Соnditiоn Monitoring and Fault Diagnosis Essay Example

Соnditiоn Monitoring and Fault Diagnosis 14

Соnditiоn Monitoring and Fault Diagnosis

Соnditiоn Monitoring and Fault Diagnosis

Operations of the centrifugal pump

A centrifugal pump is a type of hydraulic pump mostly preferred within the domestic and industrial setups. In addition, the pump is used to induce the flow or increase the pressure of the liquid and works simply compared to other types of hydraulic pumps. At the heart, it has an impeller and a series of fitted curved vanes inside the shroud plates. In most pumps, the impellers are often immersed inside water and when rotating, it makes the surrounding fluid to consequently rotate. As a result, it imparts a centrifugal force to the water and makes it move radially out. From the analysis, it is clear that the fluid receives the rotational mechanical energy; thus, the discharge side of the impeller will make the pressure and kinetic energy of the water to rise. Within the suction side, there is displacement of water, which makes negative pressure induction appropriate at the eye. The resultant low-pressure assists in sucking the water from the rivers or streams to the system and the processes continues.

The negative pressure at the eye helps to maintain the flow within the system. The radial vanes cause water to spin when the casing rotates. The volute on the other hand is a single-plane spiraled curve receding from the centre with the design of matching of the casing around the impeller within the centrifugal pump and forms the passage for the discharged water (Rishel, Durkin, & Kincaid, 2006, 122). Additionally, the volute tends to expand at some intervals and grows wider the further along the flow of water. Since the pressure of water inside the casing is huge, it is important arrange for sealing material which is imperative in arresting the leaked water through the shaft casing clearance. In such conditions, the mechanical seal is appropriate. In most pumps, the impellers are mounted on the bearings but the suction side fit on the same since it blocks the flow.

Condition monitoring and fault diagnosis

Figure 1: Bearings of the pump fitted on the same side

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A 3-Phase Induction Motor

An electric motor tends to covert the electrical energy to mechanical energy that is supplied to various types of the loads. The A.C motors operate using A.C power supply and are classified into different synchronous, single, and 3-phase inductions. Of the three, 3-phase motors are mostly used for industrial applications since they do not need any starting device. The motor derives its name from the fact that the rotor current is induced through the magnetic field rather than electrical connections. The operating principle of the motor is based on the production of the rotating magnetic field. Additionally, the motor has a stator consisting of different overlapping windings offset the electrical angle of 1200 which when connected to a 3-phase A.C power supply, it produces a rotating magnetic field that rotate at synchronous velocity.

Water pump problems, causes of failure, and detection methods

Potential failure

Probable cause

Method of detection

Corroded bearing

Contamination with corrosive substances

Failure to coat or use additives on the metallic surfaces

Exposure to moisturized environments

Aging bearing without adequate replacement

Water leakages

Weaker metallic components

the quality of the pumped fluid

inefficiency of the system

Loose connection points from vibration

Continuous leakages

Noise and heat generated during operations

Worn out mechanical seal

Aging component of the system

Failure to coat the seal

Poor connections with other components like shafts

Corrosion due to contaminated environmental conditions

Delayed monitoring and evaluation

Improper fitting of the components

Leakages

Shortened lifespan of the components

Continued vibrations and noises

Damaged impeller

Improper alignment with other components

Corrosion from the contaminations

Aging components of the system

Suspension of the solids in the fluid

Uncontrolled pressures

Cavitation

Leakages

Reduced life cycle of the components

Increased vibration and noises from poor connection

Disparity in the output and input

Using sensors to monitor the systems

To ensure high reliability within the pump systems, it is significant to employ various monitoring and diagnostic conditions. The common parameters that require monitoring are vibration, temperatures, and sound to predict the health of the rotating machines. The degradation effects within the water pumps are vibrations, noises, corrosions, debris, and pressure variations. The application of sensors offers the best method of monitoring the parameters. The commonly used sensors include temperature, vibration, and sound analyzer.

