A Boiler Full of Steam

Well the 10th November 2017 marks a major milestone – the boiler passed its initial inspection and steam test, and is now certified for use. (big smiles all round).

Picture of Engine, Boiler Etc. ready for test

Sadly, everything was too frenetic to take pictures during the steam test – but here it is just before we pressed go!

John, our inspector from SBAS Ltd (the SBA’s Boiler Inspecting Company) had been booked to arrive at 3:00pm – at 9:00am I set about final sealing of the try-cocks on the sight gauge – at 1:30pm I nearly called to cancel the appointment as no amount of fiddling and fitting would make them seal, with a constant drip from each of them at anything above 50psi 😦

Finally I made them seal with a combination of shredded graphite string and a binding of PTFE tape to seal the valve stems – dry as a bone at test pressure of 375spi, big sigh of relief. A final tightening of some of the 60+ joints in the steam circuit and we wound up with a boiler that held over 350psi for over one and a half hours without a single pump being needed. (This is a hydraulic test so the boiler is filled to the top (to exclude all the air and thereby minimise any “bangs” resulting from a failure.)

So the pressure test is complete. Next the steam and accumulation tests. So we wheel the complete set of machinery (engine, boiler, steam pumps, battery and regulator) outside (with a lot of puffing and blowing), drained the water in the boiler down to operating level, and we light the burner.

The burner needed some adjusting to get it to light and burn fairly cleanly (a little more tweaking needed) and we quickly had 10psi on the gauge (5-6 mins)  – so we turned off the burner and checked round for leaks or other problems and to let the boiler “adjust” to its new state of hotness.

All looked good so we brought it up to 50psi to check the water gauge (sight glass) was reading correctly and all the various blowdows operated correctly – they did! (more smiles).

The next step is to make sure the safety valve opens at the correct pressure and is able to control the pressure within 10% of safe working pressure with the burner full on.

So, burner on and another 10mins to come to working pressure of 250psi (17Bar) – whereupon I got an impromptu (but complete) hot shower. The safety valve did open OK, but as the water was quite high in the boiler. and had been dosed with washing soda to bring the PH up to 11 (and probably because of all the crud left in the boiler) we got a lot of water carried over into the exhaust steam (what is known as priming) which provided the aforementioned hot shower. There was enough showering down on the 240v wiring of the burner that I decided to kill the power while we dried things off….

So with a little less than a litre of diesel left for the burner we lit it once more and went for the accumulation test. By now it’s getting a little cold and dark, so reading the gauge within the billowing clouds of steam was quite hard for John, but after a few minutes he was happy that all was good – we were passed.

Not wanting to waste all this nice steam we tried the Worthington Simpson steam pump (A post on the restoration of this is on the way) in anger, and it performed quite well – supplying feed water at over 200psi….. and then we tried the engine!  after some warming thru this ran too and even the generator seemed to be making 7.5amps at a modest speed – but we highlighted the next (somewhat expected) list of jobs:

  • Two of the relief-drain valves seemed not to want to close (more clouds of steam and investigation needed)
  • The circulating pumps (engine driven) did not deliver enough cold water to the condenser to condense the exhaust steam and create the vacuum. So we are going to revert to the original design of the engine-driven pumps acting boiler feed pumps and the steam pump as a circulating pump.
  • I think I saw a couple pin-hole leaks in the feed pump plumbing which need checking
  • We need to finalise the plumbing from the cylinder drains
  • On the next run we need to get the displacement lubricator running.
  • We need to check the alternator performance to make sure we can generate the 20+amps we need to drive the inverter for the burner.

….then we can think about attempting to install the whole she-bang in the hull!!!! (Spring ’18 Launch – yes,  I think we might make it!)

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