Training Manuals on CFBC boilers & Steam Turbines

Thanking all for tremendous response ! 

1. Training Manual on CFBC Boiler (Non Reheat type) - Revised & Enlarged   

Now available on Google Books - Click here to buy from Google play

It contains following topics:

Chapter 1  - FUNDAMENTALS OF A STEAM POWER PLANT Chapter 2  - FUELS FOR POWER GENERATION Chapter 3  - PRINCIPLES OF COMBUSTION Chapter 4  - GENERAL DESCRIPTION OF A CIRCULATING FLUIDIZED BED COMBUSTION BOILER Chapter 5   -  FEATURES OF CIRCULATING FLUIDIZED BED (CFB) BOILERS Chapter 6   - HEAT EXCHANGERS IN CFBC BOILERS Chapter 7   - DESIGN AND MATERIAL CONSIDERATIONS Chapter 8   - ELECTROSTATIC PRECIPITATION AND DUST EXTRACTION Chapter 9   - DRAUGHT SYSTEM Chapter 10 - BOILER WATER CHEMISTRY Chapter 11 - OPERATION OF CFBC BOILERS Chapter 12 - PRESERVATION OF BOILER Chapter 13 - MECHANICAL MAINTENANCE OF CFBC BOILERS  Chapter 14 – BOILER PERFORMANCE OPTIMIZATION Chapter 15 - TUBE LEAKAGES IN CFBC BOILERS SYMPTOMS, CAUSES AND REMEDIES Chapter 16 - FURNACE EXPLOSION IN CFBC BOILERS – EXPLANATION, PREVENTION AND PROTECTION

2. Training Manual on Steam turbines (non-reheat) and auxiliaries 

Now available on Google Books - Click here to buy from Google play

It contains following topics:

Chapter – 1  Thermodynamics of a Steam Turbine

Chapter – 2 Steam Turbine Fundamentals

Chapter – 3 Constructional features of steam turbines

Chapter – 4 The lubricating oil system 

Chapter – 5 Steam turbine governing system

Chapter – 6 Steam turbine protection system

Chapter – 7 Turbovisory system

Chapter – 8 Turbine gland sealing system

Chapter – 9 Turbine system and cycles

Chapter – 10 Condensers, deaerators and closed feedwater heater

Chapter – 11 Main and auxiliary cooling water systems and cooling towers

Chapter – 12 Turbine Plant Pumps

Chapter – 13 Condensate and feed water treatment

Chapter – 14 Turbine Plant Operation

Chapter – 15 Turbine Plant Maintenance

Chapter – 16 Turbine performance and optimization

Highly Recommended for :

• Power Plant Professionals seeking high growth in career

• Interview preparations for power plant jobs

Why the books are recommended ?

So far the books written on thermal plants describe mostly the reheat type units. These books are intended for technical personnel working in utility plants but, again, most of them deal predominantly with the theoretical aspects of turbines and their auxiliaries and lack in practical side of the subject.

The aim is to give following benefits to the reader:

•  To provide an in-depth knowledge of plant and equipment to the plant professionals associated with industrial boilers and turbines. It is to be noted that most of the industrial thermal units (like captive power plants attached to main technological units) are of non-reheat type.

• To cover the practical aspects of thermal power stations missing in most of the books available in the market. The book describes in details the constructional features of the plant and equipment, their operation and maintenance and overhauling procedures, performance monitoring as well as troubleshooting.

• To cover the theoretical aspects of a thermal unit necessary to be known to the professionals for thorough understanding of the systems involved. This knowledge would assist them:

1.      In selecting the plant and equipment suitable to their requirement
2.      In operating and maintaining the plant with best efficiency, availability and reliability

The book is a must for those working professionals who aspire for a fast growth of their professional career. It will also be of immense help to the personnel preparing for boiler proficiency examinations.

Training Module for Thermal Power Plants

PTS has been engaged in providing Thermal power plant training solutions to professionals across spectrum.

Following is a typical training module for Thermal power plant professionals & each training day will be of 5-7 hrs.
You can choose the topics of your choice (Customized to your needs).

For further details email us - training@ptsconsultancy.com 

Or

Contact through our website mentioning your detailed requirements - Click here

PTS Conducted Power Plant Training

With Vibrant team of Meghalaya Power Limited  after training.

Prameela Technical Solutions recently conducted power plant training for Meghalaya Power Limited, Shillong

Topics included:

1. Fuel Combustion & Performance Monitoring (power plant) - 2 Days

2. Boiler & Water Chemistry - 1 Day

3. Operations of thermal power plant (CFBC boiler based) - 2 Days

All About Bearings

KNOW ALL ABOUT BEARINGS

We provide technical consultancy for all areas of thermal power plants.

