Wednesday, 28 November 2012

Water Filter Valves

On the left hand side of Sentinel 7109's water tank, there is a pair of water filter valves. These valves are in line with the pair of pipes feeding the two engine-borne boiler feed pumps.
The pair of water filter valves (not a recent photo!)
There is a flange plate at the back of each valve which fits over a hole in the tank side. When the valve is opened, water is able to pass upwards through the filter and out through the pipe on the left hand side.
Filter valve section drawing
(from S-Type Waggon Parts Manual)
The above is the best drawing I've been able to find although this is a type made for mounting horizontally on a S-Type Sentinel Waggon. Just pretend the bung numbered '7' is at the bottom below the valve spindle!

An unusual feature of the valve is that it has two seats (10). The obvious one closes the water inlet to the right; less obvious is the seat to the left which closes when the valve is fully opened. This is to stop the water from seeping out through the valve threads. I guess this is a simple, low-maintenance alternative to gland-packing the valve spindle.

The filter element and other component parts are shown below.
Component parts showing the filter mesh
As I've described in a previous article, the assembled valve has a black cap to its right. This seals an outlet which formerly supplied an injector before the cab mounted boiler feed pump was installed.
Drain plug shown highlighted
There is a drain plug at the bottom of each valve which serves two purposes: firstly to drain the filter valve to prevent frost damage and secondly to allow rubbish to be emptied from the filter. Looking back at the drawing, the detritus collected by the filter will inevitably sink to the bottom of the valve housing. So, for a vertically mounted valve, this should work quite effectively.

However, Sentinel 6515, Isebrook, which usually lives at Quainton Road, has its filter valves inverted as in the photo below!
Isebrook's inverted valves
When I examined 7109's valves, one clearly had a frangible stud which has been drilled out and replaced with a nice shiny new one.
Stud frangibility...
... and the brand new replacement
Gasket material for these will be rubberised cork sheet as there is no high temperature to contend with and only low pressure from the height of the water in the tank.

Saturday, 17 November 2012

A Sound Surround

In an earlier article, a comment questioned what might have been originally fixed to the edges of the large hole in Sentinel 7109's cab roof from which the chimneys protruded.

At the time, I did not know the answer although Norman thought he had seen something that had come from the old cab roof. Despite much searching, I'd not found anything but then on Sunday 11th Nov. 2012, I spotted something amongst 7109's bits and pieces that was obviously the right item. (Had someone been hiding it as I'm sure it wasn't there before?)!
Chimney Surround plate
Judging from the fixing holes around the edge which match those on the old cab roof, this is the correct original item. But why have an extra sheet to reduce the size of the hole at all?
The hole matches the chimney unit size
When looking at the hole size relative to the size of the twin chimney units, it becomes clearer.
Easily takes the two chimney units (1)
With the chimney surround also in place, there will be a fairly close fit to reduce rain coming in.
Easily takes the two chimney units (2)
The main reason for doing it this way is that when the surround plate is removed, there is space to remove the chimney units without having to take the whole roof off (not that this is difficult, of course!).

A second reason is that if the hole in the cab roof does not match the position of the chimneys mounted on the top of the boiler, it is a lot easier to reposition a small plate like this than to move the whole roof.

Another mystery solved! Now how many years did that take?

Monday, 5 November 2012

Defying Gravity - Raising the Roof

[To all loyal readers - an apology. Since originally publishing this article, I have been asked to revise the content. I hope that what remains is still of interest. I do try to present things exactly as they happened; Midsomer Norton's engineering facilities are not always as one would like and considerable ingenuity and determination are often needed to overcome challenges - that is what makes life interesting!].

5th November 2012, was a demonstration of how well the Midsomer Norton Monday Gang work together to overcome a difficult problem. Firstly, a picture of the end result!
Nigel's party trick!
Hmm, a bit like a spot the ball competition?
If you've followed the 'blog for some time, you'll know that Joyce had a new hat some time ago. The bright blue tarpaulin 'hat' has not lasted well and has been in urgent need of replacement by the metal cab roof itself for quite some time.
Ready for fitting
I'd made the cab roof ready for fitting in June 2012 but there it remained in the MSN goods' shed waiting to be manhandled into place. Being made of 3mm mild steel, it generally needed four people to lift it but to lift it from the ground to the top of the loco was never going to be easy. With no operational or accessible lifting machinery to hand, it really was going to be to hand!

Despite the rare good weather, I'd concluded that the roof was going to be in the shed at the end of the day yet again. However, I hadn't bargained for the determination of the Monday gang pulling together to take up the challenge. After a while, the original plan of sliding the roof up slanting ladders was looking a lot more feasible than I'd thought - and the weather was still beaming down!
Tools for the job!
Strapping the ladders to the loco cab side and attaching ropes to prevent them sliding away from the loco was an essential outcome of risk assessment. Likewise, pulling up by multiple straps as well as pushing up from below with plenty of hands was going to ensure that a single problem would not cause any undesired result.
And there you have it! Just like that!
The clue to Nigel's party trick!
I'd like to thank all the Monday gang who helped today, not forgetting Norman without whom many things would never happen!

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