Roundhouse Jack Pressure Gauge problem

[RylstonLight]

Hi all, I seek your collective wisdom?

My Roundhouse Jack class (original not special edition) developed an interesting fault when last steamed. The pressure gauge shot up to 60+ psi, whilst I was busy doing other things so I hadn't noticed the length of time it took to get to that level.

I assumed there was a problem with the safety valve and I cooled the engine, and put it to one side.

Now I have steamed it whilst watching, and the pressure went up to 60+ psi when only just warm, completely removing the pressure valve from the boiler (on a Jack it is the main filler as well) and the valve still stayed at 60 psi (ie when the boiler was completely de-pressured).

Releasing the pressure gauge allowed it to immediately rest to zero. There was a small amount of water in the syphon which I assume was turning to steam and causing pressure in the syphon. But this would infer a blockage between the syphon and the boiler pressure vessel itself. Applying back pressure with a 50ml syringe confirms no airflow backward on testing. Gentle probing with a wire through the syphon tube does not allow passage.

I am assuming some crud has blocked the tube.

I have tried heating the boiler with the pressure gauge removed; to try to blow any obstruction out. Initially there was a bead of hot water but that cleared and then no more.

Any comments about my diagnosis and any suggestions to free it. I have tried compressing the 50ml syringe (down to 7-10ml) before the syringe and tube leaks. I have tried a shot of butane with no effect (similar to unblocking gas jets) and I have tried gentle probing with wire.

Any help will be gratefully accepted.

Andy S at the Rylston Light

[RylstonLight]

Apologies for troubling you all

The secret was to boil through several times with the syphon pipe open. Eventually it cleared with a healthy plume of steam from it.

[LnBmad]

Glad you got it sorted.

[dougrail]

Good news indeed, will have to remember this!

[Gremlin]

they are real living little beasts and these things will happen, always pleasing to sort the problem out though.