Objectives of this article :

• To achieve maximum bearing performance.

• To reduce costly down time.

• To minimize labor requirements.

• To ensure that the equipment, in which the bearings are installed, runs smoothly / effectively.

Reasons for bearing failure :

	Reasons	Counter measures
1.	Bearing Quality	-          Avoid installing spurious bearings
2.	Operating Environment	-          Proper alignment. -          Protection from temperature, moisture & contamination.
3.	Proper installation	-          Knowledge of proper installation. -          Knowledge of use of proper tools.
4.	Proper Maintenance	-          Lubrication. -          Maintenance schedules. -          Monitoring operating conditions

Selection of bearing :

Each bearing type is designed to meet the requirement of specific bearing applications.

Whenever a bearing fails prematurely or repeatedly, it is very important to establish the cause of the damage, so that preventive action can be taken and proper replacement bearing can be selected.

Rolling bearings include radial and thrust bearings for radial and axial loads and some bearings are designed for continued radial and axial loads.

Generally ball bearings are recommended for light and moderate board roller bearings are recommended for heavy loads.

Ideal condition :

1)            The actual load is less than designed load.

2)            When the rolling surfaces are effectively separated by a lubricant film.

3)            When surface damage caused by contamination is limited.

Under ideal condition bearing can attain a much longer life / infinite life.

Failure is initiated by fatigue, wear, corrosion contamination, seal failure, etc.

Bearing life is defined as the number of revolutions or the number of operating hours at a given constant speed which a bearing is capable of enduring before the first sign of fatigue occurs on one of its rings or rolling elements.

Of the bearings which do fail, approximately one third “die” from old age, i.e. fatigue of the bearings surfaces.Another third fail because of poor lubrication and rest fail mainly as a result of contaminations entering the bearings or because of handling damage or faulty mounting. 

However, pattern varies between different industrial segments.

How bearing failure starts

Fatigue is the result of shear stresses cyclically appearing immediately below the load carrying surface.  After a time these stresses cause cracks which gradually extend up to the surface.  As the rolling elements pass over the cracks fragments of material break away and this is known as sapling or flaking.  The flaking progressively increases in extent and eventually makes the bearing un-serviceable.

This type of bearing damage is a relatively long drawn out process, making its presence known by increasing noise and vibration.   Therefore, it gives user adequate time to replace the bearing before it fails completely.

When cracks forms on the surface and grow into the material, surface distress is at hand.  All surface contains roughness.  If the oil film has a proper thickness in relation to the surface roughness, the probability for surface distress is very low. 

If however the load is above the fatigue load limit, normal material fatigue may sooner or later occur.

Replace with care :

Bearings are calculated to run under very specific operating conditions.  Too often, changes involving the use of a different lubricant, higher machine speeds, higher loads, and change in lubrication system,are made without anticipating possible negative effects.

Therefore, when replacing a bearing no other changes should be made, which would adverse affect bearing operation.

What to look for during operation ?

Checking the condition of a machine in operation and planning for its necessary overload is becoming an issue of increasing importance.

Bearings constitute a vital factor in all machines with rotating parts.  Condition monitoring represents a rapidly growing activity in the field of preventive maintenance.  Early indications of bearing damage allow bearings to be replaced during regularly scheduled maintenance and thus avoid unscheduled equipment downtime due to bearing failure.

Bearings in critical machinery or in severe environment should be checked frequently.  Many systems and instruments are available for monitoring bearings.

However, for practical reasons not all machines or machine functions are monitored using advanced instrument.  In these instances the machine operator or the maintenance engineer must remain alert for bearing trouble signs, such as noise, increase in temperature and vibration.

Listen, Feel and Look are three important factors.

Listen :

ü  A common way of identifying an irregularity in running is by listening.  With the help of an electronic stethoscope, abnormal noise can be detected and even traced to an individual machine component by an experienced operator.

ü  Bearings in good operating condition produce a soft purring noise.

ü  Grinding squeaking and other irregular sounds usually point to bearings in poor operating conditions. They are:

• A squeaking noise may be caused by inadequate lubrication.

• Insufficient bearing clearance can produce a metallic tone.

• Indentations in the rear ring raceway of a bearing can cause vibration resulting in a smooth, clear tone.

• Ring damage caused by blows during mounting or scoring leads to sounds, which vary according to the operating speed of the bearings.
• Intermittent noises may indicate damage to a rolling element.  The sound is generated when the damage surface is rolled over.

• Dirt in a bearing often causes a grinding sound.

