12 STEAM TURBINE OPERATION QUESTION ANSWER
Hello ! power engineers today we discussed about the 12 STEAM 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 1.What are the functions of the air balancing pipe of condensing water pump?
If air inside condensing water pump or air leakage in the pump inlet, exhaust the air through air tube to condenser to ensure the normal running of the condensing water pump.
Q 2. How to deal with the problem that un-tightness and leakage at shut-off valve during pump shutdown?
Immediately shut off the outlet valve maintaining the pump continuous running and adopt other effective measures to control and cut the reversed rotation of the feed water pump.
Q 3.Why is it necessary to trially start up after exchanged the bearing foot?
It is to observe the tightness of the disc foot. too tight causes the disc foot heated up and too loose will happen water leakage, therefore it is necessary to trially start up after exchanged the bearing foot
Q 4.How to solve the circulating water pump tripping case?
(1) start up the interlocking pump (2) shut off the pump interlocking (3) immediately check the tripping pump, if any revered running requiring shutting off the outlet valve(4) check the interlocking pump performance (5) non-interlocked standby pump shall be immediately started up (6) immediately report to the head shift to reduce the load if no standby pump or the standby pump tripped after interlocking. (7) Contact the electric engineer, to check the causes
Q 5.What is the main reason for steam evaporization at water pump?
excessive low water inlet pressure or excessive high water temperature, fault at the inlet pipe valve or jammed cause water supply inadequate and excessive pump load or retardness on re-circulating valve opening, air leakage in the inlet piping or valve disc foot.
Q6. What are the evaporization and how to deal with?
The main signal for happening the evaporization is noise sent out from the pump inlet and at the same time, the indicator of pump inlet vacuum meter, outlet manometer and ammeter abruptly move. It is not suitable to continuously maintain running at a low water level when condensing pump have evaporization, but adopt ways like restrain the outlet valve opening or make use of the recirculating valve opening or supplement softened water to condenser to increase the water level inside and eliminate pump evaporization
Q 7.What are the symbols telling the occurrence of evaporization at the inlet?
Pump current, outlet pressure, and inlet pressure, severe variation of flow rate, and noise and vibration inside the pump.
Q 8.What are the items required to check the pump running?
(1) Motor: normal current, outlet flue gas temperature, bearing temperature, bearing vibration, and running sound with good earthing and fixed anchor bolt.
(2) pump proper: normal inlet and outlet pressure, no heating disc foot and water leakage with normal running sound, smooth cooling water flowing through the bearing, non-clogged water discharging outlet, normal oil level, high quality oil and normal oil supply with no oil leakage and well-fixed coupling cover.
(3) Insulation at the connection with the pump is satisfied and fixed support & bracket and normal valve opening with no leakage
(4) Relevant instruments shall be in complete and good provision with normal indications.
Q 9.What is the permissive suction degree of vacuum for water pump?
A. it refers to the permissive vacuum value of the pump inlet: it means if the local atmospheric pressure is 10m water column with 20℃ transporting temperature and no cavitation at the inlet, the maximum vacuum at the pump inlet shall be the permissive suction degree of vacuum for water pump.
B. because if the inlet vacuum is too high, liquid at the inlet will evaporized and appear cavitation, therefore it is important to stipulate the permissive suction degree of vacuum for water pump.
12 STEAM TURBINE OPERATION QUESTION ANSWER
Q 10.Why does the water pump run reversely? Why is it necessary to prevent pump reversed running?
When the pumps run in parallel or one set of pump runs alone, if a high water column at pump outlet, one pump suddenly shut down with untight shut-off valve, the pump will run reversely. The reversed running will cause the pressure reduction at the main hose, therefore prone to bumping and loose bearing gland, even worse, may cause frictions at the moving and static parts. When reversed running appears, shut off the outlet valve to stop the rotor without permission to shut off the inlet valve prior to the full shut-off of the outlet valve in order to avoid over pressure at the inlet. It is inhibited to start up this pump during the reversed running, or not only cause system imp-action and water hammering phenomenon damaging the unit and also burn the motor due to excessive start-up momentum
Q 11.What is the pump cavitation? Is there any hazards? And how to prevent cavitation?
Because the water pressure of impeller inlet is lower than the saturated pressure under the working temperature therefore causing part of the water evaporized. The evaporized steam foam flow into the high pressure area being pressurized and condensed thereafter water around will supplement to this area and bring about the water impaction, this is the pump cavitation.
As for the cavitation hazard consist of
(1) Local water impaction inside the pump will gradual damage to the material surface causing small dot and dimple or scaling to the metal surface. on the other hand, due to water evaporization, oxygen will be separated from the water and oxide the metal parts.
(2) the unsteady cavitation process also cause vibration and noises at the water pump; at the same time, due to the steam foam stuck the impeller flow track during cavitation causing reduction at he flow rate and lift, what’s worse, it may halt the water flow. Therefore, it is required to pay attention to avoid pump cavitation.
The main measures are:
(1) adopt the double suction impeller
(2) enlarge the impeller inlet area and the width of blade inlet trim.
(3) set the front guide wheel or add the front located pump
(4) the primary impeller is of cavitation-proofing material
(5) try to increase the impeller inlet pressure
(6) avoid pump running if the transporting liquid temperature excess the designed value (7) avoid long time running if the pump does not supply water or water flow rate excessive low.
Q 12.What are the main reasons for feed water pump cavitation?
- Internal pressure reduction in the condenser
- Water level at the deaerator water tank is too low
- Long time running of the feed water pump under smaller flow rate and no load conditions
- the wrongly shut off or extremely small opening of the re-circulating valve of the feed water pump resulted in the feed water running under no flow rate or extremely small flow conditions.
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