumps, will experience a sudden load or shock in operation. Therefore, the durability or toughness, which is the amount of energy that is capable of being absorbed by a material until a material break under a sudden load, as well as the factors that influence the properties of the material, need to be known.
This resistance is one of the properties of the material which is called brittle.
ARTICLE INFO A B S T R A C T
Article history:
Accepted The peg is a component that functions as a binder between the shaft
and the hub in transmitting power and rotation. In general, the pegs are designed and made using metal materials such as mild carbon steel. In this research, the material of the coupling pin design on the centrifugal pump shaft is S45C. Where on the sample of the designed post, an impact test or the Charpy method of hitting the notch is carried out which aims to determine the amount of resistance to sudden loading, and to determine the physical changes (failure modes) experienced by the post material. In this study, the sample of the post with dimensions of 6.10 mm x 6.10 mm x 55 mm obtained a large impact strength (impact strength) in the Charpy method impact test of 0.8445 Joule/mm2. And for the physical change (failure mode) experienced by the post material against the sudden loading, it is a brittle fracture which is characterized by physical characteristics in the form of granular (like sand) on the fracture surface, and the absence of plastic deformation that occurred first.
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Keywords:
Pegs
Centrifugal Pump Impact Test Impact strength
There are frequent defects in construction that reveal a brittle fracture pattern despite being made of a ductile metal. There are several factors that cause the tendency of a metal to experience brittle fracture including; low temperature and high strain/load rate. Impact Test is useful to see the effects caused by the presence of notches, shape of notches, temperature and other factors [4-5].
The object of the problem studied in research with the topic of durability of the shaft coupling pin of the S45C centrifugal pump shaft is limited to research subjects which concentrate on determining the amount of durability in the form of shock strength (impact strength) of the coupling pin on the centrifugal pump shaft against sudden loads using the Charpy impact test method. and how the results of physical changes that occur due to a sudden loading of the clutch post material on the centrifugal pump shaft [6].
In general, the purpose of this study is the durability of the S45C centrifugal pump shaft coupling pin on a water treatment plant unit using the destructive test (impact) method. And specifically, the purpose of this study was to study the impact strength of the clutch pin on the centrifugal pump shaft against sudden loads using the Charpy method impact test and to determine the failure mode of the S45C material through physical changes that occur due to sudden (sudden) loading [7].
The results of this study are expected to provide benefits for the academic world and the industrial world in general as well as for researchers in particular, in order to contribute to the provision of data and information in knowing the size (impact strength) of the coupling pin on the centrifugal pump shaft against sudden loads using the Charpy impact test method and physical changes that occur due to sudden loading of the clutch pin on the centrifugal pump shaft [8-9].
II. Research methods A. Pump
A pump is a machine specially designed to move fluid from a place of low pressure to a place of high pressure through a pipe, the increase in the pressure of the liquid is used to overcome resistance to flow, the resistance to flow can be in the form of pressure differences, height differences or frictional resistance.
The working principle of the pump itself is based on how the fluid flows by applying a compressive force to the flowing fluid. With the presence of pressure, it is expected that the fluid can overcome obstacles when the fluid transfer process takes place. For example, if the pipe experiences a difference in elevation or height, then this pressure will allow the fluid to pass through the pipe to its destination [1].
Fluid transfer itself can occur horizontally or vertically. For example, a pump used to extract fluid from a well clearly requires vertical movement from the bottom up.
Meanwhile, there is also fluid flowing in a horizontal position which also has the potential to experience obstacles in the form of friction or turbulence. This of course makes the pressure on the fluid must be regulated in such a way as to be able to overcome these various obstacles. In the operation of heavy equipment machines requires a large discharge pressure and low suction pressure, due to low pressure on the inlet side of the pump, the fluid will rise from a certain depth, whereas due to high pressure on the discharge side will force the fluid to rise up to desired height [1].
B. Impact Strength
Shock strength is the capacity of a material to withstand or absorb impact forces before fracture.
Fracture material can be brittle or ductile. The smaller the energy absorbed, the fracture will be brittle rather than ductile. The impact test is also used to study the fracture pattern of the test specimen, whether it is brittle fracture or ductile fracture or a combination of both.
Impact Test is useful to see the effects caused by the presence of notches, shape of notches, temperature and other factors. Impact testing can also be referred to as a material test to determine the ability of a material to accept impact loads by measuring the amount of energy required to break the specimen with swing.