• Severally damaged bearing produce irregular and loud noises.

Bearing damage can certainly be detected by listening, but the damage will often reach such an extent that an immediate bearing change has to be carried out.

Using of Electronic Condition Monitoring devices are much safer and more accurate prediction than the early method of placing one end of a wooden strake or a screwdriver against the bearing housing and putting one ear to the other end.

Feel :

ü  High temperature often indicates that the bearing is acting abnormally.  Overheating is attributed to the bearing lubricant.  Running for extended period at temperatures in excess of 125°C can reduce bearing life.

ü  Causes of high bearing temperature include insufficient or excessive lubrication, impurities in the lubricant, overloading, bearing damage, insufficient clearance, pinching and high friction in the seals.

Any change in temperature can be an indication of malfunction, if the running conditions have not been altered.

Critical bearings which cause equipment downtime when they fail should ideally be equipped with a heat probe.

Look :

ü  Properly lubricated bearings that are adequately protected from dirt and moisture should not exhibit wear.

ü  However, it is advisable to visually check a bearing when it is uncovered and to periodically check the seals.

ü  Check the condition of seals near the bearings to ensure that they do not permit hot or corrosive liquids and gases to penetrate along the shaft.

ü  Keep protective collars and labyrinth seals filled with grease to ensure maximum protection.  Replace worn felt and rubber seals as soon as possible.

ü  In addition to preventing the entry of dirt seals, it is also important to keep lubricant in the bearing housing.  Lubricant leaks at seal locations should be inspected immediately for worn seals, seals defects and loose plugs.  Leaks can also result from slacking of the joint between the matching surfaces of the bearing housing or from the grease breaking down by churning and releasing free oil.

ü  In order that the automatic lubricating systems perform properly, fill them with oil or grease and ensure that the right amount of lubricant is released.

ü  Also take a good look at the lubricants’ discoloration or darkening because these are usually signs that the lubricant contains impurities.

For any queries/additional information, email us - info@ptsconsultancy.com

We provide technical consultancy for all areas of thermal power plants.

Engineering Formulas

  

Causes of Poor Performance of ESP's (Electrostatic Precipitators)

We undertake all types of works for Dry ESP  under Overhauling, Performance Enhancement, Technical troubleshooting and Erection Works. Visit our site for details.

Causes of poor performance of ESP & discussions

There are many causes of poor performance of ESP (Electrostatic Precipitators). Some of the reasons are:

·       Excess gas volume

·       Poor gas distribution

·       Tracking and air inleakage

·       Electrode breakage

·       Ash resistivity

·       Particle size

·       Electrical conditions

·       Over-full  hoppers

·       Defective collector plates

Excess gas volume

If the gas volume is high, the gas velocity through the precipitator will be high so that the time available for the charged particles to migrate to the collector plates is reduced, possibly to the extent that the particles pass out of the working zone before they can be captured. The normal gas velocity is about 2 m/s, but this may be increased by:

·       Tramp air in leakage at the boiler.

·       High air heater gas outlet temperature causing increased volume flow.

·       Poor condition of rotary air heater seals.

·       Operating the boiler with too much excess air.

Poor gas distribution

It could be that the total gas flow is satisfactory but the spatial distribution is poor, causing good performance where the gas velocity is low and for it to be poor where the velocity is high. To be completely acceptable, all the traverse point velocities should be within 25% of the average for the duct.

Tracking and air in leakage

This is a common cause of trouble because precipitator structures are physically large and have numerous access doors, etc, at which leakage can occur. If the in leakage is sufficiently high, a draft of cool and possibly moist air will pass over the insulators, steady bars, etc. As the voltage inside a precipitator is very high (40-50 k V), tracking paths may result. Therefore, it is important that access -door seals, rapping rod covers, expansion joints and other ingress points are kept in good condition and are airtight.

Apart from above hazards, there are the additional disadvantages that in leakage increases the mass flow of the gas and lowers its temperature.

Poor rapping

In the usual precipitator arrangement the wires are negatively charged and the collector plates are earthed. In the immediate vicinity of the wires the electrostatic field is so strong that corona discharge occurs. The corona ionizes the flue gases and the entrained solid particles acquire negative ions, causing them to migrate towards the relatively –positive collecting plates. A few particles acquire positive ions and theses migrate towards the discharge electrodes.

The dust which adheres to the wires and collecting plates is periodically removed by rapping.

The timing of rapping operation is important as damage can be done to the plant if it is too frequent. Also, every time rapping takes place some of the dislodged dust is re-entrained, so reducing the collection performance. On the other hand, if the interval between raps is too great, the dust build-up on the wires and the plates will be sufficient to interfere with the operation of the plant and this also will reduce its performance. Efforts should be made to determine the optimum timing.

