Friday, 8 January 2016

Boiler Fittings (8)

Thursday 7th January 2016 saw Sentinel 7109's original boiler water gauge glasses being fitted finally as in the photo below.
Right hand gauge glasses
I last wrote about these in April 2013 when I'd obtained replacement glass protectors and checked that they would fit. Now the valves are in for good (hopefully).
Gauge Glass Valve arrangement similar to 7109's
Having remembered to insert the new 3/4" stainless steel balls into the lower valves to reduce the amount of steam escaping should the glass tube break, I proceeded to attach the component parts to the boiler. The upright steel tube is very straight and is used to ensure that top and bottom valves are aligned accurately when the glass tube is tightened in place.
Steel tube passing down through the upper valve to the lower one
It was not that difficult to achieve the alignment which is probably down to the 

curved surface of the valve faces matching the curvature of the boiler. I'm glad that new valves with flat faces did not have to be used!
Upper valve
Not so obvious from these photos is that each valve face is sealed to the boiler using a combination of graphite gasket with suitable lashings of Rocol Steamseal.
Lower valve showing close fit around the steel tube
I was then able to put the glass tubes in place and tighten them up. The word 'tighten' here is quite subjective. Sentinel used hexagonal graphite packings for this situation as below.
Hexagonal glass tube packings (photo from Heritage Steam Supplies' website)
They fit around the glass tube and are compressed to seal the tube. However, they should not be overtightened to prevent the glass being destroyed and they should align with the hexagonal spaces within the screw clamping mechanism. One of the glasses did not seal well so I may not have got this right and will have to recheck.

But how did I know that the seal was not so good...? That will have to wait for my next article (and I promise it will be worth the wait!).

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