Turbine Protective Device Test – Bearing Oil Pressure Low Trip Test

The Bearing Oil Pressure Low Trip Test is a crucial procedure conducted on rotating machinery, particularly on turbines, generators, or other equipment equipped with bearings that rely on lubricating oil systems. This test is designed to ensure that the system can detect and respond appropriately to low oil pressure conditions, which could potentially lead to bearing damage or other operational issues.

1. )   Place the test lever in the Test Position
2. )   Gradually open the test valve in the sensing line of the bearing oil pressure
3. )   Verify that the bearing oil pressure low alarm is annunciate first as oil pressure drops after opening the test valve to 0.75 bars. Observe the bearing oil pressure in the pressure indicator.
4. )   Verify that the bearing oil pressure low-low trip is initiated as oil pressure drops further to < 0.5 bars and turbine trip solenoid valve is energized releasing the trip test oil pressure. Observe the trip test oil pressure drops to 0 bar. Confirm that the auto stop oil pressure remains > 9 bars.
5. )   Close the test valve in the bearing oil pressure sensing line and observe that the oil pressure is build up to > 1 bar.

Boiler Chemistry

Boiler Chemistry refers to the understanding and management of chemical processes within boilers, which are devices used to generate steam or hot water for various industrial, commercial, and residential applications. Proper boiler chemistry is crucial for ensuring efficient operation, minimizing corrosion, and preventing scale build up, which can lead to reduced efficiency, equipment damage, and safety hazards.

Key aspects of boiler chemistry management include:

1.)   Water Quality: The quality of water used in boilers is critical. It should be free from impurities such as dissolved solids, oxygen, and other contaminants that can cause corrosion or scale formation. Water treatment processes like softening, demineralization, deaeration, and chemical dosing may be employed to achieve suitable water quality.

a.     Boiler Feedwater pH = 8.5 to 9.5

b.     Boiler Steam Drum pH = 9.2 to 9.6

2.)   pH Control: Maintaining the proper pH level of boiler water is essential for preventing corrosion of metal surfaces. pH levels are typically controlled within specific ranges using alkalinity control agents or acidic additives.

3.)   Oxygen Control: Oxygen can cause corrosion in boilers, particularly in systems operating at high temperatures. Deaeration processes or the use of oxygen scavengers help remove or neutralize dissolved oxygen in boiler feedwater.

4.)   Scale and deposit control: Scale formation from minerals in water can reduce heat transfer efficiency and lead to overheating and equipment damage. Chemical treatments, such as scale inhibitors or dispersants, help prevent scale buildup inside boilers and associated piping.

5.)   Corrosion inhibitors: Various corrosion inhibitors are used to protect boiler components from corrosion. These inhibitors form a protective film on metal surfaces, preventing corrosive reactions with water or other contaminants.

6.)   Blowdown control: Periodic removal of concentrated boiler water through blowdown helps control he buildup of dissolved solids and impurities. Proper blowdown procedures are essential to maintain water quality and prevent scaling.

7.)   Monitoring and testing: Regular monitoring and testing of boiler water parameters, such as pH, alkalinity, conductivity, dissolved oxygen, and chemical concentrations, are essential for ensuring proper boiler chemistry and early detection of potential issues.

Overall effective boiler chemistry management involves a combination of proper water treatment, chemical dosing, monitoring, and maintenance practices to ensure safe and efficient boiler operation while extending equipment lifespan and minimizing downtime.

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Boiler pitting

Boiler pitting refers to localized corrosion or erosion that occurs on the internal surfaces of boiler tubes, drums, or other components exposed to high-temperature and high-pressure conditions. This type of damage is typically characterized by small, localized pits or craters on the metal surface.

Boiler pitting can occur due to various factors, including:

1.)   Chemical factors: Corrosive substances present in the boiler water, such as dissolved oxygen, carbon dioxide, or acidic compounds, can react with the metal surfaces, leading to pitting corrosion. Poor water treatment or improper chemical balance can exacerbate this problem.

2.)   Mechanical factors: Turbulence, velocity changes, or impurities in the water flow can cause localized erosion or wear on the metal surfaces, leading to pitting.