Upon inspection, the collector plate dust –layer should be less than 1 mm for high resistance dust and 3 mm for dust from coal with high sulphur. The discharge electrodes should have a very light deposit.

Electrode  breakage

The discharge electrodes consist of relatively thin wires which may be of flat, circular, star or square cross-section. In addition, they may be barbed or plain, twisted or straight and rigidly or loosely fastened, besides being made from a range of materials. Whichever arrangement is adopted, the essential requirement is that the wires should have excellent reliability. Out of the huge number in a zone, it only needs one to break to cause short-circuiting and electrical instability generally, which may seriously affect the performance of the plant.

Spark erosion is a common cause of wire failure.

The ‘unbreakable’ type of wire is becoming popular because of its inherent reliability. One method of limiting the effect on performance by breakage is to divide a complete zone into four sub-zones, so that a broken wire only affects a quarter of the zone.

Ash resistivity

An important factor in precipitator performance is the electrical conductivity of the ash itself. Poor combustion can result in a higher than normal carbon content in the ash. This causes the particles to have a lower resistivity which may cause them to be difficult to collect. This means that they can be readily re-entrained by the gas, particularly during rapping. On the other hand, if the resistivity is too high, the dust will accumulate on the collector plates and form an insulating layer, so preventing subsequent particles from surrendering their charge. Consequently, the charge on the surface layer will repel incoming dust, causing re-entrainment. In addition, a very high voltage- gradient will be built up across the dust layer which could result in flashover. Dust with high resistivity will suppress the corona discharge, seriously lowering the performance of the plant.

The resistivity of the ash is a function of the surface layers of sulfuric acid, salts and moisture, particularly the acid. If the coal contains about 2% sulfur, the resulting sulfuric acid deposition creates a desirable level of dust resistivity. If the sulfur content of the coal is very low, a highly resistive ash may be produced which is very difficult to precipitate. One remedy for this is to inject small quantities of suitable additives, such as ammonium sulfate, into the flue gas.

The desirable range of resistivity is between 10⁶ and 10¹² ohm-cm. Should the normal fuel supplies be low in sulfur and a change to alternate supplies be uneconomic, another possible remedy besides injection is to install ‘pulsed  energization’. In this, high frequency pulses are added to the rectified wave form. The resulting high ion-density corona acts along the length of the discharge electrode instead of just at discrete locations, so the dust particles are more easily precipitated. The improved performance is called the Enhancement factor given by (pulsed migration velocity)/ (unpulsed migration velocity).

Particle size

Particle sizing has an important bearing upon the efficiency of precipitations. Up to approximately 20 µm, the electrical and the drag forces combine to give a deposition velocity which increases in roughly efficient for sizes over 20 µm, the only problem being that of slight re-entrainment. Dust less than 20 µm is more difficult to capture, so the stack emission will contain a preponderance of fine particles.

Electrical conditions

Figure below shows the relationship between electrical power input and   precipitator efficiency. As one would expect, increased power results in improved performance, provided the power is useful.

For example, flashover and tracking will give high power consumption, but much of it is wasted. To find the demarcation between useful and wasted power, a simple graph is determined from tests on the plant. Starting at a low value the current is increased by suitable increments, noting the corresponding voltage. A typical diagram is shown below:

Notice that the current and voltage both increase until the voltage is about 45 k V. Thereafter increasing current is accompanied by reducing voltage. The knee of the curve determines the demarcation between stable and unstable operation, the highest stable current here being a little over 200 m A. The automatic voltage control always tries to operate the plant with the highest stable power input which can be maintained.

Causes of electrical instability include:

·       Tracking , possibly due to air ingress

·       Arcing and poor connections, possibly at sub-zone isolation selectors

·       Ineffective rapping

·       Overfull dust hoppers, causing bridging of electrodes

·       Misaligned electrodes

·       Broken discharge electrode wires

Defective collector plates

The plates are mechanically strong, but can become defective if the gas temperature falls below the dew point, allowing deposition of dilute acid. This can occur in discrete areas if cold air inleakage takes place. Alternatively, general corrosion can occur if the flue gas itself has a low temperature, possibly due to massive air ingress at defective seals on the ducts between the air heater and the precipitator, or if the ducting is corroded and holed. Frequent cold-starting of the boiler can also lead to low- temperature gas at the precipitator.

We undertake all types of works for Dry ESP  under Overhauling, Performance Enhancement, Technical troubleshooting and Erection Works. Visit our site for details.