Vibration monitoring

The water pump vibration diagnosis usually use vibration sensors to take measurements and other comparisons on the advanced dynamic model for identifying the problems which migh help to detect he early failures. The pump dynamic model has to consider accurately the major components and flexibility of the pump. Proper modeling is required for pump rotor assembly, pump casing, and external supports. In addition, the dynamic model needs to respect all the nonlinear effects and elements especially accuracy between the rotating and static assemblies within the water pumps. For most water pumps, using the rolling-element bearing which have considerable flexibilities could make the model complex. The support flexibility might be the reason behind the bound flexural whirling vibrations. The vibration sensors detect the acceleration of the shaft especially if the bearing is worn. To capture and monitor all vibration activities, there is need to fit the sensors close to the bearing and 900 rotations in capturing both vertical and horizontal acceleration.

Temperature monitoring

There are temperature sensors and guards build within the stator windings to protect the system against overheating. For advancement monitoring, it is significant to focus on the Pt100 sensors that provide analogue measurements while the MAS 711 monitors temperature not only within the stator windings but also within the major and within support bearings. Such sensors allow maximum and minimum value recording and powerful fault tracing. Temperature sensors require accuracy and flexibility. It is important to note that every temperature sensor is designed to provide an improved reliability, precision, and responsiveness to maximise the components and performance of the pumping systems. Sensory used within the pumps need to have strong and standardized technology platform that is easy to customize. Within the pumps, temperatures often increase with time during operations which might affect the bearings, impellers, and windings. To prevent, it is significant to focus on infrared sensors that record even slight temperature changes.

Sound analyzer

During operation of the pump, a lot of noises and vibrations are produced which requires close monitoring to prevent the failure of the system. It is clear that worn out systems often produces more sound than new ones due to the weakness in the connection points and reduced level of efficiency. Such noises might intensify making the operation unfriendly and uncomfortable. The major role of detecting and measuring the sound levels is to determine the component of the system that requires replacement. Consequently, any component producing a lot of noise is worn out and requires replacement.

Limitations of the condition monitoring system

Vibration sensors offering numerous advantages in detection the levels of vibrations, however, it is important to note the limitations associated with their applications. The commonly used sensors are accelerometers, velocity sensors, and proximity sensors. The merits of using the sensors include the simple installation, good responses at frequencies with the capacity of standing high temperatures, work effectively without the supply of the external power, and durability. In addition, the sensors measure static and dynamic displacements besides being cost effective. With such merits, the sensors also face various limitations including electrical and mechanical noises, bound within the frequencies, require external power for installation, and not calibrated for unknown materials. To some extent, the sensors are sensitive to high frequencies and require electronic integration for the displacement. Noise sensitivity might affect the sensors and transmitters if the rate of vibration is high.

The sound sensor can only measure up to given level beyond which there is likely occurrence of the failure within the system. The merits of the sensor in measuring the sound level include easy detection of the internal defects when validation procedures are effectively applied and only accessible from one side of the component. Additionally, it has no radiation hazard hence, there is little work disruptions. However, the changes in environmental conditions like temperatures and particulate matter might affect the sensors. The smooth sensors tend to reflect the sound efficient compared to rough surfaces. Increased noise levels might result in spurious indications, destruction, and unnecessary repairs without proper validation.

During operation of the pump, it is significant to lubricate the surfaces especially the moving parts to prevent corrosion and enhance efficiency of the system. However, the major role of the lubrication oil is to separate the roller elements and the vanes, lubricating the sliding surface within the bearings, and provision of the corrosion protection and cooling. Lubrication oil contamination has effect of the system performance especially the sensors. Viscosity of the important feature of the lubricant as the oil ensure speed, standardized temperature rates, and loads might assist in developing the film between various rotating parts. However, oil used might degrade to a point it is thick for penetration between different surfaces. Load, temperature, chemical change, and water affect viscosity.

Increment in temperature might affect the performance the performance of the system. The sensors are highly sensitive, easy to operate, and available in different accuracy depending on the heat produced by the pumps. Besides, they are accurate and offer the best method of identifying if the operation process is likely to experience failures. However, the sensors have temperature limits that when exceeded they become ineffective and greatly unreliable.