3.)   High-temperature operation: Elevated temperatures can accelerate corrosion processes and make the metal more susceptible to pitting.

4.)   Microbial growth: Microbial activity in the boiler water, such as the presence of bacteria or algae, can contribute to localized corrosion and pitting.

Boiler pitting can compromise the structural integrity of the boiler components, leading to leaks, reduced efficiency, and potentially catastrophic failures if left unchecked. Therefore, its essential to monitor boiler conditions closely and take preventive measures to mitigate the risk of pitting, including:

1.)   Proper water treatment: Implement a comprehensive water treatment program to control corrosion and scale formation in the boiler system. This may include adding corrosion inhibitors, pH control agents, and oxygen scavengers to the boiler feedwater.

2.)   Regular inspection and maintenance: Conduct regular inspections of boiler components to detect early signs of pitting or corrosion. Monitor water chemistry parameters, such as pH, dissolved oxygen levels, and conductivity, and take corrective actions as needed.

3.)   Optimized operation: Ensure proper boiler operations and maintenance practices, including proper steam and water flow rates, adequate blowdown procedures, and appropriate control of boiler water chemistry parameters.

4.)   Material selection: Choose materials for boiler construction that are resistant to corrosion and erosion under the operating conditions of the boiler.

5.)   Cleaning and descaling: Periodically clean and descale the boiler internals to remove deposits and impurities that can contribute to corrosion and pitting.

By implementing these preventive measures and maintaining strict control over boiler water chemistry, operators can minimize the risk of boiler pitting and prolong the service life of the equipment. Additionally, regular inspection and maintenance are critical for early detection and mitigation of pitting damage to ensure safe and reliable boiler operation.

What is Turbine Eccentricity?

Turbine eccentricity refers to a condition in which the rotating components of a turbine, such as the rotor, are not perfectly centred within the surrounding stationary components, such as the casing or stator. This lack of concentricity can lead to several issues in turbine operations, including:

1.)    Vibration: Eccentricity can cause uneven forces and imbalances during rotation, leading to increased vibration levels. Excessive vibration can result in equipment damage, reduced efficiency, and potential safety hazards.

2.)    Increased Wear: Uneven contact between rotating and stationary components due to eccentricity can lead to accelerated wear and tear on turbine parts. This can result in decreased reliability and increased maintenance requirements.

3.)    Efficiency Loss: Turbine efficiency may be compromised because of eccentricity, as it can lead to inefficient energy transfer between components and increased frictional losses.

4.)    Instability: In extreme cases, turbine eccentricity can cause instability in turbine operation, leading to operational issues and potential damage to the turbine and associated equipment.

To prevent or mitigate turbine eccentricity, proper design, manufacturing, and maintenance practises are essential. Regular inspection and alignment of turbine components can help identify and address eccentricity issues before they lead to significant problems. For a turbine on turning gear, an eccentricity of less than 50 mm prior start-up is desirable.

 

What is Droop (in Power Generation)?

“Droop” in the context of power systems usually refers to a control strategy used in parallel operation of generators or power sources to share load and maintain system stability. Droop control is commonly applied to control the frequency of generators in a power grid.

In a power system, multiple generators are often connected in parallel to supply power to the grid. Droop control is a method used to distribute the load among these generators and ensure a proportional response to changes in system frequency. The concept is based on the observation that as the system frequency decreases due to increased load or other factors, the generators increase their output proportionally.

The basic idea of droop control is that as the frequency decreases, each generator will slightly increase its output, and as the frequency increases, the generators will decrease their output. This way, the generators share the load in a coordinated manner without the need for constant communication between them.

The droop characteristic is typically expressed as a percentage change in speed or frequency for a given percentage change in load. For example, a droop setting of 4% would mean that if the system frequency decreased by 1%, the generator will increase its output by 4% to help restore balance.

Droop control is essential for maintaining stability in interconnected power systems, as it allows generators to respond to changes in load and maintain a balanced frequency across the grid. this control strategy helps prevent one generator from taking on too much load, minimizing the risk of instability and ensuring a reliable and coordinated power supply.

