LATEST TURBINE OPERATION QUESTION ANSWER 2018
Hello ! power engineers today we discussed about the TRENDING TURBINE OPERATION QUESTION ANSWER . these question answer is helpful for those who worked as a turbine operation engineer and who want to know more about the turbine operation . turbine is critical component of any power generation plant because its consist very critical component like thrust pad , blades , bearing etc. which takes extra care during start up of the turbine . these question answer help us the our readers know more about the turbine operation. lets discussed the question answer in detail way
Q.What are the phenomenon and solutions when vacuum reduction appears due to air leakage at the vacuum system?
As the vacuum reduces due to the air leakage, the exhaust temperature raises along with the increasing terminal difference, increasing degree of super cooled condensed water and oxygen content in the condensed water. As the leaking air is equal to the maximum air extraction of the air extractor, the vacuum will reduce to a certain value and be able to maintain at a certain value.
Q.Why it is important to emergency shut down the unit as the vacuum reduces to a certain value?
Because the vacuum reduction makes the blades overload due to the increasing steam flow rate.
Vacuum reduction will increase the axial displacement thereby causing the thrust tile being overloaded and abrased. Moreover, the reduced vacuum will increase the temperature of steam exhaust cylinder and move away from the axis prone to increase the unit vibration. After the temperature of steam exhaust cylinder increased, in order not to activate the low pressure cylinder safety valve and ensure the equipment safety, shut down the unit as the vacuum reduces to a certain value.
Q.Why does the vacuum in the condenser reduce?
The main signals of the condenser vacuum reduction during turbine running are: temperature rise at the exhaust cylinder; reduction at the vacuum meter and obvious terminal difference of the condenser. After the vacuum reduced, if maintaining the unit load without any variations, increase the inlet steam to the turbine and axial thrust force, and blade overloading. Moreover, due to the vacuum reduction, the exhaust temperature will increase thereby making the cylinder being deformed and the unit eccentrically moving away the center of gravity, thereafter causing unit vibration rise and the cooper pipe loosening, deformation and breaking due to its expansion. It is important to check out the causes and solve in time whenever vacuum reduction appears during unit running except the stipulated load reduction.
According to the different vacuum reduction speed in the condenser, two kinds of vacuum reduction are slow vacuum reduction and abrupt vacuum reduction.
The main factors for slow vacuum reduction are:
(1) Temperature rise at the circulating water inlet.
(2) Excessive high water level at the condenser.
(3) Inadequate pressure of steam supply at the bearing seal.
4) Wrongly shut off the sealing gate of the water seal valve during running.
(5) The heat load at the condenser is too large.
(6) The water level of the condensed water tank is too low.
(7) Little leakage of the vacuum system.
The main factors for abrupt vacuum reduction are:
(1) Water halting or water shortage.
(2) Large amount of leakage in the vacuum system.
(3) Full water in the condenser.
(4) Halt of steam supply from the bearing seal.
(5) Fault at the water jet pump.
(6) Improper operation at the vacuum system valve.
(7) Wrong opening vacuum breaking gate.
(8) Damage at the diaphragm of the safety valve.
Q.What are the harm if the water level of condenser is too high?
If the water level of condenser is too high, the condensed water will be super cooled resulted in the low economically running. If the water level is too high, immersing the copper end, the condenser cooling area reduces, even worse, drowning the air pipe thereof making the air ejector eject water and severe vacuum reduction at the condenser vacuum.
Q.What is the main reason for super cooling?
(1) Air Accumulated at the steam side of condenser.
(2) Condensed water level is too high during running.
(3) Excessive amount of circulating water
Q.how to deal with if the hardness of condensed water increases?
(1) If the hardness of condensed water during start-up period is very large, open the water discharging valve to blow down
(2) Shut off the air vent of the backup water jet air ejector
(3) Check the water discharging valve of all the back pressure system to be tight and compact
(4) If any slight leakage from the steel pipe of condenser, immediately inform to add sawdust
(5) If the hardness of condensed water is too large, immediately sample on-site to test pipe leakage, if any, easy to isolate
Q.Why it is necessary to deaerate for the feed water to boiler?
Because while water and air or any gas mix and contact, a part of the air dissolves into the water and part of the air dissolved in the boiler water. Oxygen from the air dissolved in the feed water is the most deadly gas causing oxidation corrosion to the thermal equipment and severely affect the safe and economy running. In addition, the gas existing in the heat exchanging devices may disturb the heat transferring; reducing heating transferring effect therefore it is necessary to do
Q.What are the normal maintenance for the condenser？
(1) Maintain the water level at the normal level.
(2) Secure no water leakage, vacuum leakage, overflow, proper opening at the air exhaust and no vibration
(3) Ensure the vacuum range of condenser within the specified range
(4) Prevent large aptitude fluctuation of water level and vacuum affecting condensing effects
(5) Frequently check and proofread the indoor vacuum meter, water level gauge and on-site instrument to in consistence
(6) The relative protection is under normal conditions
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