Identifying the trend of bearings

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From the graph, it is clear that the motor back bearing lacks steady vibration. It experiences fluctuating rates with week 5 registering the lowest and week 12 the highest vibration rates. The vibration measuring parameters need frequent monitoring from week 12 where the rate of vibration increases steadily with time. Such increment is likely to reflect the weakness within the system or the failure that requires immediate action.

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The trend presented by the vibration of the motor from bearing require frequent monitoring considering that from week 6 to week 12 the rates of vibration increases against time. The component registered the lowest vibration rate in week 6 and highest in week 5 and week 12 reflecting the ability of experiencing even higher vibration rates. Continued increase in vibration rates portray that the system experiences failure that without any rectification, higher vibration is likely to render the machinery ineffective. However, the system experienced efficiency during the first week since vibration rates reduced with time before it began increasing at high rates.

For the pump bearing, the vibration rates are at considerable levels. However, the system experienced fluctuations at early stages of the operation though the disparities in vibration rates are minimal. Although the system began with the highest vibration rates, with time, it declined and further experienced steady fluctuations signifying that there is no likely potential failure of the system.

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The amount of heat generate by the system depends on its efficiency. Heat is the major determinant of temperature levels within the operations; therefore, it is important to keep it as minimum as possible. From the graph, it is clear that levels of temperature are steady except between week 3 and week 4 when the system experienced the highest amount of temperature. The motor back bearing does not indicate the possibility of future failures from the temperatures.

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For the motor from bearing, the temperatures begin to rise slowly before continuing to fluctuate steadily. The steady temperatures indicate that the system is functioning normally is not likely to experience any failure in future with continued operation of the system.

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The pump bearing works efficiently compared to other bearing considering its steady temperatures. Through the operation period, the temperatures remain between 300C and 500C reflecting a normal performance even in the future operations.

Appropriate sensor its application

Temperature monitoring

Thermister is an appropriate temperature sensor whose name is derived from THERM-ally sensitive res-ISTER. It is special resister changes physical state of resistance when exposed to the changes in temperature. Its major advantage is its speed of responding to any change in temperature, accuracy, and repeatability. Most thermisters have Negative Temperature Coefficient of resistance, which makes the value of resistance go down with temperature increment although some have Positive Temperature Coefficient. The sensors are made from the ceramic conductor metals with metal oxide technology. The resistivity value of the sensors is often the room temperature (250C).

Vibration monitoring

Accelerometers are small vibration sensors installed directly on the safe of any vibrating object. These sensors have small masses that are suspected using flexible components operating like strings. They measure from low to high frequencies and available in different purpose and application-specified designs. The commonly used is the piezoelectric accelerometer sensor, which is reliable, versatile, and has amplitude range, which makes it popular for machinery monitoring. While selecting the vibration sensors, it is important to consider vibration level and frequency range, environmental corrosiveness, size, and weight considerations.

Leak detection

For the water pumps, the Water Alert and leak sensor cables offer the methods of monitoring the system leakages. The cable is often a multi-conductor wire embedded in a gold plate acting as extension of the sensing probes contained within the detector. If any of the sensors encounter the liquid, the Water Alert automatically activates. Is is possible to connect either one or two sensor cable to the Water Alert with the connection made with non-gender, locking connectors to ensure fast speed, and durability after installation. However, the Water Alerts are meant to work on specified setups and pipes.

Detecting corrosion and cracks

The commonly sensor used in detecting the crack is the complementary split-ring resonator (CSRRs) that is easily patterned on any ground plane of the microstrip line and the printed circuit board technology. The sensor offers merits based on its high spatial resolution, sensitivity, and simplicity of its design.

Cost and manufacturers of commercially available sensors

Thermister is manufactured by Enercorp Instruments Limited, costs approximately $10.5 per piece while complementary split-ring resonators manufactured by the Informa Limited, and costs approximately $15.4.

Reference

. New York: McGraw-HiIl. HVAC pump handbookRishel, J. B., Durkin, T. H., & Kincaid, B. L. (2006).