 

 

What will happen if Grid frequency drops below 50 Hz.?

 

If the grid frequency drops below 50 Hz, it indicates a deviation from the standard operating frequency of the electrical grid, which can have several consequences:

1.)   Decreased Power Quality: Appliances and equipment designed to operate at the standard frequency of 50 Hz may experience reduced performance or malfunction at lower frequencies. This can manifest as issues such as dimming of lights, inefficient operation of motors, or erratic behaviour of electronic devices. Some sensitive equipment, like computers or medical devices, may be particularly vulnerable to fluctuations in frequencies. Leading to potential data loss or operational errors.

2.)   Risk of blackouts: A significant drop in grid frequency indicates an imbalance between electricity supply and demand. If left unaddressed, this imbalance can lead to instability in the power system, potentially resulting in blackouts or widespread power outages. Blackouts can have severe consequences, disrupting essential services, causing economic losses, and posing risks to public safety.

3.)   Equipment damage: Electrical equipment, especially those with rotating machinery like motors and generators, may be damaged if operated at frequencies significantly lower that their rated frequency. This is because lower frequencies can cause motors to overheat or generators to experience mechanical stress beyond their design limits. Such damage can lead to costly repairs or equipment failures, further exacerbating grid instability.

4.)   Loss of synchronization: In interconnected power systems, frequency deviations can cause generator to lose synchronization with each other. Synchronization is crucial for maintaining stable power flow and voltage levels across the grid. When generators become desynchronized, it can disrupt the balance of supply and demand, leading to voltage fluctuations, power surges, and potential cascading failures that affect the entire grid.

 

To address frequency deviations and mitigate these consequences, grid operators employ various control mechanisms:

·       Adjusting power plant output

o   Grid operators can adjust the output of plants to match electricity supply with demand, helping to stabilize grid frequency.

·       Shedding load

o   In extreme cases of frequency deviation, grid operators may implement load shedding measures, temporarily disconnecting non-essential loads from the grid to reduce demand and restore balance.

·       Activating automatic generation control system

o   These systems continuously monitor grid frequency and automatically adjust the output of power plants to maintain frequency within acceptable limits.

 

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Asynchronous machine

 

An Asynchronous machine, also known as an induction machine, is one of the most common types of electric motors used across various industries worldwide. Its operation relies on the principle of electromagnetic induction, discovered by Michael Faraday in the early 19^th century.

The key components of an asynchronous machine include the stator and the rotor. The stator is the stationary part of the motor and consists of coils of wire wound around an iron core. When alternating current (AC) is supplied to the stator windings, it generates a rotating magnetic field due to the changing magnetic polarity. This rotating magnetic field induces an electric current in the rotor, which is typically made of conducting material, such as aluminium, or copper.

The rotor, being made of conductive material, experiences electromagnetic induction when exposed to the rotating magnetic field produced by the stator. As a result, currents are induced in the rotor. Which in turn generates its own magnetic field. The interaction between the rotating magnetic field in the stator and the induced magnetic field in the rotor creates a torque that causes the rotor to rotate. This rotation produces mechanical energy, which can be used to drive various industrial processes, such as pumps, fans, compressors, and conveyor belts.

One of the distinguishing features of asynchronous machines is that the speed of the rotor rotation is always slightly less that the speed of the rotating magnetic field in the stator. This speed difference, known as slip, is necessary for the motor to generate torque and produce mechanical work. The amount of slip varies depending on the load on the motor and the design characteristics of the machine.

Asynchronous machines offer several advantages, including reliability, robustness, and simplicity of design. They have fewer moving parts compared to synchronous machines, making them less prone to mechanical failure and requiring minimal maintenance. Additionally, asynchronous machines are suitable for a wide range of applications and operating conditions, making them versatile and cost-effective solutions for industrial motor-driven systems.

Overall, asynchronous machines play a crucial role in powering industrial processes worldwide, providing the mechanical energy needed for various manufacturing, processing, and transportation applications. Their efficient operation and widespread availability make them indispensable components of modern industrial infrastructure.