Question No. 1 Usually it has been found that SCC attack takes place particularly at key-ways of shrunk-on-disc rotors of low-pressure turbines. Why are key-ways prone to SCC attack? Answer: 1. Key-ways shrunk-fit each disc onto tile rotor shaft. They improve the rigidity of the connection between the disc and the central shaft However, key ways…
Question No. 1 In which turbine is velocity compounding utilized? Answer: In the Curtis turbine. Question No. 2 In which zone of steam turbines has temperature-creep rupture been observed? Answer: Damage due to creep is encountered in high temperature (exceeding 455°C) zones. That is, it has been found to occur in the control stages of…
Question No. 1 How would you stop air from leaking into a condenser? Answer: First, find the leak by passing a flame over the suspected part while the condenser is under vacuum. Leaks in the flange joints or porous castings can be stopped with asphalt paint or shellac. Tallow or heavy grease will stop leaks…
Question No. 1 How is pressure compounding accomplished? Answer: 1. This is accomplished by an arrangement with alternate rows of nozzles and moving blades. 2. Steam enters the 1st row of nozzles where it suffers a partial drop of pressure and in lieu of that its velocity gets increased. The high velocity steam passes on to the…
Question No. 1 How can problems of “excessive vibration or noise” due to piping strain be avoided on steam turbines? Answer: 1. The inlet as well as exhaust steam lines should be firmly supported to avoid strains from being imposed on the turbine. 2. Adequate allowance should be made for expansion of steam pipes due to heat….
Question No. 1 In which turbine tip leakage is a problem? Answer: Tip leakage is a problem in reaction turbines. Here, each vane forms a nozzle; steam must flow through the moving nozzle to the fixed nozzle. Steam escaping across the tips of the blades represents a loss of work. Therefore, tip seals are used…
Question No. 1 What is the function of a thrust bearing? Answer: Thrust bearings keep the rotor in its correct axial position. Question No. 2 What is done when cracks due to SCC or corrosion-fatigue are found? Answer: The damaged blade is usually replaced, as repairing is difficult. Question No. 3 What is a stage…
Question No. 1 In which section of the steam-turbine rotors is the problem of rotor failure mostly prevalent? Answer: Rotor failures occur mostly on the large low-pressure rotors. Question No. 2 In which turbines, is this pressure-velocity compounding principle employed? Answer: In the Curtis turbine. Question No. 3 What are the disadvantages of velocity compounding?…
Question No. 1 What is the possible cause of slow start up of a steam turbine? Answer: This may be due to high starting torque required by the driven equipment. Question No. 2 What is the remedy for rotor-surface cracking? Answer: Current rotor/shaft should be machined off (skin-peeling). Question No. 3 What is to be…
Question No. 1 What is the purpose of a turning gear? Answer: Heat must be prevented from warping the rotors of large turbines or high-temperature turbines of 400°C or more. When the turbine is being shut down, a motor-driven turning gearis engaged to the turbine to rotate the spindle and allow uniform cooling. Question No….