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Power-User

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Generator Hydrogen Purity Deterioration

12/31/2011 5:08 AM

We have 220 MWe generator , the rotor being cooled by Hydrogen. We are facing problem of continuous declining Hydrogen purity. We are finding Nitrogen and other gases in Hydrogen. Anyone faced similar problem before? What may be the reasons? The generator is sealed by seal oil ( ISO VG 32) by maintaining differential pressure between oil and Hydrogen.

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#1

Re: Generator Hydrogen Purity Deterioration

12/31/2011 8:05 AM

"The bearings have to be leak-tight. A hermetic seal, usually a liquid seal, is employed; a turbine oil at pressure higher than the hydrogen inside is typically used. A metal, e.g. brass, ring is pressed by springs onto the generator shaft, the oil is forced under pressure between the ring and the shaft; part of the oil flows into the hydrogen side of the generator, another part to the air side. The oil entrains a small amount of air; as the oil is recirculated, some of the air is carried over into the generator. This causes a gradual air contamination buildup and requires maintaining hydrogen purity. Scavenging systems are used for this purpose; gas (mixture of entrained air and hydrogen, released from the oil) is collected in the holding tank for the sealing oil, and released into the atmosphere; the hydrogen losses have to be replenished, either from gas cylinders or from on-site hydrogen generators. Degradation of bearings leads to higher oil leaks, which increases the amount of air transferred into the generator; increased oil consumption can be detected by a flow meter associated to each bearing.[9]"

http://en.wikipedia.org/wiki/Hydrogen-cooled_turbogenerator

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#2

Re: Generator Hydrogen Purity Deterioration

01/01/2012 2:52 AM

We are finding Nitrogen and other gases in Hydrogen.

That's a strangely familiar gas mixture....

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