Generator Air Tightness Test

Generator Air Tightness Test

• Period Of Test= 24 Hrs without a Break
• Air Pressure Drop (Allowed in 24 Hrs) : <=0.15 ksc
• Air Test Pressure = 3.5 ksc
• All LLDs Drain Closed.
• Ensure Seal Oil system in Operation
• Seal Oil DP >1.5 ksc
• AS Seal Oil Pr>4.5 ksc, start H2S Seal Oil system
• H2 Cooler Isolated
• PW in Winding is in filled condition, Winding Isolated. PW also kept Isolated.
• PW Tank at Atmospheric Pressure
• Ensure availability of  Instrument air and Bleed Out moisture from it by keeping it open till 
• Connect flexible air hose with the gas plant through the coupling and ensure no air leakage is there 
• The filling is to be done by opening the valves in the normal H2 filling line where as the valve from H2 rack side will remain closed.
• Once the air filling is commenced the test record data sheet 
• The air valve is to be opened full.
• While pressurising the LLD / Seal oil DP / Seal oil parameters are to be recorded as per the enclosed sheet.
• The generator casing is to be pressurised with instrument air up to pressure of 3.5 ksc.
• The approximate time to attain rated pressure will be around 7- 8 hrs 
• Record the time when the pressure has reached at 3.5 ksc at the special gauge fixed in the gas rack 
• Stop the air filling and shut off the valve when the test pressure has been reached (3.5bar) and then disconnect the air hose from the system to avoid further pressurisation of the system. 
• Once the rated pressure has been attained, the test can be commenced. 
• Once the test is commenced the test record data sheet is to be filled at hourly basisfor continuous 24 hrs. No break is allowed. 
• During test ensure the LLD‘s are not getting oil 
• If a pressure increase was observed in the primary water tank, a leak of the primary water system with in the generator would be expected and must be located and attended 
• If an air loss higher than 0.15 bar/ 24 hrs, a search for leakages must be made.
• Suspected areas should be brushed with Diprol or other foaming solution. The formation of bubbles (foam) indicates a leak. 
• Attend the leakages and then repeat the test until satisfactory results are obtained.
• If a satisfactory tightness is established the generator may be filled with CO2 and subsequently with H2 as per normal operation practice. 
• After the test is declared complete, the air is to be depressurised and the system is to be normalised 
• After completion of the test, the electrical purity meter system should be calibrated with pure CO2 and H2 
• Normalise the primary water coolers and take the primary water system into service.
• Normalise the all-4 hydrogen coolers 
• Then the generator may be filled with CO2 and subsequently with H2 as per normal procedure.   
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