Wednesday, 25 March 2015

Vacuum Braking (7) Implementation (1)

Nearly a year and a half ago, I designed the vacuum braking system for Sentinel 7109. Now it's time to start putting it together.

The design has evolved slightly.
Ball-style Isolating and driver's Valves and no gauge isolation valve
The actual topography of the pipe joints and links may not turn out quite like the diagram but it won't be of any consequence (he said confidently!).

Most interesting is how it will look when assembled.
This is only the beginning!
I'll put as much as possible together for a better photo before assembling it on 7109. It gets a lot worse than the above picture but I had to grab a quick camera opportunity before my wife found my enhancements to the kitchen floor!

It's a good practice to pre-assemble all the bits before installation to ensure all the connections are present and correct. There's very little room to move about in the cab and it's 25 miles away if bits are forgotten!

Saturday, 14 March 2015

What's this?

Just by the driver's right foot, until now, there has always been a little pipe poking up through Sentinel 7109's cab floor. It's near the levers in the photo below.
Above the cab floor, bottom right hand corner
From below, it bends off towards the lower part of the boiler.
Below the cab floor, left of centre
It's lurked for a very long time, possibly since 7109 was first built in 1927. The trouble is, I've never been able to work out what it was used for and hence what it should be used for. So I've removed it. (If in doubt, chuck it out!).
In all its glory!
My only inkling is that it might have been part of the injector pipework fitted from new but removed after about a year of service. An earlier article described the saga of 7109's injector.

Well, I don't know if this is the case so I'm open to all (sensible) suggestions.

Monday, 9 March 2015

Chuff Proofing (1)

Sentinel 7109's boiler top has received a lot of attention in the last five months, particularly since it has been indoors. Last October, there were no chimneys and the cab actually felt quite roomy!

The first photo below shows where the four-ringed superheater inlet dips below the boiler top surface.
October 2014
The second photo shows the first of two three-part 'superheater steady plates' to keep the superheater tubes well sealed and to prevent air being drawn in with each chuff. (Co-owner Nigel's handy-work with cardboard templates and sheet stainless steel here).
March 2015
Eventually there will be some ceramic wool etc. applied to seal the gaps even better (when we've figured out how to do it!).

Eagle eyed observers will of course notice that the first photo shows the superheater's inlet and the second shows the superheater's outlet. The inlet steady plate has still to be done. The three parts are not easy to make and have to be shaped carefully for a snug fit.

The gaps have to be well sealed in the same way that a conventional steam loco has to have a sealed smoke-box door. In either case, if there are leaks, when the loco chuffs, it draws air in through the gaps instead of up through the fire. The consequence being that it will lose steam generating efficiency.

Saturday, 7 March 2015

Boiler Plugs & Clamps

Friday 6th March was a day to complete a couple of small tasks. Some time ago, I'd been concerned about a rather inadequate looking boiler plug as in the photo below.
Boiler Plug?
The 'plug' blocked a hole in the steam space on the right near the safety valve mounting. This little item has been with the boiler since it arrived and was used during the initial hydraulic test of the boiler.

What concerned me was that the main part of the 'plug' consisted of a malleable iron socket. As a material, malleable iron is definitely not recommended for use with steam at 275psi!

The Heritage Railway Association (HRA) has produced a report on boiler washout plugs and go to great length to ensure that the correct tapered threads are used on the plug to match that of the tapered hole. Here, Sentinel have not used a tapered thread at all; it is a parallel thread (1/2" BSPP)!

After much searching, I found a source of suitable parallel plugs made from 316 stainless steel. Peter Hawkins, our boiler inspector, is happy with this as a strong enough material for the plug although he pointed out that it may be difficult to remove in future. Stainless steel tends to snag against stainless steel; however, the boiler itself is not stainless and so I have decided to take the risk. (I hope I'm right as this is a useful hole for putting water into the boiler!).

The plug is now tightened to 50Nm torque on to an annealed copper washer with Steamseal in all the right places to prevent any leaks.
Boiler Plugged!
In fact, two holes have been plugged in this manner. The other is also in the steam space but on the left hand side and was originally used to supply a steam lance (long before the invention of pressure washers for cleaning purposes).

The new and the old:
And the new one doesn't rip your clothes as you squeeze past!
The second task was to fit six [ shaped clamps to hold the boiler top plate in place. These I had made after my welding course about three years ago.
One of the six
(with lashings of graphite grease!)
This week I also spent much time (and money) obtaining the pipework and fittings to construct the vacuum braking system. The other little task on this date was transporting the steel vacuum pipe to Midsomer Norton station as below.
Have Pipe will Travel!
There's a lot of vacuum fitting ahead in the next few weeks!
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