Sentinel 7109's Polished set of gauge glass valves

All loco or waggon boilers use a gauge glass to enable the fireman to see the boiler's water level. A glass tube between an upper and lower gauge glass valve is where the actual water level can be seen. The upper and lower valves are used to ensure that the level is indicating correctly and that any doubtful muck can be jettisoned when required.

Luckily, 7109 came complete with gauge glass valves attached to the boiler although they were in an unknown condition at the time and looking fairly dull.

Gauge Glass Valves as arrived (with curved handles)

Gauge glass valves to fit Sentinel boilers are unusual in that they have to have a curved surface to match the cylindrical curvature of the boiler profile.

Gauge Glass Valves after a little cleaning
(and much improved in bright light!)

 The internal moving parts of the valves, despite my initial (naive) attempts, were not in a good state. The curved handles indicated an old design that was famed for leaking badly. 

"Klinger" Valves spindles (Photo Heritage Steam Supplies)

John Goold advised the rebuilding of the valves to the "Klinger" design and this has been completed. 

Good as new and not so dull!

The almost as-new look has been achieved by 'pickling'.  I never quite understood whether this was to do with an extended visit to the pub or a dip in an acid bath but the end result looks brilliant!