Mechanical Troubleshooting: Chapter 3
Content
Troubleshooting Equipments - Part 1
Equipment
Industrial work is highly reliable on equipment. Equipment like pumps and motors are widely used in various industries. Let’s look at the failures of each type of equipment.
Motors
Motor failure is identified by its symptoms. Motors can send off a range of warnings that something is going wrong. For example, a motor makes sounds while operating because of vibrations.
A common cause of vibration is a misalignment of a shaft. If a soft foot is not corrected, it will be difficult to fix shaft misalignment. Soft foot is when the motor feet are not in a common plane with the base.
Some of the common causes of soft foot are:
Twisted or warped machinery foundations or baseplates,
Twisted, warped, or damaged machinery feet, and
Dirt, trash, or other unwanted materials under machine feet.
We need to make sure that base plates and machine feet are clean, deburred and free from dents. Next, loosen all foot bolts. Check one foot at a time for soft foot.
We need to check soft foot on at least three corners of each foot, with a 0.005” shim or feeler gauge. If soft foot is present, correct it by shimming with the minimum number of shims possible. If an angular soft foot condition exists, cut one shim in half, leaving the tab in place, to make it easier to reposition.
Next, we want to check for any obvious signs of damage on the outside. Look for any burnt, dented, or other damaged areas on the body, fan, and shaft. If any part of a motor is damaged, we need to replace the motor.
Next, we should rotate the shaft ourselves to see if it turns smoothly. If it does not turn, we need to lubricate the shaft.
If a motor is still not operating, we need to check the electrical health of the motor. This includes checking:
Earth Resistance,
Power Supply, and
Motor Capacitor.
Earth resistance is the “natural” resistance of a motor. We can measure this resistance using a multimeter.
Make sure your multimeter dial is set to Ω or “continuity” settings. Connect the probes to the earth wire and motor frame. If the multimeter shows 0.5Ω or less, the motor is fine. Otherwise, the motor is faulty.
Next is checking the power supply of a motor. Set the multimeter dial to V setting. Connect the probes to the +/- ports of the motor. If the multimeter shows 230V or more, the power supply is fine. Otherwise, the supply is faulty.
Set the multimeter dial to the C setting to check the capacitor. Capacitance is often written as a value +/- the tolerance on the body of the capacitor. For example, if a capacitor were made as 100 μF +/- 10%, the capacitance should fall in the range of 90 to 110 uF.
Pumps
A pump will not start if the motor is not working. Motor vibrations are also responsible for the wear of a pump impeller and excessive vibration. We need to troubleshoot a pump motor to solve these problems.
Unusual sounds from a pump can result from bearing failure or a foreign object inside the pump. To troubleshoot these issues, we need to dismantle the pump and remove a foreign object or replace the bearing.
If a pump is leaking, the possible cause could be:
Broken seals due to excessive pressure and temperature, and
Loose joints due to corrosion.
Fixing a leaky pump can be as simple as tightening the fasteners around its joint. However, in other cases, the mechanical seal or gasket may need replacing.
Clogged pumps often result in overheating, as well as reduced flow. If a pump is overheating, this usually means the flow of the pump is being restricted.
Other possible causes of reduced pump flow are:
Open bypass valves,
Leaky gaskets,
Damaged impellers, and
Clogged filter inlets.
Another common problem is the presence of air and vapor formation inside a pump. To remove air from a pipe, we need to prime the pump. Priming means filling a pump with water.
Vapor formation inside a pump is called cavitation. Cavitation happens when bubbles, or voids, form within a fluid because the pressure quickly drops below the vapor pressure. Recall that vapor pressure is a pressure at which liquid molecules change into the gaseous or vapor state.
Equipment like pumps and motors are widely used in various industries. Soft foot is when motor feet are not in a common plane with the base. Unusual sounds from a pump can result from bearing failure or a foreign object inside the pump.
Troubleshooting Equipments - Part 2
In this module, we will learn about the failures of mechanical equipment. We’ll also learn how to troubleshoot these failures. Skip to quiz!
Equipment
Aside from pumps and motors, the other equipment that’s widely used in various industries are:
Blowers, and
Fans.
Let’s look at the failures of each of these pieces of equipment.
Blowers
A blower can sometimes fail to rotate. This could be from rust in the blower impeller chamber, or the motor winding could be damaged.
If there’s rust in a blower, then it’s time for a good cleaning. Turn off the power, remove it from the system, and clean the impeller chamber.
If there’s no airflow in a blower, the possible cause could be broken belts. We need to inspect V-belts for signs of cracking. If a belt is damaged or looks worn, replace it right away.
