What is the min Oxygen percentage should be maintained in boiler for continues combustion process in full load?
O2% in the flue gas after the combustion is called Excess Air (i.e. Excess O2%). This is a way to ensure combustion is complete with sufficient air. Hence O2 in the flue gas is maintained approx 1% at Full load. Understand the combustion process & refer the Optimum combustion zone in the below slides. Hope it is clear.
Minimum 1% needs to be maintain in Full load condition of boiler.
First we should ensure the load condition of boiler. Based on the boiler load, Fuel and air flow needs to be adjusted. So that we will get a proper combustion.
Some times what happens in full load condition of boiler, Readings will go to "0% "of O2 Due to carbon presence in the smoke.
This we can ensure visually through by seeing the Duct smoke itself.
If the smoke colour is observed with "Black" then we suggest customer to increase the air flow rate also this type of problem occurs due to lesser air flow rate and carbon presence in combustion. By increasing the airflow rate carbon presence in the combustion will get reduced.......
Incase smoke colour is observed with "White" it will be due to 50% of load or lesser than the load that time readings will be more than 5% of O2.
Incase Boiler load, Air and fuel flow rate is normal then the smoke colour will observed with "Blue" colour.
Seeing physically we can ensure the combustion of boilers.
Combustion not only based on the feed rate of fuel and air flow, It also depends on Calorific Value of "Fuel".
So Depends on the calorific value of fuel combustion and efficiency of boiler also will varies....
Tuesday, December 20, 2011
What is the min Oxygen percentage should be maintained in boiler, furnace.
Sunday, December 18, 2011
vibration sensors using negative voltage for sensing the vibration
For High speed rotating equipment only,we are using this negative voltage for vibration sensor.This negative voltage is always set as gap voltage between the sensor and surface of the rotating equipment.
This gap voltage is always set as -10Vdc.
This because of Ratio frequency, which is created by the controller of vibration sensor. These frequencies are generated under negative voltage only. which is also varies with respect to eddy current flow. The amplitude of this ratio frequency is measured as vibration.
For your information, Noice level is very less in negative voltage compare than positive voltage which will not affect the sensitive range of measurement of vibration.
For your information:-This concept is used in Bently neveda vibration monitoring system.
The principle is that analyzer supplies a negative voltage to transducer, who converts it into a frequency & sends it across the probe. Now as the probe comes into the area of
rotor it creates a magnetic field & with it eddy current is produced on the rotor side. This changes the amplitude of the frequency. It induces the voltage & remaining frequency
comes to the transducer through the return way. Transducer converts it into the voltage.
Now coming back to the question The gap voltage has a negative relation with the voltage induced i.e. as the gap increases the induced voltage decreases. So to make it to
into a linear relationship, negative voltage is supplied.
i.e
Gap Gap voltage
0 mm 0 vtg
1 mm -9 voltage
2 mm 18 voltage
& when the probe is in air it will have no induced voltage so all -24 voltage without induced voltage will return back.
Difference between grounding and earthing
1. What is the Difference between Earthing & Grounding?
1. Grounding means connecting the live part (it means the part which carries current under normal condition) to the earth for example neutral of power transformer.
2. Earthing means connecting the dead part (it means the part which does not carries current under normal condition) to the earth for example electrical iron etc.
3. One of the most misunderstood concepts is earthing and grounding. We all understand that it is necessary, we need to understand that there are really two separate things we are doing that we call grounding.
The first, is to reference our electrical source to earth (usually via connection to some kind of rod driven into the earth or some other metal that has direct contact with the earth). In the system, this is typically accomplished via a 120/240-3 wire system where neutral has a connection to earth at the source (for residences). Industrial power that has an earth reference has other means of referencing to earth, but generally all have some direct connection to earth. The exception of course is 440V delta which often has no earth connection.
The second thing we often call grounding is really bonding. That is when we take and connect all the metal parts in our systems that might become energized (such as if a conductor came loose). This is done with equipment grounding conductors or sometimes with conduit or raceway systems. The key is to get all the metal pieces electrically connected together. All these metal parts are then connected to the electrical reference point (neutral in the case of residences). That way if a hot conductor comes in contact with a piece of metal a current path exists back to the neutral point that causes the branch circuit protector to open up because there is a short circuit.
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth.
