Sea cock

[Killick69]

3 year old seal cock for Galley sink has started leaking when in open position. Leak is from the shaft/gland nut.I assume there is an o-ring. I tightened the gland nut, but it unscrews when the handle is moved. I do not see why a seal (o-ring) is needed. I check the old sea cock that was replaced and it does not have the gland nut (much better). Other than this the 2 sea cocks are the same. They are both Bronze and the new one was bought from Whitworths or Bias. Any ideas very welcome.
p.s. as a sideline has anyone heard of putting vegetable oil thru sea cock to maintain/lube it??

[Troppo]

HI Killick, any pics to help identify it?

troppo