The experiment was carried out using an "Impact Testing Machine" with the specimen placed on a bearing (anvil, raised to a height of h1), then released to break the specimen and rise again to a height of h2. So that the "energy" needed to break the specimen can be calculated by the formula:
E = P (h1 – h2) kg.m (1)
The height of the pendulum before and after it is dropped (h1-h2) can be expressed by the angle of the impact machine image which can be seen in Figure 1, so the energy required to break the specimen can be calculated:
E = m x g x r (cosβ – cosα) kg.m (2)
E = Energy required to break the specimen (kg.m) m = pendulum weight (25.530 kg)
g = Earth's gravitational acceleration (9.8 m/s2)
r = distance between the pendulum axis and the center of gravity of the pendulum (0.6495 m) α = Angle of the pendulum before it was dropped (maximum angle 144o)
β = Pendulum angle after breaking the specimen
Fig. 1. Schematic impact machine
The pendulum angle is 144 ̊, and the pendulum angle after breaking the specimen can be read on the tool disc. The use of the initial angle of the pendulum is 144o, this is because the design of the Impact Machine tool was designed and calibrated by the manufacturer with an initial experimental angle of 144o.
If the fracture surface area of the specimen is A (cm2), then "Impact Strength" (shock load) or also known as the Charpy number can be found by the formula:
ak = kg-m/cm2 (3)
ak = Impact strength (shock load) or Charpy number (kg-m/cm2) E = Energy required to break the specimen (kg.m)
A = Surface area of the specimen fracture (cm2).
A = B x H (mm2) (4)
B = Thickness of the impact test specimen (mm)
H = Height of impact test specimen outside notch depth (mm) H = Depth of sample notch (2 mm)
The impact test is also used to study the fracture pattern of the test specimen, whether it is brittle fracture or ductile fracture or a combination of both.
III. Method A. Material
The peg is mild steel, which functions as a lock that is inserted between the axle and hub (boss) of a wheel, gear and/or coupling so that the two are firmly connected so that they are able to continue the rotary moment or torque. The following is a sample of S45C steel pegs which can be seen in Figure 2.
Fig. 2. JIS Z 2202 impact test sample
The impact test sample pegs are the size of the coupling pins on the centrifugal pump shaft shown in Figure 3 and Figure 4 below.
Fig. 3. Schematic of the JIS Z 2202 impact test sample
Fig. 4. Schematic of the impact test sample dimensions of the clutch pin on the centrifugal pump shaft
B. Tools
1. Scrap machine
To change the surface of the workpiece into a flat surface, both terraced, angled and grooved, use a shaping machine and can be seen in Figure 5.
Gambar 5. Scrap Machine
2. Impact machine
Impact testing is carried out to determine the ability of a material to accept impact loads by measuring the amount of energy required to break the specimen by swinging it, using an impact testing machine, as shown in Figure 6 below.
Fig. 6. Impact machine 3. Optical Microscope
To find out the grain size, phase distribution, type and model of the microstructure of the material in a metal using an optical microscope, seen in Figure 7 below.
Fig. 7. Optical Microscope
Design of Research Activities and Set-up
1. Make sure the size of the sample dimensions to be tested using an impact machine is in accordance with the specified size.
2. Measure the dimensions of sample B as the wide side, and H as the high side of the sample being tested (where H is outside of the notch size that has been made).
3. Place the sample on the anvil from the impact machine, and the direction of the notch on the sample is placed or positioned back to the direction of the impact pendulum.
4. Center the test sample by positioning the notch right in the middle of the anvil.
5. Adjust the pendulum lock so that the pendulum can be raised to the desired height or rotation angle.
6. Set the initial height or initial angle (α) of the pendulum impact to 144 ̊.
7. After the angle α is obtained, release the pendulum lock so that the pendulum swings and hits or hits the test sample.
8. Look at the angle of the pendulum after hitting the test sample on the scale impact machine obtained and record it as β.
9. Observe the structure of the samples that have been tested.
IV. Results and Discussion
From the observational data obtained in the tests carried out, the amount of shock strength (impact strength) can be calculated. The magnitude of the shock strength of the clutch pin on the centrifugal pump shaft against sudden loads using the Charpy method of impact test.