If a blower is vibrating continuously, then it can be due to a loose belt or pulley. After replacing a V-belt, we should assess pulley alignment.
We can check the tightness of a belt by pushing it down in the middle with a finger. If it goes beyond a half-inch, we should make an adjustment.
Recall that lubrication is applying oil or grease to a motor to minimize friction and allow smooth movement. Grease guns are devices used to apply grease to an electric motor and bearings.
Recall that bearings support loads and also help them to rotate. Excessive temperature can build inside a blower if the bearing is not functioning correctly.
Fans
Fan systems used in industrial applications can fail in many ways. Some of the common malfunctions are:
Too much noise,
Inadequate airflow,
Lack of movement, and
Excessive fan vibration.
These failures are identified visually.
If an industrial fan makes an unusual noise, it’s likely to have incurred some damage. The following reasons can cause excessive noise from a fan:
An impeller hitting the housing,
A loose shaft or bearing,
Problems with the belt drive, and
Inadequate lubrication.
Inadequate airflow can also be a culprit for industrial fan failure. It’s caused by:
Dirty or clogged inlets,
Improper blade angle setting, and
Slow fan speed.
We need to clean a fan inlet or fan blade to troubleshoot the issue.
Excessive fan vibration is another indication of fan breakdown, which is caused by:
Impeller imbalance, and
Improperly balanced motors and pulleys.
To troubleshoot a vibration issue, we need to check that:
Key lengths are correct,
Fan shaft seals are rubbing, and
The motor has the correct bearings.
When a fan is not operating at all, it’s likely because of mechanical or electrical problems. The reasons for these problems include:
Blown fuses,
Broken belts or loose pulleys,
Wrong voltage, and
Seized bearing.
Aside from pumps and motors, other equipment that’s widely used in various industries are:
Blowers, and
Fans.
Rust in a blower impeller chamber or motor winding could result in blower failure.
Some of the common fan malfunctions are:
Too much noise,
Inadequate airflow,
Lack of movement, and
Excessive fan vibration.
Question #1: What causes a soft foot on a motor?
Broken seals
Air inside motor
Leaky joints
Motor feet are not in a common plane with the base
Scroll down for the answer...
Answer: Broken seals
Leaky joints
Soft foot occurs when the motor feet are not in a common plane with the base.
Question #2: The main areas to check for electrical failure of a single-phase motor are (select all that apply):
Capacitor
Earth Resistance
Power Supply
Weight
Scroll down for the answer...
Answer: Capacitor
Earth Resistance
Power Supply
When inspecting a single-phase motor, we always inspect the earth resistance, power supply, and capacitor.
Question #3: When checking for resistance, your multimeter should be set to:
V
Ω
C
A
Scroll down for the answer...
Answer: Ω
Resistance is measured in Ohms (Ω). The multimeter will measure resistance on this setting.
Question #4: Capacitors are labeled as:
Value
Value +/- tolerance
Tolerance +/- value
Capacitors are not labeled
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Answer: Value +/- tolerance
Remember that the value is what a part is designed for. However, tolerance needs to be included to account for slight changes part-to-part.
Question #5: What is the cause of a leaking pump? (select all that apply)
Worn impeller
Broken seals
Over tightening of flange bolts
Loose joints
Scroll down for the answer...
Answer: Broken seals
Loose joints
If a pump is leaking, the possible cause could be:
Broken seals due to excessive pressure and temperature, and
Loose joints due to corrosion.
Question #6: Clogged pumps can result in ____ as well as _____.
Overheating
Broken seals
Loose joints
Reduced flow
Scroll down for the answer...
Answer: Overheating
Reduced flow
Clogged pumps often result in overheating, as well as reduced flow.
Question #7: We replace the V-belt in a blower with the _____ size V-belt.
bigger
same
smaller
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Answer: same
We replace the V-belt in a blower with the same size V-belt.
Question #8: Grease guns are used for _________.
lubricating parts
cutting wires
filling refrigerant
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Answer: lubricating parts
Grease guns are used for lubricating parts.
Question #9: Which of the following is used to support a blower shaft and help it to rotate?
Metering device
Bearing
Grill
Vibration isolator
Scroll down for the answer...
Answer: Bearing
Bearings are used to support blower shafts and help them to rotate.
Question #10: What are the common industrial fan malfunctions that can occur? (Select all that apply)
Fan is leaking water
Too much noise
Inadequate airflow
Fan is leaking oil
Scroll down for the answer...
Answer: Too much noise
Inadequate airflow
Some of the common fan malfunctions are:
Too much noise,
Inadequate airflow,
Lack of movement, and
Excessive fan vibration.