Electrical circuits may be connected to ground (earth) for several reasons. In mains powered equipment, exposed metal parts are connected to ground to prevent contact with a dangerous voltage if electrical insulation fails. Connections to ground limit the build-up of static electricity when handling flammable products or when repairing electronic devices. In some telegraph and power transmission circuits, the earth itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor.
For measurement purposes, the Earth serves as a (reasonably) constant potential reference against which other potentials can be measured. An electrical ground system should have an appropriate current-carrying capability in order to serve as an adequate zero-voltage reference level. In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential. Where a real ground connection has a significant resistance, the approximation of zero potential is no longer valid. Stray voltages or earth potential rise effects will occur, which may create noise in signals or if large enough will produce an electric shock hazard.
The use of the term ground (or earth) is so common in electrical and electronics applications that circuits in portable electronic devices such as cell phones and media players as well as circuits in vehicles such as ships, aircraft, and spacecraft may be spoken of as having a "ground" connection without any actual connection to the Earth. This is usually a large conductor attached to one side of the power supply (such as the "ground plane" on a printed circuit board) which serves as the common return path for current from many different components in the circuit.
2. Whether earth can be used as neutral? If yes then why neutral required?
Earth
1. It is used for safety purpose. i.e whenever leakage current pass through electric machine body, earth will conduct directly to earth. So it is prevent electric shock to human body.
2. In 3 phase star connection its act as a neutral & same point connected to ground.
Neutral
3. It is one of the wires in AC circuit.
4. It is used for return path of the circuit in single phase & three phase.
Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosures, so the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations. Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground.
Ground or earth in a mains (AC power) electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment (the terms "ground" and "earth" are used synonymously here). Normally a grounding conductor does not carry current.
Neutral is a circuit conductor (that carries current in normal operation), which is connected to earth (or ground) generally at the service panel with the main disconnecting switch or breaker.
In a polyphase or three-wire (single-phase) AC system, the neutral conductor is intended to have similar voltages to each of the other circuit conductors. By this definition, a circuit must have at least three wires for one to serve as a neutral.
In the electrical trade, the conductor of a 2-wire circuit that is connected to the supply neutral point and earth ground is also referred to as the "neutral". This is formally described electrical codes as the "identified" circuit conductor.
All neutral wires of the same electrical system should have the same electrical potential, because they are all connected together through the system ground.
Earth can use as neutral but neutral can't use as earth.
1) For closing the complete circuit neutral is mandatory.
2) Once the circuit is closed then only current will flow through any Electrical & Electronic circuit so without neutral any AC Electrical & Electronic circuits won't work.
3. Why we should provide link instead of fuse in neutral line?
1. In AC power system we should not use fuse in neutral. (neutral is using at distribution level for getting single phase or 3 phase 3wire 4wire system to supply the power to the some loads), if we provide fuse in neutral, during the fault condition the fuse in neutral will be blown and the faulty current will not be grounded, this may leads to damage the whole circuit, if we provide link in the neutral the faulty current will be grounded and the circuit will be protected against the fault.
This is the purpose of providing link in neutral.
Thursday, January 13, 2011
HAPPY PONGAL - INIYA PONGAL NAL VAZHTHUKAL
Thursday, January 6, 2011
Welcome
Hi all, This is my first post for my blog - complete technical portal. You can learn about technical thing which i learnt in my carrier.
If u also want to share the exp of your technical things it fine and good.
vinoth kumar J
Friday, October 9, 2009
India, About India, Indian History, Indian Legends
mobile controlled robo for face deetection
An autonomous mobile robot with a face detection system should be
able to find human faces. The robot is controlled through a mobile phone any
where in the world .But, what‟s more useful about out MOBILE CONTROL
ROBOT USED TO FACE DETECTION is that they can find whether human are come across the restricted area.
FOR FURTHER DETAILS
While we make call to the robot it will be in auto pick up mode .we can
control the robot after the call attended .The values are feed to the
microcontroller and they can be processed. Then robot is controlled through
far away distance with another mobile the controls are front, back, right turn
left turn ,and camera rotated with 360 degrees.
The live video is capture through a web cam .video is converted into 12
frames per second after conversion each frame is compare with the predefined
algorithms mat lab for face detection system if any human faces is detected a
marking the detected face is show on system monitor.
Click Download to get the file.
DOWNLOAD