Calculation of the magnitude of the shock strength (impact strength) of the coupling pin sample on the S45C material centrifugal pump used is in accordance with the following data:
Table 1. Observation Data on Impact Test Results
No Material B
(mm) H (mm)
m (kg)
r (m)
α (°)
β (º) 1 JIS Z 2202 9,75 8,25 25,530 0,6495 144 72 2 Dimension of
pump 6,10 6,10 25,530 0,6495 144 128
1. Calculation of the shock strength of the standard size sample JIS Z 2202:
E = m x g x r (cosβ – cosα)
= 25,530 kg x 9,8 m/s2 x 0,6495 m (cos72 ̊-cos144 ̊) = 162,5 Joule (0,3090 – (-0,8090))
= 162,5 Jolue x 1,118
= 181,67 Joule
A = B x H
= 9,75 mm x 8,25 mm
= 80,43 mm2
ak =
=
= 2,258 Joule/mm2
Testing samples made from medium carbon steel S45C with dimensions designed according to the JIS Z 2202 standard against sudden loading, the test results of the material can be seen that the shock strength obtained is 23,4197 kg.m/cm2.
2. Calculation of the shock strength of the sample size of the pin size of the centrifugal pump shaft coupling:
E = m x g x r (cosβ – cosα)
= 25,530 kg x 9,8 m/s2 x 0,6495 m (cos128 ̊-cos144 ̊) = 162,5 Joule (0,6156 – (-0,8090))
= 162,5 Jolue x 0,1934
= 31,42 Joule
A = B x H
= 6,10 mm x 6,10 mm
= 37,21 mm2
ak =
=
= 0,8445 Joule/mm2
Testing samples made from medium carbon steel S45C with dimensions designed according to the clutch pin on the centrifugal pump shaft against sudden loading, the test results of the material show that the shock strength obtained is 8.6183 kg.m/cm2.
The results of physical changes occur due to a sudden loading of the clutch post material on the centrifugal pump shaft using the Charpy impact test method as follows:
In material testing, there are two types of material testing, namely destructive testing and non- destructive testing. In the destructive test, there are several tests such as; hardness test, tensile test, bending test, impact test.
In testing, the sample will be tested until it is damaged or fails. Which aims to determine the performance of the material against the force or loading.
Meanwhile, non-destructive material testing aims to detect defects, cracks by inspecting the material, both on the surface of the material and on the inside of the material. In the non destructive test there are several tests carried out such as; penetrant test, ultrasonic and magnetic flow inspection.
An impact test is carried out to find out how much the material is able to absorb the energy needed to break or damage the structure of the material, and how much impact strength is experienced in the material. In the impact test, the material will experience several failure modes (physical changes), namely: brittle fracture, ductile fracture and a combination of both fractures.
For equipment used to detect or determine failure modes (physical changes) that occur, metal microscope tools (metallography) are used. Several things will affect the type of failure of the material or sample that experiences impact strength, namely the influence of the temperature acting on the material and the type of material or materials used.
And for the results obtained from the failure mode or physical changes that arise in the material being tested can be seen in Figure 8.
Figure 8. (a) specimen failure modes; (b) the macro structure of the physical changes in the test specimens; (c) granular part
(a )
(b )
(c)
The failure modes (physical changes) that occur in the specimen are shown in Figure 12a. The failure mode (physical change) is obtained which can be seen in Figure 12b. So based on the fracture of the sample tested using the impact test it can be concluded that the failure mode experienced in the sample is brittle fracture. Where the characteristics of the brittle fracture itself can be seen in Figure 12c, with the characteristics that appear, namely the surface looks like a luminous granular form and does not experience plastic deformation beforehand.
V. Conclusion
The results of this study were to study the durability of the S45C centrifugal pump shaft coupling pin on a water treatment plant unit using the destructive test (impact) method. And specifically the purpose of this research is to study the impact strength of the clutch pin on the centrifugal pump shaft against sudden loads using the Charpy method impact test and to find out the failure mode of the S45C material through physical changes that occur due to sudden (sudden) loading:
1. The endurance in the form of the amount of energy that can be absorbed by the clutch pin on the S45C material centrifugal pump shaft in the water treatment plant unit is 31.42 Joules;
with a shock strength (impact strength) of 0.8445 Joule/mm2
2. The failure mode of the brittle fracture experienced by the coupling pin on the centrifugal pump shaft of S45C material against sudden loading or impact strength experienced by the specimen.
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