Gland Seal System

Air in-leakage and noncondensable gases removed from the condenser air removal system and the gland seal system are routed to the turbine island vents, drains and relief system, where they are... 

The following design requirement for the gland seal system supports safe operation of the plant under normal conditions ... 

Rednce the amount of active gas introdnced into the systems to the minimum practicable (such as by using fresh inactive steam instead of primary active steam in the gland seal system in the tnrbine of a boiling water reactor). 

Double with TEFC gland with air-cooled system Long seal life Pump can be run dry if flow is lost Closed-loop seal system No freeze protection of seal liquid piping More expensive than other options Compressed air or nitrogen must be supplied to seal Contamination of caustic possible if seal fails... 

The mixture of noncondensable gases discharged from the gland seal condenser blower is not normally radioactive however, it is possible for the mixture to become contaminated in the event of primary-to-secondary system leakage. 

The main condenser is designed to receive and condense the full-load main steamflow exhausted from the main turbine. It also receives discharges from auxiliary systems such as the feed water heater vents and drains and the gland sealing steam spillover and drains. To protect the condenser shells and turbine exhaust hoods from overpressurisation, steam relief blowout diaphragms are provided in the low-pressure turbine exhaust hoods. Two low-pressure feedwater heaters are located in the neck area of each condenser shell, adjacent to where their steam is bled from the low-pressure turbine. 

There is a minor requirement for the auxiliary steam system after a turbine trip, when the main condenser is a desirable component of the defence in depth capability identified within the fault schedule for cooling down the steam generators and the reactor coolant system. Failure of the auxiliary steam system during such fault transients could result in the main condenser becoming unavailable if no gland sealing steam were available. A reliable auxiliary steam system is thus desirable but not essential, because defence in depth capability is not claimed by the safety case. 

Sprii -loaded labjrinih-type gland seals are used to minimize air leakage into and steam leakage from the steam turbine. An automatic gland steam control system and condenser can be supplied. 

If a mechanical seal or a packed gland is fitted properly, a good life can be expected if the liquid is clean. If grit is in suspension, the seal manufacturer should be consulted about appropriate materials and system design. 

Face lubricated-type seals must be connected from the source of lubrication to the tap openings in the seal gland before startup. This is another predetermined environmental control feature that is mandatory for proper seal function. Where double seals are to be operated, it is necessary that the lubrication feed lines be connected to the proper ports for both circulatory or dead-end systems before equipment startup. This is very important because all types of double seals depend on the controlled pressure and flow of the sealing fluid to function properly. Even before the shaft is rotated, the sealing liquid pressure must exceed the product pressure opposing the seal. Be sure a vapor trap does not prevent the lubricant from reaching the seal face promptly. 

This pump is the same in principle as the piston type but differs in that the gland is at one end of the cylinder making its replacement easier than with the standard piston type. The sealing of piston and ram pumps has been much improved but, because of the nature of the fluids frequently used, care in selecting and maintaining the seal is very important. The piston or ram pump may be used for injections of small quantities of inhibitors to polymerisation units or of corrosion inhibitors to high pressure systems, and also for boiler feed water applications. 

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